CN116484524A - Rapid simulation and design method for performance of multi-row finned tube heat exchanger - Google Patents
Rapid simulation and design method for performance of multi-row finned tube heat exchanger Download PDFInfo
- Publication number
- CN116484524A CN116484524A CN202310409683.5A CN202310409683A CN116484524A CN 116484524 A CN116484524 A CN 116484524A CN 202310409683 A CN202310409683 A CN 202310409683A CN 116484524 A CN116484524 A CN 116484524A
- Authority
- CN
- China
- Prior art keywords
- heat exchanger
- calculation
- heat exchange
- loop
- control unit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 80
- 238000004088 simulation Methods 0.000 title claims abstract description 75
- 238000013461 design Methods 0.000 title claims abstract description 37
- 238000004364 calculation method Methods 0.000 claims abstract description 171
- 238000004422 calculation algorithm Methods 0.000 claims abstract description 26
- 238000009827 uniform distribution Methods 0.000 claims abstract description 6
- 238000005452 bending Methods 0.000 claims description 8
- 230000005484 gravity Effects 0.000 claims description 8
- 239000012530 fluid Substances 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 5
- 238000011478 gradient descent method Methods 0.000 claims description 4
- 238000012546 transfer Methods 0.000 claims description 3
- 238000004378 air conditioning Methods 0.000 abstract description 7
- 238000010438 heat treatment Methods 0.000 abstract description 4
- 238000009423 ventilation Methods 0.000 abstract description 4
- 238000011144 upstream manufacturing Methods 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 7
- 238000009826 distribution Methods 0.000 description 5
- 239000003507 refrigerant Substances 0.000 description 5
- 238000004134 energy conservation Methods 0.000 description 4
- 238000007689 inspection Methods 0.000 description 4
- 238000005057 refrigeration Methods 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000013178 mathematical model Methods 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000003872 anastomosis Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/17—Mechanical parametric or variational design
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/08—Thermal analysis or thermal optimisation
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Geometry (AREA)
- Theoretical Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Evolutionary Computation (AREA)
- Computer Hardware Design (AREA)
- General Engineering & Computer Science (AREA)
- Pure & Applied Mathematics (AREA)
- Mathematical Optimization (AREA)
- Mathematical Analysis (AREA)
- Computational Mathematics (AREA)
- Management, Administration, Business Operations System, And Electronic Commerce (AREA)
Abstract
The invention discloses a multi-row fin tube heat exchanger performance quick simulation and design method, which relates to the field of heating ventilation and air conditioning, and comprises a simplified description method of a heat exchanger structure and a quick iteration algorithm, wherein the simplified description method is based on the tube number and the loop proportion, establishes fin tube heat exchanger performance calculation logic, realizes the uniform distribution of heat exchange tubes in each row in the same loop, realizes heat exchanger model simplification according to the length combination method of each loop tube in each row, and reflects heat exchanger performance characteristics according to the working medium flowing direction and sequence; the rapid iterative algorithm is based on a simplified description method under known and/or unknown flow, and according to the established simplified model based on the tube number and the loop proportion, the heat exchanger is divided into downstream and/or upstream working conditions of a control unit, a single-row heat exchanger and a multi-row heat exchanger, so that the simulation calculation and design method of the finned tube heat exchanger is realized. The invention establishes a simplified model reflecting key parameters and local characteristics of the finned tube heat exchanger, reduces structural complexity and diversity, and improves calculation efficiency.
Description
Technical Field
The invention relates to the field of heating ventilation and air conditioning, in particular to a method for quickly simulating and designing the performance of a multi-row finned tube heat exchanger.
Background
With the continuous improvement of economical strength, comprehensive national force and living quality of people in China, the use of heating ventilation air conditioning in China is more and more widespread, and the massive use of the refrigerating air conditioning device also means the massive consumption of energy, and according to statistics, the load of the refrigerating air conditioning device can reach more than 40% of urban electricity consumption at peak time. At the same time, the large amount of refrigerant used also causes a series of environmental problems such as ozone destruction, global warming, etc. In order to solve the problems, the country gradually improves the energy consumption standard of the refrigeration device and disables the environment-friendly refrigerant, so that the energy conservation and emission reduction of the refrigeration system and related research are more important. The heat exchanger plays an important role in a plurality of industries such as refrigeration systems as important energy-saving equipment in industrial production devices. Since the fourteen-five planning, the country has greatly developed green economy and has pushed the concept of circular economy, so that heat exchangers with the characteristics of high efficiency, energy conservation, environmental protection and the like are increasingly valued and supported by the country. The heat exchanger industry is accompanied with the development of high-end equipment manufacturing industry under the state medium-long-term planning, so that the heat transfer efficiency is further emphasized, the energy-saving efficiency-increasing level is improved, and the technical breakthrough is realized. The fin tube heat exchanger is one of the most commonly used types of main stream heat exchangers in heating and ventilation equipment, and is widely used in refrigeration and air conditioning systems due to its unique advantages and characteristics. In summary, it is necessary to develop simulation and design models of the finned tube heat exchanger for guiding the optimal design of the heat exchanger.
For the finned tube heat exchanger, as the demands of downstream customers are increased, the technology of the heat exchanger industry iterates, and products of the finned tube heat exchanger gradually face to research production modes of customization, diversification and high efficiency. With the increase of the product customization demand, how to realize the rapid simulation model selection of a demand party in a few seconds from thousands of heat exchanger structures of a supply party when the structure is unknown is a key of research, and has urgent application demands. The finned tube heat exchanger has more than 20 component parameters, the calculation complexity is greatly improved due to diversified arrangement and combination, and the heat exchanger form meeting the performance requirement is very difficult to quickly find in the second-level measurement. In summary, it is needed to build a performance simulation model of the finned tube heat exchanger and develop a model selection design method, so as to provide a theoretical basis and engineering application tools for rapid performance simulation research and efficient model selection design of the heat exchanger.
In the study of heat exchanger performance simulation and design methods, a plurality of study groups have established related mathematical models, such as a three-dimensional distribution parameter simulation model of a fin tube heat exchanger based on graph theory, for a plurality of types of heat exchangers (chemical engineering journal, 2005, 6:233-238). The model can flexibly describe any refrigerant loop arrangement, quantify the refrigerant distribution in the refrigerant loop and heat conduction through the fins, solve a conservation equation through the proposed iteration method, effectively shorten simulation time, and meet simulation calculation and structure optimization of the heat exchanger with specific functions or structures. However, the method needs detailed structural parameters and needs to input the connection relation among the heat exchange tubes, and the simulation time is long for the rapid simulation design calculation of the multi-row multi-loop fin tube heat exchanger. The common type selection software has various defects and problems such as manual iterative debugging calculation, poor calculation precision, uncertain structural range and the like.
In summary, a method for rapid simulation design needs to be developed, and by combining the advantages of the method, the requirement of a second-level rapid design selection function in thousands of fin tube heat exchanger databases can be achieved, so that the problem that in air conditioning system simulation, heat exchanger performance calculation cannot be performed or the calculation process is too complex due to complex heat exchanger structure, confidentiality of suppliers and the like is solved, and meanwhile, the requirements of precision and speed are met.
Accordingly, those skilled in the art have been directed to developing a method for rapid simulation and design of the performance of a multi-row finned tube heat exchanger.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present invention aims to solve the technical problems that the multi-row multi-loop fin tube heat exchanger has a complex structure, and is difficult to quickly and reasonably describe its structural features, and has high computational complexity.
In order to achieve the above object, the present invention provides a method for rapidly simulating and designing the performance of a multi-row finned tube heat exchanger, which is characterized in that the method comprises a simplified description method and a rapid iterative algorithm of the heat exchanger structure, wherein,
the simplified description method is characterized in that logic for calculating the performance of the finned tube heat exchanger is established based on the number of tubes and the proportion of loops, uniform distribution of the heat exchange tubes in each row in the same loop is realized, the model simplification of the finned tube heat exchanger is realized according to the method that the lengths of the tubes in each loop in each row are combined into a single tube, and the performance characteristics of the heat exchanger are reflected according to the flowing direction and sequence of working media by adjusting the wind speed under the condition that the air quantity is unchanged;
The rapid iterative algorithm is based on the simplified description method under known and/or unknown flow, and according to the established simplified model based on the tube number and the loop proportion, the heat exchanger is divided into forward flow and/or reverse flow working conditions of a control unit, a single-row heat exchanger and a plurality of rows of heat exchangers, so that the simulation calculation and design method of the fin tube heat exchanger under the operating condition is realized, wherein the operating condition comprises at least one of the operating conditions of a plurality of rows of forward flow and reverse flow.
Further, the establishment of the simplified description model in the simplified description method comprises a main body heat exchange area, a collecting pipe and an elbow pipe, wherein,
the main heat exchange area adopts a control unit dividing method based on the loop proportion, calculates the number of the heat exchange tubes of each loop according to the loop proportion, and uniformly distributes the heat exchange tubes in each row of the heat exchanger to ensure that the number of the heat exchange tubes of each loop in each row is the same;
the collecting pipe is connected with an inlet heat exchange pipe of each loop through a branch pipe, the number of outlets of the branch pipes of the collecting pipe represents the number of loops of the heat exchanger, the control unit of the collecting pipe is divided by the middle position of the branch pipe connected with the collecting pipe between two adjacent loops, and the control units in the collecting pipe are numbered according to the sequence of the loops;
The control units are divided into the elbows individually by considering only the pressure drop in the elbows, and each of the elbows is regarded as one of the control units as a whole in the simulation calculation.
Further, the loop ratio characterizes a loop type, the loop ratio is a ratio of the number of loops of the heat exchanger to the number of tubes per bank,
wherein Ratio is the loop Ratio, C is the loop number, TN N N is the number of tube rows, TN is the number of tube rows C The number of pipes per loop;
calculating the number of tubes in each row of the single loop through the loop proportion, and equivalent the number of tubes to the single heat exchange tube N equi The equivalent length of the heat exchange tube is L equi ：
L equi ＝TN C/N ·L，
Wherein L is equi Is equivalent to the length of a heat exchange tube, TN C/N L is the length of the original pipe for each row of pipes in each loop.
Further, the flow regulation equation of the collecting pipe is characterized in that:
wherein G is r，h，guess ，G r，t，guess Respectively guessing the mass flow rate delta P of working medium at the inlet of collecting pipe and in single loop h，total，in ，ΔP h，total，out ，ΔP t，total The total pressure drop of the working medium at an inlet and an outlet in the collecting pipe and the total pressure drop in a single loop are respectively shown, i and j are the serial numbers of the loops;
the momentum equation of the collecting pipe is as follows:
ΔP h，total ＝ΔP h，acc +ΔP h，gra +ΔP h，f +ΔP h，joint ，
wherein DeltaP h，total Delta P is the total pressure drop generated in the collecting pipe by working medium h，acc For accelerating pressure drop generated in the collecting pipe by working medium, delta P h，gra For gravity pressure drop generated in the collecting pipe by working medium, delta P h，f For the friction pressure drop generated by working medium in the collecting pipe, delta P h，joint The pressure drop is generated at the joint of the collecting pipe control unit for working medium;
the momentum equation of the bent pipe is as follows:
ΔP t，total ＝ΔP t，f +ΔP t，acc +ΔP t，gra +ΔP bend ，
wherein DeltaP t，total Delta P is the total pressure drop of working medium in the bent pipe t，acc For accelerating pressure drop generated by working medium in the bent pipe, delta P t，gra For gravity pressure drop generated in the bend pipe by working medium, delta P t，f For the friction pressure drop generated by working medium in the bent pipe, delta P bend The bending pressure drop generated in the bent pipe by the working medium is used;
the energy equation of the control unit is as follows:
Q r +Q a +Q top +Q bottom +Q front +Q back ＝0，
wherein Q is r For the heat exchange quantity of working medium in the control unit, Q a For the heat exchange quantity of air in the control unit, Q top For the heat conduction quantity Q of the control unit above the current control unit bottom For the heat conduction quantity Q of the control unit below the current control unit front For the heat conduction quantity Q of the control unit in front of the current control unit back Is the heat conduction quantity of the control unit behind the current control unit.
Further, the heat exchange performance of the heat exchanger is calculated by adopting a harmonic mean temperature difference method:
Wherein,,for heat exchange quantity, alpha is a heat exchange coefficient, A is a heat exchange area, delta T is an average temperature difference between inner and outer fluid, and the following formula is adopted for calculation:
wherein DeltaT max And DeltaT min The maximum temperature difference and the minimum temperature difference of the working medium in the pipe and the air outside the pipe at the same side of the inlet and the outlet are obtained.
Further, the iterative simulation calculation of the control unit includes the following steps:
step 1: initializing parameters of the control unit according to the known conditions of the heat exchanger unit, wherein the flow adopts a guess value;
step 2: according to the heat exchange and pressure drop relation, calculating the heat exchange coefficient and air side pressure drop of the working medium inlet state inside and outside the pipe;
step 3: according to the air side state, the enthalpy value of the working medium at the outlet of the control unit is assumed;
step 4: calculating the enthalpy value of an air outlet, and calculating the outlet temperature of the working medium inside and outside the pipe;
step 5: calculating the heat exchange quantity of the heat exchanger;
step 6: determining whether the enthalpy difference of the working medium in the control unit meets heat exchange convergence conditions;
step 7: judging whether the temperature of the working medium outlet is crossed with the temperature of the air outlet, if so, recalculating relevant state parameters such as heat exchange quantity and the like;
step 8: and outputting state parameters of the working medium and the air at the outlet of the control unit.
Further, the iterative simulation calculation of the single-row heat exchanger and the multi-row heat exchanger, based on the iterative simulation calculation of the control unit, comprises heat exchange calculation and pressure drop calculation, and comprises the following steps:
step 1: determining convergence criteria and input parameters: taking the outlet temperature of the working medium as the convergence criterion, wherein the input parameters comprise the flow initial value of the working medium, the heat exchanger structure and the working condition parameters;
step 2: and (3) heat exchange calculation: calculating the heat exchange of the control unit, and updating the inlet state of the next control unit after the calculation is completed;
step 3: pressure drop calculation: calculating the pressure drop of the control unit, and updating the inlet state of the next control unit after the calculation is completed;
step 4: after the calculation of a single loop is completed, the heat exchange calculation and the pressure drop calculation of the next loop are carried out until the calculation of the whole heat exchanger is completed;
step 5: iterative convergence judgment, if not, updating data and executing the step 2-3;
step 6: and outputting a simulation calculation result.
Further, in the step 5, the iterative convergence determination includes a pressure drop convergence determination, a fin temperature convergence determination, and a heat exchanger performance convergence determination, wherein,
Judging whether the pressure drop converges or not according to whether the pressure drops of different loops are consistent or not, if not, adjusting the flow and carrying out heat exchange calculation and pressure drop calculation again;
the fin temperature convergence judgment is carried out, whether the fin temperature is stable or not is judged to judge whether the fin temperature is converged or not, if not, the data are updated, and heat exchange calculation and pressure drop calculation are carried out again;
judging whether the performance of the heat exchanger is converged or not according to the difference value between the temperature of the working medium outlet of the heat exchanger and a target value, if not, adjusting the guessed flow according to the difference value and a gradient descent method, and carrying out heat exchange calculation and pressure drop calculation again; the specific calculation method of the difference value comprises the following steps:
|T r，out -T r，set |＜ε，
wherein T is r，out To actually calculate the outlet temperature value, T r，set For setting the target outlet temperature value, ε is the temperature difference threshold, ε takes 0.01K.
Further, the iterative simulation calculation of the multi-row heat exchanger further includes:
in the step 2, if the loop is the last unit of a certain row of heat exchange tubes in the multi-row heat exchanger, updating the air side inlet state of the next row by taking the row as a unit; if the row is the last row of the multi-row heat exchangers, the air state is not updated any more;
In the step 3, the pressure drop calculation is sequentially performed according to the number of rows in the same loop.
Further, the rapid iterative design method, based on a target value guess and a simulation inspection algorithm, uses the heat exchange performance or the air outlet temperature of the heat exchanger as a target value, and obtains the heat exchanger row number and the loop number by setting constraint conditions, comprising the following steps:
step 1: determining an unknown quantity iteration mode and a target quantity;
step 2: calling a simplified model to perform simulation calculation;
step 3: calling a precision simulation calculation model for checking calculation;
step 4: and outputting the structural parameters of the fin tube heat exchanger.
In the preferred embodiment of the present invention, compared with the prior art, the present invention has the following beneficial technical effects:
1. the invention provides a simplified description method of a heat exchanger structure, which is formed by describing a multi-row finned tube heat exchanger based on the number of tubes and the proportion of loops, neglecting the connection relation between heat exchange tubes, constructing a rapid simulation model of the heat exchanger performance and combining rapid iterative algorithms; according to the simplified thought of combination of length of each row of tubes, logic for calculating the performance of the finned tube heat exchanger is established, the finned tube heat exchanger with any structure is characterized, a loop priority calculating method is further provided, a simplified model reflecting key parameters and local characteristics of the finned tube heat exchanger is established, structural complexity and diversity caused by changes of tube number, row number, loop number and the like are reduced, and calculating efficiency is improved;
2. The invention establishes the simulation calculation method of the fin tube heat exchanger under the conditions of single row, multiple rows, parallel flow, countercurrent and the like, realizes the rapid and accurate simulation calculation based on the simplified description method under the unknown flow, has good model prediction precision and high speed, predicts stably at non-boundary working points, and realizes the achievement that the calculation time of a single calculation example is less than 0.05 s;
3. the invention provides a high-efficiency iterative algorithm based on target value guess and simulation test, and designs various unknown parameters such as heat exchanger row number, loop number and the like when the structure is unknown, so that the rapid simulation design of the finned tube heat exchanger is realized, the structure selection design speed of the finned tube heat exchanger is high, the effect is good, the selection design of a plurality of unknown structural parameters within 5 seconds is realized, and the calculation speed is improved by about 1-2 orders of magnitude.
The conception, specific structure, and technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, features, and effects of the present invention.
Drawings
FIG. 1 is a simplified schematic illustration of a fin tube heat exchanger according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of the partitioning parameters of a control unit of a finned tube heat exchanger in accordance with a preferred embodiment of the present invention;
FIG. 3 is a schematic illustration of simulated calculations for a concurrent flow regime of a multi-row finned tube heat exchanger in accordance with a preferred embodiment of the present invention;
FIG. 4 is a schematic diagram of an alternative design algorithm for a finned tube heat exchanger in accordance with a preferred embodiment of the present invention.
Detailed Description
The following description of the preferred embodiments of the present invention refers to the accompanying drawings, which make the technical contents thereof more clear and easy to understand. The present invention may be embodied in many different forms of embodiments and the scope of the present invention is not limited to only the embodiments described herein.
In the drawings, like structural elements are referred to by like reference numerals and components having similar structure or function are referred to by like reference numerals. The dimensions and thickness of each component shown in the drawings are arbitrarily shown, and the present invention is not limited to the dimensions and thickness of each component. The thickness of the components is exaggerated in some places in the drawings for clarity of illustration.
As shown in FIG. 1, the simplified description method of the finned tube heat exchanger provided by the embodiment of the invention establishes logic for calculating the performance of the finned tube heat exchanger based on the number of tubes and the proportion of loops, realizes uniform distribution of the heat exchange tubes in each row in the same loop, and realizes model simplification of the finned tube heat exchanger according to the length of each loop in each row and the method of merging the heat exchange tubes into a single tube, and under the condition of ensuring the unchanged air quantity, the performance characteristics of the heat exchanger are reflected according to the flowing direction and sequence of working media by adjusting the air speed. Wherein the loop proportion represents the loop type, the loop proportion is the ratio of the loop number of the heat exchanger to the row number of each row,
Wherein Ratio is the loop Ratio, C is the loop number, TN N N is the number of tube rows, TN is the number of tube rows C For the number of pipes per loop.
Calculating the number of tubes in each row of a single loop through the proportion of the loops, and equivalent the number of the tubes to be a single heat exchange tube N equi The equivalent heat exchange tube length is L equi ：
L equi ＝TN C/N ·L，
Wherein L is equi Is equivalent to the length of a heat exchange tube, TN C/N L is the length of the original pipe for each row of pipes in each loop.
The establishment of the simplified description model in the simplified description method comprises a main body heat exchange area, a collecting pipe and an elbow pipe, wherein,
the main body heat exchange area adopts a control unit division method based on loop proportion, as shown in fig. 2, the number of the heat exchange tubes of each loop is calculated according to the loop proportion, and the heat exchange tubes are uniformly distributed in each row of the heat exchanger, so that the same number of the heat exchange tubes of each loop in each row is ensured; the collecting pipe is connected with an inlet heat exchange pipe of each loop through a branch pipe, the number of outlets of the branch pipes of the collecting pipe represents the number of loops of the heat exchanger, a control unit of the collecting pipe is divided by the middle position of the two adjacent loops connected with the collecting pipe, and the control units in the collecting pipe are numbered according to the sequence of the loops; the control units are divided into the elbows individually by considering only the pressure drop in the elbows, and each of the elbows is regarded as one of the control units in simulation calculation.
The flow regulation equation of the collecting pipe is as follows:
wherein G is r，h，guess ，G r，t，guess Respectively guessing the mass flow rate delta P of working medium at the inlet of collecting pipe and in single loop h，total，in ，ΔP h，total，out ，ΔP t，total The total pressure drop of the working medium at an inlet and an outlet in the collecting pipe and the total pressure drop in a single loop are respectively shown, i and j are the serial numbers of the loops;
the momentum equation of the collecting pipe is as follows:
ΔP h，total ＝ΔP h，acc +ΔP h，gra +ΔP h，f +ΔP h，joint ，
wherein DeltaP h，total Delta P is the total pressure drop generated in the collecting pipe by working medium h，acc For accelerating pressure drop generated in the collecting pipe by working medium, delta P h，gra For gravity pressure drop generated in the collecting pipe by working medium, delta P h，f For the friction pressure drop generated by working medium in the collecting pipe, delta P h，joint The pressure drop is generated at the joint of the collecting pipe control unit for working medium;
the momentum equation of the bent pipe is as follows:
ΔP t，total ＝ΔP t，f +ΔP t，acc +ΔP t，gra +ΔP bend ，
wherein DeltaP t，tptal Delta P is the total pressure drop of working medium in the bent pipe t，acc For accelerating pressure drop generated by working medium in the bent pipe, delta P t，gra For gravity pressure drop generated in the bend pipe by working medium, delta P t，f For the friction pressure drop generated by working medium in the bent pipe, delta P bend The bending pressure drop generated in the bent pipe by the working medium is used;
the energy equation of the control unit is:
Q r +Q a +Q top +Q bottom +Q front +Q back ＝0，
wherein Q is r For the heat exchange quantity of working medium in the control unit, Q a For the heat exchange quantity of air in the control unit, Q top For the heat conduction quantity Q of the control unit above the current control unit bottom For the heat conduction quantity Q of the control unit below the current control unit front For the heat conduction quantity Q of the control unit in front of the current control unit back Is the heat conduction quantity of the control unit behind the current control unit.
The heat exchange performance of the heat exchanger is calculated by adopting a harmonic mean temperature difference method:
wherein,,for heat exchange quantity, alpha is a heat exchange coefficient, A is a heat exchange area, delta T is an average temperature difference between inner and outer fluid, and the following formula is adopted for calculation:
wherein DeltaT max And DeltaT min The maximum temperature difference and the minimum temperature difference of the working medium in the pipe and the air outside the pipe at the same side of the inlet and the outlet are obtained.
In the preferred embodiment of the invention, aiming at the problems that the multi-row multi-loop finned tube heat exchanger is complex in structure, difficult to quickly and reasonably describe the structural characteristics and high in calculation complexity, the invention provides a simplified description method of the heat exchanger structure, describes the multi-row finned tube heat exchanger based on the number of tubes and the proportion of loops, ignores the connection relation among the heat exchange tubes, constructs a quick simulation model of the heat exchanger performance, and is formed by combining a quick iterative algorithm. According to the simplified thought of combination of length of each row of tubes, establishing logic for calculating the performance of the finned tube heat exchanger, characterizing the finned tube heat exchanger with any structure, further providing a calculation method of loop priority, and realizing uniform distribution of the heat exchange tubes with the same loop in each row based on a model description method of tube number and loop proportion on the basis of a three-dimensional distribution parameter model; further, according to the method of combining the lengths of the pipes of each loop in each row, the number of the pipes of each loop in each row is simplified into a single heat exchange pipe, and model simplification is realized; and reflecting the performance characteristics of the heat exchanger according to the flow direction and sequence of the working medium. The method omits the connection relation of the heat exchange tubes, simplifies the structure description method and can still ensure the simulation speed and precision. The invention reduces the structural complexity and diversity caused by the changes of the tube number, the row number, the loop number and the like by establishing the simplified model reflecting the key parameters and the local characteristics of the finned tube heat exchanger, and improves the calculation efficiency.
As shown in FIG. 3, the simulation calculation method for the downstream state of the multi-row finned tube heat exchanger provided by the embodiment of the invention is based on the simplified description method of the finned tube heat exchanger under the known and/or unknown flow, and the heat exchanger is divided into downstream and/or countercurrent working conditions of a control unit, a single-row heat exchanger and the multi-row heat exchanger according to the established simplified model based on the number of tubes and the proportion of loops, so that the simulation calculation of the finned tube heat exchanger under the multi-row, downstream and countercurrent running conditions is realized, and the simulation calculation comprises an initialization parameter module, a heat exchange calculation module, a pressure drop calculation module and a convergence iteration module.
The iterative simulation calculation of the control unit comprises the following steps:
step 1: initializing parameters of a control unit according to known conditions of the heat exchanger unit, wherein the flow adopts a guess value;
step 2: according to the heat exchange and pressure drop relation, calculating the heat exchange coefficient and air side pressure drop in the state of the working medium inlet inside and outside the pipe;
step 3: according to the air side state, the enthalpy value of the working medium at the outlet of the control unit is assumed;
step 4: calculating the enthalpy value of an air outlet, and calculating the outlet temperature of working media inside and outside the pipe;
step 5: calculating the heat exchange quantity of the heat exchanger;
step 6: determining whether enthalpy difference of working media in the control unit meets heat exchange convergence conditions;
Step 7: judging whether the temperature of the working medium outlet is crossed with the temperature of the air outlet, if so, recalculating relevant state parameters such as heat exchange quantity and the like;
step 8: and outputting state parameters of working medium and air at the outlet of the control unit.
Iterative simulation calculation of a single-row heat exchanger and a multi-row heat exchanger, which is based on iterative simulation calculation of a control unit and comprises heat exchange calculation and pressure drop calculation, comprises the following steps:
step 1: determining convergence criteria and input parameters: taking the outlet temperature of the working medium as a convergence criterion, wherein the input parameters comprise the flow initial value of the working medium, the heat exchanger structure and the working condition parameters;
step 2: and (3) heat exchange calculation: calculating the heat exchange of the control unit, and updating the inlet state of the next control unit after the calculation is completed;
step 3: pressure drop calculation: calculating the pressure drop of the control unit, and updating the inlet state of the next control unit after the calculation is completed;
step 4: after the calculation of a single loop is completed, the heat exchange calculation and the pressure drop calculation of the next loop are carried out until the calculation of the whole heat exchanger is completed;
step 5: iterative convergence judgment, if not, updating data and executing the step 2-3;
when the iterative convergence judgment is carried out, the iterative convergence judgment comprises pressure drop convergence judgment, fin temperature convergence judgment and heat exchanger performance convergence judgment, wherein,
Judging whether the pressure drop converges or not according to whether the pressure drops of different loops are consistent or not, if not, adjusting the flow and carrying out heat exchange calculation and pressure drop calculation again;
judging whether the fin temperature is stable or not to judge whether the fin temperature is converged or not, if not, updating data and carrying out heat exchange calculation and pressure drop calculation again;
and judging whether the performance of the heat exchanger is converged or not according to the difference value between the temperature of the working medium outlet of the heat exchanger and the target value, if not, adjusting the guess flow according to the difference value and the gradient descent method, and carrying out heat exchange calculation and pressure drop calculation again.
The specific calculation method of the difference value comprises the following steps:
|T r，out -T r，set |＜ε，
wherein T is r，out To actually calculate the outlet temperature value, T r，set For setting the target outlet temperature value, ε is the temperature difference threshold, ε takes 0.01K.
Step 6: and outputting a simulation calculation result.
The iterative simulation calculation of the multi-row heat exchanger needs to consider the influence of the row number of the heat exchangers, and besides the iterative simulation calculation content of the single-row heat exchanger, the iterative simulation calculation method further comprises the following steps:
in step 2, if the loop is the last unit of a certain row of heat exchange tubes in the multi-row heat exchanger, updating the air side inlet state of the next row by taking the row as a unit; if the row is the last row of the multi-row heat exchangers, the air state is not updated any more;
In step 3, pressure drop calculation is sequentially performed in the same loop according to the number of rows.
In the preferred embodiment of the invention, aiming at the problems that when the structure is known, the multi-row multi-loop finned tube heat exchanger lacks a corresponding calculation method under the conditions of the known flow and the like and the calculation time is long, a simulation calculation method of the finned tube heat exchanger under the conditions of single row, multi-row concurrent flow and the like is established, the quick and accurate simulation calculation can be carried out based on a simplified description method under the known flow and the unknown flow, and the flow value and the upper limit and the lower limit of the basic anastomosis target heat exchange quantity are given based on an energy conservation-based initial flow value automatic calculation method under the unknown flow; adopting a Newton iteration flow rapid calculation method to realize flow optimization; the decoupling calculation mode of heat exchange and pressure drop alternate iteration is adopted, so that the simulation speed is improved, the model prediction precision is good, the speed is high, and the prediction is stable at non-boundary working condition points; the result that the calculation time of a single example is less than 0.05s is realized.
As shown in fig. 4, the embodiment of the invention provides a design algorithm for selecting the fin tube heat exchanger, the rapid iterative design method is based on a target value guess and a simulation inspection algorithm, the heat exchange performance or the air outlet temperature of the heat exchanger is taken as a target value, and the heat exchanger row number and the loop number are obtained by setting constraint conditions, and the method comprises the following steps:
Step 1: determining an unknown quantity iteration mode and a target quantity;
step 2: calling a simplified model to perform simulation calculation;
step 3: calling a precision simulation calculation model for checking calculation;
step 4: and outputting the structural parameters of the fin tube heat exchanger.
Aiming at the problem that when the structure is unknown, the model selection design calculation of various structural parameters in a database of tens of thousands of finned tube heat exchangers cannot be realized, the embodiment of the invention provides a high-efficiency iterative algorithm based on target value guess and simulation test, when the structure is unknown, various unknown parameters such as heat exchanger row number, loop number and the like are designed, the rapid simulation design efficiency of the finned tube heat exchanger is realized, firstly, the working medium is assumed to be uniformly distributed in each loop in the finned tube heat exchanger, and if the air is uniformly distributed, the equivalent of the whole loop can be simplified into a single heat exchange tube; secondly, determining an iteration sequence according to the unknown quantity, setting an initial reference value, guessing a corresponding structural variable through the proportion of the target heat exchange quantity, and finally, performing calculation and inspection through a coupling simulation prediction model, wherein the fin tube heat exchanger structure has high design speed and good effect; realizing the achievement of model selection design of a plurality of unknown structural parameters within 5 seconds; the calculation speed is increased by about 1-2 orders of magnitude.
The present invention will be described in detail with reference to preferred embodiments thereof.
The invention provides a method for quickly simulating and designing the performance of a multi-row finned tube heat exchanger, which is formed by combining a simplified description method and a quick iterative algorithm, and meets the actual simulation type selection requirement.
As shown in fig. 1-2, the simplified description method establishes logic of fin tube heat exchanger performance calculation based on the thought of tube number and loop proportion, realizes uniform distribution of heat exchange tubes in the same loop in each row, further realizes model simplification according to the method of combining tube lengths in each loop in each row, correspondingly adjusts wind speed under the condition of ensuring constant wind quantity, and reflects heat exchanger performance characteristics according to the flowing direction and sequence of working media.
The simplified description model establishment comprises a main body heat exchange area, a collecting pipe and an elbow pipe.
The collecting pipe is connected with the inlet heat exchange pipe of each loop through the branch pipe, so that the number of outlets of the branch pipe of the collecting pipe represents the number of loops of the heat exchanger. The invention takes the middle position of the branch pipe of two adjacent loops connected with the collecting pipe as the basis for dividing the control unit. The control units of the collecting pipes are numbered according to the sequence of the loops, and the consistency of the number of the control units and the number of the loops is ensured. The common numbering form of the collecting pipe and the loop marks the heat exchange pipe into which the working medium flows for the first time as a #1 loop, and the rest heat exchange pipes connected with the collecting pipe branch pipes are sequentially numbered.
Flow regulation equation of collecting pipe:
wherein: g r，h，guess ，G r，t，guess A guess value of the mass flow of the working medium at the inlet of the collecting pipe and in a single loop is obtained; ΔP h，total，in ，ΔP h，total，out ，ΔP t，total The total pressure drop of the working medium in the inlet collecting pipe and the outlet collecting pipe and the total pressure drop in a single loop; i, j is the loop number.
Manifold momentum equation:
ΔP h，total ＝ΔP h，acc +ΔP h，gra +ΔP h，f +ΔP h，joint equation 2
Wherein: ΔP h，total The total pressure drop of the working medium in the collecting pipe is generated; ΔP h，acc The pressure drop is accelerated generated in the collecting pipe by working medium; ΔP h，gra The gravity pressure drop is generated in the collecting pipe for working medium; ΔP h，f The friction pressure drop generated in the collecting pipe for working medium; ΔP h，joint Control sheet for working medium in collecting pipePressure drop at the meta-junction.
For a fin tube heat exchanger with multiple loops and multiple tubes, the heat exchange tubes in the horizontal direction and the vertical direction are connected through U-shaped bending sections in order to ensure smooth flow of working media in the heat exchange tubes.
Compared with a finned tube heat exchanger, the flow heat exchange in the bent tube is negligible, and the influence of the overall heat exchange effect is negligible. On the other hand, however, the pressure drop caused by the flow in the bent pipe is much greater than that of the straight pipe section with the same size due to the large bending pressure loss of the fluid at the bending position, so that the pressure drop in the bent pipe must be considered. The bending sections need to be divided into control units individually, each bent pipe is regarded as one control unit as a whole in simulation calculation, and only the influence on pressure drop is considered.
Bend momentum equation:
ΔP t，total ＝ΔP t，f +ΔP t，acc +ΔP t，gra +ΔP bend equation 3
Wherein: ΔP t，total The total pressure drop of the working medium in the bent pipe is generated; ΔP t，acc The accelerating pressure drop generated in the bent pipe by the working medium is adopted; ΔP t，gra The gravity pressure drop is generated in the bent pipe by working medium; ΔP t，f The friction pressure drop generated in the bent pipe by the working medium is used; ΔP bend Is the bending pressure drop generated in the bent pipe by the working medium.
For the working main body of the fin tube heat exchanger, the three-dimensional distribution parameter model of the heat exchange tubes needs to divide the control units based on the specific geometric structural characteristics such as the tube number, the row number and the like. The invention adopts a control unit dividing method based on loop proportion, according to the loop proportion, the number of the heat exchange tubes of each loop can be obtained, and the heat exchange tubes are uniformly distributed in each row of the heat exchanger, so that the same number of the heat exchange tubes of each loop in each row is ensured.
The calculation mode of the loop proportion Ratio is provided, the loop proportion is the Ratio of the loop number of the heat exchanger to the tube number of each row, namely the tube number of each row to the tube number of each loop, and the loop type is represented:
wherein: ratio is the loop Ratio; c is the number of loops; TN (TN) N For each row of tubes; n is the number of tube rows; TN (TN) C For the number of pipes per loop.
The parameter of the loop ratio Radio is proposed to reflect the relationship among the factors affecting the number of pipes, the number of rows and the number of loops. The number of the tubes in each row of the single loop can be obtained by the proportion of the loops, and the number of the tubes is equivalent to the number of the single heat exchange tube N equi The equivalent heat exchange tube length is L equi ：
L equi ＝TN C/N L equation 5
Wherein: l (L) equi Is equivalent to the length of a heat exchange tube; TN (TN) C/N The number of tubes per loop in each row; l is the length of the original tube.
The fin tube heat exchanger is described in simplified terms based on the circuit ratio and the length per row of tubes. The number of tubes in each circuit in each row can be simplified into a single heat exchange tube to perform performance calculation, so that the complexity and diversity caused by the change of the number of tubes, the number of rows, the number of circuits and the like are reduced.
The different positions of the control units in the heat exchanger can lead to different energy transfer modes, the established control equation can also have corresponding differences, and axial heat conduction is not considered according to the assumption, so that the non-boundary control unit receives the heat exchange quantity of air and working media and is influenced by the heat conduction of the upper control unit, the lower control unit, the front control unit and the rear control unit, and the total quantity of energy flowing in and out of the control unit in a steady state is ensured to be equal; when a control unit is at a boundary, the corresponding portion of adjacent control units becomes the heat exchange of the environment with the control unit.
Energy equation:
Q r +Q a +Q top +Q bottom +Q front +Q back =0 equation 6
Wherein: q (Q) r For changing working-media in the control unitHeat quantity; qa is the heat exchange amount of air in the control unit; q (Q) top The heat conduction quantity of the control unit above the current control unit is calculated; q (Q) bottom The heat conduction quantity of the control unit below the current control unit is obtained; q (Q) front The heat conduction quantity of the control unit in front of the current control unit is obtained; q (Q) back Is the heat conduction quantity of the control unit behind the current control unit.
The heat exchange performance of the heat exchanger is calculated mainly by adopting an average temperature difference method:
wherein:is the heat exchange quantity; alpha is a heat exchange coefficient; a is the heat exchange area; delta T is the average temperature difference between the inner and outer fluids. />
According to the method, a calculation mode of the harmonic mean temperature difference is adopted, and the heat exchange effect of the heat exchanger is limited by the small temperature difference part, so that the influence of the small temperature difference part of the internal and external cold and hot fluids can be highlighted, and the problem that the logarithmic mean temperature difference cannot be calculated in the iteration process is avoided. In DeltaT max And DeltaT min Refers to the difference in temperature between the working medium in the pipe and the air outside the pipe at the same side of the inlet and the outlet, and the different forms are adopted when the working medium and the air outside the pipe are arranged in countercurrent or downstream:
wherein: delta T max Is the maximum temperature difference; delta T min Is the minimum temperature difference.
As shown in FIG. 3, the rapid simulation iterative algorithm provided by the preferred embodiment of the invention can realize rapid and accurate simulation calculation and design calculation of the fin tube heat exchanger under the running conditions of multiple rows of concurrent and countercurrent flow and the like according to the simplified model based on the number of tubes and the proportion of loops and based on the simplified description method under the known and unknown flow, and the heat exchanger is divided into a control unit, a single row of heat exchangers and concurrent and countercurrent flow working conditions of the multiple rows of heat exchangers, so as to develop a targeted solving algorithm under the known and unknown flow.
The control unit is used as the most basic unit in the mathematical model of the heat exchanger, and the accuracy of the calculation of the overall performance of the heat exchanger is fundamentally determined. The solution algorithm of the control unit directly influences the accuracy of the simulation calculation of the heat exchanger model, and the solution efficiency directly influences the overall calculation time consumption.
The calculation flow is as follows:
1) Initializing parameters of a control unit according to known conditions of the heat exchanger unit, wherein the flow adopts a guess value;
2) Calculating the heat exchange coefficient and air side pressure drop of the working medium in the state of the inlet and the outlet of the pipe according to the heat exchange and pressure drop association;
3) According to the air side state, the enthalpy value of the working medium at the outlet of the control unit is assumed;
4) Calculating the enthalpy value of an air outlet, and further calculating the outlet temperature of working media inside and outside the pipe;
5) Solving the heat exchange quantity based on a heat exchanger performance calculation principle;
6) Determining whether enthalpy difference of working media in the control unit can meet heat exchange convergence conditions;
7) Judging whether the temperature of the working medium outlet is crossed with the air outlet or not;
8) According to the temperature crossing, the heat exchange of the internal and external fluids reaches balance at a certain position of the control unit, and at the moment, according to the condition that the temperature of the working medium outlet in the pipe is the same as the temperature of the air inlet, the relevant state parameters such as heat exchange quantity and the like are recalculated;
9) And outputting state parameters of working medium and air at the outlet of the control unit.
The algorithm of the single-row heat exchanger is established based on the solving algorithm of the control unit and consists of four parts, and the heat exchange and the pressure drop of the heat exchanger are calculated respectively. The fin tube heat exchanger has various solving conditions, so that the algorithm design not only uses the temperature of the side outlet of the working medium as a limiting index under unknown flow, but also uses the temperature of the inlet of the working medium as an input condition under known flow. The algorithm comprises the following calculation flow:
1) Determining convergence criteria and input parameters;
under the calculation condition of unknown flow, the outlet temperature of the working medium is used as a judgment basis for judging whether iteration converges or not. According to energy conservation, the initial flow value of the working medium is estimated preliminarily on the assumption that the heat exchange quantity of the working medium side is the same as that of the air side, and relevant parameters such as the structure, the working condition and the like of the heat exchanger are determined. And carrying out division design of the control units according to the division modes and the numbering rules of the control units, and generating calculation logic.
2) Calculating a heat exchange part;
deducing the sequence of the control unit, if the control unit is not the final unit of the loop at the moment, calculating the heat exchange of the unit according to the calculation method; after the current calculation is completed, updating the entry state of the next unit; if this is the final unit, the pressure drop is calculated.
3) Performing a calculation of the pressure drop portion;
and the calculation flow is the same as that of the heat exchange part, and after the single-loop calculation is completed, the heat exchange pressure drop calculation of the next loop is performed until the calculation of all the whole heat exchangers is completed.
4) An iterative convergence judging part;
after the calculation of the whole heat exchanger is completed, firstly, whether the pressure drop convergence is consistent or not is judged according to the pressure drops of different loops. If the flow is not converged, flow adjustment is needed, and heat exchange pressure drop calculation is performed again. Otherwise, judging the stability of the temperature of the fins, if the temperature of the fins is not converged, updating the related data, and carrying out heat exchange pressure drop calculation again. If yes, performance convergence is illustrated, and finally whether the performance of the heat exchanger meets the target requirement is judged; comparing the calculated working medium outlet temperature with a target value according to the heat exchanger, if
|T r，out -T r，set I < ε formula 9
Then convergence; otherwise, according to the difference between the actual calculated temperature and the target value, the guess flow is adjusted according to the gradient descent method, and the heat exchange pressure drop calculation is returned. Wherein: t (T) r，out To actually calculate the outlet temperature value, T r，set To set targetThe outlet temperature value epsilon is an error value epsilon and can be designed according to actual conditions, and 0.01K can be obtained according to engineering experience.
5) And outputting a simulation calculation result.
In the concurrent state of the multi-row heat exchanger, the calculation flow is as follows:
1) Determining convergence criteria and input parameters;
2) Calculating a heat exchange part;
deducing the sequence of the control unit, if the control unit is not the final unit of the loop at the moment, carrying out heat exchange calculation, and updating the inlet state of the working medium side of the next unit; if the unit is the last unit of the heat exchange tube of the loop, updating the air side inlet state of the next row by taking the row as a unit; if the air state is not updated again at the last row of the heat exchanger at this time, the calculation of the pressure drop part is performed until the control unit is the last unit of the loop.
3) Performing a calculation of the pressure drop portion;
the calculation flow is the same as that of the heat exchange part, pressure drop calculation is sequentially carried out in the same loop according to the row number, and then the pressure drop heat exchange characteristic of the next loop is calculated until all the whole heat exchangers are calculated.
4) An iterative convergence judging part;
5) And outputting a simulation calculation result.
As shown in FIG. 4, the rapid iterative design algorithm provided by the preferred embodiment of the invention takes the heat exchange performance or the air outlet temperature of the heat exchanger as a target value, designs various unknown parameters such as the number of rows of the heat exchanger, the number of loops and the like when the structure is unknown by setting various constraint conditions, and realizes the rapid simulation design efficiency of the finned tube heat exchanger by the proposed efficient iterative algorithm based on target value guess and simulation test.
The selective design calculation of the fin tube heat exchanger adopts a rapid iteration method based on target value guess and simulation test:
the method firstly assumes that the working medium is uniformly distributed in each loop in the finned tube heat exchanger, and if the air is uniformly distributed, the equivalent of the whole loop can be simplified into calculation of a single heat exchange tube. When the method is simplified, the position of the loop in the heat exchanger needs to be judged, and different calculation modes are adopted, so that the calculation complexity is reduced.
In the actual traversal, the "fin type-fin pitch-row number-loop type" is used as an iterative sequence, and an initial reference value for each unknown quantity is set.
If the number of rows is unknown, according to the same fin type and fin spacing, the heat exchange quantity among different rows approximates to a power relation, the common 3 rows of heat exchangers are used as reference values for calculation, the corresponding rows are guessed through the proportion of the target heat exchange quantity, the calculation times of the number of rows and the loop type of the heat exchangers are reduced, the calculation quantity is further reduced, and the calculation speed is greatly improved.
And next, coupling the heat exchanger parameters selected by the method with a simulation prediction model to perform calculation and inspection, and if the parameters meet the target constraint. Various structural parameters and key performance indicators of the heat exchanger are output. According to practical engineering experience, the method meets application requirements.
According to the method, on the basis of three-dimensional distribution parameters, key parameters of fin tube heat exchangers with different structures are represented according to a simplified thought of combining lengths of each row of tubes based on a model description method of tube numbers and loop proportions. Therefore, aiming at the fin tube heat exchanger with a specific structure, simplification reflecting the local characteristics of the heat exchanger can be established, and the calculation efficiency is improved. According to the invention, by combining the operation conditions of the heat exchanger, a rapid simulation and design iterative algorithm is established, so that the heat exchange pressure drop capacity of the heat exchanger under different working media inside and outside the tube and working conditions can be rapidly calculated, the outlet state of the working media inside and outside the tube can be obtained, and the proper structural characteristics of the finned tube heat exchanger can be obtained according to the target performance; simultaneously, the precision and speed requirements of the simulation model selection design are met; the model prediction precision is good, and the prediction is stable at non-boundary working condition points; the method has the advantages that the aim of selecting a plurality of unknown structural parameters in the single calculation example with calculation time less than 0.05s and 5s is fulfilled, the performance of the heat exchanger is accurately and efficiently reflected, and compared with a model needing modeling and solving, the calculation speed is improved by about 1-2 orders of magnitude.
The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.
Claims (10)
1. A method for quickly simulating and designing the performance of multi-row finned tube heat exchanger is characterized by comprising a simplified description method and a quick iterative algorithm of the heat exchanger structure,
the simplified description method is characterized in that logic for calculating the performance of the finned tube heat exchanger is established based on the number of tubes and the proportion of loops, uniform distribution of the heat exchange tubes in each row in the same loop is realized, the model simplification of the finned tube heat exchanger is realized according to the method that the lengths of the tubes in each loop in each row are combined into a single tube, and the performance characteristics of the heat exchanger are reflected according to the flowing direction and sequence of working media by adjusting the wind speed under the condition that the air quantity is unchanged;
the rapid iterative algorithm is based on the simplified description method under known and/or unknown flow, and according to the established simplified model based on the tube number and the loop proportion, the heat exchanger is divided into forward flow and/or reverse flow working conditions of a control unit, a single-row heat exchanger and a plurality of rows of heat exchangers, so that the simulation calculation and design method of the fin tube heat exchanger under the operating condition is realized, wherein the operating condition comprises at least one of the operating conditions of a plurality of rows of forward flow and reverse flow.
2. The method of claim 1, wherein the simplified description model is built up from a main heat transfer area, a header and a bent pipe, wherein,
the main heat exchange area adopts a control unit dividing method based on the loop proportion, calculates the number of the heat exchange tubes of each loop according to the loop proportion, and uniformly distributes the heat exchange tubes in each row of the heat exchanger to ensure that the number of the heat exchange tubes of each loop in each row is the same;
the collecting pipe is connected with an inlet heat exchange pipe of each loop through a branch pipe, the number of outlets of the branch pipes of the collecting pipe represents the number of loops of the heat exchanger, the control unit of the collecting pipe is divided by the middle position of the branch pipe connected with the collecting pipe between two adjacent loops, and the control units in the collecting pipe are numbered according to the sequence of the loops;
the control units are divided into the elbows individually by considering only the pressure drop in the elbows, and each of the elbows is regarded as one of the control units as a whole in the simulation calculation.
3. The method of claim 2, wherein the circuit ratio characterizes a circuit type, the circuit ratio being a ratio of the number of heat exchanger circuits to the number of tubes per bank,
Wherein Ratio is the loop Ratio, C is the loop number, TN N N is the number of tube rows, TN is the number of tube rows C The number of pipes per loop;
calculating the number of tubes in each row of the single loop through the loop proportion, and equivalent the number of tubes to the single heat exchange tube N equi The equivalent length of the heat exchange tube is L equi ：
L equi ＝TN C/N ·L，
Wherein L is equi Is equivalent to the length of a heat exchange tube, TN C/N L is the length of the original pipe for each row of pipes in each loop.
4. A method according to claim 3, wherein the manifold flow rate adjustment equation is:
wherein G is r，h，guess ，G r，t，guess Respectively guessing the mass flow rate delta P of working medium at the inlet of collecting pipe and in single loop h，total，in ，ΔP h，total，out ，ΔP t，total The total pressure drop of the working medium at an inlet and an outlet in the collecting pipe and the total pressure drop in a single loop are respectively shown, i and j are the serial numbers of the loops;
the momentum equation of the collecting pipe is as follows:
ΔP h，total ＝ΔP h，acc +ΔP h，gra +ΔP h，f +ΔP h，joint ，
wherein DeltaP h，total Delta P is the total pressure drop generated in the collecting pipe by working medium h，acc For accelerating pressure drop generated in the collecting pipe by working medium, delta P h，gra For gravity pressure drop generated in the collecting pipe by working medium, delta P h，f For the friction pressure drop generated by working medium in the collecting pipe, delta P h，joint The pressure drop is generated at the joint of the collecting pipe control unit for working medium;
the momentum equation of the bent pipe is as follows:
ΔP t，total ＝ΔP t，f +ΔP t，acc +ΔP t，gra +ΔP bend ，
wherein DeltaP t，total Delta P is the total pressure drop of working medium in the bent pipe t，acc For accelerating pressure drop generated by working medium in the bent pipe, delta P t，gra For gravity pressure drop generated in the bend pipe by working medium, delta P t，f For the friction pressure drop generated by working medium in the bent pipe, delta P bend The bending pressure drop generated in the bent pipe by the working medium is used;
the energy equation of the control unit is as follows:
Q r +Q a +Q top +Q bottom +Q front +Q back ＝0，
wherein Q is r For the heat exchange quantity of working medium in the control unit, Q a For the heat exchange quantity of air in the control unit, Q top For the heat conduction quantity Q of the control unit above the current control unit bottom For the heat conduction quantity Q of the control unit below the current control unit front For the heat conduction quantity Q of the control unit in front of the current control unit back Is the heat conduction quantity of the control unit behind the current control unit.
5. The method of claim 4, wherein the heat exchange performance calculation of the heat exchanger is calculated using a harmonic mean temperature difference method:
wherein,,for heat exchange quantity, alpha is a heat exchange coefficient, A is a heat exchange area, delta T is an average temperature difference between inner and outer fluid, and the following formula is adopted for calculation:
wherein DeltaT max And DeltaT min The maximum temperature difference and the minimum temperature difference of the working medium in the pipe and the air outside the pipe at the same side of the inlet and the outlet are obtained.
6. The method of claim 1, wherein the iterative simulation calculation of the control unit comprises the steps of:
Step 1: initializing parameters of the control unit according to the known conditions of the heat exchanger unit, wherein the flow adopts a guess value;
step 2: according to the heat exchange and pressure drop relation, calculating the heat exchange coefficient and air side pressure drop of the working medium inlet state inside and outside the pipe;
step 3: according to the air side state, the enthalpy value of the working medium at the outlet of the control unit is assumed;
step 4: calculating the enthalpy value of an air outlet, and calculating the outlet temperature of the working medium inside and outside the pipe;
step 5: calculating the heat exchange quantity of the heat exchanger;
step 6: determining whether the enthalpy difference of the working medium in the control unit meets heat exchange convergence conditions;
step 7: judging whether the temperature of the working medium outlet is crossed with the temperature of the air outlet, if so, recalculating relevant state parameters such as heat exchange quantity and the like;
step 8: and outputting state parameters of the working medium and the air at the outlet of the control unit.
7. The method of claim 1, wherein the iterative simulated calculations of the single row heat exchanger and the multiple row heat exchanger, based on the iterative simulated calculations of the control unit, include heat exchange calculations and pressure drop calculations, comprise the steps of:
step 1: determining convergence criteria and input parameters: taking the outlet temperature of the working medium as the convergence criterion, wherein the input parameters comprise the flow initial value of the working medium, the heat exchanger structure and the working condition parameters;
Step 2: and (3) heat exchange calculation: calculating the heat exchange of the control unit, and updating the inlet state of the next control unit after the calculation is completed;
step 3: pressure drop calculation: calculating the pressure drop of the control unit, and updating the inlet state of the next control unit after the calculation is completed;
step 4: after the calculation of a single loop is completed, the heat exchange calculation and the pressure drop calculation of the next loop are carried out until the calculation of the whole heat exchanger is completed;
step 5: iterative convergence judgment, if not, updating data and executing the step 2-3;
step 6: and outputting a simulation calculation result.
8. The method of claim 7, wherein in said step 5, said iterative convergence determination comprises a pressure drop convergence determination, a fin temperature convergence determination, and a heat exchanger performance convergence determination, wherein,
judging whether the pressure drop converges or not according to whether the pressure drops of different loops are consistent or not, if not, adjusting the flow and carrying out heat exchange calculation and pressure drop calculation again;
the fin temperature convergence judgment is carried out, whether the fin temperature is stable or not is judged to judge whether the fin temperature is converged or not, if not, the data are updated, and heat exchange calculation and pressure drop calculation are carried out again;
Judging whether the performance of the heat exchanger is converged or not according to the difference value between the temperature of the working medium outlet of the heat exchanger and a target value, if not, adjusting the guessed flow according to the difference value and a gradient descent method, and carrying out heat exchange calculation and pressure drop calculation again; the specific calculation method of the difference value comprises the following steps:
|T r，out -T r，set |<ε，
wherein T is r，out To actually calculate the outlet temperature value, T r，set For setting the target outlet temperature value, ε is the temperature difference threshold, ε takes 0.01K.
9. The method of claim 8, wherein the iterative simulation calculation of the multiple row heat exchanger further comprises:
in the step 2, if the loop is the last unit of a certain row of heat exchange tubes in the multi-row heat exchanger, updating the air side inlet state of the next row by taking the row as a unit; if the row is the last row of the multi-row heat exchangers, the air state is not updated any more;
in the step 3, the pressure drop calculation is sequentially performed according to the number of rows in the same loop.
10. The method of claim 9, wherein the fast iterative design method, based on a target value guess and a simulation test algorithm, takes the heat exchange performance or the air outlet temperature of the heat exchanger as a target value, and obtains the heat exchanger row number and the loop number by setting constraint conditions, comprising the following steps:
Step 1: determining an unknown quantity iteration mode and a target quantity;
step 2: calling a simplified model to perform simulation calculation;
step 3: calling a precision simulation calculation model for checking calculation;
step 4: and outputting the structural parameters of the fin tube heat exchanger.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310409683.5A CN116484524A (en) | 2023-04-17 | 2023-04-17 | Rapid simulation and design method for performance of multi-row finned tube heat exchanger |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310409683.5A CN116484524A (en) | 2023-04-17 | 2023-04-17 | Rapid simulation and design method for performance of multi-row finned tube heat exchanger |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116484524A true CN116484524A (en) | 2023-07-25 |
Family
ID=87218879
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310409683.5A Pending CN116484524A (en) | 2023-04-17 | 2023-04-17 | Rapid simulation and design method for performance of multi-row finned tube heat exchanger |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116484524A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117131627A (en) * | 2023-08-22 | 2023-11-28 | 鞍钢股份有限公司 | Design method of area-control tubular heat exchanger |
-
2023
- 2023-04-17 CN CN202310409683.5A patent/CN116484524A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117131627A (en) * | 2023-08-22 | 2023-11-28 | 鞍钢股份有限公司 | Design method of area-control tubular heat exchanger |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102779217B (en) | Computer simulation performance computation method of refrigeration system under frosting working condition | |
| CN106647329B (en) | Equivalent modeling method for heat supply pipe network | |
| CN109508851A (en) | A kind of small-sized lead base heap supercritical carbon dioxide cycle generating system comprehensive performance evaluation method | |
| CN111125938B (en) | Suboptimal algorithm-based optimization design method for large central air-conditioning chilled water pipe network | |
| CN103542621A (en) | Design method of general combination pipe diameter air conditioner heat exchange equipment fluid passage | |
| CN110059388B (en) | Parameter distribution modeling simulation method for condenser of nuclear power plant along working medium flowing direction | |
| CN110110416A (en) | A kind of cold net cooling supply optimization method of distributed energy based on graph theory | |
| CN116484524A (en) | Rapid simulation and design method for performance of multi-row finned tube heat exchanger | |
| Larsen et al. | Equivalent models for district heating systems | |
| CN110866213A (en) | Multi-network steady-state energy flow analysis method and device for electricity-gas integrated energy system | |
| CN112241563B (en) | Optimization algorithm for pipe well | |
| CN115422811A (en) | Modeling method of Modelica language-based indirect evaporative cooling heat exchanger model | |
| CN114048572A (en) | Design calculation method of large variable-physical-property shell-and-tube heat exchanger | |
| CN105160116A (en) | Optimization design method for uniform liquid distribution of heat exchanger | |
| CN112580272A (en) | Optimized design method of LNG air temperature type gasifier based on numerical simulation | |
| CN110955984A (en) | Simulation method and system of plate heat exchanger | |
| CN109522644A (en) | A kind of enhanced heat exchange surface comprehensive performance evaluation method | |
| CN115234973A (en) | Method for determining dynamic heat supply strategy of heat supply network | |
| Thevenard et al. | Development of a stratified tank model with immersed heat exchangers in ESP-r | |
| CN109611949B (en) | Pipeline thermal calculation method and monitoring and heating system adopting same | |
| Chengwei et al. | Steady State Hydraulic and Thermal Simulation Model of Natural Gas Pipeline Network Based on Logistic Regression and Newton Rapson Adaptive Iteration Algorithm | |
| Ke et al. | Genetic Algorithm-Based Path Planning for Refrigeration Plant Room Pipelines | |
| CN118424035B (en) | Efficient heat exchange control method for multi-tube pass coiled tube type heat exchanger | |
| Pu et al. | Modelling and numerical simulation of heat transfer and hydrodynamic performance of multi-pass parallel flow condensers–A novel algebraic method to determine flow distribution | |
| Libreros et al. | Critical Review of the Theoretical, Experimental and Computational Fluid Dynamics Methods for Designing Plate Fin Heat Exchangers. |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |