CN110298492B - Method for evaluating energy-saving reconstruction benefits of condenser vacuumizing system - Google Patents
Method for evaluating energy-saving reconstruction benefits of condenser vacuumizing system Download PDFInfo
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Abstract
The invention relates to an evaluation method for energy-saving reconstruction benefits of a condenser vacuumizing system, which comprises the following steps: step 1) counting vacuum tightness data of condensers on high and low pressure sides of a unit; step 2) obtaining an optimal running mode of the running combination of the circulating pumps according to historical running data of the unit and cold end optimization; step 3) measuring pressure change values of the high-low pressure side condenser at different load points after the vacuumizing system is modified; step 4) calculating the condensation heat exchange coefficient K in the condenser in the operation mode before the vacuum pumping system at each load point is modified0And the condensation heat exchange coefficient K in the condenser in the operation mode after the vacuum pumping system is improved1. The invention has the beneficial effects that: the energy-saving benefit of the vacuum pumping system reconstruction project can be counted in real time within a set time period and in an actual operation boundary condition, and detailed statistics and test data are provided for summarizing, popularizing and reconstructing schemes of the reconstruction project.
Description
Technical Field
The invention relates to a condenser vacuumizing system in a cold end system of a thermal power generating set, in particular to an evaluation method for energy-saving improvement benefits of the condenser vacuumizing system.
Background
The efficiency of the thermal power generator set mainly depends on parameters of a hot end and a cold end of a thermal cycle (Rankine cycle), the parameters of the hot end are mainly reflected on main steam pressure and temperature of a boiler side, and are determined during design and construction of the set. In addition, after the unit is put into operation, the investment of energy-saving reconstruction projects for improving hot end parameters of the thermodynamic system is generally large, the return years are long, and the implementation difficulty is large. Almost half of heat generated by coal combustion is taken away from the cold end part of the thermodynamic system, and according to thermodynamic characteristic data of a low-pressure cylinder of a related unit, the power supply coal consumption rate of the unit can be reduced by about 1% when the pressure of a condenser of the cold end system is reduced by 1kPa, so that the thermodynamic system has huge energy-saving potential. In the actual operation process, monitoring measuring points of the operation state of cold end system equipment are few, and influence on the economy of a unit is not obvious in representing the parameters of a hotter end, so that the pressure of a condenser in a cold end system deviates from a design value (an ideal value) in the actual operation process; at this moment, energy-saving transformation or operation mode adjustment is carried out on the cold end system, and the input and output are generally high. At present, the energy-saving modification of auxiliary equipment of a cold end system is gradually paid attention to, such as the energy-saving modification related to a condenser vacuum-pumping system.
Condenser vacuum pumping system is an important component of cold end system, and condenser vacuum pumping system mainly configures as water ring vacuum pump at present, and its main use is: when the unit is started, the condenser vacuum is quickly established to meet the starting requirement of the unit; when the unit normally operates, non-condensing gas leaking into the condenser is pumped out, the condensing heat exchange coefficient of the condenser is improved, the pressure of the condenser reaches the optimal vacuum, and certain energy is consumed during operation. Therefore, the main technical route of energy-saving modification is divided into two parts: 1) the first scheme considers that: when the condenser is less tight, less air leaks into the condenser, the suction capacity of the water-ring vacuum pump is larger in model selection during design, and the operation power consumption is larger. A more representative transformation scheme is to add a group of water ring-Roots high-efficiency vacuum pump set to replace the water ring type vacuum pump set in normal operation. 2) The second modification scheme is that: when the temperature of cooling water is higher, the water ring vacuum pump is easy to generate cavitation, the suction volume is smaller, the suction volume is increased, the mass concentration of air in the condenser is reduced, the condensation heat exchange coefficient of the condenser is improved, and the end difference of the condenser is reduced, so that the pressure of the condenser is reduced. Typical modification schemes include: a working liquid depth cooling device of a water ring type vacuum pump set is added; a group of steam jet type vacuum pumping systems is added to replace a water ring type vacuum pump set.
Because the water ring type vacuum pumping system has more influence factors on operation, under respective boundary conditions, the two transformation schemes can achieve the purposes of energy conservation and consumption reduction. However, under the actual operation boundary condition of a certain unit, the energy-saving benefit after the vacuum pumping system is modified lacks an effective evaluation method at present, and specific energy-saving benefit data cannot be provided for such modified projects, so that the popularization of the modification of the vacuum pumping system and the model selection of the modification scheme are hindered.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: at present, two completely different technical routes exist in the overall idea of the steam condenser vacuum pumping system modification scheme, the corresponding energy-saving target can be achieved under a specific operation boundary, an effective statistical and evaluation method is not available at present for calculating and evaluating the energy-saving benefit generated by the vacuum pumping system modification project under the actual operation boundary condition, and obstacles are set for popularization and evaluation of the vacuum pumping system modification project in the same type of unit. The invention provides an evaluation method for energy-saving improvement benefits of a condenser vacuumizing system, which can calculate the energy-saving benefits generated by the improvement of the vacuumizing system under the actual operation boundary conditions of a unit (the vacuum tightness of the condenser, the running mode of a pump, the load of the unit and the inlet temperature of circulating water) in a set time period.
The technical scheme adopted by the invention for solving the technical problem is as follows: a method for evaluating energy-saving improvement benefits of a condenser vacuumizing system comprises the following steps:
the method comprises the steps that firstly, vacuum tightness data of condensers on high and low pressure sides of a unit are counted, a statistical average value of the vacuum tightness of the condensers when the unit normally operates is obtained, and the data are used as a reference value of the tightness of the condensers of the unit;
and secondly, calculating the unit load rate, the circulating pump operation combination and the flow rate corresponding to different temperature intervals by taking the circulating water inlet temperature as a horizontal coordinate according to the optimal operation mode of the circulating pump operation combination obtained by the unit historical operation data and cold end optimization:
in a third step, each or several temperature intervals [ t ] in the second step can be selected0，t1]…, measuring pressure change values of the high-low pressure side condenser at different load points by a switching comparison test method of the vacuumizing system between operation modes before and after the transformation;
a fourth step of setting a temperature interval t for each temperature interval in the third step0，t1]…, calculating the condensation heat transfer coefficient K in the condenser in the running mode before the vacuum pumping system at each load point is modified by using the variable working condition model of the condenser according to the load of the unit, the circulating water flow, the inlet temperature of the circulating water and the pressure value of the condenser under the known conditions0And the condensation heat exchange coefficient K in the condenser in the operation mode after the vacuum pumping system is improved1And the ratio thereof is mu-K0/K1；
In the comparison test process, other factors (such as unit load, circulating water temperature, circulating water flow, condenser tightness, condenser tube bundle cleaning coefficient and the like) influencing the condensation heat exchange coefficient except the pumping capacity of the vacuum-pumping system are consistent, so the mu value can be defined as an influencing factor of the pumping capacity change on the condenser heat exchange coefficient before and after the vacuum-pumping system is switched;
at other boundariesWhen the condition is set, when the suction volume of the vacuum-pumping system is increased to a certain value, the mass concentration of air in the condenser is lower, the influence on the condensation heat exchange coefficient is reduced, at the moment, the suction volume of the vacuum-pumping system is continuously increased, the condensation heat exchange coefficient tends to be stable, and the numerical value K of the condensation heat exchange coefficient tends to be stablePFMeasured by increasing the suction capacity by operating several sets of vacuum pumping systems in parallel, which is associated with K0、K1Is a ratio of0＝K0/KPF，μ1＝K1/KPF(ii) a The value eliminates the influence of other factors except the pumping amount of the vacuum-pumping system on the condensation heat exchange coefficient, and can reflect the influence degree of the pumping amount of the vacuum-pumping system on the condensation heat exchange coefficient; for a water-ring vacuum pump vacuum pumping system, when the unit tightness is fixed, the pumping quantity is positively correlated with the difference delta p between the condenser pressure and the saturation pressure corresponding to the temperature of the working fluid of the water-ring vacuum pump, so mu0Can be simplified as a function of Δ p; the pumping capacity of the modified vacuum-pumping system (steam jet type) is generally not easy to be influenced by the external environment, and the mu of the modified vacuum-pumping system is1Is substantially unchanged; or the pumping quantity after modification is large enough (the deep cooling project of the working liquid of the water-ring vacuum pump), and the mu of the pumping quantity is1Is basically 1, so mu can be simplified into a functional relation of delta p;
the fifth step, aiming at any temperature interval [ t ]0，t1]…, when the actual running mode of the pump combination is the corresponding value in the second step, the temperature point t and the unit load P are respectively calculated by the variable working condition model of the condenserelThe pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping systemH、△pL；
The sixth step, aiming at any temperature interval [ t0，t1]…, when the actual running mode of the combination of the circulating pumps does not correspond to the statistical value of the second step, the flow rate of the combination of the circulating pumps is known, and the temperature point t and the unit load P are calculated respectively by the calculation method in the fifth stepelThe pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping systemH、△pL；
The seventh step, when there are more interval points in the second step, the third stepWhen the test interval point in the step is not completely covered, for the interval which is not covered in the test, the calculation method in the fifth step is utilized to calculate the pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping system at different temperatures and different loads in the temperature intervalH、△pL；
Eighthly, according to the thermal characteristic data of the low-pressure cylinder, the pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping system at different temperatures and different loadsH、△pLThe variation value converted into the low-pressure cylinder output is delta Pel；
The ninth step, respectively calculating the energy consumed by the self operation of the vacuum-pumping systems under different operation modes of the vacuum-pumping systems, and calculating the energy difference delta P consumed by the two vacuum-pumping systems before and after the transformationheThe net gain of energy saving before and after the switching of the vacuum pumping system is delta Pel-△PheFor a steam jet type vacuum pumping system, the consumed steam can be converted into equivalent power consumption by using an equivalent enthalpy drop method;
tenth step, reading the actual operation boundary conditions (load, circulating water inlet temperature and pump combination) of the unit at certain time intervals (5min) by referring to the principle of calculus in a set time period, and respectively calculating the pressure change value delta p of the high-low pressure condenser after the vacuum pumping system is switched at the boundary conditionsH、△pLAnd the variation value delta P of the low-pressure cylinder outputelAnd energy saving net gain Δ Pel-△PheAnd then accumulating the energy-saving net income on a time coordinate value, and calculating to obtain the total energy-saving benefit value Pejs of the vacuum-pumping system reconstruction project in the time period.
Preferably, the method comprises the following steps: in the third step, the specific test method is as follows: get [ t ]0，t1]The temperature range, the circulating water inlet temperature of the test working condition is about the middle value of the temperature range and is (t)0+t1) 2; the condenser vacuum tightness is a reference value counted in the first step of the unit, and the circulating pump combination is a circulating pump combination P corresponding to the temperature interval1(ii) a The number of the test condition load points can be generally selected from about 3 to 5 (for example, 50 percent load rate, 75 percent load rate)% load rate and 100% load rate), continuously carrying out a vacuum pumping system switching comparison test aiming at each load point, enabling the load of the unit to be consistent with the state of the thermodynamic system before and after switching, and correcting the pressure value of the condenser by using a condenser variable working condition model for the difference between the temperature of a condenser circulating water inlet and the load in the comparison working condition before and after switching, wherein the difference of the condenser pressure value after correction in the comparison test can be considered to be caused by the change of the operation mode of the vacuum pumping system.
Preferably, the method comprises the following steps: in the fourth step, a difference value delta p (a characteristic value of the pumping quantity of a water ring vacuum pump pumping vacuum system) of the saturation pressure corresponding to the temperature of the condenser and the working liquid of the water ring vacuum pump is used as an abscissa, and a relational expression of mu and delta p can be fitted through tests at a plurality of load points; the value of the air pressure sensor can reflect the influence of the change of the suction volume on the heat exchange coefficient of the condenser before and after the switching of the vacuum pumping system.
Preferably, the method comprises the following steps: in the calculation method of the fifth step and the sixth step, the pressure change value delta p of the condenser at the high and low pressure sidesH、△pLThe proportional relation of the heat exchange coefficient K is calculated through a relation mu (delta p) fitted by tests, and in the calculation process, the end difference of the working liquid cooler of the water ring vacuum pump is kept unchanged, namely the difference value between the working liquid temperature of the water ring vacuum pump and the inlet temperature of circulating water is kept unchanged.
Preferably, the method comprises the following steps: in the seventh step, for the temperature interval not covered by the test, the circulating water flow rate of the circulating pump combination corresponding to the interval needs to be known, the relational expression mu (delta p) of the influence factor of the vacuumizing system on the condensing heat exchange coefficient of the condenser can be referred to the test measured value of the adjacent temperature interval, and the others are consistent with the calculation method in the fifth step and the sixth step.
The invention has the beneficial effects that: the invention provides an evaluation method for energy-saving improvement income of a condenser vacuumizing system, which can be used for carrying out real-time statistics on the energy-saving income of a vacuumizing system improvement project in an actual operation boundary condition within a set time period, and provides detailed statistics and test data for summarizing, popularizing and improving schemes of the type of improvement project.
Drawings
FIG. 1 is a graph showing the ratio mu of the condensation heat transfer coefficient in the operation mode before and after the vacuum pumping system is modified;
FIG. 2 is a graph of the variable back pressure characteristic of the low pressure cylinder measured in a 660MW unit test.
Detailed Description
The present invention will be further described with reference to the following examples. The following examples are set forth merely to aid in the understanding of the invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
By analyzing the operation characteristics of the water-ring type vacuumizing system and combining the internal condensation heat exchange rule of the condenser, the operation boundary conditions of the vacuumizing system are classified on the basis of theoretical analysis, and an evaluation method is provided for counting the energy-saving benefits of the vacuumizing system modification project under the actual operation boundary conditions. The evaluation method of the energy-saving improvement income of the condenser vacuumizing system is used for evaluating the energy-saving effect of the condenser vacuumizing system improvement and provides decision basis for the selection of the improvement scheme of the vacuumizing system of the same type of unit.
The vacuumizing system is a water ring type vacuumizing system before modification, because the vacuum tightness of a unit generally cannot reach an excellent value, the modification direction generally increases the pumping capacity of the vacuumizing system, and the modified type selection is generally a steam jet type vacuumizing system or an original water ring type vacuum pump working solution additionally provided with a deep cooling device. When the vacuum pump operates normally, the improved vacuumizing system generally replaces the original water-ring vacuum pump to operate, and the water-ring vacuum pump vacuumizing system is only used when the unit is started and condenser vacuum is established. For better vacuum tightness, the improvement scheme for reducing the suction amount of the vacuum-pumping system generally reflects the energy-saving benefit in the aspect of reducing the power consumption of the vacuum-pumping system, and the statistics is easier.
The evaluation method of the energy-saving reconstruction benefits of the condenser vacuumizing system comprises the following steps:
the method comprises the steps of firstly, counting the vacuum tightness of a condenser at the high-pressure side and the low-pressure side of a unit, namely, after the unit normally operates, regularly carrying out the vacuum tightness test work of the condenser according to the requirements of relevant regulations, looking up relevant records during counting, and weighting a condenser vacuum tightness reference value according to the time period of continuous operation of each record to obtain an average value of the vacuum tightness reference value.
And secondly, the optimal running mode of the circulating pump after cold end optimization is based on the inlet water temperature of circulating water and the unit load, but the unit load changes constantly, and in order to avoid frequent start and stop of the circulating water pump, the current regulation of the running mode of the circulating pump of the unit mainly takes the circulating water temperature as the main basis in the actual running and takes the average load rate in the temperature interval into consideration. The following formula is a corresponding relation between the running modes of two supercritical unit circulating pumps and a temperature interval of a certain power plant, the two unit circulating water systems adopt a main pipe system to run, 4 circulating water pumps are configured, and each circulating water pump has two running modes of high speed and low speed:
and thirdly, establishing pressure change values of the high-pressure side condenser and the low-pressure side condenser at different load points by a switching comparison test method of the vacuumizing system between the operation modes before and after the transformation. The test method and apparatus have the following requirements:
1) before and after the vacuum pumping system is switched, the change of the pressure value of the condenser is generally small, in order to accurately measure the change value, an ASME standard mesh cage probe is generally adopted as a pressure measuring point of the condenser, a test instrument is a 0.05-grade absolute pressure transmitter, and the precision of a data acquisition unit is 0.02 grade or higher. The circulating water inlet temperature, the circulating water outlet temperature, and the water ring vacuum pump working fluid temperature can be measured using high precision thermal resistors (e.g., PT100 platinum resistor).
2) The test should be carried out under the better state of condenser leakproofness, should carry out condenser leakproofness test before the test begins, confirms that evacuation system equipment state is good before the transformation, and when the test result is less than the reference value, the accessible is artifical puts into a certain amount of air and is adjusted, and the bleed point should keep away from evacuation system extraction opening, guarantees the inside abundant mixture of air of putting in the condenser.
3) The test should be carried out continuously, the condition of the unit load and the thermodynamic system before and after switching is ensured to be consistent, the condenser pressure value should be corrected by using a condenser variable working condition model for the difference between the condenser circulating water inlet temperature and the load in the comparison working condition before and after switching, and the difference of the condenser pressure value after correction in the comparison test can be considered to be caused by the change of the operation mode of the vacuum pumping system.
According to the principle, the table 1 shows the switching comparison test result of the vacuumizing system for deep cooling and transformation of the working fluid of the water-ring vacuum pump in a certain 660MW unit and a certain temperature interval, and the table 2 shows the switching comparison test result of the steam jet type vacuumizing system in a certain 1000MW unit and a certain temperature interval.
TABLE 1 results of the switching contrast test of the vacuum-pumping system for deep cooling transformation of the working liquid of a water-ring vacuum pump
TABLE 2 results of steam injection type evacuation system switching comparative test
And fourthly, taking the test working condition in the third step shown in the table 1 as an example, calculating the condensation heat exchange coefficient K in the condenser in the operation mode before the vacuum pumping system at each load point is modified by using the variable working condition model of the condenser according to the load of the unit, the circulating water flow, the circulating water inlet temperature and the pressure value of the condenser under the known conditions0And the condensation heat exchange coefficient K in the condenser in the operation mode after the vacuum pumping system is improved1And the ratio mu ═ K0/K1Table 1 shows the heat transfer coefficient (K) of condensation in the vacuum pumping system switching comparative test of deep cooling transformation of working fluid of water ring vacuum pump0、K1) The calculation results are shown in the tableFIG. 3 shows a graph of the relationship between the μ value and the characteristic value (Δ p) of the suction amount of the water ring vacuum pumping system, as shown in FIG. 1.
TABLE 3 calculation results of the heat transfer coefficient of condensation in the vacuum pumping system switching comparative test
And fifthly, the calculation method comprises the following steps: in Table 1, the combination of the circulating pumps corresponding to the temperature interval is two pumps and three pumps (three high speeds), and taking the temperature interval as an example, the load P of the unit at other temperature points telThe pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping systemH、△pLThe numerical value of the heat exchange coefficient can be calculated through a condenser variable working condition model, as shown in table 4, the proportional relation of the condensation heat exchange coefficient in the calculation process can be calculated by referring to a data fitting relation mu (delta p) in table 3, and the end difference of the working liquid cooler of the water ring vacuum pump is kept unchanged.
TABLE 4 example of part of the calculation regime in the fifth step
Sixthly, calculating the pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping system under the working conditions of different loads and circulating water inlet temperature when other circulating pumps are combined in the temperature intervalH、△pLThe numerical value of (c).
Seventhly, calculating the pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping system under the working conditions of different loads and circulating water inlet temperatures in the uncovered temperature interval of the test working condition pointH、△pLThe relation mu (delta p) of the influence factor of the switching of the vacuum pumping system on the condensation heat exchange coefficient of the condenser can refer to the measured value of the adjacent temperature interval. The calculation method is similar to the calculation method described in the fifth step. Taking the working conditions of table 1 as an example, the results of the calculation in the sixth step and the seventh step are shown in table 5.
TABLE 5 partial example of the calculation conditions in the sixth and seventh steps
Eighthly, the thermal characteristic data of the variable back pressure of the low pressure cylinder can be obtained by measuring through a steam turbine manufacturer or a field test method, and fig. 2 is a curve diagram of the variable back pressure characteristic of the low pressure cylinder measured by a 660MW unit test. According to the characteristic curve shown in the figure, the average value ([. DELTA.p ]) of the pressure change of the high-low pressure side condenser caused by the modification of the vacuum-pumping system can be obtainedH+△pL]And/2) converted into a variation value of the low-pressure cylinder output as delta Pel。
The ninth step, calculating the energy difference value delta P consumed by the two vacuum-pumping systems before and after the reconstructionhe. The specific method comprises the following steps: for the steam jet type vacuumizing system, the equivalent power consumption can be converted into the steam consumed by the steam jet type vacuumizing system through an equivalent enthalpy drop method, and the value is obtained by subtracting the generated energy of # 8-stage extracted steam extruded by the ejector regenerative system from the generated energy of the consumed steam in the steam turbine set. Delta PheSubtracting the power of the water ring vacuum pump set from the equivalent generated energy, and aiming at the working liquid cooling project of the water ring vacuum pump set, the difference value delta PheThe energy consumed by the air conditioning unit. Then the energy-saving net gain before and after the switching of the vacuum-pumping system can be calculated as delta Pel-△Phe。
And tenth step, reading the actual operation boundary conditions (load, circulating water inlet temperature and pump combination) of the unit from a unit PI database at certain time intervals (5min) by referring to the principle of calculus within a set time period (1 year), and calculating the pressure change value delta p of the high-low pressure condenser at the boundary conditions by the method in the fifth, sixth, seventh, eighth and ninth steps after the vacuum pumping system is switchedH、△pLDelta P of the variation of the low pressure cylinder outputelAnd energy saving net profit DeltaPel-△PheAnd then accumulating the energy-saving net income on a time coordinate value, and calculating to obtain the total energy-saving benefit value Pejs of the vacuum-pumping system reconstruction project in the time period.
FIG. 1 is a graph showing the ratio mu of the heat transfer coefficient of condensation in the operating mode before and after the vacuum pumping system is modified. The abscissa in the graph is the difference value delta p (the characteristic value of the pumping capacity of a water-ring vacuum pump pumping system) of the condenser pressure and the saturation pressure corresponding to the temperature of the working liquid of the water-ring vacuum pump; the ordinate is the condensation heat exchange coefficient K in the condenser in the operation mode before the vacuum pumping system is transformed0And the condensation heat exchange coefficient K in the condenser in the operation mode after the vacuum pumping system is improved1Ratio of (u) to (K)0/K1。
FIG. 2 is a graph of the variable back pressure characteristic of the low pressure cylinder measured in a 660MW unit test. The abscissa in the figure is Δ pcThe difference value between the actual pressure of the condenser and the rated pressure (4.85kPa) is obtained; ordinate is f ═ Pel0-Pel)/Pel0In which P isel0The electric power is the electric power when the pressure of the condenser is a rated value; pelThe electric power is corresponding to the actual condenser pressure.
Claims (5)
1. The method for evaluating the energy-saving reconstruction benefits of the condenser vacuumizing system is characterized by comprising the following steps of: the method comprises the following steps:
the method comprises the steps that firstly, vacuum tightness data of condensers on high and low pressure sides of a unit are counted, a statistical average value of the vacuum tightness of the condensers when the unit normally operates is obtained, and the data are used as a reference value of the tightness of the condensers of the unit;
secondly, according to the historical operation data of the unit and the optimal operation mode of the circulating pump operation combination obtained by cold end optimization, taking the inlet water temperature of circulating water as a horizontal coordinate, and counting the unit load rate and the circulating pump operation combination corresponding to different temperature intervals;
third, each or several temperature intervals [ t ] in the second step are selected0，t1]…, measuring pressure change values of the high-low pressure side condenser at different load points by a switching comparison test method of the vacuumizing system between operation modes before and after the transformation;
a fourth step of setting a temperature interval t for each temperature interval in the third step0，t1]… at several load points, byUnder the known conditions, the load, the circulating water flow, the circulating water inlet temperature and the condenser pressure value of the unit are calculated by utilizing a condenser variable working condition model to obtain the condensing heat exchange coefficient K in the condenser in the operation mode before the vacuum pumping system at each load point is modified0And the condensation heat exchange coefficient K in the condenser in the operation mode after the vacuum pumping system is improved1And the ratio thereof is mu-K0/K1；
The fifth step, aiming at any temperature interval [ t ]0，t1]…, when the actual running mode of the pump combination is the corresponding value in the second step, the temperature point t and the unit load P are respectively calculated by the variable working condition model of the condenserelThe pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping systemH、△pL；
The sixth step, aiming at any temperature interval [ t0，t1]…, when the actual running mode of the combination of the circulating pumps does not correspond to the statistical value of the second step, knowing the flow rate of the combination of the circulating pumps, respectively calculating the temperature point t and the unit load P by the calculation method in the fifth stepelThe pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping systemH、△pL；
And seventhly, when the number of interval points in the second step is more and the test interval points in the third step are not completely covered, calculating the pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping system at different temperatures and different loads in the temperature interval by using the calculation method in the fifth step for the interval which is not covered by the testH、△pL；
Eighthly, according to the thermal characteristic data of the low-pressure cylinder, the pressure change value delta p of the condenser at the high-low pressure side caused by the transformation of the vacuum-pumping system at different temperatures and different loadsH、△pLThe variation value converted into the low-pressure cylinder output is delta Pel；
The ninth step, respectively calculating the energy consumed by the self operation of the vacuum-pumping systems under different operation modes of the vacuum-pumping systems, and calculating the energy difference delta P consumed by the two vacuum-pumping systems before and after the transformationheVacuum-pumping system cutterThe net gain of energy saving before and after changing is delta Pel-△Phe；
Tenth step, reading the actual operation boundary conditions of the unit respectively within a set time period and taking 5min as a time interval, and respectively calculating the pressure change value delta p of the high-low pressure condenser after the vacuum pumping system is switched at the boundary conditionsH、△pLAnd the variation value delta P of the low-pressure cylinder outputelAnd energy saving net gain Δ Pel-△PheAnd then accumulating the energy-saving net income on a time coordinate value, and calculating to obtain the total energy-saving benefit value Pejs of the vacuum-pumping system modification project in the time period.
2. The evaluation method of the energy-saving improvement yield of the condenser vacuumizing system according to claim 1, characterized by comprising the following steps: in the third step, the specific test method is as follows: get [ t ]0，t1]The temperature range is the middle value of the circulating water inlet temperature of the test working condition and is (t)0+t1) 2; the condenser vacuum tightness is a reference value counted in the first step of the unit, and the circulating pump combination is a circulating pump combination P corresponding to the temperature interval1(ii) a 3 to 5 load points under test conditions are selected, a vacuumizing system switching comparison test at each load point is continuously carried out, the unit load before and after switching is consistent with the state of a thermodynamic system, the condenser pressure value is corrected by using a condenser variable condition model according to the difference between the condenser circulating water inlet temperature and the load in the comparison conditions before and after switching, and the difference of the condenser pressure value after correction in the comparison test is caused by the change of the operation mode of the vacuumizing system.
3. The evaluation method of the energy-saving improvement yield of the condenser vacuumizing system according to claim 1, characterized by comprising the following steps: and in the fourth step, fitting a relational expression between mu and delta p through tests at a plurality of load points by taking the difference delta p between the condenser pressure and the saturation pressure corresponding to the working liquid temperature of the water ring vacuum pump as an abscissa.
4. Condenser vacuum pumping system section according to claim 1The evaluation method capable of improving the yield is characterized in that: in the calculation method of the fifth step and the sixth step, the pressure change value delta p of the condenser at the high and low pressure sidesH、△pLThe proportional relation is calculated by a relation mu (delta p) fitted by tests, and in the calculation process, the end difference of the working liquid cooler of the water ring vacuum pump is kept unchanged, namely the difference value between the working liquid temperature of the water ring vacuum pump and the inlet temperature of circulating water is kept unchanged.
5. The evaluation method of the energy-saving improvement yield of the condenser vacuumizing system according to claim 1, characterized by comprising the following steps: in the calculation method of the seventh step, for the temperature interval which is not covered by the test, the relational expression mu (delta p) of the influence factor of the vacuumizing system on the condensation heat exchange coefficient of the condenser is switched to refer to the test measured value of the adjacent temperature interval, and the other steps are consistent with the calculation methods of the fifth step and the sixth step.
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