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WO1999061135A1 - Method and device for cool-drying - Google Patents

Method and device for cool-drying Download PDF

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Publication number
WO1999061135A1
WO1999061135A1 PCT/BE1999/000059 BE9900059W WO9961135A1 WO 1999061135 A1 WO1999061135 A1 WO 1999061135A1 BE 9900059 W BE9900059 W BE 9900059W WO 9961135 A1 WO9961135 A1 WO 9961135A1
Authority
WO
WIPO (PCT)
Prior art keywords
evaporator
temperature
measured
heat exchanger
motor
Prior art date
Application number
PCT/BE1999/000059
Other languages
French (fr)
Inventor
Peter Albert Lauwers
Original Assignee
Atlas Copco Airpower, Naamloze Vennootschap
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=25663138&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=WO1999061135(A1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Priority claimed from BE9800397A external-priority patent/BE1011932A3/en
Priority to HU0204171A priority Critical patent/HU222974B1/en
Priority to DE69905042T priority patent/DE69905042T2/en
Priority to US09/700,701 priority patent/US6460359B1/en
Priority to AU39219/99A priority patent/AU744515B2/en
Priority to DK99921993T priority patent/DK1089803T3/en
Priority to EP99921993A priority patent/EP1089803B1/en
Application filed by Atlas Copco Airpower, Naamloze Vennootschap filed Critical Atlas Copco Airpower, Naamloze Vennootschap
Priority to NZ508321A priority patent/NZ508321A/en
Priority to AT99921993T priority patent/ATE231409T1/en
Priority to KR1020007013235A priority patent/KR20010043805A/en
Priority to CA002333152A priority patent/CA2333152C/en
Priority to JP2000550583A priority patent/JP2002516168A/en
Publication of WO1999061135A1 publication Critical patent/WO1999061135A1/en
Priority to NO20005957A priority patent/NO317887B1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/26Drying gases or vapours
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D5/00Condensation of vapours; Recovering volatile solvents by condensation
    • B01D5/0033Other features
    • B01D5/0039Recuperation of heat, e.g. use of heat pump(s), compression
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/26Drying gases or vapours
    • B01D53/265Drying gases or vapours by refrigeration (condensation)
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00Fluid-circulation arrangements
    • F25B41/30Expansion means; Dispositions thereof
    • F25B41/31Expansion valves
    • F25B41/34Expansion valves with the valve member being actuated by electric means, e.g. by piezoelectric actuators
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00Control issues
    • F25B2600/02Compressor control
    • F25B2600/021Inverters therefor
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21Temperatures
    • F25B2700/2117Temperatures of an evaporator
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B47/00Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/006Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass for preventing frost
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00Arrangement or mounting of control or safety devices
    • F25B49/02Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F25B49/025Motor control arrangements
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Definitions

  • the present invention concerns a method for cool -drying gas containing water vapor, whereby this gas is guided through the secondary part of a heat exchanger whose primary part is the evaporator of a cooling circuit which also contains a compressor which is driven by an electric motor, a condenser, an expansion means between the outlet of the condenser and the inlet of the evaporator, and whereby the above-mentioned cooling circuit is thus controlled as a function of the load that the cooling capacity is adjusted without any ice being formed in the evaporator.
  • Such methods are used among others for drying compressed air .
  • Compressed air which is supplied by a compressor is in most cases saturated with water vapor or, in other words, has a relative humidity of 100%. This implies that there is condensation at the slightest decrease of temperature. The water of condensation causes corrosion in the pipes and tools, and the equipment will wear out prematurely.
  • Cool -drying is based on the principle that, by lowering the temperature, moisture from the air or the gas condenses, after which the water of condensation is separated in the liquid separator and after which the air or the gas is heated again, as a result of which this air or this gas is no longer saturated. The heat is discharged by the cooling circuit in the evaporator.
  • a necessary condition is that the temperature of the evaporator is higher than 0°C.
  • the temperature is measured on the inlet of the evaporator, or, since there is a definite connection between the temperature of the evaporator and the pressure of the evaporator for a specific cooling liquid in the cooling circuit, the pressure is measured before or after the evaporator.
  • the cooling circuit is then controlled such that the temperature of the evaporator or the pressure of the evaporator has the required value, and for example the pressure of the evaporator coincides with a temperature which is situated a few degrees below the required lowest air temperature or LAT, but not below 0°C.
  • the motor of the compressor of the cooling circuit which is driven at a constant frequency is switched on and off as a function of the temperature of the evaporator. If this pressure of the evaporator decreases too much, said motor is stopped. If the pressure of the evaporator subsequently increases too much as the expansion valve is still open, the motor is started again.
  • Another known method consists in measuring the lowest air temperature (LAT) on the outlet of the secondary part of the heat exchanger and to switch off the motor of the compressor of the cooling circuit when the temperature threatens to drop below 0°C.
  • LAT lowest air temperature
  • This method whereby the motor is thus also switched on and off, offers the same disadvantages as the preceding one.
  • Another possibility for regulating the pressure of the evaporator would consist in selecting an evaporator which is large enough and in carrying back hot gases on the outlet of the compressor to the inlet of the compressor by means of a bypass .
  • This regulation method is disadvantageous in that, since the compressor motor is continuously working, also when there is no load or when the load is low, the energy consumption is equal to the energy consumption at a nominal load, as the high and low pressure in the cooling circuit are continuously kept at a constant level .
  • the object of the invention is a method for cool -drying which does not have the above-mentioned and other disadvantages and which makes it possible to save energy in a simple manner, without any pressure variations in the cooling circuit and without much wear of the compressor and its motor.
  • this object is accomplished in that the cooling circuit is controlled by adjusting the rotational speed of the motor.
  • the pressure of the evaporator can be measured and the above-mentioned cooling circuit can be controlled as a function of the measured pressure of the evaporator.
  • the lowest gas temperature (LAT) can be measured and the above-mentioned cooling circuit is controlled as a function of this lowest gas temperature (LAT) .
  • the dew point temperature of the gas can be measured and the above- mentioned cooling circuit is controlled as a function of this dew point .
  • the rotational speed of the motor is adjusted by modifying the frequency of the supply current.
  • the ambient temperature is measured and the rotational speed of the motor is adjusted as a function of the measured ambient temperature .
  • the energy consumption of the above-mentioned cool- dryers is too high, and they require relatively large and expensive components in order to supply the cooling output.
  • the required cooling output may be kept lower, such that the cool -dryer can be made less large.
  • the rotational speed of the motor of the compressor is adjusted such that the lowest air or gas temperature on the outlet of the evaporator is 20°C lower than the measured ambient temperature, without dropping below 3°C, however.
  • the invention also concerns a device for cool -drying or a cool -dryer which is particularly suitable for applying the above-mentioned method.
  • the invention in particular concerns a device for cool- drying, containing a heat exchanger whose primary part is the evaporator of a cooling circuit which also contains a compressor which is driven by an electric motor, a condenser, an expansion means between the outlet of the condenser and the inlet of the evaporator, a control device to control the above-mentioned motor and measuring means coupled thereto, whereas the secondary part of the heat exchanger is part of a pipe for the gas and a liquid separator is erected on the outlet of said heat exchanger, in said pipe, whereby the device contains means to adjust the rotational speed of the motor while the control device controls these means as a function of the value measured by the measuring means .
  • the measuring means may be provided on the cooling circuit and they may be means to measure the temperature of the evaporator or the pressure of the evaporator.
  • the measuring means may also be provided on the pipe for the gas, in the secondary part of the heat exchanger or downstream to it, and they may be means to measure the lowest gas temperature (LAT) or means to measure the dew point .
  • LAT lowest gas temperature
  • the means for regulating the rotational speed of the motor consist of a frequency converter.
  • the cool -dryer contains means for measuring the ambient temperature which are also coupled to the control device, and this control device is such that it adjusts the speed of the motor both as a function of the value measured by the measuring means and as a function of the temperature measured by the means for measuring the ambient temperature .
  • figure 1 represents a block diagram of a device for cool -drying according to the invention
  • figure 2 represents a block diagram analogous to that of figure 1, but in relation to another embodiment of the invention.
  • the device for cool -drying which is schematically represented in figure 1 mainly contains a heat exchanger 1 whose primary part forms the evaporator 2 of a cooling circuit 3 in which are also successively erected an electric motor 4 driven by a compressor 5, a condenser 6 and an expansion valve 7.
  • This cooling circuit is filled with cooling fluid, for example freon 404a, whose direction of flow is represented by the arrow 8.
  • the secondary part 1A of the heat exchanger 1 is part of the pipe 9 for humid air to be dried, whose direction of flow is represented by the arrow 10.
  • this pipe 9 may possibly extend through a pre-cooler or recuperation heat exchanger 12 with one part and subsequently, after the liquid separator 11, extend again through the recuperation heat exchanger 12, counterflow to the above- mentioned part.
  • the heat exchanger 1 is a liquid/air heat exchanger and, from a constructional point of view, may form a whole with the possible recuperation heat exchanger 12 which is an air/air heat exchanger.
  • the expansion valve 7 is a thermostatic valve whose thermostatic element is coupled to a bulb 14 provided on the outlet of the evaporator 2 on the cooling circuit 3 by means of a copper guide 13 and which is filled with the same cooling liquid.
  • this expansion valve is an electronic valve, however, which is coupled to a temperature gauge erected on the far end of the evaporator 2 or after it .
  • the expansion valve 7 may be replaced by a capillary tube.
  • the compressor 5 is a volumetric compressor which supplies an almost invariable volume flow at an invariable rotational speed, for example a spiral compressor, whereas the motor 4 is an electric motor whose rotational speed can be adjusted by changing the frequency. Also, this motor 4 is coupled to a frequency converter 15 which is controlled by a control device consisting of a built-in PID controller 16.
  • the frequency converter 15 may for example adjust the frequency between 0 and 400 Hz and forms means to adjust the rotational speed of the motor 4.
  • the PID controller 16 is connected to measuring means 18 via a pipe 17 to measure the pressure of the evaporator, for example a pressure transmitter with a pressure range from -1 tot 12 bar which transforms the pressure in an electric signal, in particular a current, which is erected on the inlet or the outlet of the evaporator 2, as is represented in the figure by means of a dashed line.
  • a pressure transmitter with a pressure range from -1 tot 12 bar which transforms the pressure in an electric signal, in particular a current, which is erected on the inlet or the outlet of the evaporator 2, as is represented in the figure by means of a dashed line.
  • the PID controller 16 is connected to the measuring means 20 via a pipe 19 to measure the temperature of the evaporator, for example a thermocouple in the cooling circuit 3, on the inlet of the evaporator 2 and thus between this evaporator 2 and the expansion valve 7.
  • the PID controller 16 is connected to means 22 via a pipe 21 to measure the ambient temperature and which transform this temperature into an electric signal, in particular a current.
  • the working of the cool-dryer is as follows:
  • the air to be dried is carried through the pipe 9 and thus through the heat exchanger 1, counterflow to the cooling fluid in the evaporator 2 of the cooling circuit 3.
  • the cold air which contains less moisture after this liquid separator 11 but yet has a relative humidity of 100%, is heated in the recuperation heat exchanger 12, as a result of which the relative humidity decreases to about 50%, while the fresh air to be dried is already partly cooled in this heat exchanger 12 before being supplied to the heat exchanger 1.
  • the air on the outlet of the recuperation heat exchanger 12 is thus drier than on the inlet of the heat exchanger 1.
  • the air in the heat exchanger 1 is not cooled below 3°C, which is the LAT for low ambient temperatures.
  • the LAT may be higher and may be cooled to an LAT which is 20°C lower than the ambient temperature, and in any case not below 3°C.
  • Said LAT is situated 2 to 3°C above the actual temperature of the evaporator which is measured by the measuring means 20.
  • the above-mentioned LAT conditions are met by adjusting the rotational speed of the motor 4 as a function of the temperature of the evaporator measured by the measuring means 20 by means of the PID controller 16 and the frequency converter 15 controlled by it in the one embodiment, or the pressure of the evaporator measured by the measuring means 18 in the other embodiment.
  • the cooling output is equal to the mass flow of cooling liquid circulating in the cooling circuit 3, multiplied by the enthalpy difference of the air before and after the heat exchanger 1.
  • the mass flow is the volume flow of the compressor 5, multiplied by the density of the cooling liquid in the suction condition, which itself depends on the temperature of the evaporator and the overheating.
  • the PID controller 16 adjusts the measured temperature or pressure by adjusting the rotational speed, so that this temperature is a few degrees lower than the above- mentioned LAT, but yet higher than 0°C, the pressure of the evaporator is reached respectively, which coincides with a temperature which is a few degrees lower than the LAT and which is for example equal to 1°C, whereby for freon R404a, the pressure of the evaporator is effectively about 5.2 bar.
  • the PID controller 16 coupled to it can take this temperature into account .
  • the rotational speed of the motor 4 is than adjusted such that, as long as the ambient temperature is low, in particular below 23 °C, the above-mentioned condition is met and thus the LAT on the outlet of the secondary part 1A of the heat exchanger 1 is about 3°C, but at a higher ambient temperature, this LAT is 20 °C lower than the ambient temperature measured by the means 21.
  • the pressure of the evaporator has a set point which is a few degrees lower than the required LAT.
  • the temperature which is obtained by subtracting some 22 °C from the ambient temperature, can be calibrated as the set point of the PID controller 16.
  • a minimum and a maximum set point may possibly be set in the PID controller 16, whereby the minimum is 1°C.
  • this set point can be adjusted for example via a control panel or via an analogous inlet .
  • the frequency is adjusted between for example 30 and 75 Hz.
  • the maximum load of the cool -drying device is relatively small, since, at higher ambient temperatures, the LAT can be higher than 3°C, as a result of which the cooling output decreases and the components may thus be less expensive and cooling fluid is saved on.
  • the cooling fluid which has been heated in the compressor 5 as a result of the compression is cooled until it has a liquid state, whereby use can be made of a fan or of cooling water to discharge the heat to the environment .
  • the motor 4 is automatically switched off.
  • the liquid cooling fluid may possibly be collected in a receptacle and/or it may be further cooled by an extra heat exchanger.
  • the expansion valve 7 the liquid cooling fluid is expanded to a constant evaporator pressure, which of course results in a temperature decrease.
  • the expansion valve 7 only controls the overheating in the evaporator 2 and makes sure that the evaporator 2 is always optimally used, but it cannot be used to the control the pressure or temperature of the evaporator.
  • thermostatic expansion valve 7 By applying a thermostatic expansion valve 7, there will always be overheating after the evaporator 2, so that there is no danger of cooling liquid entering the compressor 5, so that there is no need for a liquid separator in the cooling circuit 3 and so that the amount of cooling fluid is restricted.
  • This overheating is measured by distracting the temperature measured by the bulb 14 from the temperature of the evaporator, either before the evaporator 2 (internal equalization) or after the evaporator (external equalization) .
  • This difference is compared to a set value by the expansion valve 7 and, in case of a deviation, the expansion valve 7 will correct it by opening or by closing.
  • the degree of overheating has an influence on the LAT, but we may assume that this overheating is kept at a practically constant level by the expansion valve.
  • the slave control circuit is the above- described control with the PID controller 16, whereas the master control circuit could adjust the set point of the pressure or temperature of the evaporator as a function of the actual LAT, and thus could for example lower the set point if the LAT remains too high as the overheating after the evaporator 2 is too high.
  • the pressure or temperature of the evaporator is adjusted by modifying the rotational speed, it may be possible to entirely switch off the motor 4 in case the load is zero, for example by placing a thermostatic sensor in the heat exchanger 1 which, should the temperature in the evaporator 2 drop to zero degrees, switches off the motor 4 and starts it again as soon as the temperature has risen to 3°C.
  • the embodiment of the invention represented in figure 2 mainly differs from the above-described embodiments in that the measuring means 18 for measuring the pressure of the evaporator and/or the measuring means 20 for measuring the temperature of the evaporator provided on the cooling circuit 3 have been replaced by measuring means 23 for measuring the lowest air temperature (LAT) .
  • These measuring means 23 have been provided on the pipe 9, either in the secondary part 1A of the heat exchanger 1, for example on the surface of the evaporator 2, or as represented in figure 2, downstream the heat exchanger 1, for example between this heat exchanger 1 and the liquid separator 11.
  • the PID controller 16 is then connected to these measuring means 23 and to the means 22 for measuring the ambient temperature by means of a pipe 21.
  • the PID controller 16 controls the frequency converter 15 and thus the rotational speed of the motor 4 as a function of the measured lowest air temperature LAT.
  • Measuring the LAT offers a major advantage in that the temperature of the cooling fluid may be lower than 0°C without the evaporator thereby freezing up, i.e. before ice is formed on the air side of the evaporator, since this phenomenon is determined by the LAT.
  • the heat exchanger 1 can be made very compact .
  • the PID controller 16 will order the speed of the motor 4 to increase, decrease respectively, such that, as long as the ambient temperature measured by the temperature gauge 22 is low, in particular lower than 23 °C, this measured LAT temperature will not drop below some 3°C, so as to make sure that the evaporator 2 will not freeze up.
  • the cooling is thus adjusted according to the load, whereby the evaporator temperatures on the side of the cooling fluid may drop below zero without the evaporator 2 freezing up on the air side, however.
  • the heat exchanger 1 can be made relatively compact, which also implies savings on the cost of the device.
  • the overheating in the evaporator 2 is controlled by the expansion valve 7 , as a result of which the cooling fluid expands.
  • the lowest air temperature is adjusted by modifying the rotational speed of the motor 4, it may be possible in this embodiment as well to entirely switch off the motor 4 in case of a zero load.
  • the measuring means 23 for measuring the lowest air temperature are replaced by measuring means for measuring the dew point of said air.
  • Such measuring means or dew point gauges are available on the market and hence are not further described here.
  • the dew point of the air is thus measured on the same place.
  • the working is analogous to the above-described working, whereby the speed of the motor 4 is thus adjusted such that the cooling in the heat exchanger 1 is optimal, but the evaporator 2 is prevented from freezing up.
  • control device may contain another controller, for example a PI or P controller.
  • the ambient temperature is preferably also taken into account, among others to restrict the output of the device, it is possible, according to a simpler embodiment, to adjust the rotational speed of the motor 4 merely as a function of the evaporator temperature, the evaporator pressure, the lowest gas temperature or the dew point of the gas.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • General Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Drying Of Solid Materials (AREA)
  • Drying Of Gases (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Processing Of Solid Wastes (AREA)
  • Motor Or Generator Cooling System (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Abstract

The present invention concerns a method for cool-drying gas containing water vapor, whereby this gas is guided through the secondary part of a heat exchanger (1) whose primary part is the evaporator (2) of a cooling circuit (3) which also contains a compressor (5) which is driven by an electric motor (4), a condenser (6), an expansion means (7) between the outlet of the condenser (6) and the inlet of the evaporator (2), and whereby the above-mentioned cooling circuit (3) is thus controlled as a function of the load that the cooling capacity is adjusted without any ice being formed in the evaporator (2), characterized in that the cooling circuit is controlled by adjusting the rotational speed of the motor (4).

Description

Method and device for cool -drying.
The present invention concerns a method for cool -drying gas containing water vapor, whereby this gas is guided through the secondary part of a heat exchanger whose primary part is the evaporator of a cooling circuit which also contains a compressor which is driven by an electric motor, a condenser, an expansion means between the outlet of the condenser and the inlet of the evaporator, and whereby the above-mentioned cooling circuit is thus controlled as a function of the load that the cooling capacity is adjusted without any ice being formed in the evaporator.
Such methods are used among others for drying compressed air .
Compressed air which is supplied by a compressor is in most cases saturated with water vapor or, in other words, has a relative humidity of 100%. This implies that there is condensation at the slightest decrease of temperature. The water of condensation causes corrosion in the pipes and tools, and the equipment will wear out prematurely.
That is why the compressed air is dried, which may be done in the above-mentioned manner, by means of cool- drying. Also other air than compressed air or other gases may be dried in this manner. Cool -drying is based on the principle that, by lowering the temperature, moisture from the air or the gas condenses, after which the water of condensation is separated in the liquid separator and after which the air or the gas is heated again, as a result of which this air or this gas is no longer saturated. The heat is discharged by the cooling circuit in the evaporator.
The same applies to other gases than air, and each time air is referred to hereafter, the same also applies to other gases than air.
In practice, there is an ISO-standard which determines the possible dew point and the corresponding lowest air temperature for reference values.
In order to prevent the lowest air temperature from dropping below 0°C and thus the evaporator from freezing up, a necessary condition is that the temperature of the evaporator is higher than 0°C.
According to known methods, to this end, the temperature is measured on the inlet of the evaporator, or, since there is a definite connection between the temperature of the evaporator and the pressure of the evaporator for a specific cooling liquid in the cooling circuit, the pressure is measured before or after the evaporator.
The cooling circuit is then controlled such that the temperature of the evaporator or the pressure of the evaporator has the required value, and for example the pressure of the evaporator coincides with a temperature which is situated a few degrees below the required lowest air temperature or LAT, but not below 0°C.
According to these known methods for cool -drying, the motor of the compressor of the cooling circuit which is driven at a constant frequency is switched on and off as a function of the temperature of the evaporator. If this pressure of the evaporator decreases too much, said motor is stopped. If the pressure of the evaporator subsequently increases too much as the expansion valve is still open, the motor is started again.
Such a regulation makes it possible for the compressor to be switched off when the load drops beneath the cooling capacity, as a result of which the energy consumption will decrease. The surplus of cooling capacity is stored in a thermal mass. However, this regulation is very disadvantageous as the compressor is continuously switched on and off in case of a small load, while also the pressure of the evaporator and the dew points fluctuate strongly. Moreover, the cool -dryer must be built relatively large.
Another known method consists in measuring the lowest air temperature (LAT) on the outlet of the secondary part of the heat exchanger and to switch off the motor of the compressor of the cooling circuit when the temperature threatens to drop below 0°C. This method, whereby the motor is thus also switched on and off, offers the same disadvantages as the preceding one. Another possibility for regulating the pressure of the evaporator would consist in selecting an evaporator which is large enough and in carrying back hot gases on the outlet of the compressor to the inlet of the compressor by means of a bypass .
This regulation method is disadvantageous in that, since the compressor motor is continuously working, also when there is no load or when the load is low, the energy consumption is equal to the energy consumption at a nominal load, as the high and low pressure in the cooling circuit are continuously kept at a constant level .
The object of the invention is a method for cool -drying which does not have the above-mentioned and other disadvantages and which makes it possible to save energy in a simple manner, without any pressure variations in the cooling circuit and without much wear of the compressor and its motor.
In accordance with the invention, this object is accomplished in that the cooling circuit is controlled by adjusting the rotational speed of the motor.
Instead of switching the motor on or off, its speed is adjusted. By increasing the rotational speed of the motor, more mass flow of cooling liquid can be pumped round, and thus can be obtained a higher cooling output. The temperature of the evaporator can be measured and the above-mentioned cooling circuit can be controlled as a function of the measured temperature of the evaporator.
According to another embodiment, the pressure of the evaporator can be measured and the above-mentioned cooling circuit can be controlled as a function of the measured pressure of the evaporator.
According to yet another embodiment, the lowest gas temperature (LAT) can be measured and the above-mentioned cooling circuit is controlled as a function of this lowest gas temperature (LAT) .
According to yet another embodiment, the dew point temperature of the gas can be measured and the above- mentioned cooling circuit is controlled as a function of this dew point .
Preferably, the rotational speed of the motor is adjusted by modifying the frequency of the supply current.
According to a special embodiment of the invention, the ambient temperature is measured and the rotational speed of the motor is adjusted as a function of the measured ambient temperature .
At high ambient temperatures, whereby the air or the gas is also relatively warm and may contain more moisture than when it is cold, it is not necessary to cool it to
3°C in the heat exchanger in order to obtain dry air. Thus, the energy consumption of the above-mentioned cool- dryers is too high, and they require relatively large and expensive components in order to supply the cooling output. By taking into account said ambient temperature, the required cooling output may be kept lower, such that the cool -dryer can be made less large.
Preferably, the rotational speed of the motor of the compressor is adjusted such that the lowest air or gas temperature on the outlet of the evaporator is 20°C lower than the measured ambient temperature, without dropping below 3°C, however.
It is assumed that, when the outgoing air or the outgoing gas has a relative humidity of 50%, the danger of corrosion in pipes and equipment is excluded, and the above-mentioned control device guarantees that said relative humidity will not be higher than 50%.
The invention also concerns a device for cool -drying or a cool -dryer which is particularly suitable for applying the above-mentioned method.
The invention in particular concerns a device for cool- drying, containing a heat exchanger whose primary part is the evaporator of a cooling circuit which also contains a compressor which is driven by an electric motor, a condenser, an expansion means between the outlet of the condenser and the inlet of the evaporator, a control device to control the above-mentioned motor and measuring means coupled thereto, whereas the secondary part of the heat exchanger is part of a pipe for the gas and a liquid separator is erected on the outlet of said heat exchanger, in said pipe, whereby the device contains means to adjust the rotational speed of the motor while the control device controls these means as a function of the value measured by the measuring means .
The measuring means may be provided on the cooling circuit and they may be means to measure the temperature of the evaporator or the pressure of the evaporator.
However, the measuring means may also be provided on the pipe for the gas, in the secondary part of the heat exchanger or downstream to it, and they may be means to measure the lowest gas temperature (LAT) or means to measure the dew point .
Preferably, the means for regulating the rotational speed of the motor consist of a frequency converter.
According to a special embodiment of the invention, the cool -dryer contains means for measuring the ambient temperature which are also coupled to the control device, and this control device is such that it adjusts the speed of the motor both as a function of the value measured by the measuring means and as a function of the temperature measured by the means for measuring the ambient temperature .
In order to better explain the characteristics of the invention, the following preferred embodiments of a cool- dryer according to the invention are described as an example only without being limitative in any way, with reference to the accompanying drawings, in which:
figure 1 represents a block diagram of a device for cool -drying according to the invention; figure 2 represents a block diagram analogous to that of figure 1, but in relation to another embodiment of the invention.
The device for cool -drying which is schematically represented in figure 1 mainly contains a heat exchanger 1 whose primary part forms the evaporator 2 of a cooling circuit 3 in which are also successively erected an electric motor 4 driven by a compressor 5, a condenser 6 and an expansion valve 7.
This cooling circuit is filled with cooling fluid, for example freon 404a, whose direction of flow is represented by the arrow 8.
The secondary part 1A of the heat exchanger 1 is part of the pipe 9 for humid air to be dried, whose direction of flow is represented by the arrow 10.
After the heat exchanger 1, i.e. on its outlet, a liquid separator 11 is erected in the pipe 9.
Before it reaches the heat exchanger 1, this pipe 9 may possibly extend through a pre-cooler or recuperation heat exchanger 12 with one part and subsequently, after the liquid separator 11, extend again through the recuperation heat exchanger 12, counterflow to the above- mentioned part.
The heat exchanger 1 is a liquid/air heat exchanger and, from a constructional point of view, may form a whole with the possible recuperation heat exchanger 12 which is an air/air heat exchanger.
The expansion valve 7 is a thermostatic valve whose thermostatic element is coupled to a bulb 14 provided on the outlet of the evaporator 2 on the cooling circuit 3 by means of a copper guide 13 and which is filled with the same cooling liquid.
According to a variant which is not represented in the figure, this expansion valve is an electronic valve, however, which is coupled to a temperature gauge erected on the far end of the evaporator 2 or after it .
In small cool-dryers, the expansion valve 7 may be replaced by a capillary tube.
The compressor 5 is a volumetric compressor which supplies an almost invariable volume flow at an invariable rotational speed, for example a spiral compressor, whereas the motor 4 is an electric motor whose rotational speed can be adjusted by changing the frequency. Also, this motor 4 is coupled to a frequency converter 15 which is controlled by a control device consisting of a built-in PID controller 16.
The frequency converter 15 may for example adjust the frequency between 0 and 400 Hz and forms means to adjust the rotational speed of the motor 4.
According to a first embodiment, the PID controller 16 is connected to measuring means 18 via a pipe 17 to measure the pressure of the evaporator, for example a pressure transmitter with a pressure range from -1 tot 12 bar which transforms the pressure in an electric signal, in particular a current, which is erected on the inlet or the outlet of the evaporator 2, as is represented in the figure by means of a dashed line.
According to a second embodiment, the PID controller 16 is connected to the measuring means 20 via a pipe 19 to measure the temperature of the evaporator, for example a thermocouple in the cooling circuit 3, on the inlet of the evaporator 2 and thus between this evaporator 2 and the expansion valve 7.
Indeed, for a given cooling fluid, there is a definite connection between the temperature of the evaporator and the pressure of the evaporator. The higher the temperature, the higher the pressure. Strictly speaking, this connection is not linear, but in the field of operation, i.e. between 0°C and 25°C, the deviation from a linear is to be practically neglected. In both embodiments, the PID controller 16 is connected to means 22 via a pipe 21 to measure the ambient temperature and which transform this temperature into an electric signal, in particular a current.
The working of the cool-dryer is as follows:
The air to be dried is carried through the pipe 9 and thus through the heat exchanger 1, counterflow to the cooling fluid in the evaporator 2 of the cooling circuit 3.
In this heat exchanger 1, the damp air is cooled, as a result of which condensation is formed which is separated in the liquid separator 11.
The cold air, which contains less moisture after this liquid separator 11 but yet has a relative humidity of 100%, is heated in the recuperation heat exchanger 12, as a result of which the relative humidity decreases to about 50%, while the fresh air to be dried is already partly cooled in this heat exchanger 12 before being supplied to the heat exchanger 1.
The air on the outlet of the recuperation heat exchanger 12 is thus drier than on the inlet of the heat exchanger 1. In order to prevent the evaporator 2 from freezing, the air in the heat exchanger 1 is not cooled below 3°C, which is the LAT for low ambient temperatures.
With higher ambient temperatures, the LAT may be higher and may be cooled to an LAT which is 20°C lower than the ambient temperature, and in any case not below 3°C.
Is the LAT too high, this means that there is not enough cooling and thus not enough condensation of moisture to sufficiently dry the air.
Said LAT is situated 2 to 3°C above the actual temperature of the evaporator which is measured by the measuring means 20.
The above-mentioned LAT conditions are met by adjusting the rotational speed of the motor 4 as a function of the temperature of the evaporator measured by the measuring means 20 by means of the PID controller 16 and the frequency converter 15 controlled by it in the one embodiment, or the pressure of the evaporator measured by the measuring means 18 in the other embodiment.
The cooling output is equal to the mass flow of cooling liquid circulating in the cooling circuit 3, multiplied by the enthalpy difference of the air before and after the heat exchanger 1. By increasing the rotational speed of the motor 4, the compressor 5 can pump round more mass flow, and thus can be supplied a larger output with the same enthalpy difference. The mass flow is the volume flow of the compressor 5, multiplied by the density of the cooling liquid in the suction condition, which itself depends on the temperature of the evaporator and the overheating.
The PID controller 16 adjusts the measured temperature or pressure by adjusting the rotational speed, so that this temperature is a few degrees lower than the above- mentioned LAT, but yet higher than 0°C, the pressure of the evaporator is reached respectively, which coincides with a temperature which is a few degrees lower than the LAT and which is for example equal to 1°C, whereby for freon R404a, the pressure of the evaporator is effectively about 5.2 bar.
In this manner, the cooling output is adjusted to the load.
As the means 22 also measure the ambient temperature, the PID controller 16 coupled to it can take this temperature into account .
By means of the PID controller 16 and the frequency converter 15 controlled by it, the rotational speed of the motor 4 is than adjusted such that, as long as the ambient temperature is low, in particular below 23 °C, the above-mentioned condition is met and thus the LAT on the outlet of the secondary part 1A of the heat exchanger 1 is about 3°C, but at a higher ambient temperature, this LAT is 20 °C lower than the ambient temperature measured by the means 21. The pressure of the evaporator has a set point which is a few degrees lower than the required LAT. The temperature which is obtained by subtracting some 22 °C from the ambient temperature, can be calibrated as the set point of the PID controller 16.
A minimum and a maximum set point may possibly be set in the PID controller 16, whereby the minimum is 1°C. When calibrating the PID controller 16, this set point can be adjusted for example via a control panel or via an analogous inlet .
The frequency is adjusted between for example 30 and 75 Hz.
The maximum load of the cool -drying device is relatively small, since, at higher ambient temperatures, the LAT can be higher than 3°C, as a result of which the cooling output decreases and the components may thus be less expensive and cooling fluid is saved on.
In the condenser 6, the cooling fluid which has been heated in the compressor 5 as a result of the compression, is cooled until it has a liquid state, whereby use can be made of a fan or of cooling water to discharge the heat to the environment .
When the pressure in the condenser 6 is too high, the motor 4 is automatically switched off. After the condenser 6, the liquid cooling fluid may possibly be collected in a receptacle and/or it may be further cooled by an extra heat exchanger.
Thanks to the expansion valve 7, the liquid cooling fluid is expanded to a constant evaporator pressure, which of course results in a temperature decrease.
The expansion valve 7 only controls the overheating in the evaporator 2 and makes sure that the evaporator 2 is always optimally used, but it cannot be used to the control the pressure or temperature of the evaporator.
By applying a thermostatic expansion valve 7, there will always be overheating after the evaporator 2, so that there is no danger of cooling liquid entering the compressor 5, so that there is no need for a liquid separator in the cooling circuit 3 and so that the amount of cooling fluid is restricted.
This overheating is measured by distracting the temperature measured by the bulb 14 from the temperature of the evaporator, either before the evaporator 2 (internal equalization) or after the evaporator (external equalization) . This difference is compared to a set value by the expansion valve 7 and, in case of a deviation, the expansion valve 7 will correct it by opening or by closing. The degree of overheating has an influence on the LAT, but we may assume that this overheating is kept at a practically constant level by the expansion valve.
If necessary, this influence of the overheating can be taken into account by for example a sort of master/slave control circuit. The slave control circuit is the above- described control with the PID controller 16, whereas the master control circuit could adjust the set point of the pressure or temperature of the evaporator as a function of the actual LAT, and thus could for example lower the set point if the LAT remains too high as the overheating after the evaporator 2 is too high.
Although the pressure or temperature of the evaporator is adjusted by modifying the rotational speed, it may be possible to entirely switch off the motor 4 in case the load is zero, for example by placing a thermostatic sensor in the heat exchanger 1 which, should the temperature in the evaporator 2 drop to zero degrees, switches off the motor 4 and starts it again as soon as the temperature has risen to 3°C.
The embodiment of the invention represented in figure 2 mainly differs from the above-described embodiments in that the measuring means 18 for measuring the pressure of the evaporator and/or the measuring means 20 for measuring the temperature of the evaporator provided on the cooling circuit 3 have been replaced by measuring means 23 for measuring the lowest air temperature (LAT) . These measuring means 23 have been provided on the pipe 9, either in the secondary part 1A of the heat exchanger 1, for example on the surface of the evaporator 2, or as represented in figure 2, downstream the heat exchanger 1, for example between this heat exchanger 1 and the liquid separator 11.
The PID controller 16 is then connected to these measuring means 23 and to the means 22 for measuring the ambient temperature by means of a pipe 21.
In this embodiment, the PID controller 16 controls the frequency converter 15 and thus the rotational speed of the motor 4 as a function of the measured lowest air temperature LAT.
Measuring the LAT offers a major advantage in that the temperature of the cooling fluid may be lower than 0°C without the evaporator thereby freezing up, i.e. before ice is formed on the air side of the evaporator, since this phenomenon is determined by the LAT.
Since with low evaporator temperatures, for example -5°C, on the side of the cooling fluid, and major temperature differences, for example of 8°C (between +3°C and -5°C) , there may be evaporation without any danger of freezing, the heat exchanger 1 can be made very compact .
If the measured lowest air temperature LAT rises or drops, the PID controller 16 will order the speed of the motor 4 to increase, decrease respectively, such that, as long as the ambient temperature measured by the temperature gauge 22 is low, in particular lower than 23 °C, this measured LAT temperature will not drop below some 3°C, so as to make sure that the evaporator 2 will not freeze up.
Thanks to this control, the cooling is thus adjusted according to the load, whereby the evaporator temperatures on the side of the cooling fluid may drop below zero without the evaporator 2 freezing up on the air side, however. As a result, not only the energy consumption of the motor 4 is restricted to a minimum, but the heat exchanger 1 can be made relatively compact, which also implies savings on the cost of the device.
In this embodiment also, the overheating in the evaporator 2 is controlled by the expansion valve 7 , as a result of which the cooling fluid expands.
Although the lowest air temperature is adjusted by modifying the rotational speed of the motor 4, it may be possible in this embodiment as well to entirely switch off the motor 4 in case of a zero load.
According to a variant of the preceding embodiment which is not represented in the figures, the measuring means 23 for measuring the lowest air temperature are replaced by measuring means for measuring the dew point of said air. Such measuring means or dew point gauges are available on the market and hence are not further described here. Instead of the LAT, the dew point of the air is thus measured on the same place. The working is analogous to the above-described working, whereby the speed of the motor 4 is thus adjusted such that the cooling in the heat exchanger 1 is optimal, but the evaporator 2 is prevented from freezing up.
The invention is by no means limited to the above- described embodiments represented in the accompanying drawing; on the contrary, such a method and device for cool -drying can be made in all sorts of variants while still remaining within the scope of the invention.
In particular, instead of a PID controller 16, the control device may contain another controller, for example a PI or P controller. Although the ambient temperature is preferably also taken into account, among others to restrict the output of the device, it is possible, according to a simpler embodiment, to adjust the rotational speed of the motor 4 merely as a function of the evaporator temperature, the evaporator pressure, the lowest gas temperature or the dew point of the gas.
Instead of damp air, other gases than air containing water vapor can be dried in the same manner and with the same device. The LAT is then the lowest gas temperature.

Claims

Claims .
1. Method for cool-drying gas containing water vapor, whereby this gas is guided through the secondary part
(1A) of a heat exchanger (1) whose primary part is the evaporator (2) of a cooling circuit (3) which also contains a compressor (5) which is driven by an electric motor (4) , a condenser (6) , an expansion means (7) between the outlet of the condenser (6) and the inlet of the evaporator (2) , and whereby the above-mentioned cooling circuit (3) is thus controlled as a function of the load that the cooling capacity is adjusted without any ice being formed in the evaporator (2) , characterized in that the cooling circuit (3) is controlled by adjusting the rotational speed of the motor (4) .
2. Method according to claim 1, characterized in that the temperature of the evaporator is measured and in that the above-mentioned cooling circuit (3) is controlled as a function of the measured evaporator temperature.
3. Method according to claim 2, characterized in that the rotational speed of the motor (4) is adjusted such that the evaporator temperature is situated 2 to 3°C below the lowest gas temperature (LAT) .
4. Method according to claim 1, characterized in that the pressure of the evaporator is measured and in that the above-mentioned cooling circuit (3) is controlled as a function of the measured evaporator pressure.
5. Method according to claim 4, characterized in that the pressure of the evaporator is kept at a value which coincides with a temperature which is situated 2 to 3°C under this lowest gas temperature (LAT) , whereby this lowest gas temperature (LAT) is kept at minimum 3°C.
6. Method according to claim 1, characterized in that the lowest gas temperature (LAT) is measured and in that the above-mentioned cooling circuit (3) is controlled as a function of this lowest gas temperature (LAT) .
7. Method according to claim 6, characterized in that the lowest gas temperature (LAT) is measured on the outlet of the secondary part (1A) of the heat exchanger (1) .
8. Method according to claim 1, characterized in that the dew point of the gas is measured and in that the above- mentioned cooling circuit (3) is controlled as a function of this dew point.
9. Method according to any of the preceding claims, characterized in that the cooling circuit is controlled such that the temperature of the evaporator on the side of the cooling fluid drops below zero without this evaporator freezing up on the air side.
10. Method according to any of the preceding claims, characterized in that the rotational speed of the motor (4) is adjusted by modifying the frequency of the supply current .
11. Method according to any of the preceding claims, characterized in that the ambient temperature is measured and the rotational speed of the motor (4) is adjusted, taking into account the measured ambient temperature.
12. Method according to claim 11, characterized in that the rotational speed of the motor (4) of the compressor (5) is adjusted such that the lowest gas temperature (LAT) on the outlet of the evaporator (2) is 20°C below the measured ambient temperature, without dropping below 3°C however.
13. Method according to any of the preceding claims, characterized in that the cooling medium is expanded by an expansion valve (7) before the evaporator (2) and in that the overheating is measured after the evaporator (2) and compared to a set value whereby, in case of deviation, the expansion valve (7) will correct this by opening or by closing.
14. Method according to any of the preceding claims, characterized in that, after the heat exchanger (1) and the liquid separator (11) , the gas to be dried is heated in a recuperation heat exchanger (12) by the gas to be dried which is supplied to the first heat exchanger (1) .
15. Device for cool-drying, containing a heat exchanger (1) whose primary part is the evaporator (2) of a cooling circuit (3) which also contains a compressor (5) which is driven by an electric motor (4) , a condenser (6) , an expansion means (7) between the outlet of the condenser
(6) and the inlet of the evaporator (2) , a control device
(16) to control the above-mentioned motor (4) and measuring means (18, 20 or 23) coupled thereto, whereas the secondary part (1A) of the heat exchanger (1) is part of a pipe (9) for the gas, and a liquid separator (11) is erected on the outlet of said heat exchanger (11) , in said pipe (9) , characterized in that the device contains means (15) to adjust the rotational speed of the motor (4) while the control device (16) controls these means (15) as a function of the value measured by the measuring means (18 or 20) .
16. Device according to claim 15, characterized in that the measuring means (20) are provided on the cooling circuit (3) and are means to measure the temperature of the evaporator.
17. Device according to claim 15, characterized in that the measuring means (18) are provided on the cooling circuit
(3) and are means to measure the pressure of the evaporator.
18. Device according to claim 15, characterized in that the measuring means (23) are provided on the pipe (9) for the gas in or downstream to the secondary part (1A) of the heat exchanger (1) , and are means to measure the lowest gas temperature (LAT) .
19. Device according to claim 15, characterized in that the measuring means are provided on the pipe (9) for the gas in or downstream to the secondary part (1A) of the heat exchanger (1), and are means to measure the dew point.
20. Device according to any of claims 15 to 19, characterized in that the means for adjusting the rotational speed of the motor consist of a frequency converter (15) .
21. Device according to any of claims 15 to 20, characterized in that it contains means (22) for measuring the ambient temperature which are also coupled to the control device (16) and in that this control device (16) is such that it adjusts the rotational speed of the motor (4) both as a function of the value measured by the measuring means (18, 20 or 23) and as a function of the ambient temperature measured by the means (22) .
22. Device according to any of claims 15 to 21, characterized in that the control device is a PID control (16), a PI control or a P control.
AMENDED CLAIMS
[received by the International Bureau on 07 October 1999 (07.10.99); original claims 1, 4-22 replaced by new claims 1-19 remaining claims unchanged (5 pages)]
1. Method for cool-drying gas containing water vapor, whereby this gas is guided through the secondary part (1A) of a heat exchanger (1) whose primary part is the evaporator (2) of a cooling circuit (3) which also contains a compressor (5) which is driven by an electric motor (4) , a condenser (6) , an expansion means (7) between the outlet of the condenser (6) and the inlet of the evaporator (2), and whereby the above-mentioned cooling circuit (3) is thus controlled as a function of the load that the cooling capacity is adjusted without any ice being formed in the evaporator (2), characterized in that the cooling circuit (3) is controlled by adjusting the rotational speed of the motor (4) as a function of a measured temperature of the gas or the evaporator.
2. Method according to claim 1, characterized in that the temperature of the evaporator (2) is measured and in that the above-mentioned cooling circuit (3) is controlled as a function of the measured evaporator temperature.
3. Method according to claim 2, characterized in that the rotational speed of the motor (4) is adjusted such that the evaporator temperature is situated 2 to 3°C below the lowest gas temperature (LAT) .
4. Method according to claim 1, characterized in that the lowest gas temperature (LAT) is measured and in that the above-mentioned cooling circuit (3) is controlled as a function of this lowest gas temperature (LAT) .
5. Method according to claim 4, characterized in that the lowest gas temperature (LAT) is measured on the outlet of the secondary part (1A) of the heat exchanger (1) .
6. Method according to claim 1, characterized in that the dew point of the gas is measured and in that the above- mentioned cooling circuit (3) is controlled as a function of this dew point .
7. Method according to any of the preceding claims, characterized in that the cooling circuit is controlled such that the temperature of the evaporator on the side of the cooling fluid drops below zero without this evaporator freezing up on the air side.
8. Method according to any of the preceding claims, characterized in that the rotational speed of the motor
(4) is adjusted by modifying the frequency of the supply current .
9. Method according to any of the preceding claims, characterized in that the ambient temperature is measured and the rotational speed of the motor (4) is adjusted, taking into account the measured ambient temperature .
10. Method according to claim 9, characterized in that the rotational speed of the motor (4) of the compressor
(5) is adjusted such that the lowest gas temperature
AMENDLϋ SHEET (ARTICLE 19) (LAT) on the outlet of the evaporator (2) is 20°C below the measured ambient temperature, without dropping below 3°C however.
11. Method according to any of the preceding claims, characterized in that the cooling medium is expanded by an expansion valve (7) before the evaporator (2) and in that the overheating is measured after the evaporator (2) and compared to a set value whereby, in case of deviation, the expansion valve (7) will correct this by opening or by closing.
12. Method according to any of the preceding claims, characterized in that, after the heat exchanger (1) and the liquid separator (11) , the gas to be dried is heated in a recuperation heat exchanger (12) by the gas to be dried which is supplied to the first heat exchanger (1) .
13. Device for cool-drying, containing a heat exchanger (1) whose primary part is the evaporator (2) of a cooling circuit (3) which also contains a compressor (5) which is driven by an electric motor (4) , a condenser (6) , an expansion means (7) between the outlet of the condenser
(6) and the inlet of the evaporator (2) , a control device (16) to control the above-mentioned motor (4) and measuring means (18, 20 or 23) coupled thereto, whereas the secondary part (1A) of the heat exchanger (1) is part of a pipe (9) for the gas, and a liquid separator (11) is erected on the outlet of said heat exchanger (11) , in said pipe (9) , characterized in that the device contains means (15) to adjust the rotational speed of the motor (4) while the control device (16) controls these means (15) as a function of a temperature of the gas or the evaporator measured by the measuring means (18 or 20) .
14. Device according to claim 13, characterized in that the temperature measuring means (20) are provided on the cooling circuit (3) and are means to measure the temperature of the evaporator.
15. Device according to claim 13, characterized in that the temperature measuring means (23) are provided on the pipe (9) for the gas in or downstream to the secondary part (1A) of the heat exchanger (1) , and are means to measure the lowest gas temperature (LAT) .
16. Device according to claim 13, characterized in that the measuring means are provided on the pipe (9) for the gas in or downstream to the secondary part (1A) of the heat exchanger (1) , and are means to measure the dew point .
17. Device according to any of claims 13 to 16, characterized in that the means for adjusting the rotational speed of the motor consist of a frequency converter (15) .
18. Device according to any of claims 13 to 17, characterized in that it contains means (22) for measuring the ambient temperature which are also coupled to the control device (16) and in that this control device (16) is such that it adjusts the rotational speed of the motor (4) both as a function of the value measured by the measuring means (18, 20 or 23) and as a function of the ambient temperature measured by the means (22) .
19. Device according to any of claims 13 to 18, characterized in that the control device is a PID control (16) , a PI control or a P control.
A ENDE T '!Λ1 C
PCT/BE1999/000059 1998-05-26 1999-05-11 Method and device for cool-drying WO1999061135A1 (en)

Priority Applications (12)

Application Number Priority Date Filing Date Title
CA002333152A CA2333152C (en) 1998-05-26 1999-05-11 Method and device for cool-drying
JP2000550583A JP2002516168A (en) 1998-05-26 1999-05-11 Cooling drying method and apparatus
NZ508321A NZ508321A (en) 1998-05-26 1999-05-11 Method and device for cool-drying
US09/700,701 US6460359B1 (en) 1998-05-26 1999-05-11 Method and device for cool-drying
AU39219/99A AU744515B2 (en) 1998-05-26 1999-05-11 Method and device for cool-drying
DK99921993T DK1089803T3 (en) 1998-05-26 1999-05-11 Process and apparatus for cooling drying
EP99921993A EP1089803B1 (en) 1998-05-26 1999-05-11 Method and device for cool-drying
HU0204171A HU222974B1 (en) 1998-05-26 1999-05-11 Method and device for cool-drying gas containing water vapor
DE69905042T DE69905042T2 (en) 1998-05-26 1999-05-11 METHOD AND DEVICE FOR COOLING DRYING
AT99921993T ATE231409T1 (en) 1998-05-26 1999-05-11 METHOD AND DEVICE FOR COOL DRYING
KR1020007013235A KR20010043805A (en) 1998-05-26 1999-05-11 Method and device cool-drying
NO20005957A NO317887B1 (en) 1998-05-26 2000-11-24 Dress drying gas with water vapor content

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BE9800397A BE1011932A3 (en) 1998-05-26 1998-05-26 Method and device for cool drying
BE9800397 1998-05-26
BE9800687A BE1012132A6 (en) 1998-05-26 1998-09-24 Method and device for cooling drying.
BE9800687 1998-09-24

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EP (1) EP1089803B1 (en)
JP (1) JP2002516168A (en)
KR (1) KR20010043805A (en)
CN (1) CN1143724C (en)
AT (1) ATE231409T1 (en)
AU (1) AU744515B2 (en)
BE (1) BE1012132A6 (en)
CA (1) CA2333152C (en)
CZ (1) CZ20004374A3 (en)
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EP1240936A1 (en) * 2001-03-12 2002-09-18 truffi International S.A. Compressed air drier with cooling cycle and method for using such a drier
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US7175136B2 (en) 2003-04-16 2007-02-13 The Boeing Company Method and apparatus for detecting conditions conducive to ice formation
NL1023791C2 (en) 2003-07-01 2005-01-04 Lely Entpr Ag Milking installation.
US7260949B2 (en) * 2004-10-20 2007-08-28 Ingersoll-Rand Company Compressor variable dryer system
BE1016430A3 (en) * 2005-02-01 2006-10-03 Atlas Copco Airpower Nv DEVICE FOR DRYING GAS.
BE1016649A3 (en) * 2005-06-17 2007-04-03 Atlas Copco Airpower Nv IMPROVED METHOD FOR REFRIGERATING.
BE1016734A3 (en) * 2005-08-25 2007-05-08 Atlas Copco Airpower Nv IMPROVED DEVICE FOR COOLING.
BE1017362A3 (en) * 2006-11-10 2008-07-01 Atlas Copco Airpower Nv METHOD FOR REFRIGERATING.
US8006503B2 (en) * 2006-11-15 2011-08-30 Ingersoll-Rand Company Energy recovery system and method for a refrigerated dehumidification process
KR101293382B1 (en) * 2008-10-27 2013-08-05 가부시키가이샤 다쯔노 Gasoline vapor recovery device
US20130014527A1 (en) * 2011-07-12 2013-01-17 A.P. Moller - Maersk A/S Temperature control in a refrigerated transport container
CN103245481B (en) * 2013-05-07 2015-07-15 杭州电子科技大学 Frequency conversion technology based detection method for air resistance characteristic of large-scale variable-load heat exchanger
PT3140025T (en) * 2014-05-09 2019-02-04 Nv Atlas Copco Airpower Method and device for cool-drying a gas with circulating cooling liquid with bypass line
CN104141604A (en) * 2014-06-30 2014-11-12 深圳市英威腾电气股份有限公司 Frequency converter special for air compressor and air compressor variable-frequency drive control system
CN105129743B (en) * 2015-09-14 2018-04-20 河南平高电气股份有限公司 One kind is used for SF6The de-watering apparatus of gas concentration unit
US10674752B2 (en) * 2016-02-04 2020-06-09 Jds Consulting Vapor pressure control system
DE102017116198A1 (en) * 2017-07-18 2019-01-24 DÖLCO GmbH Method for operating an evaporator and cooling device
CN109137145A (en) * 2018-07-16 2019-01-04 绍兴百慧科技有限公司 A kind of solvent recovery unit of solution electrostatic spinning
CN109140842B (en) * 2018-09-07 2020-12-11 北京京仪自动化装备技术有限公司 Method and device for controlling electronic expansion valve based on superheat degree
CN110953176A (en) * 2018-09-26 2020-04-03 上海梅山钢铁股份有限公司 Adjustment control method for improving dew point temperature of compressed air
US11709004B2 (en) 2020-12-16 2023-07-25 Lennox Industries Inc. Method and a system for preventing a freeze event using refrigerant temperature

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4392877A (en) * 1981-10-06 1983-07-12 Phillips Petroleum Company Constraint control of a fractional distillation process
DE3522974A1 (en) * 1985-06-27 1987-01-02 Via Gmbh Hot-gas bypass control for the refrigerant circuit of a freezing compressed-air dryer or the like
DE8712812U1 (en) * 1987-09-23 1989-02-16 VIA Gesellschaft für Verfahrenstechnik mbH, 4000 Düsseldorf Compressed air dryer
FR2648055A1 (en) * 1989-06-08 1990-12-14 Mouren Alexandre Improvement of the drying of gases by refrigeration method with variable dew point

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4459519A (en) * 1974-06-24 1984-07-10 General Electric Company Electronically commutated motor systems and control therefor
US5035119A (en) * 1984-08-08 1991-07-30 Alsenz Richard H Apparatus for monitoring solenoid expansion valve flow rates
JPH01153324A (en) * 1987-12-10 1989-06-15 Diesel Kiki Co Ltd Vehicle air-conditioning device
US5065593A (en) * 1990-09-18 1991-11-19 Electric Power Research Institute, Inc. Method for controlling indoor coil freeze-up of heat pumps and air conditioners
US5203179A (en) * 1992-03-04 1993-04-20 Ecoair Corporation Control system for an air conditioning/refrigeration system
DE19736818A1 (en) * 1997-08-23 1999-02-25 Behr Gmbh & Co Method and device for evaporator icing-protected air conditioning control
US6161393A (en) * 1998-02-14 2000-12-19 Bascobert; Rene F Control system for mobile air conditioning apparatus
US6029465A (en) * 1998-02-14 2000-02-29 Bascobert; Rene F Control system for mobile air conditioning apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4392877A (en) * 1981-10-06 1983-07-12 Phillips Petroleum Company Constraint control of a fractional distillation process
DE3522974A1 (en) * 1985-06-27 1987-01-02 Via Gmbh Hot-gas bypass control for the refrigerant circuit of a freezing compressed-air dryer or the like
DE8712812U1 (en) * 1987-09-23 1989-02-16 VIA Gesellschaft für Verfahrenstechnik mbH, 4000 Düsseldorf Compressed air dryer
FR2648055A1 (en) * 1989-06-08 1990-12-14 Mouren Alexandre Improvement of the drying of gases by refrigeration method with variable dew point

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6516622B1 (en) 2000-06-13 2003-02-11 Belair Technologies, Llc Method and apparatus for variable frequency controlled compressor and fan
US6817198B2 (en) 2000-06-13 2004-11-16 Belair Technologies, Llc Method and apparatus for variable frequency controlled compressor and fan
EP1240936A1 (en) * 2001-03-12 2002-09-18 truffi International S.A. Compressed air drier with cooling cycle and method for using such a drier
WO2011116434A1 (en) * 2010-02-24 2011-09-29 Atlas Copco Airpower, Naamloze Vennootschap Method and device for cool drying a gas
BE1019199A3 (en) * 2010-02-24 2012-04-03 Atlas Copco Airpower Nv METHOD AND APPARATUS FOR COOLING GAS.
US10561980B2 (en) 2010-02-24 2020-02-18 Atlas Copco Airpower, Naamloze Vennootschap Method and device for cool drying a gas
US9476621B2 (en) 2010-11-16 2016-10-25 Atlas Copco Airpower, Naamloze Vennootschap Device and method for cool drying a gas
CN102022873A (en) * 2010-12-01 2011-04-20 上海共和真空技术有限公司 Water flow adjusting device for refrigeration system of freeze-dryer
WO2013132046A1 (en) * 2012-03-09 2013-09-12 Visteon Global Technologies, Inc. Device and method for icing prevention regulation for heat pump evaporators
US10914504B2 (en) 2012-03-09 2021-02-09 Audi Ag Device and method for icing prevention regulation for heat pump evaporators
CN105229393A (en) * 2014-02-24 2016-01-06 伸和控制工业股份有限公司 Refrigerating plant
CN110762954A (en) * 2019-10-22 2020-02-07 万海东 Energy-saving drying system and working method thereof

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PL344468A1 (en) 2001-11-05
EP1089803B1 (en) 2003-01-22
DE69905042D1 (en) 2003-02-27
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AU3921999A (en) 1999-12-13
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CN1307499A (en) 2001-08-08
NO317887B1 (en) 2004-12-27
US6460359B1 (en) 2002-10-08
HUP0204171A2 (en) 2003-03-28
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CN1143724C (en) 2004-03-31
EP1089803A1 (en) 2001-04-11

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