Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28B—STEAM OR VAPOUR CONDENSERS
  • F28B1/00—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser
  • F28B1/06—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser using air or other gas as the cooling medium
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B40/00—Subcoolers, desuperheaters or superheaters
  • F25B40/02—Subcoolers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B49/00—Arrangement or mounting of control or safety devices
  • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
  • F25B49/027—Condenser control arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D5/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, using the cooling effect of natural or forced evaporation
  • F28D5/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, using the cooling effect of natural or forced evaporation in which the evaporating medium flows in a continuous film or trickles freely over the conduits
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F25/00—Component parts of trickle coolers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2339/00—Details of evaporators; Details of condensers
  • F25B2339/04—Details of condensers
  • F25B2339/041—Details of condensers of evaporative condensers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
  • F25B2400/07—Details of compressors or related parts
  • F25B2400/075—Details of compressors or related parts with parallel compressors

Definitions

• the present invention relates to a method for operating a refrigeration system
• a refrigerant circuit in which to condensate the refrigerant in said circuit a cooling water circuit is used, incorporating an evaporative condenser, evaporation losses from said condenser being topped up with the aid of make-up water being supplied to the condenser via a heat exchanger with the aid of which the liquid refrigerant of the refrigeration circuit is subcooled.
• cooling circuit normally incorporates a liquid vessel from which refrigerant is supplied to an evaporator. In the latter, the refrigerant evaporates
• the evaporative condenser may also comprise a combination of a cooling tower and a water-cooled condenser.
• a method in accordance with the type described in the preamble is known from Swiss Patent 392,576. According to this known method, cooling is carried out using a refrigerant which flows into a closed cooling circuit which includes an expansion device and a compressor and a heat exchanger. Cooling water which is heated in the heat exchanger and gives off the heat to an evaporative condenser also
• makeup water is metered more or less continuously into the receptacle tank of the condenser.
• the make-up water is brought into the water circulation circuit via a recirculation pump.
• the make-up water is generally fed in at a temperature of from 10 to 15°C
• the known method utilizes the relatively cold make-up water in the high-grade section of a cooling circuit.
• the actual heat exchange which takes place between the relatively cold make-up water and the refrigerant in the cooling circuit is not measured.
• the object of the present invention is to provide a method in which the heat exchange which takes place between the relatively cold make-up water and the refrigerant can be used to gain more information about the performance and efficiency of the cooling system.
• make-up water from the source is fed to the condenser via the heat exchanger.
• the cooling capacity Qo can be calculated using a flow meter for the make-up water and by measuring the temperatures of the make-up water. Both the flow measurement of the make-up water and the temperature measurements can be carried out with a very high level of accuracy. This also means that the instantaneous cooling capacity Qo can be calculated very accurately.
• the cooling capacity has to be calculated on the basis of a measurement of the flow of refrigerant which flows from the liquid vessel to the evaporator. The fact that a meter has to be placed in this line means an additional restriction in this line. Moreover, it may be that refrigerant flows through this line not only in the liquid phase but also in the gas phase.
• the measures according to the present invention replace the complex, expensive and inaccurate measurement of the refrigerant flow with an accurate measurement, which is easy to carry out, of the make-up water flow and the temperature change of the make-up water and the refrigerant.
• the method comprises the following steps: - measuring the electric power (Pe) consumed for the purpose of operating the compressor(s) from the cooling system,
• the electric power (Pe) consumed can also be measured with a high level of accuracy.
• the instantaneous performance, i.e. the COP, of the cooling system can be calculated in a simple manner. This in turn means that a user always has information about the instantaneous performance of the cooling plant.
• this method comprises the following steps:
• the method comprises the following steps:
• the refrigerant is injected from the liquid vessel to the said heat exchanger in a modulating manner. This is because the make-up water is fed to the water receptacle tank virtually continuously. If the refrigerant is then introduced from the liquid vessel into the cooling circuit via a line which is alternately open and closed, no refrigerant flows through the heat exchanger when the line is closed, and at those moments the possible cooling potential of the make-up water supplied is still lost.
• the present invention moreover relates to a cooling system intended to carry out the method according to the present invention.
• Figure 1 shows an overview of an industrial cooling plant according to the prior art.
• Figure 2 shows a diagrammatic overview of a cooling plant according to the present invention.
• Figure 3 shows the log P-H diagram of a possible cooling system according to the present invention in which NH 3 is used as the refrigerant.
• FIG 1 diagrammatically depicts a cooling plant 1 which is much used in the prior art.
• This cooling system comprises a cooling medium circuit including a liquid vessel 2, an evaporator 3 and a screw-type compressor 4 and an oil cooler 5.
• the refrigerant is supplied to an evaporative condenser 6 with the aid of a screw-type compressor.
• This evaporative condenser is fed with the aid of water from a water receptacle tank 7.
• make-up water is supplied, with the aid of a line 8, from a source (not shown).
• the compression step in the refrigerant circuit is carried out by means of screw-type compressors. These are cooled with the aid of oil coolers to which liquid refrigerant is regularly supplied from the liquid vessel using a thermosyphon system. Part of the refrigerant will evaporate as a result of heat exchange with the oil coolers. The heated refrigerant is then returned to the liquid vessel.
• FIG. 2 shows a cooling system 20 according to the present invention.
• the cooling device 20 comprises a heat exchanger 21.
• the heat exchanger 21 is connected, on the one hand, to the feed line for springwater or tap water 22 and is connected, on the other hand, to the outlet line 23 from the liquid vessel 2.
• the refrigerant will be cooled by the relatively cold make-up water before it is delivered to the evaporator 3.
• the relatively cold make-up water is used in the relatively "high-grade" section of the cooling circuit.
• the refrigerant can be injected from the liquid vessel to the said heat exchanger in a modulating manner.
• the cooling system 20 is equipped with two compressors. It is clear that the system may also comprise more compressors. Each of the compressors is provided with a measuring element 24, with the aid of which the electric power consumed by the compressors can be measured.
• the evaporative condenser 6 is also provided with a measuring element 25, in order to be able to measure the electric power consumed by the fan of the evaporative condenser 6.
• the method according to the present invention it is possible to measure the volume of make-up water which is supplied to the water receptacle tank 7 through the line 8. Moreover, the temperature of the make-up water is measured before the make-up water in the line 8 flows into the heat exchanger and after the make-up water has flowed out of the heat exchanger 21. These temperature measurements, as well as the flow measurement of the make-up water, together provide the total amount of heat supplied to the water. Moreover, in the line 23 it is possible to measure the difference in temperature of the refrigerant before the refrigerant in the line 23 is cooled by the make-up water and after it has been cooled with the make-up water. The refrigerant mass flow can be determined on the basis of these measurements and the calculated amount of heat supplied to the water.
• the instantaneous cooling capacity Qo can be determined using the measured value for the suction pressure Po and the condenser pressure Pc and the refrigerant mass flow determined. This therefore means that a cooling capacity of the cooling system 20 is known at all times. This instantaneous cooling capacity Qo can be displayed as required, for example on a control panel.
• This COP is defined by dividing the instantaneous cooling capacity Qo by the value for the electric power Pe consumed.
• This instantaneous performance, i.e. the COP can also be displayed as required.
• the present invention can also be used to optimize the supply of make-up water to the evaporative condenser. This is achieved as follows: on the basis of a one-off hardness measurement of the make-up water, a desired thickening factor is determined, for example 2.
• the thickening factor is the maximum permissible increase in the quantity of salts in the water which is situated in the water receptacle tank. During use of the system 20, the volume of water in the water receptacle tank
• the temperature difference in the refrigerant before it flows into the heat exchanger and after it has flowed out of the heat exchanger is measured.
• the refrigerant mass flow is determined using the calculated amount of heat which is supplied to the water in the heat exchanger 21.
• the instantaneous cooling capacity Qo and the load of the condenser Qc are respectively determined. Then, the correct volume of make-up water is determined on the basis of the
• the volume of make-up water to be supplied which flows to the receptacle tank per unit time is adjusted on the basis of the calculated volume of make-up water.
• the appropriate cooling circuit is illustrated in the log P-H diagram as represented in Figure 3.
• the refrigerant mass flow which circulates per hour is:
• Another possible advantageous application is in water-cooled cooling systems for air-conditioning purposes. These systems are generally combined with cooling towers. By positioning a liquid subcooler between the condenser and the evaporator upstream of the injection component (thermostatic expansion valve, high-pressure float or throttling port), it is possible to achieve the same resultant as that described above and in practice to achieve increases in capacity of from 8 to 10%. Naturally, the control would have to take place in the same way as that described above.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Devices That Are Associated With Refrigeration Equipment (AREA)
• Other Air-Conditioning Systems (AREA)
• Treatment Of Water By Ion Exchange (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)
• Sorption Type Refrigeration Machines (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1997
  • 1997-10-23 NL NL1007346A patent/NL1007346C2/nl not_active IP Right Cessation
• 1998
  • 1998-10-23 BR BR9813258-0A patent/BR9813258A/pt not_active IP Right Cessation
  • 1998-10-23 EP EP98951823A patent/EP1025404B1/fr not_active Expired - Lifetime
  • 1998-10-23 DK DK98951823T patent/DK1025404T3/da active
  • 1998-10-23 ES ES98951823T patent/ES2175805T3/es not_active Expired - Lifetime
  • 1998-10-23 AU AU97666/98A patent/AU9766698A/en not_active Abandoned
  • 1998-10-23 AT AT98951823T patent/ATE217410T1/de not_active IP Right Cessation
  • 1998-10-23 WO PCT/NL1998/000609 patent/WO1999020958A1/fr active IP Right Grant
  • 1998-10-23 DE DE69805319T patent/DE69805319T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

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