WO2006022541A1 - A method and a cooling system in which a refrigerant is used as a cooling agent and as a defrosting agent - Google Patents

A method and a cooling system in which a refrigerant is used as a cooling agent and as a defrosting agent Download PDF

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Publication number
WO2006022541A1
WO2006022541A1 PCT/NL2005/000610 NL2005000610W WO2006022541A1 WO 2006022541 A1 WO2006022541 A1 WO 2006022541A1 NL 2005000610 W NL2005000610 W NL 2005000610W WO 2006022541 A1 WO2006022541 A1 WO 2006022541A1
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WIPO (PCT)
Prior art keywords
cooler
refrigerant
cooling
parallel
defrosting
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/NL2005/000610
Other languages
French (fr)
Inventor
Johannes Pieter Van Der Stoel
Ronald Jacobus Franciscus Vermeeren
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Original Assignee
Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
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Publication of WO2006022541A1 publication Critical patent/WO2006022541A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • 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
    • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/02—Defrosting cycles
    • 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
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/06—Removing frost
    • 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
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • 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—Component parts or details not otherwise provided for in this subclass
    • F25B2400/07—Details of compressors or related parts
    • F25B2400/075—Details of compressors or related parts with parallel compressors
    • 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
    • F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit

Definitions

  • the present invention relates to a method in which a refrigerant is used as a cooling agent and as a defrosting agent, and a cooling system for carrying out said method.
  • Coolers that are industrially applied are defrosted periodically to remove ice from the cooler, which ice is formed inside the coolers as a result of moisture present in the air to be cooled. Such periodical defrosting is needed to ensure that the coolers continue to perform at an appropriate level.
  • defrosting methods are known in the art. It is, for instance, known that coolers, in which NH3 is used as the cooling agent, can be defrosted by leading hot NH3 gas from the compressor into the cooler to be defrosted. However, such a defrosting method is relatively time-consuming making its application less attractive.
  • Another way to defrost a cooler is to provide the cooler with a separate circuit through which heated glycol can be recirculated. It will be understood that such a method is expensive since it requires a separate circuit to be arranged in the cooler.
  • Object of the present invention is to provide a method in which in an effective and relatively simple manner a refrigerant can be used as a cooling agent and as a defrosting agent. Surprisingly, it has been found that this object can be realised by passing the refrigerant during cooling at a high pressure through the cooler and reducing the pressure of the refrigerant during defrosting of the cooler.
  • the present invention relates to a method for cooling a medium and defrosting a second ary side of a cooler, in which a refrigerant is used as a cooling agent and as a defrosting agent, wherein the cooling of the medium is established by passing the refrigerant at a high pressure through a primary side of the cooler, whereby the medium to be cooled is passed through the secondary side of the cooler, and wherein the defrosting of the cooler is established by decreasing the gas pressure of the refrigerant in the primary side of the cooler to such an extent that ice which is adhered to the secondary side of the cooler is released.
  • a major advantage of the present invention is the fact that the energy which is needed to decrease the gas pressure of the refrigerant brings about the production of cold, which is attractive from energy-consumption perspective, and which clearly is not the case in the known defrosting processes.
  • the gas pressure of the refrigerant in the primary side of the cooler is decreased by means of a compressor which is arranged downstream the cooler.
  • the flow of refrigerant to the cooler is reduced during defrosting when compared to the flow of refrigerant as applied during cooling.
  • This can, for instance, be realised by at least partly closing expansion means that are located upstream the cooler.
  • the gas pressure of the refrigerant in the primary side of the cooler is in such a range that the equivalent boiling temperature of the refrigerant is lower than -5O 0 C. More preferably, the gas pressure of the refrigerant in the primary side of the cooler is in such a range that the equivalent boiling temperature of the refrigerant is lower than -60 0 C.
  • the refrigerant circulation rate is preferably in the range of from 1-10, and more preferably in the range of from 3-5.
  • the refrigerant circulation rate is defined as the ratio of the amount of refrigerant mass which is led into the cooler and the amount of refrigerant vapour mass which comes out of the cooler.
  • a refrigerant can be used which enables the ice to be removed from the secondary side of the cooler.
  • Suitable refrigerants include for instance liquid nitrogen, refrigerants like R14, R23, R32, R50, R170, R1150 and R410A, and CO 2 -
  • the refrigerant to be used in accordance with the present invention comprises CO2.
  • use is made of one type of refrigerant.
  • the gas pressure of CO2 present in the primary side of the cooler is reduced to such extent that dry ice is obtained in the primary side of the cooler, which is accompanied with such a low temperature that ice adhered to the secondary side of the cooler is released.
  • the refrigerant can alternately or simultaneously be used as a cooling agent and as a defrosting agent.
  • the refrigerant can alternately be used as a cooling agent and as a defrosting agent when use is made of a two-stage process, wherein in a first stage the cooling takes place, and in a second stage the defrosting of the cooler takes place.
  • it can also be the case to carry out the method as one- stage process wherein cooling and defrosting is established simultaneously by using a decreased gas pressure of the refrigerant.
  • the refrigerant is preferably simultaneously used as a cooling agent and as a defrosting agent.
  • coolers can be used in accordance with the present invention. Suitable coolers include finned tubes, shell and tube heat exchangers, and contact freezers which comprise a number of elements in between which the material to be cooled can be arranged.
  • the present method is suitably integrated with a method for cooling a material located between the elements of the contact freezer.
  • the cooler is connected to two compressors which are connected in parallel at cooling conditions so as to form a two stage refrigeration system, and wherein the compressors are connected in series at defrost conditions so as to form a three stage refrigeration system.
  • the present invention further relates to a cooling system for carrying out the method according to the present invention, which system comprises a cooler which is provided with means to allow refrigerant to pass through the primary side of the cooler, means to allow the medium to be cooled to pass through the secondary side of the cooler, which cooler is connected to two or more compressors for decreasing the pressure of the refrigerant in the primary side of the cooler, whereby the suction sides of the compressors can alternately be connected in parallel and in series to the cooler or in parallel and in a combination of in parallel and in series to the cooler, means for connecting the compressors alternately in parallel and in series to the cooler or means for connecting the compressors alternately in parallel and in a combination of in parallel and in series to the cooler, and a heat exchanger to which the high pressure sides of the compressors can alternately be connected in parallel and in series or in parallel and in a combination of in parallel and in series, which heat exchanger is connected to a circuit for feeding the refrigerant into the cooler.
  • the heat exchanger is connected to an expansion device
  • the cooling system comprises a plurality of coolers which are connected to the compressor and the circuit, whereby the coolers are arranged in parallel.
  • the cooling system can for instance comprise a contact freezer or a plurality of contact freezers.
  • Cooling systems usually consist of one or more compressors, one or more evaporators, one or more condensers and one or more expansion devices.
  • CO2 cooling systems are usually two-stage installations in which CO2 is the refrigerant for the low-temperature stage.
  • An example of the low-temperature stage of a CO2 cooling system in accordance with the present invention is depicted in Figure 1.
  • Figure 1 also shows a defrost compressor [11] with ducts, a liquid-vapour separator [10] and valves [9].
  • the valves [9] of the defrost circuit are closed and the evaporators [7] supply cold to the air or the product to be cooled.
  • liquid refrigerant CO2
  • the heat from the product and/or the air to be cooled causes a (partial) evaporation of the refrigerant.
  • the two-phase mixture flows through the one-way valves [8] to the vessel [4], where liquid and vapour are separated.
  • the vapour is extracted from the vessel by suction using a compressor [I].
  • the compressor [1] the refrigerant vapour is compressed to a higher pressure, temperature and boiling point.
  • the cascade condenser [2] the vapour then condenses. Subsequently, the liquid flows through expansion device [3] into the vessel [4].
  • Condensation of refrigerant takes place in the cascade condenser [2].
  • the condensation heat causes the evaporation of refrigerant in the high- temperature stage of the cooling system.
  • this refrigerant vapour is brought to a temperature and boiling point which is higher than the temperature of the environment.
  • the refrigerant concerned condenses against the environment and the liquid flows through an expansion device into the cascade condenser [2].
  • the expansion device [6] which is located upstream the evaporator will be closed or in any case throttled as far as necessary so that less refrigerant flows into the evaporator.
  • a control valve will take over this function. Consequently, the valve [9] downstream the evaporator [7] will be opened and the defrost compressor [11] will be started.
  • the capacity of this compressor [11] should be large enough to extract more vapour than the amount of vapour that is formed due to the heat load on the evaporator [7]. In this way, a decrease of refrigerant pressure will be realised, resulting in a decrease of temperature and boiling point.
  • FIG. 2 An illustration of this process is shown in Figure 2 wherein CO2 is used as refrigerant.
  • the flat part of the curve refers to the transition from liquid to solid CO 2 (dry ice).
  • the transition to solid CO2 does not damage the evaporator due to expansion.
  • a one-way valve [8] between the vessel [4] and the evaporator [7] prevents the vapour flowing from the vessel [4] to the evaporator [7] during defrosting.
  • the discharge vapour of the defrost compressor [11] is led to the vessel [4].
  • the defrost compressor [11] will be switched off and the expansion device [6] will be opened again.
  • This method of ice removal is very energy efficient. No heat will be brought in into the product or the coldstore. The energy that is used for defrosting also leads to a further cooling of the product and the evaporator [7].
  • the defrost compressor [11] can also be used as refrigeration compressor for useful cold supply.
  • Figure 3 illustrates how the addition of only a few ducts [12, 13] and valves [14, 15, 16] enables the defrost compressor to be used as refrigeration compressor.
  • valve [14] is opened and the defrost compressor extracts refrigerant vapour from vessel [4] through duct [12].
  • the discharge vapour flows through valve [16] and duct [13] to the cascade condensor.
  • Valve [15] is closed.
  • valves [14] and [16] are closed and valve [15] is opened, which gives the same result as in figure 1.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Defrosting Systems (AREA)

Abstract

The invention provides a method for cooling a medium and defrosting a secondary side of a cooler (7), in which a refrigerant is used as a cooling agent and as a defrosting agent, wherein the cooling of the medium is established by passing the refrigerant at a high pressure through a primary side of the cooler (7), whereby the medium to be cooled is passed through the secondary side of the cooler, and wherein the defrosting of the cooler is established by decreasing the gas pressure of the refrigerant in the primary side of the cooler to such an extent that ice which is adhered to the secondary side of the cooler is released. The invention further comprises a cooling system for carrying out said method.

Description

Title: A method and a cooling system in which a refrigerant is used as a cooling agent and as a defrosting agent
The present invention relates to a method in which a refrigerant is used as a cooling agent and as a defrosting agent, and a cooling system for carrying out said method.
Coolers that are industrially applied are defrosted periodically to remove ice from the cooler, which ice is formed inside the coolers as a result of moisture present in the air to be cooled. Such periodical defrosting is needed to ensure that the coolers continue to perform at an appropriate level.
A variety of defrosting methods are known in the art. It is, for instance, known that coolers, in which NH3 is used as the cooling agent, can be defrosted by leading hot NH3 gas from the compressor into the cooler to be defrosted. However, such a defrosting method is relatively time-consuming making its application less attractive.
Another way to defrost a cooler is to provide the cooler with a separate circuit through which heated glycol can be recirculated. It will be understood that such a method is expensive since it requires a separate circuit to be arranged in the cooler.
It is further possible to defrost coolers electrically by using electric elements arranged on the secondary side of a cooler through which the air passes. Such system has the drawback that much energy is required to bring about an effective removal of ice, whereas in addition hot spots may be created which could weaken the cooler.
Yet another alternative approach is based on sprinkling the cooler with hot water or glycol. However, this approach has the disadvantage that products may be damaged by way of pollution or ice adherence. Object of the present invention is to provide a method in which in an effective and relatively simple manner a refrigerant can be used as a cooling agent and as a defrosting agent. Surprisingly, it has been found that this object can be realised by passing the refrigerant during cooling at a high pressure through the cooler and reducing the pressure of the refrigerant during defrosting of the cooler.
Accordingly, the present invention relates to a method for cooling a medium and defrosting a second ary side of a cooler, in which a refrigerant is used as a cooling agent and as a defrosting agent, wherein the cooling of the medium is established by passing the refrigerant at a high pressure through a primary side of the cooler, whereby the medium to be cooled is passed through the secondary side of the cooler, and wherein the defrosting of the cooler is established by decreasing the gas pressure of the refrigerant in the primary side of the cooler to such an extent that ice which is adhered to the secondary side of the cooler is released.
A major advantage of the present invention is the fact that the energy which is needed to decrease the gas pressure of the refrigerant brings about the production of cold, which is attractive from energy-consumption perspective, and which clearly is not the case in the known defrosting processes.
Suitably, the gas pressure of the refrigerant in the primary side of the cooler is decreased by means of a compressor which is arranged downstream the cooler.
In a preferred embodiment of the present invention, the flow of refrigerant to the cooler is reduced during defrosting when compared to the flow of refrigerant as applied during cooling. This can, for instance, be realised by at least partly closing expansion means that are located upstream the cooler.
Preferably, the gas pressure of the refrigerant in the primary side of the cooler is in such a range that the equivalent boiling temperature of the refrigerant is lower than -5O0C. More preferably, the gas pressure of the refrigerant in the primary side of the cooler is in such a range that the equivalent boiling temperature of the refrigerant is lower than -600C.
In the method according to the present invention, the refrigerant circulation rate is preferably in the range of from 1-10, and more preferably in the range of from 3-5. In the context of the present invention the refrigerant circulation rate is defined as the ratio of the amount of refrigerant mass which is led into the cooler and the amount of refrigerant vapour mass which comes out of the cooler.
In accordance with the present invention a refrigerant can be used which enables the ice to be removed from the secondary side of the cooler.
Suitable refrigerants that can be used include for instance liquid nitrogen, refrigerants like R14, R23, R32, R50, R170, R1150 and R410A, and CO2-
Preferably, the refrigerant to be used in accordance with the present invention comprises CO2.
Preferably, use is made of one type of refrigerant.
When use is made of CO2 as refrigerant, the gas pressure of CO2 present in the primary side of the cooler is reduced to such extent that dry ice is obtained in the primary side of the cooler, which is accompanied with such a low temperature that ice adhered to the secondary side of the cooler is released.
In the method according to the present invention, the refrigerant can alternately or simultaneously be used as a cooling agent and as a defrosting agent. The refrigerant can alternately be used as a cooling agent and as a defrosting agent when use is made of a two-stage process, wherein in a first stage the cooling takes place, and in a second stage the defrosting of the cooler takes place. However, it can also be the case to carry out the method as one- stage process wherein cooling and defrosting is established simultaneously by using a decreased gas pressure of the refrigerant. In accordance with the present invention the refrigerant is preferably simultaneously used as a cooling agent and as a defrosting agent.
Various types of coolers can be used in accordance with the present invention. Suitable coolers include finned tubes, shell and tube heat exchangers, and contact freezers which comprise a number of elements in between which the material to be cooled can be arranged.
When the cooler used in accordance with the present invention is a contact freezer, the present method is suitably integrated with a method for cooling a material located between the elements of the contact freezer. In another preferred embodiment of the present invention, the cooler is connected to two compressors which are connected in parallel at cooling conditions so as to form a two stage refrigeration system, and wherein the compressors are connected in series at defrost conditions so as to form a three stage refrigeration system. The present invention further relates to a cooling system for carrying out the method according to the present invention, which system comprises a cooler which is provided with means to allow refrigerant to pass through the primary side of the cooler, means to allow the medium to be cooled to pass through the secondary side of the cooler, which cooler is connected to two or more compressors for decreasing the pressure of the refrigerant in the primary side of the cooler, whereby the suction sides of the compressors can alternately be connected in parallel and in series to the cooler or in parallel and in a combination of in parallel and in series to the cooler, means for connecting the compressors alternately in parallel and in series to the cooler or means for connecting the compressors alternately in parallel and in a combination of in parallel and in series to the cooler, and a heat exchanger to which the high pressure sides of the compressors can alternately be connected in parallel and in series or in parallel and in a combination of in parallel and in series, which heat exchanger is connected to a circuit for feeding the refrigerant into the cooler. Preferably, the heat exchanger is connected to an expansion device, which expansion device is connected to the cooler.
In a preferred embodiment of the present invention, the cooling system comprises a plurality of coolers which are connected to the compressor and the circuit, whereby the coolers are arranged in parallel. The cooling system can for instance comprise a contact freezer or a plurality of contact freezers.
Cooling systems usually consist of one or more compressors, one or more evaporators, one or more condensers and one or more expansion devices. CO2 cooling systems are usually two-stage installations in which CO2 is the refrigerant for the low-temperature stage. An example of the low-temperature stage of a CO2 cooling system in accordance with the present invention is depicted in Figure 1. Figure 1 also shows a defrost compressor [11] with ducts, a liquid-vapour separator [10] and valves [9].
During normal operation of the cooling system, the valves [9] of the defrost circuit are closed and the evaporators [7] supply cold to the air or the product to be cooled. To this purpose liquid refrigerant (CO2) is pumped from the vessel [4] by means of the pump [5], through the expansion devices [6] into the evaporators [7]. The heat from the product and/or the air to be cooled causes a (partial) evaporation of the refrigerant. The two-phase mixture flows through the one-way valves [8] to the vessel [4], where liquid and vapour are separated. The vapour is extracted from the vessel by suction using a compressor [I]. In the compressor [1] the refrigerant vapour is compressed to a higher pressure, temperature and boiling point. In the cascade condenser [2] the vapour then condenses. Subsequently, the liquid flows through expansion device [3] into the vessel [4].
Condensation of refrigerant takes place in the cascade condenser [2]. The condensation heat causes the evaporation of refrigerant in the high- temperature stage of the cooling system. By way of a (not depicted ) high- temperature stage compressor, this refrigerant vapour is brought to a temperature and boiling point which is higher than the temperature of the environment. The refrigerant concerned condenses against the environment and the liquid flows through an expansion device into the cascade condenser [2].
As soon as an evaporator has to be defrosted, the expansion device [6] which is located upstream the evaporator will be closed or in any case throttled as far as necessary so that less refrigerant flows into the evaporator. In case a fixed restriction is used as expansion device, a control valve will take over this function. Consequently, the valve [9] downstream the evaporator [7] will be opened and the defrost compressor [11] will be started. The capacity of this compressor [11] should be large enough to extract more vapour than the amount of vapour that is formed due to the heat load on the evaporator [7]. In this way, a decrease of refrigerant pressure will be realised, resulting in a decrease of temperature and boiling point. An illustration of this process is shown in Figure 2 wherein CO2 is used as refrigerant. The flat part of the curve refers to the transition from liquid to solid CO 2 (dry ice). As the density of dry ice is higher than that of liquid CO2, the transition to solid CO2, does not damage the evaporator due to expansion. By decreasing the pressure and consequently the temperature in the evaporator [7], the adhesion forces of the ice at the secondary side of the evaporator [7] will decrease far enough to cause the ice to be removed from the secondary side. A one-way valve [8] between the vessel [4] and the evaporator [7] prevents the vapour flowing from the vessel [4] to the evaporator [7] during defrosting.
The discharge vapour of the defrost compressor [11] is led to the vessel [4]. As soon as the ice is removed from the evaporator [7], the defrost compressor [11] will be switched off and the expansion device [6] will be opened again. This method of ice removal is very energy efficient. No heat will be brought in into the product or the coldstore. The energy that is used for defrosting also leads to a further cooling of the product and the evaporator [7].
The defrost compressor [11] can also be used as refrigeration compressor for useful cold supply. Figure 3 illustrates how the addition of only a few ducts [12, 13] and valves [14, 15, 16] enables the defrost compressor to be used as refrigeration compressor. During normal operation valve [14] is opened and the defrost compressor extracts refrigerant vapour from vessel [4] through duct [12]. The discharge vapour flows through valve [16] and duct [13] to the cascade condensor. Valve [15] is closed. In the defrost mode valves [14] and [16] are closed and valve [15] is opened, which gives the same result as in figure 1.

Claims

Claims
1. A method for cooling a medium and defrosting a secondary side of a cooler, in which a refrigerant is used as a cooling agent and as a defrosting agent, wherein the cooling of the medium is established by passing the refrigerant at a high pressure through a primary side of the cooler, whereby the medium to be cooled is passed through the secondary side of the cooler, and wherein the defrosting of the cooler is established by decreasing the gas pressure of the refrigerant in the primary side of the cooler to such an extent that ice which is adhered to the secondary side of the cooler is released.
2. A method according to claim 1, wherein the gas pressure of the refrigerant is decreased by means of a compressor which is arranged downstream the cooler.
3. A method according to claim 1 or 2, wherein the flow of refrigerant to the cooler is reduced during defrosting when compared to the flow of refrigerant as applied during cooling.
4. A method according to any one of claims 1-3, wherein the gas pressure of the refrigerant in the first part of the cooler is in such a range that the equivalent boiling temperature is lower than -50°C.
5. A method according to claim 4, wherein the gas pressure of the refrigerant is in such a range that the equivalent boiling temperature is lower than -600C.
6. A method according to any one of claims 1-5, wherein the refrigerant circulation rate is in the range of from 1-10.
7. A method according to any one of claims 1-6, wherein the refrigerant comprises CO2-
8. A method according to any one of claims 1-7, wherein the cooler comprises a contact freezer, and the method is integrated with a method for cooling a material located between the elements of the contact freezer.
9. A method according to any one of claims 1-8, wherein the cooler is connected to two compressors which are connected in parallel at cooling conditions so as to form a two stage refrigeration system, and wherein the compressors are connected in series at defrost conditions so as to form a three stage refrigeration system.
10. A cooling system for carrying out the method according to any one of claims 1-9, which system comprises a cooler which is provided with means to allow refrigerant to pass through the primary side of the cooler, means to allow the medium to be cooled to pass through the secondary side of the cooler, which cooler is connected to two or more compressors for decreasing the pressure of the refrigerant in the primary side of the cooler, whereby the suction sides of the compressors can alternately be connected in parallel and in series to the cooler or in parallel and in a combination of in parallel and in series to the cooler, means for connecting the compressors alternately in parallel or in series to the cooler or means for connecting the compressors alternately in parallel and in a combination of in parallel and in series to the cooler, and a heat exchanger to which the high pressure sides of the compressors can alternately be connected in parallel and in series or in parallel and in a combination of in parallel and in series, which heat exchanger is connected to a circuit for feeding the refrigerant into the cooler.
11. A cooling system according to claim 10, wherein the heat exchanger is connected to an expansion device, which expansion device is connected to the cooler.
12. A cooling system according to claim 10 or 11, wherein the cooling system comprises a contact freezer or a plurality of contact freezers.
PCT/NL2005/000610 2004-08-24 2005-08-23 A method and a cooling system in which a refrigerant is used as a cooling agent and as a defrosting agent Ceased WO2006022541A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP04077391.3 2004-08-24
EP04077391A EP1630495A1 (en) 2004-08-24 2004-08-24 A method and a cooling system in which a refrigerant is used as a cooling agent and/or as a defrosting agent

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WO2006022541A1 true WO2006022541A1 (en) 2006-03-02

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PCT/NL2005/000610 Ceased WO2006022541A1 (en) 2004-08-24 2005-08-23 A method and a cooling system in which a refrigerant is used as a cooling agent and as a defrosting agent

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105157268A (en) * 2015-08-25 2015-12-16 吴家伟 CO2 cascade refrigeration system with hot gas defrosting function

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008112549A2 (en) * 2007-03-09 2008-09-18 Johnson Controls Technology Company Heat exchanger
MX366606B (en) 2013-12-17 2019-07-16 Maekawa Seisakusho Kk Sublimation defrost system for refrigeration devices and sublimation defrost method.
WO2024179931A1 (en) * 2023-03-01 2024-09-06 DSI Dantech A/S Method of operating a plate freezer

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5485455A (en) * 1977-12-21 1979-07-07 Mitsubishi Electric Corp Refrigerating system
US4224801A (en) * 1978-11-13 1980-09-30 Lewis Tyree Jr Stored cryogenic refrigeration
DE3004114A1 (en) * 1979-04-18 1980-11-06 Liquid Carbonic De Espana S A Low temperatures produced for refrigeration - where solidified carbon di:oxide is suspended in liq. and fed through evaporator-sublimator located in cold chamber
US5013217A (en) * 1988-01-29 1991-05-07 Kabushiki Kaisha Toshiba Compressing apparatus with extended variable capacity range and capacity control method thereof
US5042262A (en) * 1990-05-08 1991-08-27 Liquid Carbonic Corporation Food freezer
JPH0480545A (en) * 1990-07-20 1992-03-13 Matsushita Electric Ind Co Ltd Heat pump type air conditioner
US5400615A (en) * 1991-07-31 1995-03-28 Thornliebank Industrial Estate Cooling system incorporating a secondary heat transfer circuit
US5570585A (en) * 1994-10-03 1996-11-05 Vaynberg; Mikhail Universal cooling system automatically configured to operate in compound or single compressor mode
US5715702A (en) * 1996-11-15 1998-02-10 Frigoscandia Equipment Ab Refrigeration system
JP2000314566A (en) * 1999-04-30 2000-11-14 Daikin Ind Ltd Air conditioner
JP2002243350A (en) * 2001-02-16 2002-08-28 Sanden Corp Refrigerating system

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5485455A (en) * 1977-12-21 1979-07-07 Mitsubishi Electric Corp Refrigerating system
US4224801A (en) * 1978-11-13 1980-09-30 Lewis Tyree Jr Stored cryogenic refrigeration
DE3004114A1 (en) * 1979-04-18 1980-11-06 Liquid Carbonic De Espana S A Low temperatures produced for refrigeration - where solidified carbon di:oxide is suspended in liq. and fed through evaporator-sublimator located in cold chamber
US5013217A (en) * 1988-01-29 1991-05-07 Kabushiki Kaisha Toshiba Compressing apparatus with extended variable capacity range and capacity control method thereof
US5042262A (en) * 1990-05-08 1991-08-27 Liquid Carbonic Corporation Food freezer
JPH0480545A (en) * 1990-07-20 1992-03-13 Matsushita Electric Ind Co Ltd Heat pump type air conditioner
US5400615A (en) * 1991-07-31 1995-03-28 Thornliebank Industrial Estate Cooling system incorporating a secondary heat transfer circuit
US5570585A (en) * 1994-10-03 1996-11-05 Vaynberg; Mikhail Universal cooling system automatically configured to operate in compound or single compressor mode
US5715702A (en) * 1996-11-15 1998-02-10 Frigoscandia Equipment Ab Refrigeration system
JP2000314566A (en) * 1999-04-30 2000-11-14 Daikin Ind Ltd Air conditioner
JP2002243350A (en) * 2001-02-16 2002-08-28 Sanden Corp Refrigerating system

Non-Patent Citations (6)

* Cited by examiner, † Cited by third party
Title
KENNEDY C: "THE FUTURE OF FROZEN FOODS", FOOD, SCIENCE AND TECHNOLOGY, MARCEL DEKKER, NEW YORK, NY, US, vol. 14, no. 4, 2000, pages 195 - 197, XP008056189, ISSN: 0891-8961 *
PATENT ABSTRACTS OF JAPAN vol. 003, no. 108 (M - 072) 11 September 1979 (1979-09-11) *
PATENT ABSTRACTS OF JAPAN vol. 016, no. 293 (M - 1273) 29 June 1992 (1992-06-29) *
PATENT ABSTRACTS OF JAPAN vol. 2000, no. 14 5 March 2001 (2001-03-05) *
PATENT ABSTRACTS OF JAPAN vol. 2002, no. 12 12 December 2002 (2002-12-12) *
S. ESTRADA-FLORES: "Novel cryogenic technologies for the freezing of food products", THE OFFICIAL JOURNAL OF AIRAH, July 2002 (2002-07-01), Australia, pages 16 - 21, XP008056214 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105157268A (en) * 2015-08-25 2015-12-16 吴家伟 CO2 cascade refrigeration system with hot gas defrosting function

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