AU2005263201B2 - Refrigeration system - Google Patents

Description

P:\OpGMS\Proseuon\ERA Pty LdM26495M AUL 264950 m ded speci pagesdc-2/07/2O9 REFRIGERATION SYSTEM FIELD OF THE INVENTION 5 This invention relates to refrigeration systems for enclosed spaces and in particular but not only to a eutectic system that continues to provide temperature control over an enclosed space during periods when external power is not necessarily available. BACKGROUND TO THE INVENTION 10 The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of 15 endeavour to which this specification relates. Many refrigeration systems are required to provide cooling without necessarily having access to a continuous supply of electricity. In some cases electrical power is not available for large parts of the day in remote areas or for mobile systems. In others, the systems are 20 required to avoid consumption of power during peak periods. Conventional eutectic systems have been developed to operate under these circumstances, but do not provide adequate temperature control for many purposes. Solar power systems with storage batteries have been developed but are relatively expensive and cannot guarantee that electricity will be available. 25 SUMMARY OF THE INVENTION The present invention seeks to provide a refrigeration system using a eutectic subsystem with temperature control that can operate without external power for useful periods of 30 time, or at least to provide an alternative to existing systems.

P:\OperGMS\Pocion\F.RA Ply Ltd\12&495X AU\12649500 amended speci pages doc-22//210) - lA In one aspect the invention is a refrigeration system for an enclosure, including: a first cooling subsystem that is powered by an external source, a second cooling subsystem that is not necessarily electrically powered by an external source, a first thermal pathway by which the first cooling subsystem, when powered, cools the second cooling subsystem, a 5 second thermal pathway by which the second cooling subsystem cools the enclosure without requiring electrical power from an external source, and a controller in the second thermal pathway that operates to maintain the enclosure at a predetermined temperature. Preferably the second thermal pathway is a refrigerant loop that conveys heat from the 10 enclosure to the second cooling subsystem by convection. Refrigerant in the loop circulates by evaporation from C:\Documents md Scdngs\axs\Desktop\1 2496862 PCTart34amendments.do-21/04/06 PCT/AU2005/001082 Received 21 April 2006 -2 a relatively low location to a relatively high location in the enclosure, followed by condensation and descent under gravity within the second subsystem. Preferably the controller includes a valve that regulates the flow of refrigerant around the loop without need of power from an external source. 5 Preferably the first cooling subsystem includes a compressor/condenser arrangement that is powered by mains electricity and the second cooling subsystem includes an insulated eutectic tank. In one embodiment the first thermal pathway includes a refrigerant loop between the first cooling subsystem and the second cooling subsystem, separate from the second thermal pathway. In 10 another embodiment the first and second pathways are combined, so that the first cooling subsystem, when powered, cools both the second cooling subsystem and the enclosure. In another aspect the invention is a method of cooling an enclosure, including: operating an electrically powered cooling system to extract heat from a non-electrically-powered cooling 15 system, cooling the enclosure by convective transfer of heat from the enclosure to the non-powered cooling system, and controlling the transfer of heat to maintain the enclosure at a predetermined temperature. Preferably the method further includes ceasing operation of the powered cooling system during 20 periods when power is not available, and continuing to cool-the enclosure during such periods by convective transfer of heat from the enclosure to the non-powered cooling system. Transfer of heat from the enclosure to the non-powered system is controlled to maintain the enclosure at a predetermined temperature 25 The enclosure may be a merchandiser, a cold storage room, a cabinet for medical supplies, a transportable container or an air conditioned room, for example. In a further aspect the invention resides in a cooling system, including: a heat absorbing tank, an enclosure to be cooled by the tank, and a refrigerant loop which links the tank and the enclosure but 30 does not include an electrically powered compressor/condenser arrangement, wherein refrigerant circulates in the loop by evaporation and upwards movement caused by input of heat from the enclosure followed by condensation and downward movement caused by output of heat to the tank. Amended Sheet

IPEA/AU

WO 2006/007663 PCT/AU2005/001082 -3 LIST OF FIGURES Preferred embodiments of the invention will be described with respect to the 5 accompanying drawings, of which: Figures 1A and 2B schematically show alternative refrigeration systems, Figures 2A and 2B schematically show the alternative systems in more detail, Figure 3 shows a solenoid device that may be used as a valve in either system, Figure 4 shows a heat exchanger that may be used in either system, and 10 Figures 5a, 5b, 5c are views of a merchandiser with a refrigeration system. DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings it will be appreciated that the invention may be implemented in a 15 range of different ways for a range of different purposes. The systems described here are given by way of example only. It will also be appreciated that many components of these systems are of a conventional nature and need not be described in detail. Figures 1A and 1B show alternative refrigeration systems, each arranged to cool an 20 enclosure 10. Each system includes a first cooling subsystem 11, typically compressor/condenser equipment that is electrically powered from an external source 16 such as mains electricity, and a second cooling subsystem 12, typically a eutectic device that is generally without an external power supply. A first thermal pathway 13, typically a refrigerant loop, links the first and second cooling subsystems, while a second thermal 25 pathway 14, also typically a refrigerant loop, links the second cooling subsystem with the enclosure. A temperature detector 17 in the second cooling system determines when operation of the first cooling system is required, while a temperature detector 18 in the enclosure determines when operation of the second cooling system is required. 30 In Figure 1A the thermal pathways are separate and the first cooling subsystem 11 acts to cool the second cooling subsystem 12 which in turn cools the enclosure. In Figure 1B the PAOper\ALC\Specfications as fllcd\l 2496862 pct speci 203.doc-29/08/06 -4 pathways are partially combined so that the first cooling subsystem cools both the second subsystem and the enclosure. In both cases, movement of refrigerant along the first pathway is generally driven by electrical power supplied to the first cooling system, while movement of refrigerant along the second pathway is generally driven by gravity and/or convection without need 5 of external electrical power. A controller 15 such as a solenoid valve is provided in the second thermal pathway to control movement of the refrigerant in response to the detector 18 and thereby control the temperature of the enclosure. The natural processes of convection and gravity are stopped by the controller from time to time, as required to maintain the temperature. Various alternative arrangements of the subsystems and pathways are possible. 10 Figure 2A shows the refrigeration system of Figure 1A in more detail. The first cooling system 11 includes a compressor 20, a condenser 21, a float 22, a heat exchanger 23 and a capillary brake 24. The second cooling system 12 includes an insulated tank 28 containing a eutectic solution or other material, such as brine or ethylene glycol. The enclosure 10 is a refrigeration cabinet in this 15 example. A refrigerant loop including an accumulator 25 forms the first thermal pathway 13 between the cooling systems, and might be considered as part of the first cooling system. A refrigerant loop forms the second thermal pathway 14 between the second cooling system and the enclosure, and includes one or more evaporators 26 and 27 in the enclosure. The second loop might be considered as part of the second cooling system. 20 The compressor system 11 in Figure 2A is able to cool the system 12 when power is available from source 16. Refrigerant in the loop 13 enters the compressor 20 as a relatively cool low pressure gas and is delivered to the condenser 21 as a relatively warm high pressure gas. The condenser dissipates heat from the gas into the atmosphere and produces a warm liquid within the loop. The 25 float 22 and brake 24 are control devices that regulate the flow of liquid along loop 13 from the condenser to the eutectic tank, particularly when the system is started and the tank is relatively warm. The liquid is cooled by expansion through these devices. Once in the tank 28 the liquid refrigerant in loop 13 absorbs heat from the eutectic material by evaporating and then returning to the compressor through the heat exchanger as a gas. The accumulator 25 is a trap that prevents any 30 unevaporated liquid refrigerant from reaching the compressor. Amended Sheet TmP A/ATT WO 2006/007663 PCT/AU2005/001082 The eutectic system 12 in Figure 2A cools the enclosure 10 without necessarily using power from an external source or being in direct contact with the enclosure. Refrigerant loop 14 is arranged so that the refrigerant circulates in response to the effects of gravity 5 and convection with the overall rate of flow determined by the controller 15. Refrigerant cools and descends within tank 28 and passes as a liquid from the tank into the enclosure. The refrigerant enters at a relatively low point in the enclosure and depending on the temperature of the enclosure, is either pushed up toward the roof evaporator 27 or begins to evaporate initially in the base evaporator 26. The liquid thereby absorbs heat from the 10 enclosure and returns to the tank 28 as a gas from a relatively high point in the enclosure. Figure 2B shows a refrigeration system in which the thermal pathways are combined, as an alternative to the system in Figure 2A. The compressor subsystem 11 cools either the eutectic subsystem 12 alone, or both the eutectic subsystem and the enclosure, depending 15 on the status of controller 15. The system of Figure 2B cools the enclosure more quickly under a heavy load but the combined pathways require a common refrigerant and are more difficult to repair in the event of a leak. On the other hand, the system of Figure 2B allows use of different refrigerants that may be selected for performance of the particular loop. 20 Figure 3 shows a solenoid valve 15 in more detail. The valve is operated by a microprocessor (not shown) that monitors the temperature detectors 17 and 18 and draws power from a battery (not shown). A pair of coils 30 are pulsed to open and close the seat 31 of the valve when required by the microprocessor. The valve is normally held in a closed position by a spring 32 and requires no power in that position. Similarly the valve 25 may be held open by a magnet 33 without additional power. An appropriate coil is pulsed to change the open or closed status of the seat requiring minimal power for a short period of time. Other valve systems that operate from temperature differentials and do not require battery power might also be used. 30 Figure 4 shows a heat exchanger 23 of Figures 2A and 2B in more detail. Warm liquid refrigerant passing from the condenser 21 through the high side float 22 reaches the heat WO 2006/007663 PCT/AU2005/001082 -6 exchanger as a cool liquid with some vapour. Relatively cold vapour from the eutectic tank also passes through the heat exchanger when moving back to the compressor 20. The cold vapour from the tank sub-cools the liquid and vapour from the float to form a cool liquid without vapour moving towards the capillary brake 24. The level of heat exchange 5 between the inflowing and outflowing liquids and vapours is determined to enhance the efficiency of the compressor. Figures 5a, 5b and 5c are sectional views of a merchandiser that incorporates a refrigeration system as shown in Figure 2A or 2B. The merchandiser includes a cabinet 50 10 with front doors 51, shelves 52 for products such as food or drink, and may be mounted on wheels 53. Refrigerant from a eutectic tank 12 located in the rear of the cabinet flows through the base evaporator 26 upwards to the roof evaporator 27, as indicated, and then returns to the tank. Valve 15 between the eutectic tank and the roof evaporator controls the flow of refrigerant. An optional fan 54 in the roof of the cabinet drives air flow 15 downwards through the roof evaporator to the base evaporator, as indicated. The fan is powered by mains electricity and is generally not operated when power is not available. As shown in Figure 5c, the compressor 20 is located in an upper part of the rear of the cabinet in this example. The condenser 21 is located on one side at the rear of the cabinet 20 and may have a fan 55 to assist dispersal of heat when power is available. A relatively small compressor can be used because the effect of sudden or heavy loads in the cabinet, such as opening of the front doors and stocking of the shelves, is buffered by heat absorption in the eutectic tank. Operation of the compressor can also be optimised for predetermined time periods with a reduced number of start events. 25

Claims (20)

1. A refrigeration system for an enclosure, including: a first cooling subsystem that is powered by an external source, 5 a second cooling subsystem that is not necessarily electrically powered by an external source, a first thermal pathway by which the first cooling subsystem, when powered, cools the second cooling subsystem, a second thermal pathway by which the second cooling subsystem cools the 10 enclosure without requiring electrical power from an external source, and a controller in the second thermal pathway that operates to maintain the enclosure at a predetermined temperature.

2. The system of claim 1 wherein the second thermal pathway is a refrigerant loop 15 that conveys heat from the enclosure to the second cooling subsystem by convection.

3. The system of claim 2 wherein refrigerant in the loop circulates by evaporation from a relatively low location to a relatively high location in the enclosure, followed by condensation and descent under gravity within the second subsystem. 20

4. The system of claim I wherein the controller includes a valve that regulates the flow of refrigerant around the second thermal pathway without need of power from an external source. 25

5. The system of claim I wherein the first cooling subsystem includes a compressor/condenser arrangement that is powered by mains electricity and the second cooling subsystem includes an insulated eutectic tank.

6. The system of claim 1 wherein the first thermal pathway includes a refrigerant loop 30 between the first cooling subsystem and the second cooling subsystem, separate from the second thermal pathway. PAOpnGMS\Pro utionERA Piy Li264950) AU\12649500 aedd cbmsdoc-27A)7/2W) -8

7. The system of claim I wherein the first and second pathways are partially combined, so that the first cooling subsystem, when powered, cools both the second cooling subsystem and the enclosure. 5

8. A method of cooling an enclosure, including: operating an electrically powered cooling system to extract heat from a non electrically-powered cooling system, cooling the enclosure by convective transfer of heat from the enclosure to the non 10 electrically-powered cooling system, and controlling the transfer of heat to maintain the enclosure at a predetermined temperature.

9. The method of claim 8 further including: 15 ceasing operation of the electrically powered cooling system during periods when electrical power is not available, and continuing to cool the enclosure during such periods by convective transfer of heat from the enclosure to the non-electrically-powered cooling system. 20

10. The method of claim 8 wherein transfer of heat from the enclosure occurs through a refrigerant loop in which refrigerant circulates by evaporation from a relatively low location in the enclosure to a relatively high location in the enclosure, followed by condensation and descent under gravity within the non-electrically-powered cooling system. 25

11. The method of claim 8 wherein the electrically powered cooling system includes a refrigerant loop driven by a compressor/condenser arrangement and the non-electrically powered cooling system includes a refrigerant loop driven by convection and gravity. P\0pcrtCMS\P t ion\ERA Pty Ud\1264951K) AUU26495(K) mnded clims doc.27/07/20X)9 -9

12. The method of claim 8 further including operating the electrically powered cooling system to cool both the non-electrically-powered cooling system and the enclosure through a system of linked refrigerant loops. 5

13. The method of claim 8 wherein the enclosure is a merchandiser, a cold storage room, a cabinet for medical supplies, a transportable container or an air conditioned room.

14. A cooling system, including: a heat absorbing tank, an enclosure to be cooled by the tank, and a refrigerant loop 10 which links the tank and the enclosure but does not include an electrically powered compressor/condenser arrangement, wherein refrigerant circulates in the refrigerant loop by evaporation and upwards movement caused by input of heat from the enclosure followed by condensation and downward movement caused by output of heat to the tank. 15

15. A cooling system according to claim 14 further including a controller which opens and closes the refrigerant loop to maintain the enclosure at a predetermined temperature.

16. A cooling system according to claim 15 wherein the controller is a battery powered 20 solenoid which operates a valve in the refrigerant loop in response to a temperature detector in the enclosure.

17. A cooling system according to claim 14 further including a second refrigerant loop with an electrically powered compressor/condenser arrangement which cools the heat 25 absorbing tank when required and when electrical power is available.

18. A cooling system according to claim 14 wherein the heat absorbing tank is a eutectic tank and the enclosure is a merchandiser, a cold storage room, a cabinet for medical supplies, a transportable container or an air conditioned room. 30 P:\OperGMS\Preuion\ERA Pty Ud\1264951X) AU\I 26499NI amended claims doc-27A)7/2(XN9 - 10

19. A refrigeration system for an enclosure, substantially as hereinbefore described with reference to the accompanying drawings.

20. A method of cooling an enclosure, substantially as hereinbefore described with 5 reference to the accompanying drawings.