GB2117884A

GB2117884A - Heat transfer device

Info

Publication number: GB2117884A
Application number: GB8309331A
Authority: GB
Inventors: John Ernest Mousley; Joseph Sweeney
Original assignee: BIRMINGHAM HEAT PUMPS Ltd
Current assignee: BIRMINGHAM HEAT PUMPS Ltd
Priority date: 1982-04-07
Filing date: 1983-04-06
Publication date: 1983-10-19
Also published as: GB2117884B; GB8309331D0

Abstract

A heat transfer device 1 for space cooling of the type in which a vaporisable refrigerant is circulated in a closed circuit including an evaporator 3 for collecting heat from air passed over the evaporator thus vaporising the refrigerant, a compressor 4 to compress the vaporised refrigerant and a condenser 5 to dissipate the heat collected to condense the refrigerant. The closed refrigerant circuit is housed in a casing 2 which is positioned in a cold space the air temperature of which is to be controlled and the heat generated during operation of the device 1 is prevented from returning to the cold space by surrounding the condenser 5 with thermally insulating material and positioning the compressor 4 in the air flow path to the evaporator 3. The condenser 5 forms part of a heat exchanger 18 connected to supply and return lines for circulation of a cooling fluid, e.g. water, to which the heat dissipated by the condenser is transferred. The device 1 may form part of a combined space cooling/water heating system in which the heat dissipated by the condenser is utilised to heat the water in a hot water supply. <IMAGE>

Description

SPECIFICATION Heat transfer device This invention concerns improvements in or relating to heat transfer devices for space cooling such as in meat/vegetable cold rooms, beer cellars and the like.

Heat transfer devices for space cooling are known in which a vaporisable refrigerant is circulated in a closed circuit including an evaporator for collecting heat from air passed over the evaporator thus vaporising the refrigerant, a compressor to compress the vaporised refrigerant and a condenser for dissipating the heat collected to condense the refrigerant. It is usual for the evaporator to be located within the cold space to extract heat from the air thereby cooling the space to the required temperature and for the compressor and condenser to be located externally of the cold space to dissipate the collected heat, e.g. by force convection of air over the condenser, outside the cold space.A disadvantage of such systems is that initial installation is complicated and time-consuming requiring skilled technicians to complete the refrigerant circuit between the evaporator and the compressor and condenser. Furthermore any subsequent maintenance work requiring repair to or replacement of any part of the circuit often results in the device being shut down rendering the cold space inoperative for a considerable period of time.

It is an object of the present invention to provide a heat transfer device for space cooling which avoids the disadvantages of the known devices.

According to one aspect of the present invention a heat transfer device for space cooling comprises a casing housing a closed circuit containing a vaporisable refrigerant, the circuit including an evaporator for collecting heat from air passed over the evaporator thus vaporising the refrigerant, a compressor to compress the vaporised refrigerant and a condenser for dissipating the heat collected to condense the refrigerant wherein the condenser is surrounded by thermally insulating material and the compressor is positioned in the air flow path to the evaporator.

In the heat transfer device according to the present invention the evaporator, compressor and condenser are in a self-contained unit which is located within the cold space and the heat generated during operation is prevented from escaping into the cold space by thermally insulating the condenser from the cold space and by cooling the compressor by directing the air flow to the evaporator over the compressor.

Preferably the casing is divided into two compartments, one containing the condenser and the other containing the evaporator and compressor.

Preferably said other compartment has an air inlet opening and an air outlet opening and means, e.g. a fan, is provided to draw air from the cold space in through the inlet opening and direct it first over the compressor and then over the evaporator, the cooler air returning to the cold space through the outlet opening.

In a preferred construction said other compartment is sub-divided into two chambers, one containing the compressor and the other containing the evaporator, by an internal partition wall having an opening in which the fan, driven by an electric motor, is mounted. Preferably the air inlet opening, the fan opening and the air outlet opening are axially aligned to provide a direct flow path through said other compartment. The compressor is mounted in the flow path between the air inlet opening and the fan opening and the evaporator is mounted in the flow path between the fan opening and the air outlet opening, preferably adjacent to and in front of the air outlet opening.

The evaporator is preferably of looped construction to facilitate heat collection and comprises one or more rows of closely spaced loops, optionally enclosed by fins to improve heat collection.

Preferably the condenser is constructed and arranged to be in heat exchange relationship with a cooling fluid, e.g. water, to which the heat collected by the evaporator is transferred. For example the condenser may comprise one coil of a twin coil heat exchanger the other coil of which is adapted for connection to supply and return lines for the cooling fluid. Preferably the cooling fluid is circulated through said other coil by means of a pump located within said one compartment.

Conveniently the heat exchanger and pump are totally encapsulated by the thermally insulating material, e.g. mineral fibre which fills the compartment thereby insulating the condenser from the cold space in which the device is positioned.

The compressor, fan and pump are operable in response to the temperature sensed by a thermostat mounted in the air inlet opening to sense the temperature of the cold space in which the device is mounted. Preferably the thermostat is operable to actuate the compressor, fan and pump when the temperature in the cold space exceeds a predetermined maximum level and to switch off the compressor, fan and pump when the temperature drops to a predetermined minimum level. Alternatively the fan is operated independently of the compressor and pump and may be run continuously to provide air circulation within the cold space at all times.

According to a further aspect of the present invention a combined space cooling/water heating system comprises a heat transfer device according to the first aspect of the invention wherein the heat dissipated by the condenser is utilized to heat the water in a hot water supply.

According to yet a further aspect of the present invention a combined space cooling/water heating system comprises a heat transfer device located within a cold space, said device comprising a casing housing a closed refrigerant circuit containing a vaporisable refrigerant, the circuit including an evaporator for collecting heat from air passed over the evaporator thus vaporising the refrigerant, a compressor to compress the vaporised refrigerant and a condenser for dissipating the heat collected to condense the refrigerant, the condenser being thermally insulated from the cold space and forming part of a heat exchanger connected via supply and return lines to a reservoir of cooling water and means for circulating the cooling water between the reservoir and the heat exchanger.

The invention will now be described in more detail, by way of example only, with reference to the accompanying schematic drawings wherein: Figure 1 is a side view of the heat transfer device according to the present invention; Figure 2 is a front view of the heat transfer device shown in Figure 1; Figure 3 shows a first embodiment of a combined space cooling/water heating system incorporating the heat transfer device shown in Figures 1 and 2; Figure 4 shows a modification to the system shown in Figure 3; and Figure 5 shows a second embodiment of a combined space cooling/water heating system incorporating the heat transfer device shown in Figures 1 and 2.

The heat transfer device 1 shown in Figures 1 and 2 of the accompanying drawings comprises a rectangular casing 2 housing a closed refrigerant circuit including an evaporator 3, compressor 4, condenser 5, receiver 6 and expansion device 7 through which a vaporisable refrigerant, e.g.

Arcton F12 (registered Trade Mark) ex Cl. is circulated.

The casing 2 is divided by an internal horizontal partition wall 8 into upper and lower compartments 9 and 10 respectively. The condenser 5 is positioned in the upper compartment and the evaporator 3 and compressor 4 are positioned in the lower compartment. The lower compartment 10 has an air inlet opening (not shown) formed in one side of the casing and an air outlet opening (not shown) formed in the opposite side and is sub-divided into front and rear chambers 11 and 12 respectively, as viewed in the direction of air flow shown by Arrow A in Figure 1, by a vertical partition wall 13 having a central aperture 14 in which a fan 1 5 driven by an electric motor 1 6 is mounted. The air inlet and outlet openings and the aperture 14 are axially aligned.The compressor 4 is in the front chamber 11 in the air flow path between the air inlet opening and the aperture 14. The evaporator 3 comprising four rows 1 7 of closely spaced loops enclosed by fins (not shown) is positioned in the rear chamber 1 2 in front of the air outlet opening.

The condenser 5 comprises the outer coil of a twin coil heat exchanger 1 8 the inner coil of which has an inlet 1 9 and an outlet 20 for the circulation of a heat exchange fluid, e.g. water, by means of a pump 21 mounted in the upper compartment 9.

The heat exchanger 18 and pump 21 are completely encapsulated by thermally insulating material, e.g. mineral fibre, which fills the upper compartment 9.

A two-way thermostat (not shown) mounted in the air inlet opening to the front chamber 11 is operable to sense the temperature in a cold space in which the device is mounted in use and a control box 25 mounted in the front chamber 11 is operable in response to the temperature sensed by the thermostat to actuate the compressor 4, fan 15 and pump 21 when the temperature in the cold space exceeds a predetermined maximum level and to switch off the same components when the temperature falls to a predetermined minimum level.

In use the device 1 is mounted in a cold space in which the air temperature is to be controlled and connected to a power supply for the compressor 4, fan 15 and pump 21. The inlet 19 and outlet 20 of the heat exchanger 18 are connected via isolation valves 22 and 23 provided in supply and return lines (not shown) for the cooling fluid. The length of the supply and return lines entering the cold space is kept to a minimum and is thermally insulated to prevent heat exchange between the cooling fluid and the air in the cold space.When the temperature sensed by the thermostat exceeds a predetermined maximum level the compressor 4, fan 1 5 and pump 21 are actuated and air drawn in through the inlet opening by fan 1 5 is directed over the compressor 4 to cool the iatter and then through the evaporator 3 which extracts heat from the air thus vaporising the refrigerant passing through the evaporator so that the air is returned to the cold space through the air outlet opening at a lower temperature. Vaporised refrigerant leaving the evaporator 3 is passed in line 24 through the receiver 6 where it is further heated by heat exchange with condensed liquid refrigerant in receiver 6 before entering the compressor 4 where it is compressed thereby increasing its temperature.The hot refrigerant is then passed through the condenser 5 where it gives up its heat to the fluid circulating through the outer coil of the heat exchanger 1 8 and is condensed before returning to the evaporator 3 via receiver 6 where it is cooled by heat exchange with vaporised refrigerant in line 24 and expansion device 7. The above cycle is repeated until the air temperature in the cold space is reduced to a predetermined minimum level at which the thermostat switches off the compressor 4, fan 1 5 and pump 21 to prevent a further reduction in the air temperature by heat exchange with the evaporator 3. If the temperature subsequently rises above the maximum level the compressor 4, fan 15 and pump 21 are re-actuated causing a reduction in the air temperature as above-described so that the air temperature is maintained between the maximum and minimum levels.

It will be apparent from the foregoing that the present invention provides a heat transfer device in which the evaporator, compressor and condenser are located in the cold space in which control of the air temperature is required and the heat generated by operation of the device is prevented from returning to the cold space by thermally insulating the condenser from the cold space and placing the compressor in the air flow to the evaporator. As a result a compact selfcontained unit is obtained which is easily and quickly installed in the required location since the refrigerant circuit is complete within the device and the only connections required are those to the inlet and outlet of the heat exchanger for circulation of the cooling fluid and to a power supply for the compressor, fan and pump.

Furthermore the device can be easily removed for maintenance/repair work by closing the isolation valves 22 and 23 and disconnecting the inlet 19 and outlet 20 of the heat exchanger enabling a substitute device to be installed so that the length of time during which the cooling system is inoperative is reduced to a minimum.

Referring now to Figures 3, 4 and 5 there are shown embodiments of combined space cooling/water heating systems incorporating the above-described heat transfer device 1 in which the device 1 is located in a cold space (not shown) and is operable to control the air temperature in the cold space and the heat generated is utilised to heat the water in a hot water supply thereby reducing the cost of heating the water by conventional means, e.g. immersion heater, boiler etc.

The system shown in Figure 3 comprises a hot water storage cylinder 30 provided with conventional heating means 31 connected via a line 32 to an intermediate cylinder 33 which in turn is connected via line 34 to a cold water feed tank (not shown) supplied directly from the mains in known manner.

The heat exchanger of device 1 is connected via supply and return lines 35 and 36 to the intermediate cylinder. During operation of the device 1 to reduce the air temperature in the cold space the water in the intermediate cylinder 33 is circulated through the inner coil of the heat exchanger and is heated by heat exchange with the hot refrigerant passing through the outer coil.

As a result the temperature of the water in intermediate cylinder 33 is gradually raised and water drawn off from the storage cylinder 30 via outlet line 37 leading to the various outlet points (not shown) is replaced by water from the intermedia.e cylinder 33 which has been preheated to a higher temperature than the cold water in the feed tank thereby reducing the heat requirement in storage cylinder 30, i.e. the extent to which the conventional heating means 31 is used to heat the water is reduced.

The system shown in Figure 4 is a modification of the system shown in Figure 3 and like reference numerals are used to indicate similar parts. The modification consists in the provision of a threeway valve 40 in the return line 36 from the heat exchanger of device 1 which is operable to divert the water through auxiliary cooling means 41, e.g.

a fan coil, when the temperature of the water in the intermediate cylinder 33 sensed by a thermostat 42 reaches a predetermined level, for example the normal condensing temperature of the refrigerant thereby enabling the device 1 to continue its cooling operation in the cold space.

The system shown in Figure 5 has a storage cylinder 50 provided with conventional heating means 51 connected in series with an intermediate cylinder 52 connected via line 53 to a cold water feed tank (not shown). This system differs from that of Figures 3 and 4 in that the heat exchanger of device 1 may be connected via the supply and return lines 35 and 36 to either one of the storage cylinder 50 and the intermediate cylinder 52 thereby considerably increasing the volume of water available for circulation through the heat exchanger during operation of the device 1 in the cold space.More particularly supply line 35 is connected via lines 35a and 35b to the storage cylinder 50 and intermediate cylinder 52 respectively and return line 36 includes a threeway valve 54 operable to control the flow of water through lines 36a and 36b to the storage cylinder 50 and intermediate cylinder 52 in response to the temperature of the water in the storage cylinder 50 sensed by a thermostat 55. During operation of the device 1 to reduce the air temperature in the cold space if the water temperature sensed by thermostat 55 is below a predetermined level, for example the normal condensing temperature of the refrigerant, valve 54 is actuated to connect lines 36 and 36a causing the water in the storage cylinder to be circulated through the inner coil of the heat exchanger and heated by heat exchange with the hot refrigerant passing through the outer coil.When the temperature of the water in the storage cylinder 50 reaches the predetermined level valve 54 is actuated to connect lines 36 and 36b causing the water in the intermediate cylinder 52 to be circulated through the inner coil of the heat exchanger and heated by heat exchange with the hot refrigerant passing through the outer coil.

If the temperature of the water in the storage cylinder 50 falls below the predetermined level, e.g. if hot water is drawn off via outlet line 56 and is replaced by cooler water from the intermediate cylinder, thermostat 55 actuates valve 54 to reconnect lines 36 and 36a causing the water in the storage cylinder to be circulated through the inner coil of the heat exchanger and heated to the predetermined level. if the temperature of the water in both the storage cylinder 50 and the intermediate cylinder 52 reaches the predetermined level a thermostat 57 in the intermediate cylinder 52 is operable to actuate a pump 58 to pass the water in the intermediate cylinder 52 through auxiliary cooling means 59, e.g. a fan coil, to cool the water below the predetermined temperature before passing via lines 35b, 35 to the inner coil of the heat exchanger thereby enabling the device 1 to continue its cooling operation.

It will be understood the invention is not restricted to the above-described heat transfer device which may be modified in a number of ways, for example the evaporator may comprise any number of rows of loops and may be of any other construction known to those skilled in the art. Likewise the heat exchanger may be of any other construction known to those skilled in the art. The condenser and pump may be in the lower compartment and the evaporator and compressor in the upper compartment. The compartment containing the evaporator and compressor may be partitioned into two chambers as described or the fan may be mounted in the air inlet opening and the air flow directed over the compressor and through the evaporator.The maximum and minimum temperature levels may be pre-set to any required temperatures, for example the maximum and minimum temperatures may be within a few degrees of one another so that a fairly constant temperature is maintained in the cold space.

Also although the device has been described with particular reference to its incorporation in a system in which the heat dissipated by the condenser is used to heat the water in a hot water supply, it will be understood that other uses may be found for the dissipated heat, for example it could be used to provide or supplement the heating of water or air for a central heating system. Alternatively the device may be used as a space cooler only and the heat dissipated to atmosphere.

Furthermore it will be appreciated that the device is not restricted to use in a cold room or beer cellar but may be in other locations, both domestic and industrial, e.g. in a kitchen or in a computer room, where it may be used to extract excess heat or provide a cooling load. Excess heat which is extracted may be recycled into usable heat e.g. to heat a fluid. The device also has applications in air conditioning systems where it may be used to provide a total or partial cooling load. The device may include a heater to provide a source of heat if required, e.g. if the temperature falls below the minimum level for any reason.

Claims

1. A heat transfer device for space cooling comprises a casing housing a closed refrigerant circuit containing a vaporisable refrigerant, the circuit including an evaporator for collecting heat from air passed over the evaporator thus vaporising the refrigerant, a compressor to compress the vaporised refrigerant and a condenser for dissipating the heat collected to condense the refrigerant wherein the condenser is surrounded by thermally insulating material and the compressor is positioned in the air flow path to the evaporator.

2. A device according to claim 1 wherein the casing is divided into two compartments, one containing the condenser and the other containing the evaporator and the compressor.

3. A device according to claim 2 wherein said other compartment has an air inlet opening and an air outlet opening.

4. A device according to claim 3 including a fan arranged to draw air contained in a cold space in which the device is located in use through the inlet opening and direct it firstly over the compressor and then over the evaporator, the cooler air returning to the cold space through the outlet opening.

5. A device according to claim 4 wherein said other compartment is sub-divided into two chambers, one containing the compressor the other containing the evaporator, by an internal partition wall having an opening in which the fan is mounted.

6. A device according to claim 5 wherein the air inlet and outlet openings and the partition wall opening are axially aligned.

7. A device according to claim 6 wherein the compressor is mounted in the air flow path between the air inlet opening and the partition wall opening and the evaporator is mounted in the airflow path between the partition wall opening and the air outlet opening.

8. A device according to claim 7 wherein the evaporator is mounted adjacent to and in front of the air outlet opening.

9. A device according to any one of claims 2 to 8 wherein the evaporator is of looped construction.

10. A device according to claim 9 wherein the evaporator loops are enclosed by fins.

11. A device according to any one of claims 2 to 10 wherein the condenser is constructed and arranged to be in heat exchange relationship with a cooling fluid.

1 2. A device according to claim 11 wherein the condenser comprises one coil of a twin coil heat exchanger the other coil of which is adapted for connection to supply and return lines for the cooling fluid.

13. A device according to claim 11 or claim 12 wherein the cooling fluid is circulated by means of a pump.

14. A device according to claim 1 3 wherein the pump is located in said one compartment.

1 5. A device according to claim 14 wherein the heat exchanger and pump are totally encapsulated by the thermally insulating material.

1 6. A device according to any one of the preceding claims including a thermostat mounted on the outside of the casing to sense the air temperature in a cold space in which the device is located in use and to operate the device in response to the temperature sensed.

1 7. A device according to claim 1 6 wherein the thermostat is operable to actuate the device when the air temperature exceeds a predetermined level and to switch off the device when the air temperature falls to a minimum level.

18. A device according to claim 17 including a heater operable when the air temperature drops below the minimum level.

1 9. A heat transfer device for space cooling substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

20. A combined space cooling/water heating system incorporating a heat transfer device according to any one of the preceding claims.

21. A combined space cooling/water heating system comprises a heat transfer device located within a cold space, said device comprising a casing housing a closed refrigerant circuit containing a vaporisable refrigerant, the circuit including an evaporator for collecting heat from air passed over the evaporator thus vaporising the refrigerant, a compressor to compress the vaporised refrigerant and a condenser for dissipating the heat collected to condense the refrigerant, the condenser being thermally insulated from the cold space and forming part of a heat exchanger connected via supply and return lines to a reservoir of cooling water and means for circulating the cooling water between the reservoir and the heat exchanger.

22. A system according to claim 21 including a thermostat for sensing the temperature of the cooling water and operable to actuate valve means in one of the supply and return lines to divert the cooling water through auxiliary cooling means when the temperature of the cooling water exceeds a predetermined level.

23. A system according to claim 21 or claim 22 wherein the reservoir comprises an intermediate cylinder having an inlet connected to a supply of cold water and an outlet connected to a hot water storage cylinder.

24. A system according to claim 21 wherein the reservoir comprises a hot water storage cylinder and an intermediate cylinder connected in series, the intermediate cylinder having an inlet connected to cold water supply.

25. A system according to claim 24 wherein the cooling water is circulated between the storage cylinder and the heat exchanger until the temperature of the water in the storage cylinder reaches a predetermined level whereupon valve means is actuated to circulate the cooling water between the intermediate cylinder and the heat exchanger.

26. A system according to claim 25 wherein the circulating water is passed through auxiliary cooling means when the temperature of the water in the storage cylinder and the intermediate cylinder reaches predetermined levels.

27. A system according to claim 26 wherein said predetermined levels are the same and correspond to the normal condensing temperature of the compressor.

28. A combined space cooling/water heating system substantially as hereinbefore described with reference to any one of Figures 3, 4 and 5 of the accompanying drawings.

29. A central heating system incorporating a heat transfer device according to any one of claims 1 to 1 9.

30. An air conditioning system incorporating a heat transfer device according to any one of claims 1 to 19.