GB1569550A - Apparatuses for the production of heat or cold - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO APPARATUSES FOR THE PRODUCTION OF HEAT OR COLD (71) 1, ROGER BERNARD, a French citizen of, Rue des Treytins, Lotissement Beverley Le Vigean, 33320 Eysines, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to improved apparatus for the production of cold or heat using the Rankine cycle.

It is known that, during this cycle, a coolant fluid, usually a fluorinated hydrocarbon such as one of those known under the trade name "Freon", is subjected consecutively to compression, condensation, expansion and vapourization.

Several types of heat transfer installations using the Rankine cycle are known to be used for the production either of cold (refrigerating units) or of heat (heat pumps).

In the case of refrigerating units only, these apparatuses may be classified as follows: in one type the coolant fluid is pressurized by means of a compressor, usually driven by an electric motor; this type uses a large amount of electric power; in the thermal compression types, the coolant fluid is compressed by heating in a container, which has the advantage of making it possible to use heat sources at moderate temperatures, for example from industrial waste or from deep water. On the other hand, existing units of this type have the disadvantage that they operate intermittently, since they can produce cold only after the coolant fluid has been pressurized for some time.These units are also very difficult to use if the temperature of the heat source is variable; finally, there are absorption units using an auxiliary fluid which absorbs the coolant fluid at a low temperature and releases it at a higher temperature. These units are complex and require a heat source with very little temperature fluctuation. If they are to operate substantially continuously, they must be fitted with pumps operating at a high pressure differential or with pressurized auxiliary gas tanks.

In order to overcome the irregular operation of this latter type of unit, but without using large amounts of electric power, it has been proposed to equip them with two boiler-absorbers with staggered operating cycles. A switching system equipped with a temperature sensor must be provided to change the boiler-absorbers over when the temperature in the boiler-absorber which is being heated reaches a predetermined value.

If it is to operate properly, a unit of this kind requires that the temperature of the source from which the boiler-absorbers are heated shall remain approximately constant.

This type of unit is at present used for air conditioning automobiles, where the source of heat is the engine cooling water.

Accordingly, it is an object of this invention to at least partially overcome the disadvantages of the previous units by providing an improved apparatus of the thermal compression type.

To this end, in one of its aspects, the in vention provides an apparatus for the production of cold or heat using the Rankine cycle, said apparatus providing a main circuit for the circulation of a coolant fluid, the said apparatus comprising, consecutively in the direction of circulation of the said coolant fluid: means for compressing the said coolant fluid by the exchange of heat between it and a source of heat, means for condensing the coolant fluid by the exchange of heat, a pressure relief means. a heat exchange evaporator which provides a flow of cooling air, and a pump which returns the coolant fluid in the gaseous phase to the said compressing means, said compressing means comprising at least two heat exchangers between the fluid and the source of heat, switching means being provided for feeding the condenser successively from each of the said heat exchangers and, at the same time, for connecting to the pump delivery an exchanger other than that which feeds the condenser, the switching sequence being such that the operating cycles of the said heat exchangers are alternated.

The term "pump" is used here to indicate an element operating at a low pressure differential, but it is to be understood that irs structure may be that of a compressor.

Switching means will generally be provided to ensure that the source of heat cooperates only with the exchanger or exchangers which are full of coolant fluid at the time.

In order that the apparatus may function with a source of heat having a wide range of temperatures, the pressure relief means, of the thermostat type, is designed for high condensation temperatures and to keep the low pressure (downstream of the evaporator) at a substantially constant value.

The switching means will generally operate in a predetermined and unalterable time cycle. This arrangement has the advantage of being very simple and reliable. It obviously could not be used with the previously mentioned absorption units using two alternating boiler-absorbers because of the wide fluctuations in time taken to pressurize the boiler-absorbers.

The most important, but by no means the only, application of the invention is for air conditioning residential or industrial premises, especially in countries where the climate is of the Mediterranean or desert type. The source of heat in this case may be a solar collector supplying hot water, the temperature of which will fluctuate over a wide range in a twentyfour-hour cycle. The essential purpose of the apparatus will in this case be for the evaporator to cool a flow of air entering the premises. A flow of air will also be generally used to remove heat from the condenser, although a liquid such as water could also be used.The flows of heated and cooled air may be collected in a module equipped with registers allowing the flows of air to be mixed and distributed to the premises at a temperature which may be anywhere between that at the evaporator outlet and that at the condenser outlet. This avoids the well-known disadvantage of heat pumps, namely that they do not work well at fluctuating temperature and power levels.

Operating regularity may be still further improved by providing, immediately downstream of the condenser, an accumulator which will continue to feed the group consisting of the pressure relief valve and the evaporator during the few seconds in which the exchangers are isolated during a change over.

In order to reduce, as much as possible, the electric power to be supplied to the return pump for the coolant fluid, it is desirable that there be an almost complete pressure balance between the suction side of the pump and the container which it feeds, before filling of the said container is commenced. To this end, the pressure in the container to be filled may be reduced to the low pressure downstream of the evaporator with no interruption of the refrigerating operation of the evaporator. This reduction may be obtained by first opening an electrically operated filler valve on the container with the pump still halted (using the leakage through normal pumps, even of the volumetric type) and then expanding a small amount of the high pressure coolant fluid into the container by means of an auxiliary circuit having a secondary pressure relief valve.

Further objects and advantages of the invention will appear from the following description of one embodiment thereof which is given as a non-restrictive example, in conjunction with the following drawings attached hereto.

Fig. 1 is a diagrammatic representation of the main components of the apparatus; and Fig. 2 is a chronogram indicating the status of the valves and pumps during successive phases of an operating cycle.

In order to simplify matters, it will be assumed that the apparatus illustrated in Fig. 1 is to be used for air conditioning a building, and that the heat and cold is transferred from the coolant fluid to a flow of atmospheric air. It should be understood, however, that this application is in no way exclusive.

The apparatus may be regarded as comprising consecutively, in the direction of the circulation of the coolant fluid, which will generally be one of the conventional fluids such as difluoromonochloromethane or di fluorodichloromethane: heat exchange means 10 in which the cold producing fluid is compressed by thermal means; a condenser 12: a small capacity accumulator 11 designed to eliminate irregular operation in passing from one phase to the other in a cycle; a thermostat controlled pressure relief means 13, usually a simple restriction; an evaporator 14, downstream of which is located the temperature-sensitive bulb of pressure relief 13; and a volumetric pump 15 which returns the coolant fluid to the exchange means 10. In this embodiment, the heat exchange means comprise two identical containers 16a, 16b. Container 16a, for example, is equipped with an electrically operated filler valve 17a connecting it to delivery line 19 from pump 15, and with an electrically operated valve 18a connecting it to condenser 12. If valve 18a is in a given direction, it must be connected in series with a non-return valve (not shown).

Located inside container 16a are a circulat ing coil 19a for a fluid constituting the heat source and an electrical resistance 20a for additional heating. As will be seen hereinafter, resistance 20a is designed to heat a fluid in the gaseous phase and, for this reason, it must be of low specific power (for example 2 W/cm2). Pressure relief means 13 must be capable of restoring the fluid to a predetermined low pressure even at the maximum value of high pressure produced by the climatic conditions in the area where the unit is installed. On the other hand, it should generally be controlled by a temperature sensitive bulb located downstream of evaporator 14.

Where the energy for compressing the fluid by heat is derived from the sun, coil 19a may be associated with a circuit comprising a solar collector 21 and a circulating pump 22, the delivery line from which has two branches; one connecting to coil 19a through electrically operated valve 23a, the other connecting to coil 19b through valve 23b. The fluid transferring the heat from collector 21 to the coil 19a returns to the collector 21, through a branch 24a and a return line 25. The coil may be made of copper, for example, while the container 16a is made of steel to withstand the maximum pressure reached, taking into account the applicable safety factors. As may be seen, container 1 6b contains the same components as container 16a and therefore needs no description.

It should be noted in passing that solar collectors 21 need not have an extremely high temperature output. In practice, a coil input temperatuer of over 25"C is sufficient to operate the apparatus.

Condenser 12 may be of a design which is conventional in refrigerating equipment except that it must be able to ensure condensation even at high inlet temperatures, which means that the heat exchange area must be larger. The condenser 12 may be in the form of a heat exchange core located in the flow of air from a fan 26. When the apparatus is being used to cool a building, fan 26 blows outside air onto the heat exchange core in condenser 12. Pressure relief 13 and evaporator 14 may also be of conventional design. When the apparatus is used for cooling the air in a building, a fan 27 blows incoming air through the heat exchange core in the evaporator 14.

Volumetric pump 15 may be a conventional piston-type pump operating at all times at a low pressure differential. All it has to supply is the barometric pressure corresponding to the difference between evaporator 14 and exchangers 10, plus any low residual pressure in the container to be filled. The apparatus also comprises an auxiliary circuit making it possible to limit the pressure reached in the containers immediately prior to filling. This circuit comprises a line 28 equipped with a secondary pressure relief valve 29 connected upstream to the main circuit between accumulator 11 and pressure relief 13 and dividing downstream into two branches connected to containers 16a and 16b through electrically operated valves 30a and 30b respectively.

All of the components may be controlled, in an unalterable time sequence, for example by rotating cams in a sequencer 32 acting upon switches controlling the electrically operated valves and pumps 15 and 22.

The operating sequence may, for example, be as shown diagrammatically in Fig. 2, in which a full cycle T corresponds to one revolution or half a revolution of cam rotating at a constant velocity. The thick portions of the various lines indicate periods of activation (pumps operating or valves open) of the components whose reference numbers are shown on the left.

1. A cycle will be assumed to start when valve 23a and circulating pump 22 have just been energized. This causes con tainer 1 6a to be heated, and at this point pump 15 is still inactive. Valve 30b is open and a small flow of cooled fluid expands into container 16b where it vaporizes to reduce the pressure to a valve close to the pressure upstream of pump 15. Valves 17a, 18a, 18b, 23b and 30a are closed while valve 17b is open. During this first phase, which may last for a few seconds, accumulator 11 maintains a flow of coolant fluid in the main circuit, through pressure re lief 13 and evaporator 14. The high pressure fluid, in a gaseous phase, con denses in condenser 12; the pressure of the liquid is reduced by pressure re lief 13 so that it takes back a gaseous state in evaporator 14.

2. At the end of phase 1, valve 30a closes Valve 18a opens, allowing pressurized container 16a to feed coolant fluid to the circuit. Container 16a remains pressurized by a constant heating sup plied by the circulation of fluid from solar collector 21 through valve 23a and coil 19a. Valve 30b closes. Pump 15 is energized to return the coolant fluid which has passed into the vapour phase in evaporator 14 through valve 17b to container 16b.

3. At the end of phase 2, valve 23a closes and pump 22 stops, thus cutting off the supply of heat to container 16a. How ever, the pressure obtained in the said container is sufficient to feed coolant fluid to the main circuit, and this fluid is then returned by pump 15 to con tainer 16b.

4. Phase 4 begins when container 16b is full of coolant fluid in the gaseous phase and when container 16a becomes empty and the pressure therein drops.

During phase 4, all of the electrically operated valves are closed except valve 17a, and the pumps 15, 22 are halted.

The pressures begin to balance through pump 15 and accumulator 11 feeds the condenser 12 for a few seconds.

5. Phase 5 may be regarded as sym metrical with phase 1. Container 1 6b starts being heated up by the circula tion of fluid from solar collector 21, valve 23b being open and pump 22 energized. The opening of valve 30a allows the equalization of pressures up stream and downstream of pump 15 to proceed.

6. Phase 6 is symmetrical with phase 2, the functions of containers 1 6a and 1 6b being reversed.

The cycle is finally terminated by phases 7 and 8 which may be regarded as symmetrical with phases 3 and 4.

The electrically-operated valves and pumps may be controlled by a set of switches which are caused to open and close by rotating cams driven by a single motor. Each of these cams is shaped to provide open and closed periods corresponding to those indicated in Fig. 2.

The following characteristics are given, by way of example, as applicable to an apparatus designed to operate in a desert climate and to provide approximately 60,000 BTU/hr cooling, the source of energy being water at a temperature of between 25 and 100"C from a solar collector.

The cold-producing fluid is CHF2CI, the boiling temperature of which, at atmospheric pressure, is about --41"C. The apparatus is designed to operate at a high pressure, upstream of pressuer relief 13, of between approximately 17 and 15 atmospheres. The pressure relief 13, of the DANFOSS type, serves to provide low pressure, of the order of 5 atmospheres to the evaporator 14. The components are of conventional design.

There are two containers 1 6a and 16b, they are made of steel, as is accumulator 11, and they have a capacity of a few litres. The evaporator 14 is of commercial design, of the "FRIGA" or "ECO" brand, for example, as is the condenser 12. The volumetric pump 15 has a power of 1 kW and operates at a pressure differential of less than 0.5 atmosphere. Period T is of several minutes. It should be noted in passing that a conventional apparatus, with mechanical compression, produces a refrigerating output of the order of 11,000 BTU/hr only for about 1 kW of mechanical power.

Control block 32 houses the switching cams, their drive motor and the control for the pressure limiting circuit. It may also contain an element which, in the event of momentary failure of the power source collector is used), energizes resistances 20a and 20b in suitable sequence.

The invention is obviously not restricted to the particular example or embodiment illustrated and described herein. It is applicable regardless of the source of thermal energy (which may be of geothermal origin or may consist of industrial or power-station waste). It may be used as a refrigerator or as a heat pump. It may also be equipped with an ambient thermostat which, as soon as the desired temperature has been reached, shuts off all supplies except those to fans 26 and 27. The evaporator 14 may be of the submerged type, which makes it possible to use a pump 15 operating in the liquid phase. The present patent obviously also covers such variants and any others within the scope of equivalents.

WHAT I CLAIM IS:- 1. An apparatus for the production of cold or heat using the Rankine cycle, said apparatus providing a main circuit for the circulation of a coolant fluid, the said apparatus comprising, consecutively in the direction of circulation of the said coolant fluid: means for compressing the said coolant fluid by the exchange of heat between it and a source of heat, means for condensing the coolant fluid by the exchange of heat, a pressure relief means, a heat exchange evaporator which provides a flow of cooling air, and a pump which returns the coolant fluid to the said compressing means, said compressing means comprising at least two heat exchangers between the fluid and the source of heat, switching means being provided for feeding the condenser successively from each of the said heat exchangers and, at the same time, for connecting to the pump delivery an exchanger other than that which feeds the condenser, the switching sequence being such that the operating cycles of the said heat exchangers are alternated.

2. Apparatus according to claim 1, wherein the switching means bring about exchanges of heat only between the source of heat and that heat exchanger which feeds the condenser or is about to feed the condenser.

3. Apparatus according to claim 2, wherein the source of heat is provided by the circulation of secondary fluid heated by a solar collector or by industrial waste.

4. Apparatus according to claim 1, wherein the condenser operates by the exchange of heat between the coolant fluid and a flow of atmospheric air.

5. Apparatus according to claim 1, further including a pressure reducing circuit downstream of the condenser, said pres

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. full of coolant fluid in the gaseous phase and when container 16a becomes empty and the pressure therein drops. During phase 4, all of the electrically operated valves are closed except valve 17a, and the pumps 15, 22 are halted. The pressures begin to balance through pump 15 and accumulator 11 feeds the condenser 12 for a few seconds. 5. Phase 5 may be regarded as sym metrical with phase 1. Container 1 6b starts being heated up by the circula tion of fluid from solar collector 21, valve 23b being open and pump 22 energized. The opening of valve 30a allows the equalization of pressures up stream and downstream of pump 15 to proceed. 6. Phase 6 is symmetrical with phase 2, the functions of containers 1 6a and 1 6b being reversed. The cycle is finally terminated by phases 7 and 8 which may be regarded as symmetrical with phases 3 and 4. The electrically-operated valves and pumps may be controlled by a set of switches which are caused to open and close by rotating cams driven by a single motor. Each of these cams is shaped to provide open and closed periods corresponding to those indicated in Fig. 2. The following characteristics are given, by way of example, as applicable to an apparatus designed to operate in a desert climate and to provide approximately 60,000 BTU/hr cooling, the source of energy being water at a temperature of between 25 and 100"C from a solar collector. The cold-producing fluid is CHF2CI, the boiling temperature of which, at atmospheric pressure, is about --41"C. The apparatus is designed to operate at a high pressure, upstream of pressuer relief 13, of between approximately 17 and 15 atmospheres. The pressure relief 13, of the DANFOSS type, serves to provide low pressure, of the order of 5 atmospheres to the evaporator 14. The components are of conventional design. There are two containers 1 6a and 16b, they are made of steel, as is accumulator 11, and they have a capacity of a few litres. The evaporator 14 is of commercial design, of the "FRIGA" or "ECO" brand, for example, as is the condenser 12. The volumetric pump 15 has a power of 1 kW and operates at a pressure differential of less than 0.5 atmosphere. Period T is of several minutes. It should be noted in passing that a conventional apparatus, with mechanical compression, produces a refrigerating output of the order of 11,000 BTU/hr only for about 1 kW of mechanical power. Control block 32 houses the switching cams, their drive motor and the control for the pressure limiting circuit. It may also contain an element which, in the event of momentary failure of the power source collector is used), energizes resistances 20a and 20b in suitable sequence. The invention is obviously not restricted to the particular example or embodiment illustrated and described herein. It is applicable regardless of the source of thermal energy (which may be of geothermal origin or may consist of industrial or power-station waste). It may be used as a refrigerator or as a heat pump. It may also be equipped with an ambient thermostat which, as soon as the desired temperature has been reached, shuts off all supplies except those to fans 26 and 27. The evaporator 14 may be of the submerged type, which makes it possible to use a pump 15 operating in the liquid phase. The present patent obviously also covers such variants and any others within the scope of equivalents. WHAT I CLAIM IS:-

1. An apparatus for the production of cold or heat using the Rankine cycle, said apparatus providing a main circuit for the circulation of a coolant fluid, the said apparatus comprising, consecutively in the direction of circulation of the said coolant fluid: means for compressing the said coolant fluid by the exchange of heat between it and a source of heat, means for condensing the coolant fluid by the exchange of heat, a pressure relief means, a heat exchange evaporator which provides a flow of cooling air, and a pump which returns the coolant fluid to the said compressing means, said compressing means comprising at least two heat exchangers between the fluid and the source of heat, switching means being provided for feeding the condenser successively from each of the said heat exchangers and, at the same time, for connecting to the pump delivery an exchanger other than that which feeds the condenser, the switching sequence being such that the operating cycles of the said heat exchangers are alternated.

2. Apparatus according to claim 1, wherein the switching means bring about exchanges of heat only between the source of heat and that heat exchanger which feeds the condenser or is about to feed the condenser.

3. Apparatus according to claim 2, wherein the source of heat is provided by the circulation of secondary fluid heated by a solar collector or by industrial waste.

4. Apparatus according to claim 1, wherein the condenser operates by the exchange of heat between the coolant fluid and a flow of atmospheric air.

5. Apparatus according to claim 1, further including a pressure reducing circuit downstream of the condenser, said pres

sure reducing circuit comprising a pressure relief means and valves electrically operable to provide a small amount of condensed coolant fluid back to the heat exchanger which is then at low pressure.

6. Apparatus according to claim 1, wherein the main circuit further includes an accumulator located downstream of the condenser.

7. Apparatus according to claim 1, wherein the heat exchangers each have additional heating elements, such as electrical resistance elements.

8. Apparatus according to claim 1, wherein the pump is of the low differential pressure, volumetric type.

9. Apparatus according to claim 1, wherein the switching means include electrically operated valves located in the main circuit upstream and downstream of the heat exchangers and on the means connecting the source of heat to the heat exchangers.

10. Apparatus according to claim 9, wherein the switching means also includes a control element using a predetermined time sequence.

11. Apparatus according to claim 4, further including means for mixing the said flows of air from the condenser and the evaporator in order to supply air at a temperature adjustable between the air temperature at the condenser and that at the evaporator.

12. Apparatus according to claim 10, wherein the switching means establishes the following sequence of operation: (a) with the coolant pump stopped, the downstream side of this pump is connected to the first heat exchanger, with the second heat exchanger isolated in order to achieve partial pressure balance between the upstream and the downstream side of the said pump; (b) an auxiliary pressure reducing circuit is opened temporarily between the downstream side of the condensing means and the first heat exchanger, thus decreasing still further the pressure in the said first heat exchanger connected to the pump; and (c) the pump which returns the fluid to the first heat exchanger is activated and, at the same time, the valve feeding coolant fluid from the condensation means to the second heat exchanger is opened.

13. Apparatus for the production of cold or heat using the Rankine cycle, constructed and adapted to operate substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

13. Apparatus for the production of cold or heat using the Rankine cycle, constructed and adapted to operate substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

sure reducing circuit comprising a pressure relief means and valves electrically operable to provide a small amount of condensed coolant fluid back to the heat exchanger which is then at low pressure.

6. Apparatus according to claim 1, wherein the main circuit further includes an accumulator located downstream of the condenser.

7. Apparatus according to claim 1, wherein the heat exchangers each have additional heating elements, such as electrical resistance elements.

8. Apparatus according to claim 1, wherein the pump is of the low differential pressure, volumetric type.

9. Apparatus according to claim 1, wherein the switching means include electrically operated valves located in the main circuit upstream and downstream of the heat exchangers and on the means connecting the source of heat to the heat exchangers.

10. Apparatus according to claim 9, wherein the switching means also includes a control element using a predetermined time sequence.

11. Apparatus according to claim 4, further including means for mixing the said flows of air from the condenser and the evaporator in order to supply air at a temperature adjustable between the air temperature at the condenser and that at the evaporator.

12. Apparatus according to claim 10, wherein the switching means establishes the following sequence of operation: (a) with the coolant pump stopped, the downstream side of this pump is connected to the first heat exchanger, with the second heat exchanger isolated in order to achieve partial pressure balance between the upstream and the downstream side of the said pump; (b) an auxiliary pressure reducing circuit is opened temporarily between the downstream side of the condensing means and the first heat exchanger, thus decreasing still further the pressure in the said first heat exchanger connected to the pump; and (c) the pump which returns the fluid to the first heat exchanger is activated and, at the same time, the valve feeding coolant fluid from the condensation means to the second heat exchanger is opened.