GB2052712A

GB2052712A - Energy Transfer System

Info

Publication number: GB2052712A
Application number: GB8017607A
Authority: GB
Original assignee: VENTLINE Manufacturing Ltd
Current assignee: VENTLINE Manufacturing Ltd
Priority date: 1979-06-01
Filing date: 1980-05-29
Publication date: 1981-01-28
Also published as: DE3020434A1; AU532576B2; FR2458031B3; FR2458031A1; IL60196A0; ES492043A0; AU5883580A; GB2052712B; ES8101757A1

Abstract

A heat pump system utilizing the waste heat of a closed cycle refrigeration means to heat a liquid e.g. water comprises a compressor 18, evaporator 14, condenser 22 and expansion valve 26 wherein the liquid is supplied via the condenser through lines 30, 32 to a liquid reservoir 34 at a flow rate controlled by a valve 50 in the line 32 responsive to means 49 sensing conditions at the discharge of the compressor. In a modification means are provided for sensing the temperature at the top and bottom of the reservoir for controlling operation of the compressor according to predetermined differences in the two temperatures. <IMAGE>

Description

SPECIFICATION Energy Transfer System Description of the Prior Art In an example of a prior art system, as shown in USA patent specification 3,922,876 (Thomas I Wetherington Jr), an energy conservation system is disclosed for utilizing the waste heat from an air conditioner or refrigeration system to heat water.

A pump is provided between a water reservoir and a heat exchanger for circulating the water. A temperature sensor is thermally coupled to the water and electrically coupled to the pump for rendering the pump inoperative when the temperature of the water in the reservoir is at or above a preselected temperature. A temperature operated valve is interposed between the heat exchanger and the reservoir, such that only water heated to a predetermined temperature is delivered to the reservoir. Such a system has several disadvantages arising in particular therefrom that it basicaily senses only the water temperature to control the water flow rate through the heat exchanger. By watching only the ater temperature, the compressor head pressure could increase excessively and this results in decreased life of the compressor and less efficiency.Also if there is an interruption in the flow circulation of the water, the water at the temperature sensor may be cool or cold and yet in the remaining part of the system the water may be overheated because the refrigeration system will continue to operate. Thus excessive pressures may occur in the compressor.

The success of any energy transfer system depends on the cost of the system involved compared to the saving of the cost of energy utilized. The compressor in turn generally forms the most expensive part of such a system and also is the part which is mostly prone to failure. It therefore is extremely important to ensure that the compressor efficiency is as high as possible and that the life of the compressor is extended for as long as possible. This important aspect is not taken care of in the prior USA patent specification. Other disadvantages of the system disclosed in the USA patent specification are that the refrigeration system may wander because the water temperature is used for control purposes (in other words an external factor in so far as the compressor is concerned) instead of controlling an internal factor in the compressor as such.The system as suggested therefore will use more energy than is necessary and thereby electricity will be wasted.

Although the present invention would generally involve "water" it must be understood that the invention is applicable to any suitable liquid and the specification and claims therefore must be understood not to be restricted to water.

Summary of Invention According to the invention, an energy transfer system includes (a) refrigeration means having in a closed cycle a compressor for a compressible refrigerant, a heat exchanger, a refrigerant flow rate control member and an evaporator; (b) a liquid reservoir; (c) liquid supply means for supplying liquid to the heat exchanger for transferring heat from the refrigerant thereto; (d) liquid discharge means for leading the liquid from the heat exchanger to the liquid reservoir; (e) a compressor sensing means for sensing a particular condition at the discharge of the compressor; and (f) a flow rate control means operatively coupled to the compressor sensing means and being adapted to control the liquid flow rate through the heat exchanger in dependence on conditions sensed by the compressor sensing means at the discharge of the compressor.

The compressor sensing means may be adapted to sense the temperature in the discharge of the compressor, and/or the pressure in the discharge of the compressor.

The refrigerant flow rate control member may be an expansion valve, or a capillary tube.

The liquid reservoir may include an additional heater for heating the liquid when required.

A bypass may be provided between the compressor discharge and the inlet to the evaporator, a solenoid valve in the bypass, and control means responsive to the suction pressure of the compressor for causing the refrigerant to be bypassed directly from the compressor to the evaporator should the suction pressure of the compressor drop below a predetermined value, and also being responsive to rising suction pressure of the compressor to close the solenoid valve in the bypass when a predetermined suction pressure is reached.

A temperature sensing means may be provided for sensing the temperature at the bottom of the liquid reservoir, the temperature sensing means being adapted to cause inoperation of the compressor if the temperature sensed reaches a predetermined value.

A first temperature sensing means may be provided for sensing the temperature in an upper level in the liquid reservoir, and a second temperature sensing means adapted for sensing the temperature at a lower level, both temperature sensing means being coupled electrically to the compressor to allow activation of the compressor only if particular low temperatures are sensed, and both temperature sensing means being interconnected to deactivate the compressor when the lower sensor exceeds a predetermined temperature.

The second temperature sensing means may be adapted to sense the temperature at the floor of the liquid reservoir, or at the liquid supply inlet to the reservoir, or at any suitable position in the liquid supply to the reservoir.

The heat exchanger may have a precooler through which liquid is passed prior to reaching the heat exchanger.

Liquid may be supplied directly from a supply source to the heat exchanger, and a pump may be provided for pumping liquid from the supply source to the heat exchanger.

Alternatively, liquid may be supplied from the liquid reservoir to the heat exchanger.

The liquid reservoir may have a discharge for discharging liquid from the upper level of the reservoir and/or the liquid reservoir may have a discharge for discharging liquid under gravity from the liquid reservoir.

The liquid may be water.

Also according to the invention, an energy transfer system, includes (a) refrigeration means having in a closed cycle a compressor for a compressible refrigerant, a heat exchanger, a refrigerant flow rate control member and an evaporator; (b) a liquid reservoir; (c) liquid supply means for supplying liquid to the heat exchanger for transferring heat from the refrigerant thereto; (d) liquid discharge means for leading the liquid from the heat exchanger to the liquid reservoir; (e) a compressor sensing means for sensing a particular condition at the discharge of the compressor; (f) a flow rate control means; adapted to control the liquid flow rate through the heat exchanger; and (g) a first temperature sensing means provided for sensing the temperature in an upper level in the liquid reservoir, and a second temperature sensing means adapted for sensing the temperature at a lower level, both temperature sensing means being coupled electrically to the compressor to allow activation of the compressor only if particular low temperatures are sensed, and both temperature sensing means being interconnected to deactivate the compressor when the lower sensor exceeds a predetermined temperature.

The Drawings The invention will now be described by way of example with reference to the accompanying schematic drawings.

In the drawings there is shown in Fig. 1 a flow chart block diagram of a first embodiment of an energy transfer system in accordance with the invention and including a gravity liquid reservoir; and Fig. 2 a flow chart block diagram of a second embodiment of an energy transfer system in accordance with the invention and including a pressurised liquid reservoir.

Description of the Preferred Embodiments in the description below reference is made to systems in which the liquid heated is water.

However, as mentioned before, any other suitable liquids may be heated, such as chemical treatment liquid, oil, washing liquid mixtures, etc.

Referring now to Fig. 1 , the energy transfer system 10 includes a refrigeration means having in closed cycle an evaporator 12, which is adapted to be cooled off by a fan 14 and which is joined by way of a refrigerant flow line 1 6 to a compressor 1 8. The compressor 18, having an inlet or suction side and an outlet or discharge side, is electrically or otherwise operated but details of the operation circuits are not shown.

From the compressor 1 8 a flow line 20 leads to a condensor or heat exchanger 22, and from here the flow line 24 extends to a refrigerant flow rate control member in the form of an expansion valve 26 (which may be replaced by a suitable capillary tube), which is coupled by means of the flow line 28 to the evaporator 12.

In the embodiment as illustrated in Fig. 1, water is supplied directly from the mains supply along the water supply line 30 to the heat exchanger 22, and the discharge takes place via the flow line 32 to the reservoir, which is in the form of a storage tank or vessel 34. In this case a gravity system 36 is involved and the tank 34 is open to atmosphere.

The tank 34 is provided with a standby electrical heater 38 having its own controlling thermostat 40. Should the water in the tank 34 be unused for a long period of time, the temperature will drop from its initial predetermined temperature (e.g. 600C). These losses are common to all storage vessels whether used in conjunction with heat pumps or not. Loss of heat of this nature is due to radiation and conduction iosses. When the temperature reaches the set point of the thermostat 40 (e.g. 55 OC), the heater 38 will be activated provided the system 10 is not supplying hot water at that moment.

The size of the heater 38 therefore is usually based on the lowest total input power to the system 10.

Although the auxiliary heater 38 can be capable of acting as a partial standby for hot water supply in the event of a pump failure, an additional electrical heater 42 may also be installed in a similar position so that, combined with the auxiliary heater 38, the heater 42 could have a capacity equivalent to the entire system output. This standby heater 42 would then be controlled by its own thermostat via the system 10 in the same manner as the heater 38.

Accordingly, it would be isolated while the unit would function normally. In this manner it would be possible to have a 100% standby system at relatively low cost.

Discharge takes place from the tank 34 through the outlet line 44. The outlet line 44 is just above the heater 38 so that in the event of system malfunction, the heater 38 will always be covered with water.

A water level detector 46 consists of an airpipe which conveys a pressure signal to the energy transfer system 10 to control the duration of hot water conduction via the system. This detector 46 may be substituted by a thermostat or other suitable temperature sensing means.

The sequence of the operation is as follows: Water is supplied continuously at mains pressure to the system 10 via the supply pipe 30.

If the water level is too low in the tank 34, a reduced pressure signal will be transmitted by the pressure probe 46, which will in turn cause operation of the compressor 18 so as to produce hot water. Water will then flow through the heat exchanger 22 back into the top of the storage vessel 34 until a level is reached where the sensor 46 switches off the compressor 18 and thereby the system 10. A pump 48 may, if deemed necessary, be provided in the flow line 30.

While the system 10 is in operation, the water flow rate is maintained to control a relatively constant outlet temperature (e.g. 600C). This is done by way of a compressor sensing means 49 (e.g. a pressure sensor or a thermostat) coupled to the discharge of the compressor 1 8, and being adapted, depending on the conditions sensed, to control the flow rate by way of a flow rate control means in the form of a valve 50 in the flow line 32.

The heat injected into the water is extracted from the air drawn over the evaporator 12 by the fan 14. If the outside air temperature drops, the water will still leave the system 10 at the predetermined temperature (e.g. 600C) but the comparatively lower output of the unit under these conditions, will necessitate a decreased water flow rate in order to maintain the required water outlet temperature. The flow rate is reduced by adjustment of the valve 50 via the head pressure and/or temperature of the compressor 1 8.

In the event of sustained very cold periods, frosting might occur on the evaporator 12, in which case a solenoid valve 52 will operate to bypass hot refrigerant gas along the flow line 54 directly through the cold evaporator 12 until the ice has thawed. This is done by means of a detector 56 adapted to detect the suction pressure of the compressor 18 and, when this pressure drops below a predetermined value, then the solenoid valve 52 is activated and the fan 14 is switched off. On rising suction pressure when reaching a predetermined value, the detector 56 will turn off the valve 52 and reactivate the fan 14.

In the discharge line 44 a pump 58 may be provided for supplying water to various outlets 60 as may be required by an end user.

Referring now to Fig. 2, a pressurised storage vessel system 62 is illustrated. As the internal operation of the heat exchange system 10 is the same as that described in connection with Fig. 1, the description of the similar parts and their operation will not be repeated and will be indicated by means of the same reference numerals.

In the embodiment illustrated in Fig. 2, the cold mains water is fed through the supply pipe 64 via a pipe 68 into the bottom of the water reservoir or storage vessel or tank 70. There may be an interposing pressure regulator 66 located between the pipes 64 and 68. Whenever water is drawn off from the tank 70, cold water flows into the bottom of the tank 70 so as exactly to replace the water that has been consumed. The basic difference between the gravity system (Fig. 1) and the pressurised or closed vessel system (Fig. 2) therefore is that the water temperature in the gravity system is always at a predetermined temperature (e.g. 600C) while in the case of the pressurised tank 70 there always is a layer of cold water in the bottom of the tank 70.

As the cold water in the bottom of the tank 70 rises, it is detected by a first thermostat 72 located in the tank 70 a short distance up from the bottom of the tank. This thermostat 70 is adapted to activate the compressor 1 8. A pump 74, which draws water from the bottom of the pressurised vessel 70, passes it through the heat exchanger 22, and deposits it at the predetermined temperature back into the top of the tank 70 after having passed through the heat exchanger 22. This procedure continues until the tank is full of heated water at the predetermined temperature. For determining this condition a second thermostat 76 can be located at the bottom of the tank 70 (or in the flow line 68 or in the flow line 78).

The discharge from the tank 70 takes place through the discharge pipe 80 to various outlets 82. A pump 84 may be provided in the pipe 80 if required.

The provision of two thermostats, namely one thermostat 72 inbetween the floor and the upper level in the tank 70 and a second thermostat 76 at the floor or in the flow line 68 or 78, is such that, only when both thermostats show sensing cold water, will the system 10 start to operate.

The thermostats 70, 76 are interlocked in such a manner that the compressor 18 (and thereby the system 10) will only be deactivated when the lower thermostat senses a relatively high temperature (e.g. 300C). This results in a longer running period of the compressor 1 8. Accordingly there is no continuous on/off switching of the compressor resulting in high wear and tear and short life.

The refrigerant in the system 10 may be freon 22, (Registered Trade Mark).

If necessary, a subcooler 86 may be provided downstream of the heat exchanger 22. The water therefore will first pass through the subcooler 86 and then through the heat exchanger 22.

The system in accordance with the invention provides that the water discharge temperatures are in excess of the condensing temperatures, by, say 50C, due to the effect of superheat. This makes it possible to lower condensing pressures and thereby it contributes considerably to the efficiency. Obviously, due to the fact that lower condensing pressures and/or temperatures are used, the life of the compressor is increased.

Also, due to the control of the temperature sensor 76, which ensures that the water in the conduit 78 does not exceed a certain temperature (e.g. 280C), a facility for extensive subcooling is provided. Thereby the efficiency of the system improves.

Claims

1. An energy transfer system, which includes (a) refrigeration means having in a closed cycle a compressor for a compressible refrigerant, a heat exchanger, a refrigerant flow rate control member and an evaporator; (b) a liquid reservoir; (c) liquid supply means for supplying liquid to the heat exchangerfor transferring heat from the refrigerant thereto; (d) liquid discharge means for leading the liquid from the heat exchanger to the liquid reservoir; (e) a compressor sensing means for sensing a particular condition at the discharge of the compressor; and (f) a flow rate control means operatively coupled to the compressor sensing means and being adapted to control the liquid flow rate through the heat exchanger in dependence on conditions sensed by the compressor sensing means at the discharge of the compressor.

2. A system as claimed in claim 1, in which the compressor sensing means is adapted to sense the temperature in the discharge of the compressor.

3. A system as claimed in claim 1 or in claim 2, in which the compressor sensing means is adapted to sense the pressure in the discharge of the compressor.

4. A system as claimed in any one of the preceding cairns, in which the refrigerant flow rate control member is an expansion valve.

5. A system as claimed in any one of claims 1 to 3, in which the refrigerant flow rate control member is a capillary tube.

6. A system as claimed in any one of the preceding claims, in which the liquid reservoir includes an additional heater for heating the liquid when required.

7. A system as claimed in any one of the preceding claims, in which a bypass is provided between the compressor discharge and the inlet to the evaporator, a solenoid valve in the bypass, and control means responsive to the suction pressure of the compressor for causing the refrigerant to be bypassed directly from the compressor to the evaporator should the suction pressure of the compressor drop below a predetermined value, and also being responsive to rising suction pressure of the compressor to close the solenoid vale in the bypass when a predetermined suction pressure is reached.

8. A system as claimed in any one of the preceding claims, in which a temperature sensing means is provided for sensing the temperature at the bottom of the liquid reservoir, the temperature sensing means being adapted to cause inoperation of the compressor if the temperature sensed reaches a predetermined value.

9. A system as claimed in any one of the preceding claims, in which a first temperature sensing means is provided for sensing the temperature in an upper level in the liquid reservoir, and a second temperature sensing means adapted for sensing the temperature at a lower level, both temperature sensing means being coupled electrically to the compressor to allow activation of the compressor only if particular low temperatures are sensed, and both temperature sensing means being interconnected to deactivate the compressor when the lower sensor exceeds a predetermined temperature.

10. A system as claimed in claim 9, in which the second temperature sensing means is adapted to sense the temperature at the floor of the liquid reservoir.

11. A system as claimed in claim 9, in which the second temperature sensing means is adapted to sense the temperature at the liquid supply inlet to the reservoir.

12. A system as claimed in claim 9, in which the second temperature sensing means is adapted to sense the temperature at any suitable position in the liquid supply to the reservoir.

13. A system as claimed in any one of the preceding claims, in which the heat exchanger has a precooler through which liquid is passed prior to reaching the heat exchanger.

14. A system as claimed in any one of the preceding claims, in which liquid is supplied directly from a supply source to the heat exchanger.

15. A system as claimed in claim 14, in which a pump is provided for pumping liquid from the supply source to the heat exchanger.

16. A system as claimed in any one of the preceding claims, in which liquid is supplied from a liquid reservoir to the heat exchanger.

1 7. A system as claimed in any one of the preceding claims, in which the liquid reservoir has a discharge for discharging liquid from the upper level of the reservoir.

18. A system as claimed in any one of the preceding claims, in which the liquid reservoir has a discharge for discharging liquid under gravity from the liquid reservoir.

19. A system as claimed in any one of the preceding claims, in which the liquid is water.

20. An energy transfer system, which includes (a) refrigeration means having in a closed cycle a compressor for a compressible refrigerant, a heat exchanger, a refrigerant flow rate control member and an evaporator; (b) a liquid reservoir; (c) liquid supply means for supplying liquid to the heat exchanger for transferring heat from the refrigerant thereto; (d) liquid discharge means for leading the liquid from the heat exchanger to the liquid reservoir; (e) a compressor sensing means for sensing a particular condition at the discharge of the compressor; (f) a flow rate control means; adapted to control the liquid flow rate through the heat exchanger; and (g) a first temperature sensing means provided for sensing the temperature in an upper level in the liquid reservoir, and a second temperature sensing means adapted for sensing the temperature at a lower level, both temperature sensing means being coupled electrically to the compressor to allow activation of the compressor only if particular low temperatures are sensed, and both temperature sensing means being interconnected to deactivate the compressor when the lower sensor exceeds a predetermined temperature.

21. An energy transfer system substantially as hereinbefore described with reference to Fig. 1 or Fig. 2 of the accompanying schematic drawings.