US3091944A - Heat pump system - Google Patents

Description

June 1963 D. VAN DEN BERGE ETAL HEAT PUMP SYSTEM Filed Oct. 31. 1961 I N V E N T 0 R S D E N B E R G T G. M l N E m 0 O o 2 A T T O R N E Y S United States Patent 3,091,944 HEAT PUMP SYSTEM Dick Van Den Barge and Robert G. Miner, both of La Crosse, Wis, assignors to The Trane Company, La Crosse, Win, a corporation of Wisconsin Filed Oct. 31, 1961, Ser. No. 149,076 4 Claims. (Cl. 6ZP-197) This invention relates generally to a heat pump refrigcrating system and more particularly to a heat pump retrigeration system which incorporates a high side pressure control when the temperature of the coolant passing over the heat exchanger acting as a condenser is below that necessary for proper operation of the expansion means.

In recent years, the air conditioning industry has had serious problems in the use of air conditioning equipment Where the temperature of the cooling fluid, employed as the heat absorbing medium for the heat exchanger acting as a condenser, is abnormally low. The employment of such low temperature heat absorbing medium results in a drop in high side pressure below a predetermined level causing a reduction in the useful capacity of the heat exchanger acting 'as an evaporator due to inadequate operating pressures at the expansion means. The solution to the problem naturally entails raising or maintaining the high side pressure. Basically, this is done by flooding or reducing the effectiveness of the heat exchanger acting as a condenser when the high side pressure falls below a predetermined minimum.

In the normal heat pump operation employing air [on both the heat exchangers the above problem is prevalent on both the heating and cooling cycles. On the cooling cycle when the temperature of the condensing medium is below that desired the evaporator does not perform the cooling performance required to maintain proper comfort conditions in the conditioned space. On the heating cycle the heat exchange medium being heated by the heat exchanger acting as a condenser is normally of a very low temperature causing insufiicient pressure at the expansion means resulting in premature icing of the heat exchanger acting as an evaporator and in stopping of the compressor on low pressure cut-out due to low suction pressure.

It is, therefore, an object of the invention to provide automatic control of the head or high side pressure in a heat pump system by flooding the heat exchanger acting as a condenser in response to high side pressures.

Another object of the invention is to provide a hot gas bypass conduit fiom the compressor discharge line to the liquid line between the condenser and receiver and to provide pressure responsive means in the bypass conduit and in the condenser outlet conduit to control the effective condensing surface of the condenser.

A third object of the invention is to provide a heat pump refrigeration cycle with a hot gas bypass conduit extending from the compressor discharge line to the liquid line and bypassing the condenser a'nd to provide a pressure responsive valve at the junction of the hot ga bypass conduit and the liquid line to automatically maintain the proper high side pressure at low ambient coolant temperatures.

A still further object of the invention is to provide a heat pump refrigeration cycle with hot gas bypass conduit from the compressor discharge line to the liquid line and bypassing the condenser and to provide pressure responsive valves in the hot gas bypass conduit and in the liquid line between the condenser and the junction of the bypass conduit and the liquid line to control the high side pressure.

Other objects and advantages of the invention will be 3,091,944 Patented June 4, 1963 clearly apparent as the specification proceeds to describe the invention with reference to the accompanying drawings in which:

FIGURE 1 is a schematic representation of a refrigeration system incorporating the invention in the preferred embodiment; and

FIGURE 2 schematically represents another form of the invention.

FIGURE 1 shows the preferred embodiment of the in,- vention incorporated in a refrigeration system including a compressor 10, an outdoor heat exchanger 12, a receiver 14, expansion means 16 and 17, and an indoor heat exchanger 18. Expansion means 16 and 17 are shown as expansion valves responsive to suction, but obviously other expansion devices may be used without departing from the scope of the invention. A tour vvay reversing valve 20 of any conventional construction is connected between the heat exchangers 18 land 12. A high pressure cut-out 22 is connected to discharge line 24 to stop the compressor 10 in case of unusually high discharge pressures. A low pressure cut-out 26 is connected to suction conduit 28 to stop the operation of compressor 10 in case of unusually low suction pressures.

On the normal cooling cycle hot uncondensed refrigerant will pass through conduit 24, reversing valve 20, conduit 30 to the outdoor heat exchanger 12 :and be condensed therein. Liquid refrigerant from heat exchanger 12 will then flow to receiver 14 through conduits 32 and 34, check valve 36, conduits 38 and 4-0, and three Way pressure responsive valve 42. From receiver 14 liquid refrigerant flows through conduit 44, check valve 46', conduit 48, expands through expansion valve 16, passes through conduits 5i and 52, absorbs heat from the air to be conditioned in the indoor heat exchanger 18 and returns to the compressor 10 through conduit 54, reversing valve 20, and conduit 28. On the normal heating cycle, the position of reversing valve 2b is reversed and hot uncondensed refrigerant is delivered to indoor heat exchanger 18 through conduits 24 and 54 where the refrigerant is condensed and gives up heat to the heat exchange medium passing through the heat exchanger. Condensed refrigerant then flows to receiver 14 through conduit 52, check valve 56, conduits 53 and 4t), and three way pressure responsive valve 42. Liquid refrigerant from the receiver flows through conduit 6i), check valve 62, conduit 64, expands through expansion valve 17 and passes into the outdoor heat exchanger 12 via conduitsds and 32 wherein it absorbs heat from the heat exchange medium passing over the heat exchanger. The vaporized refiriger-ant is then returned to the compressor via conduit 3%, reversing valve 20, and suction conduit 28.

Three way pressure responsive valve 42 consists of casing 70, inlet port 72 connected to hot gas bypass line 74, inlet port 76 connected to liquid line 40, and outlet port 78 connected to receiver 14. A flexible diaphragm 89 of metal or other suitable material is secured to casing 70 and moves valve head 82 between valve ports 84 and 86, depending on the pressure in chamber 88 acting against the force of spring WP. Screw member 92 is provided for adjustment of the compression of spring 90.

Under either the normal heating or cooling operation of our improved heat pump cycle when the heat exchange medium passing over the heat exchanger acting as a condenser is above a predetermined minimum temperature, 'hot uncondensed refrigerant will pass through conduit 74 into chamber 88 of pressure responsive valve 42 and act against diaphragm '80 and spring 90 to move valve head 82 to the left and thereby close valve port 84 and open port 86. As described hereinbefore the liquid refrigerant from either indoor heat exchanger 12 Assume for discussion purposes that the heat exchange medium passing over the indoor heat exchanger 18 is primarily air recirculated from the area being conditioued and the heat exchange medium passing over the outdoor heat exchanger is ambient air. It can readily be seen that when the refrigeration system is in operation on the normal cooling cycle there will be periods when the ambient air temperature will be lower than that required for proper condensing. This naturally will result in reduced pressure at the expansion valve IG'the-reby reducing the effective capacity of the heat exchanger 18. Conversely, when the refrigeration system is operating on the heating cycle, a problem is encountered on start-up since the recirculated air is cooler than desired resulting in reduced condensing temperatures across the indoor heat exchanger causing reduced effectiveness of the outdoor heat exchanger 12. This reduced effectiveness of the outdoor heat exchanger 12 resulting in cutting off the compressor on low pressure cut-out and constant reversing of the refrigeration cycle to defrost the outside heat exchanger 12 because of premature icing. Both the cutting out of the compressor and constant reversing of the reversing valve result in excessive wear on the components of the system and very slow heating of the space to be conditioned. Our improved heat pump refrigeration cycle provides high side pressure control on both the heating and cooling cycles to alleviate the above mentioned problems.

As indicated above, control of head pressure is necessary on both the heating and cooling cycles. Our new and improved high side pressure control is effective on both the heating and cooling cycles. Basically our control will flood the outdoor heat exchanger 12 on cool ing when the ambient air temperature is below a predetermined minimum or will flood the indoor heat exchanger 18 on the heating cycle when the recirculated air temperature is below a predetermined minimum.

Operation-FIGURE 1 Assuming that either one or the other of the above adverse conditions exist and control of high side pressure is necessary, the refrigeration system will automatically flood the heat exchanger acting as a condenser. Due to one or the other of the above mentioned adverse conditions the high side pressure will be reduced causing a reduction of operating pressure at either expansion valve 16 or expansion valve 17 depending on whether the system is heating or cooling. The pressure in hot gas bypass 74 will also be reduced and the spring 90 in conjunction with the diagram 80 will move valve head 82 to the right, opening valve port 84 and throttling valve port 86. This has a twofold effect on the system. First, liquid will back up in the heat exchanger acting as a condenser decreasing the effective condensing surface and causing an increase in head pressure. This is accomplished since little or no liquid can flow to the receiver 14 through conduit 40 because of the throttling effect of valve head 82 on valve port 86 of three way valve 42. Therefore the liquid condensed in the heat exchanger acting as a condenser will accumulate in the heat exchanger causing the head pressure to build up. Secondly, hot gas from the bypass 74 will pass into the receiver 14 by way of valve port 84- and thereby warm the refrigerant in the receiver causing an increase in pressure which is transmitted to the expansion valve connected to the heat exchanger acting as an evaporator. During periods when low temperature air is passing over the heat exchanger acting as a condenser the valve 42 modulates so that the system substantially reaches an equilibrium at which the high side pressure is satisfactory for proper operation of the expansion means. When the high or normal temperature air is passing over the heat exchanger acting as a condenser, the high side pressure will increase to the proper operating pressure and valve port 84 will be closed by the pressure transmitted to chamber 88 by conduit 74 and the liquid from the heat exchanger acting as a condenser will pass into the receiver 14 and the system will resume normal operation.

Modification 0 FIGURE 2 Looking now to FIGURE 2, there is shown a modified form of the invention. The basic refrigerant components shown in FIGURE 1 will be denoted by the same reference numbers in FIGURE 2. Instead of having a single three Way pressure responsive valve connected to the hot gas bypass conduit 74 and to the liquid line 40, I have provided a pressure regulating valve 94 in the hot gas bypass conduit 74 and a back pressure valve 96 in the liquid line 40.

Pressure regulating valve 94 and back pressure valve 96 are similar in construction in that each valve has a casing 98, a diaphragm 100 secured to the casing 98, a spring 10-2 with adjusting nut 104 exerting pressure on diaphragm 100, valve stem 106 attached to the diaphragm 100, and with a valve head 108 attached .to valve stem 106. Valve 94 differs from valve 96 in that a rise in pressure will close valve 94 but will open valve 96. This is accomplished by locating the valve head 108 of valve 94 on the outlet side of the valve port 110. Note valve 96 where the valve head 108 is on the inlet side of valve port 112.

In normal operation when the air temperature is sufficiently high to maintain proper operating pressures, the discharge pressure will act on diaphragm 100 of pressure regulating valve 94 and maintain valve head 108 against valve port 110- to shut off the passage of hot gas from the conduit 74 to the receiver 14. At the same time, the pressure in the liquid line 40 will act on the diaphragm 100 of back pressure valve 96 to maintain the valve head 108 away from the port 112 against the action of the spring 102. To refrigerant will pass consecutively through discharge conduit 24, the heat exchanger acting as a condenser, back pressure valve 96, receiver 14, expansion valve, heat exchanger acting as an evaporator, and back to the compressor 10 through suction line 28.

As the high side or head pressure decreases, the diaphragm of valve 94 will start to open valve port 110 by moving valve head 108 to the right. If the high side pressure continues to decrease, the valve head 108 of valve 94 will move to a position where valve port 110' is completely open. The tensions on springs 102 are set so that the pressure regulating valve 94 will open completely on decreasing pressure and then after a further decrease of pressure, the back pressure valve 96 will start to close. As in the modification of FIGURE 1, back pressure valve 96 will throttle the conduit 40 which provides communication between the heat exchangers and the receiver, when the head pressure is low. This will cause condensed liquid to back up in the heat exchanger acting as a condenser. This modification is completely automatic and is operated directly from the pressures in the system in order to flood the condenser in accordance with the high side. pressure drop. On increasing pressure, the above operation will be reversed and the back pressure valve 96 will be completely open before the pressure regulating valve 94 starts to close.

It can readily be seen that we have provided a new and improved high side pressure control for heat pump systems which automatically reacts to a drop in head pressure to partially or completely flood the heat exchanger acting as a. condenser. Such control provides proper operating temperatures and pressures when operating on the cooling cycle with low ambient air conditions surrounding the heat exchanger acting as a condenser. Our

system further eliminates on the heating cycle premature icing of the heat exchanger acting as an evaporator and eliminates unnecessary Wear on the compressor due to excessive starting and stopping of the compressor on low pressure cut-out.

Looking further at our new and novel head pressure control for heat pump systems, it is obvious that we have provided a control which is comparatively small in size, easy and inexpensive to manufacture, and gives positive control of the flooding of the heat exchanger acting as a condenser. Note that in both forms of the invention during conditions of high air temperaure, the hot gas bypass is positively closed, and that the compressor discharge pressure acts directly on the held up liquid in the heat exchanger acting as a condenser to force the liquid out of the heat exchanger and allows it to operate at full capacity.

Although we have described in detail the preferred embodiments of our invention, we contemplate that many changes may be made without departing from the scope or spirit of our invention, and we desire to be limited only by the claims.

We claim:

1. A reversible cycle refrigeration system comprising: an indoor heat exchanger, an outdoor heat exchanger, conduit means for carrying liquid refrigerant connecting said indoor heat exchanger to said outdoor heat exchanger, expansion means operably associated with said heat exchangers, a compressor having a suction line and a discharge line, reversing means connected to said discharge and suction lines to reversibly connect said discharge and suction line to said heat exchangers for effecting flow of refrigerant through said system in either direction whereby said system may be operated on a cooling cycle with the outdoor coil functioning as a condenser or on a heating cycle with the outdoor coil functioning as a condenser or on a heating cycle with the indoor coil functioning as a condenser, a hot gas bypass line connected to said discharge line, and automatic pressure responsive valve means connected to said conduit means and said hot gas bypass line to restrict the flow of refrigerant from said indoor heat exchanger when the system is operating on the heating cycle and the temperature of the heat exchange medium passing through said indoor heat exchanger is below a predetermined minimum and to restrict the flow of refrigerant from said outdoor heat exchanger when the system is operating in the cooling cycle and the temperature of the heat exchange medium passing through said outdoor heat exchanger is below a predetermined minimum.

2. A reversible cycle refrigeration system comprising: an indoor heat exchanger, an outdoor heat exchanger, conduit means for carrying liquid refrigerant connecting said indoor heat exchanger to said outdoor heat exchanger, a receiver connected to said conduit means, expansion means operably associated with said heat exchangers, a compressor having a suction line and a discharge line, reversing means connected to said discharge and suction lines to reversibly connect said discharge and suction line to said heat exchangers for effecting flow of refrigerant through said system in either direction whereby said system may be operated on a cooling cycle with the outdoor coil functioning as a condenser or on a heating cycle with the indoor coil functioning as a condenser, a hot gas bypass line connected to said discharge line, and automatic pressure responsive valve means connected to said receiver, said conduit means, and said hot gas bypass line to restrict the flow of refrigerant from said indoor heat exchanger when the system is operating on the heating cycle and the temperature of the heat exchange medium passing through said indoor heat exchanger is below a predetermined minimum and to restrict the flow of refrigerant from said outdoor heat exchanger when the system is operating in the cooling cycle and the temperature of the heat exchange medium passing through said outdoor heat exchanger is below a predetermined minimum.

3. The structure of claim 2 wherein said automatic pressure responsive valve means is a three way pressure controlled valve with one port connected to said hot gas bypass line, a second port connected to said conduit means, and a third port in communication with said receiver.

4. The structure of claim 3 wherein said automatic pressure responsive valve means is :a pressure regulating valve in said hot gas bypass line and a back pressure valve in said conduit means.

References Cited in the file of this patent UNITED STATES PATENTS 2,874,550 Musson Feb. 24, 1959 2,954,681 McCormack Oct. 4, 1960 2,976,696 Rhea Mar. 28, 1961

Claims (1)

1. A REVERSIBLE CYCLE REFRIGERATION SYSTEM COMPRISING: AN INDOOR HEAT EXCHANGER, AN OUTDOOR HEAT EXCHANGER, CONDUIT MEANS FOR CARRYING LIQUID REFRIGERANT CONNECTING SAID INDOOR HEAT EXCHANGER TO SAID OUTDOOR HEAT EXCHANGER, EXPANSION MEANS OPERABLY ASSOCIATED WITH SAID HEAT EXCHANGERS, A COMPRESSOR HAVING A SUCTION LINE AND A DISCHARGE LINE, REVERSING MEANS CONNECTED TO SAID DISCHARGE AND SUCTION LINE TO REVERSIBLY CONNECT SAID DISCHARGE AND SUCTION LINE TO SAID HEAT EXCHANGERS FOR EFFECTING FLOW OF REFRIGERANT THROUGH SAID SYSTEM IN EITHER DIRECTION WHEREBY SAID SYSTEM MAY BE OPERATED ON A COOLING CYCLE WITH THE OUTDOOR COIL FUNCTIONING AS A CONDENSER OR ON A HEATING CYCLE WITH THE OUTDOOR COIL FUNCITONING AS A CONDENSER OR ON A HEATING CYCLE WITH THE INDOOR COIL FUNCTIONING AS A CONDENSER, A HOT GAS BYPASS LINE CONNECTED TO SAID DISCHARGE LINE, AND AUTOMATIC PRESSURE RESPONSIVE VALVE MEANS CONNECTED TO SAID CONDUIT MEANS AND SAID HOT GAS BYPASS LINE TO RESTRICT THE FLOW OF REFRIGERANT FROM SAID INDOOR HEAT EXCHANGER WHEN THE SYSTEM IS OPERATING ON THE HEATING CYCLE AND THE TEMPERATURE OF THE HEAT EXCHANGE MEDIUM PASSING THROUGH SAID INDOOR HEAT EXCHANGER IS BELOW A PREDETERMINED MINIMUM AND TO RESTRICT THE FLOW OF REFRIGERANT FROM SAID OUTDOOR HEAT EXCHANGER WHEN THE SYSTEM IS OPERATING IN THE COOLING CYCLE AND THE TEMPERATURE OF THE HEAT EXCHANGE MEDIUM PASSING THROUGH SAID OUTDOOR HEAT EXCHANGER IS BELOW A PREDETERMINED MINIMUM.

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