US3643462A

US3643462A - Variable capacity refrigeration system and controls

Info

Publication number: US3643462A
Application number: US73544A
Authority: US
Inventors: Arthur H Eberhart
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1970-09-18
Filing date: 1970-09-18
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22
Also published as: JPS4924016B1; JPS476839A

Abstract

A refrigeration system for a room air conditioner having an outside heat exchanger with two separate refrigerant flow passages connected either directly or through an expansion device as controlled by a reversing valve. One of the passages is substantially more restrictive than the other. The reversing valve is responsive to the room temperature so that when full capacity cooling is required, the valve directs refrigerant flow from the first passage to the substantially more restrictive second passage and then through the expansion device so that the heat exchanger functions as a normal condenser; however, when reduced capacity cooling is desired, the valve directs refrigerant flow from the first passage, through the expansion device, then through the second restrictive passage which passage than functions similar to an evaporator and reduces the cooling capacity of the system. Further, with this arrangement, the reduced capacity operation permits a reduction of power for driving the compressor. Controls to stop and start the compressor and to control the valve are also provided along with an evaporator having multiple inlets to prevent freezeup when the system is operated continuously.

Description

tlnttcd htates Patent [151 s it-antes Eherhnrt Wish. 123.2, W72

[54] t/Altllthlhh C/tlPACll'lFtI [57] ansrttacr litElFllilllGlElltA'lFllUhl SltS'lFEll/ll AND tCU hJ'HMULS Primary Examiner Meyer Perlin A!t0rney-F. 1-1. Henson and E. C. Arenz A refrigeration system for a room air conditioner having an outside heat exchanger with two separate refrigerant flow passages connected either directly or through an expansion device as controlled by a reversing valve. One of the passages is substantially more restrictive than the other. The reversing valve is responsive to the room temperature so that when full capacity cooling is required, the valve directs refrigerant flow from the first passage to the substantially more restrictive second passage and then through the expansion device so that the heat exchanger functions as a normal condenser; however, when reduced capacity cooling is desired, the valve directs refrigerant flow from the first passage, through the expansion device, then through the second restrictive passage which passage than functions similar to an evaporator and reduces the cooling capacity of the system. Further, with this arrangement, the reduced capacity operation permits a reduction of power for driving the compressor. Controls to stop and start the compressor and to control the valve are also provided along with an evaporator having multiple inlets to prevent freezeup when the system is operated continuously.

8 tl'llrnims, 5 Drawing Figures VAIIIAIIILIE EARACITI! REFRIGERATIOI I SYSTEM ANE CONTROLS BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to a refrigeration system for a room air conditioner and more specifically to such a system having a normally continuously operating compressor and an outside heat exchanger having separate refrigerant flow passages with valve means interposed therebetween to direct the flow through the heat exchanger so as to control the cooling capacity of the system and also the power consumption of the compressor.

This invention also relates to the control means for such a system and more specifically to a start-stop control for the compressor responsive to room temperature and a valve control for setting the cooling capacity of the system at either full capacity or a reduced capacity in response to room tempera ture.

2. Description of the Prior Art:

Varying the capacity of a normally continuously operating compressor of the refrigeration system of a room air conditioner to overcome known disadvantages of intermittent operation of the compressor, such as wear on the compressor, and room temperature differentials that tend to be uncom fortablc but which are necessary to eliminate rapid cycling of the compressor, are known and can best be classified as either a modulating-type control or a step-type control.

An example of a modulating-type capacity control would be a throttling device on the suction line of a compressor that is controlled by means continually responsive to the temperature of the return air through the evaporator.

An example of a step type control would be a two-position valve such as a reversing valve on either the suction or discharge side of the compressor that permits the normal refrigerant flow path during full capacity but, in response to a sufficiently lower temperature, directs the refrigerant through an alternate path of stepped reduction in capacity.

The systems above described, although capable of reducing the cooling capacity, do not generally provide a commensurate reduction of power for the compressor when operating at reduced cooling.

In general, a compressor will draw somewhat lower power if the discharge pressure is reduced such as in the present inven tion by chilling the condenser surface by evaporating liquid therein. It will also draw somewhat lower power if the suction gas density (indicated by lower evaporating temperature) is reduced, causing each compressor suction stroke to draw less refrigerant into the cylinder. However, in order to obtain sig nificant power reduction in reduced capacity operation it is necessary to lower both the discharge pressure and the suction gas density.

This invention is directed to a refrigeration system for an air conditioner having a normally continuously running compressor and providing a stepped reduction in cooling capacity with a commensurate significant reduction in power required by the compressor in accordance with the above principle, along with controls therefor and an evaporator that permits continu ous operation without significant frost accumulation.

SUMMARY OF THE INVENTION The invention comprises a variable capacity refrigeration system for a room air conditioner having a normally continuously operating compressor and controls therefor. The system includes an outside heat exchanger having two separate refrigerant flow passages with one passage being substantially more restrictive than the other. The passages are connected through a reversing valve either directly or with an expansion device interposed therebetween. The valve is activated by a solenoid responsive to room temperature. When the room temperature rises to a preset degree, the valve directs the refrigerant to flow through the first passage of the heat exchanger, then through the restrictive passage and then through the expansion device so that the heat exchanger functions as a condenser and the system operates at full capacity similar to any well'known refrigeration system. However, when the temperature falls to a lower preset degree, the valve directs the refrigerant from the first passage, through the expansion device, then through the restrictive passage of the heat exchanger. This reduces both the discharge and suction pressure of the compressor, reducing capacity and reducing the power required to drive the compressor.

The controls of the present invention control both start and stop of the compressor and the flow path through the valve to determine the capacity of operation in response to room temperature. The controls also permit the compressor to start at the reduced capacity, reducing the initial load on the motor windings.

DRAWING DESCRIPTION FIG. I is a diagrammatic view of the refrigeration system for the present invention showing refrigerant flow at full capacity;

FIG. 2 is a diagrammatic view of the refrigerant flow through the condenser of the above system at reduced cupaci- 3;

IFIG. 3 is a diagrammatic view of an alternate refrigeration system showing refrigerant flow at full capacity;

FIG. 4 is a diagrammatic view of the refrigerant lIow through the condenser of the system of FIG. 3 at reduced capacity; and

FIG. 5 is a circuit diagram of the control arrangement for the refrigeration system of the present invention, and showing an optional anticipator heater for the temperature sensing bulb.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I the refrigeration system diagrammatically illustrated is to be used in a room air conditioner of well known construction (not shown) and which has usual fans 4 and 6 driven by motor 8 for circulating room air over the evaporator coils, and outside air over the outside heat exchanger coils, respectively. Also, it is to be understood that the compressor W is of the conventional type which is onclosed in a sealed casing which also houses the motor for driving the compressor, and the valve 30 is a well-known solenoiddriven reversing valve.

The refrigeration system of the present invention generally comprises a compressor IQ for compressing the refrigerant in the system. The high-pressure refrigerant is discharged from the compressor It) into a discharge conduit I i leading to the outside heat exchanger 2t).

The outside heat exchanger 20 has two separate passages disposed in heat exchange relationship with each other. The first refrigerant passage 2I initially receives the refrigerant from the discharge conduit Ill and delivers it to the inlet 35 of a reversing valve 3t FIG. H illustrates the system operating at full capacity in which condition the switching means or slide 3i of valve 30 directs the refrigerant from the first refrigerant passage 2ll through the valve port 36 to the second refrigerant passage 22 of the heat exchanger 20. Passage 22 is a substantially more restrictive passage than passage 21 for reasons which will be explained later.

Upon exiting from the restricted second passage 22, the refrigerant flows through an expansion means 23, such as a capillary tube, through valve port 37 into valve Ell where it is directed by slide 3i through outlet 38 into refrigerant conduit means 32 which leads to the evaporator as through distributor conduitdll.

The evaporator 40 has a plurality of separate passages 42, 13%, ti t, and 45 (there being four shown) leading from the dis tributor conduit 4P1, through the evaporator 10 to suction conduit means as and I7 leading to the suction inlet ilt of the compressor llil completing the refrigerant flow cycle.

FIG. 2 diagrammatically shows the outside heat exchanger 20 and valve 30 of the system of FIG. 1 but shows the different flow path of the refrigerant therethrough when the system is operating at reduced capacity. As such, the refrigerant in the first passage 21 is directed by valve 30 through the expansion device 23 prior to its passage through the restrictive second passage 22 of the heat exchanger 20. From the second passage the refrigerant is then directed through outlet 38 to the refrigerant conduit means 32 by slide 31 of valve 30 after which the system and refrigerant flow are the same as described in relation to FIG. 1.

FIGS. 3 and 4 show another system similar to that shown in FIG. 1; however, the valve 30 directs the refrigerant flow somewhat differently and a second expansion device 33 has been inserted in the refrigerant conduit means 32.

Referring to FIG. 3 the system is shown operating at full capacity in which condition the slide 31 of valve 30 blocks the refrigerant flow through ports 37 and 38 to the restrictive second refrigerant passage 22 but discharges it directly from the outlet 36 into the refrigerant conduit 32 containing the second expansion means 33 with the flow from there being identical to FIG. 1.

In the reduced capacity flow of the system as shown in FIG. 4, the slide 31 directs the flow from the first refrigerant passage 21 of the heat exchanger 20 through the expansion means 23 to the second refrigerant passage 22 and then to the refrigerant conduit means 32 and second expansion device 33 with the flow from there being identical to the system of FIG. 1.

The operation of the system of either FIG. 1 or FIG. 3 at full capacity cooling is similar to the present well-known refrigeration system for room air conditioners, as the restrictive second refrigerant passage 22 of the heat exchanger 20 being on the high side of the system, does not affect full capacity operation. Thus, refrigerant is discharged from the compressor as a hot superheated gas and flows through the heat exchanger where it is cooled to a subcoolcd liquid prior to passing through an expansion means (23 in FIG. I or 33 in FIG. 3), In this configuration, heat exchanger 20 functions solely as a condenser.

From the expansion means it is directed to the evaporator 40 where the liquid refrigerant is vaporized to a superheated gas prior to entering the compression suction inlet 48 to repeat the cycle. Operation of the system as above described produces the maximum cooling obtainable in the system and requires the greatest output by the compressor motor.

A reduced cooling capacity at a lower power requirement is produced in the system by switching the slide 31 of the valve (FIG. 2) such that the refrigerant is directed through the expansion device 23 prior to the second restrictive passage 22 of the heat exchanger. In this instance the second restrictive passage 22, being on the downstream side of the expansion device 23 acts as an evaporator and permits a limited heat ab sorption in the refrigerant therein. The passageways 21 and 22 are adjacent and in heat transfer relationship, permitting the refrigerant in passage 22 to absorb heat from the first passage 21 thereby cooling the refrigerant at the discharge ll of the compressor. The relation between discharge pressure and temperature being such that a lower discharge temperature results in a lower discharge pressure which in turn requires less power from the compressor motor.

The heat absorbed by the refrigerant in the second restrictive passage 22 reduces the amount of heat the refrigerant is capable of absorbing in the evaporator and thereby reduces the capacity of the evaporator 40. Further, the restrictive passage 22, during reduced capacity operation being on the downstream side of the expansion means 23, greatly affects the suction pressure. This is because restrictions in the flow line in the low side of the system reduce the suction pressure much more than the same restrictions in the high side increase the discharge pressure. Such reduction in suction pressure reduces the mass flow of refrigerant passing through the compressor and thereby reduces the power requirements of the compressor and-the cooling capacityof the system.

Thus the cooling capacity of the system is decreased when the restrictive passage 22 of condenser 20 is downstream of the expansion device 23 by decreasing the amount of heat the refrigerant is capable of absorbing by the amount it has absorbed in the condenser 20 and also by reducing the mass flow of the refrigerant available to absorb heat, and the power required to drive the compressor is reduced by reducing the discharge pressure and also by reducing the mass flow of refrigerant that the compressor pumps.

The insertion of the second expansion means 33 in FIGS. 3 and 4 permits the second restrictive passage 22 of the heat exchanger 20 to be blocked from refrigerant flow during full capacity operation by the valve 30, and act as an evaporator in the same manner above described during reduced capacity operation. It is to be understood that the first refrigerant passage of FIG. 3 is sized so as to provide sufficient heat exchange capacity so as to be the condenser in this system with no decrease in refrigeration capacity.

The start-stop operation of the compressor and the cooling capacity required of the system of the present invention are controlled as illustrated in the circuit diagram of FIG. 5. The primary controlling element is a heat sensing element 50 such as a vapor pressure bulb which is placed so as to be responsive to room temperature. Vapor pressure from the bulb 50 is transmitted through a capillary Sll to control means 60 having a compressor switch means 62 for controlling the start-stop of the compressor and solenoid switch means 66 for controlling slide 31 of valve 30 thereby controlling the cooling output of the system and which switch can be termed a comfort control.

Compressor switch means 62, as shown, comprises a switch blade 61 connected to one line L2 of a power supply and a compressor contact 63 connected in series with the compressor 10 to another line L ofa power supply, and an electrically isolated off contact 64. The position of the switch blade M is controlled by the vapor pressure within the bulb 50 as is well known in the art.

The comfort control switch 66 also comprises a switch blade 67, connnectcd in series with compressor contact 63, and first and second stationary contacts (65 and 68). The first contact 68 is connected in series to one side of the solenoid winding 69 which has its other side connected to line I... The second contact 65 is connected to an optional rheostat 70 series connected to one side of resistance heater 7l which has its other side connected to L,. The heater is located adjacent the bulb 50. It is apparent that the second contact 65 could also be electrically isolated from the circuit if desired which would be similar to the present circuit when the resistance of the rheostat is increased to an amount that eliminates current flow through that line. Again, the position of switch blade 67 is controlled by the vapor pressure in bulb 50.

A variable speed fan motor 8 has one side connected to line L, and its opposite side connected through manual switch means 74 for selecting fan speed. The common terminal of switch 74 is connected to manually operated switch 75, which may be moved to contact 76 to run the fans with the compressor, or to contact '77 to run the fans independently.

Operation of the controls and system of the present invention will now be described with the rheostat 70 assumed to be set to exclude the heater 71 from the circuit. The circuit diagram as shown in FIG. 5 shows the compressor control 62 on and the comfort control 66 actuating the solenoid 69 and thus the valve slide 31 to full capacity cooling position. However, the compressor control 62 and comfort control 66 are each set to be actuated by the bulb at different temperatures. For example, the compressor control would be set to actuate the compressor at approximately 76 F. and stop the compressor at approximately 73 F., while the comfort control would be set to actuate the solenoid at F. and release the solenoid at 76 F. Therefore, assuming the room temperature sensed by the bulb 50 is less than 76 F., such as might typically be the ease during the early hours of a summer day, the compressor 10 is off," the fan motor 8 being connected through the compressor contact 63 is also off and the comfort control switch 67 would be closed to contact 65 so that slide 311 of valve 30 would be so disposed that the system is set for reduced capacity operation such as shown in Fi 2. An in crease in the temperature of the room to 76 F. would cause the compressor to be actuated by the switch blade oil moving to contact 63, also closing the circuit to fan motor However, the comfort control switch would remain as above described so that the system would start at reduced capacity operation decreasing the starting shock on the compressor motor. Further assuming that the reduced capacity cooling was not sufficient to compensate for the increase in room temperature as the day progressed, the room temperature would continue to rise until it reached 80 F., at which point the comfort control switch would change the system to full capacity operation by the switch blade 67 moving from contact d to contact (iii thereby actuating the solenoid and positioning the slide Bl to the position as illustrated in FIG. ll. The full capacity cooling being sufficient to cool the room, would lower the temperature thereof until the bulb 50 sensed a temperature of 76 F. whereupon the switch blade r57 of the comfort control would again move to contact as opening the solenoid circuit putting the system back to reduced capacity operation. The compressor would operate continuously with the system continuing to cycle between full capacity cooling and reduced capacity cooling as above described until a period, such as evening, when the reduced capacity operation was sufficient to continue lowering the temperature of the room to 73 at which time the compressor switch oil would return to contact tidstopping the compressor and the fan.

As seen from the above discussion using temperatures that could be considered typical, the comfort control can maintain the room temperature within a relatively small differential (e.g., 76 F. the lowest and 80 F. the warmest). However, ifa smaller differential is desired the rheostat 70 of the circuit of FIG. 5 can be adjusted so as to allow current to flow through the heater 7ll adjacent the bulb 556* to heat the bulb approximately 2 F. above the room temperature. As seen in FilG. 5, the circuit through the heater 71 is completed only when the compressor circuit is closed and when the switch or of the comfort control is on contact as placing the system in reduced capacity cooling. From the above discussion, this occurs when the room temperature has been lowered to 76 F, Actuation of the heater 'lll at this time would have the bulb 5d sense a torn perature of 78 F. so that when the room temperature actually rises to 78 the bulb 50 senses 80 F. and switches the comfort control to full capacity cooling, taking the heater out of operation again. The cycling of the cooling capacity in such instance would then occur within a room temperature range of 76 to 78 F. It is obvious that the rheostat 7t) could be adjusted to provide more or less heat to the bulb St} and thus vary the above differential as desired.

The above system and controls provide a normally continuously operating compressor in a refrigeration system whose cooling capacity is varied in response to the room tempera' ture. Such continuous operation means that the evaporator ift will also be continuously cold with respect to the room tem perature. To eliminate excessive frost accumulation, which would inhibit the heat transfer ability of the evaporator along with producing droplets of water as the frost melts when the system is stopped, an evaporator W is provided having a plu rality of separate passages (42, d3, and d5) thcrethrough from the common distributor conduit ill. This distributes the available refrigerant to widely separated points of the evaporator so that the final expansion is not concentrated in one one small area producing a cold spot which, even on reduced capacity, could accumulate frost. The manifold instead distributes the refrigerant for final expansion in many areas providing the desired total cooling with no area being cold enough to maintain frost thereon, especially during reduced capacity operation.

To summarize the advantage of the present invention, the refrigeration system provides a normally continuously operating compressor increasing the life of the hermetically sealed motor-compressor unit. The system also provides variable capacity cooling with the further advantage of requiring less power at the reduced capacity cooling commensurate with the decrease in capacity. it has been calculated that under normal conditions the system of the present invention would require, on a reduced cooling capacity of about 50 percent, approximately percent of the total power required when operating at full capacity. it is evident that the power required by the fan, which is a part of the total power, is the same at either capacity. Further, the system eliminates rapid compressor onoff cycling to maintain a desired temperature range, and, by always passing the refrigerant through the evaporator, eliminates compressor slugging.

The controls of the invention, in conjunction with the refrigeration system provide a temperature comfort range for controlling the capacity cooling required of the system separate and distinct from the compressor operating range. Further the controls permit compressor startup at reduced capacity, further reducing the starting shock on the compressor motor lengthening its life.

i claim as my invention;

ll. An air conditioning unit having a compressor, flow control valve means, evaporator, expansion means, and an outside heat exchanger connected in refrigerant flow communication 3 and wherein said outside heat exchanger comprises:

a first refrigerant passage connected between the discharge of said compressor and said valve means and a substantially more restrictive second refrigerant passage having opposite ends in communication with said flow control valve means with said expansion means between one of said opposite ends of said second passage and said flow control means; and

means for controlling said valve to direct refrigerant flow through said outside heat exchanger in a direction to utilize said outside heat exchanger at full capacity wholly as a condenser in accordance with a higher demand for cooling, and for shifting said valve to direct refrigerant llow through said outside heat exchanger in a direction to utilize said first passage as a condenser and said second passage as an evaporator by directing refrigerant first through said expansion means and then through said second passage in accordance with a relatively lower demand for cooling.

2. The refrigeration system ofclaim ll including:

drive means connected to said compressor for normally continuously driving said compressor; and,

stop-start means for said drive means responsive to ambient room temperature.

Fl. The refrigeration system of claim 2 further including:

means for controlling said valve, said means operative between a first position and a second position in response to ambient room temperature.

4i. The refrigeration system of claim 3 wherein said control means is operative to position said valve means to direct fluid flow through said expansion means prior to said second refrigerant passage of said heat exchanger when in said first position and through said second refrigerant passage prior to said expansion means in said second position.

5. The refrigeration system of claim 3 wherein said control means is operative to position said valve means to direct fluid flow through said expansion means prior to said second refrigerant passage of said heat exchanger when in said first position and prevent refrigerant flow through said second refrigerant passage when in said second position.

s. The refrigeration system of claim l] further including: evaporator inlet means, said inlet means comprising distributor means having a plurality of separate refrigerant passages extending therefrom through said evaporator.

"7. An air conditioning unit according to claim ll including a temperature sensing means for sensing room temperature and a compressor control means for starting or stopping the com pressor and wherein said valve control means for shifting said flow control valve and said compressor control means are independently responsive to the temperature of the temperature sensing means.

8. An air conditioning unit according to claim 7 further including;

a heater disposed adjacent to said temperature sensing means; and means to actuate said heater in response to the temperature sensed by said temperature sensing means.

Claims

1. An air conditioning unit having a compressor, flow control valve means, evaporator, expansion means, and an outside heat exchanger connected in refrigerant flow communication and wherein said outside heat exchanger comprises: a first refrigerant passage connected between the discharge of said compressor and said valve means and a substantially more restrictive second refrigerant passage having opposite ends in communication with said flow control valve means with said expansion means between one of said opposite ends of said second passage and said flow control means; and means for controlling said valve to direct refrigerant flow through said outside heat exchanger in a direction to utilize said outside heat exchanger at full capacity wholly as a condenser in accordance with a higher demand for cooling, and for shifting said valve to direct refrigerant flow through said outside heat exchanger in a direction to utilize said first passage as a condenser and said second passage as an evaporator by directing refrigerant first through said expansion means and then through said second passage in accordance with a relatively lower demand for cooling.

2. The refrigeration system of claim 1 including: drive means connected to said compressor for normally continuously driving said compressor; and, stop-start means for said drive means responsive to ambient room temperature.

3. The refrigeration system of claim 2 further including: means for controlling said valve, said means operative between a first position and a second position in response to ambient room temperature.

4. The refrigeration system of claim 3 wherein said control means is operative to position said valve means to direct fluid flow through said expansion means prior to said second refrigerant passage of said heat exchanger when in said first position and through said second refrigerant passage prior to said expansion means in said second position.

6. The refrigeration system of claim 1 further including: evaporator inlet means, said inlet means comprising distributor means having a plurality of separate refrigerant passages extending therefrom through said evaporator.

7. An air conditioning unit according to claim 1 including a temperature sensing means for sensing room temperature and a compressor control means for starting or stopping the compressor and wherein said valve control means for shifting said flow control valve and said compressor control means are independently responsive to the temperature of the temperature sensing means.

8. An air conditioning unit according to claim 7 further including; a heater disposed adjacent to said temperature sensing means; and means to actuate said heater in response to the temperature sensed by said temperature sensing means.