US3006164A

US3006164A - Reversible refrigeration system

Info

Publication number: US3006164A
Application number: US59431A
Authority: US
Inventors: Stephen L Mcmillan
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1960-09-29
Filing date: 1960-09-29
Publication date: 1961-10-31
Anticipated expiration: 1978-10-31

Description

Oct. 31, 1961 s. L. MCMILLAN 3,006,164

REVERSIBLE REFRIGERATION SYSTEM Filed Sept. 29, 1960 INVENTOR. STEPHEN L. MMILLAN HIS ATTORNEY The present invention relates to an improved reversible refrigeration system employing a capillary restricting means between the heat exchangers thereof and incorporating an arrangement for cooling the hermetic motor of the system and for changing the flow restriction in the system when the system is reversed from heating to cooling and vice versa.

An injection cooling arrangement of the above-described type is disclosed in the invention of the application of James L. Schulze, Serial No. 860,848, filed December 21, 1959, now Patent No. 2,967,410, dated January 10, 1961, and assigned to the assignee of the present application. My present invention is an improvement over the Schulze invention which invention was made by the said James L. Schulze prior to my invention. I, therefore, do not herein claim as my invention anything shown or described in said Schulze application, which is to be regarded as prior art with respect to this present application.

It is an object of the present invention to provide an improved arrangement in a reversible refrigeration system for injecting condensed refrigerant into the hermetic casing for cooling the motor during operation of the system in either direction and for automatically reducing the flow restriction in the system during the cooling cycle as compared to that during the heating cycle.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and formin a part of this specification.

In accordance with the present invention, there is provided a reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure including a motor-compressor unit sealed within a hermetic casing and connected in reversible refrigerant flow relationship with an indoor heat exchanger and an outdoor heat exchanger. A first capillary is connected between the heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure as refrigerant flows through the system. A discharge passage leads from the compressor into the hermetic casing for conducting high pressure discharge gas from the compressor into. the casing for cooling the motor of the unit. A portion of this discharge passage takes the form of an aspirating means, such as a venturi or jet pump, which means creates a region of lower pressure in the high pressure gas flowing through the passage. A liquid refrigerant bypass tube is conected in parallel with the capillary between the heat exchangers so that one of its opposite ends always communicates with condensed refrigerant in one oi the heat exchangers regardless of the direction of refrigerant flow through the system. Connecting at some intermediate point on the bypass tube is a liqtL'd refrigerant supply conduit, having its opposite end conmeeting with the low pressure region of the aspirating means for introducing liquid refrigerant into the aspirating means to be mixed with and to cool the high pressure gas flowing therethrough. On opposite sides of the connecting point between the refrigerant bypass tube and the refrigerant conduit leading to the aspirating means are check valves, each operable to permit flow of liquid refrigerant through the tube in the direction of the refrigerant conduit leading to the aspirating means but Bfihdlh i Patented Oct. 31, 39G! preventing flow in the direction away from the refrigerant conduit. Also connected between the indoor heat exchanger and a point between the check valves of the refrigerant bypass tube is a second capillary adapted to promote flow of refrigerant around the check valve adjacent the indoor heat exchanger when refrigerant flow is in the direction from the outdoor heat exchanger toward the indoor heat exchanger. When the direction of refrigerant flow through the system is from the indoor heat exchanger toward the outdoor heat exchanger, the check valve adjacent the outdoor heat exchanger completely stops flow of refrigerant toward the outdoor heat exchanger except through the first capillary connected between the two heat exchangers.

For a better understanding of the invention reference may be had to the accompanying drawing, thesingle figure of which illustrates in somewhat schematic form a reversible refrigeration system incorporating the present invention.

Referring now to the drawing, there is shown a revers ible cycle of refrigeration system for use in an air conditioner of the type adapted to both heat and cool air from an enclosure. 'Fo-r compressing and pumping refrigerant through the system there is provided a motorcompressor unit, generally designated by the reference numeral 2. The motor-compressor unit 2 is mounted in a hermetically sealed casing 3 which houses the compressor 4 and its drive motor 6 and which is suitable for containing the high pressure refrigerant gas. A suction line '7 connects directly with the suction inlet of the compressor and carries low pressure refrigerant gas to the compressor. A discharge line 8 is connected to the case for carrying the high pressure gas from within the .case into the remaining portion of the system. The discharge and suction lines are both connected to a reversing valve 9. Also connected to the reversing valve E are a pair of conduits l1 and 12 which lead respectively to the indoor and outdoor heat exchangers or coils 13 and '14.

included in the system for the purpose of expanding refrigerant from condensing pressure to evaporator pres sure is a first capillary expansion means or tube 16. This tube operates as an expansion means during both the cooling and heating cycles and maintains a predetermined pressure differential between the evaporator and condenser regardless of the direction of refrigerant flow.

In an air conditioning unit of this type, the indoor coil 13 is arranged for heating or cooling air from the enclosure, while the outdoor coil 14 is arranged for either rejecting heat to or extracting heat from the outside atmosphere. The reversing valve 9 is selectively reversible to direct discharge gas into either one of the

lines

11 and 12 while receiving low pressure gas from the other line, thereby making the system reversible for either heating or cooling an enclosure. Thus, if it is desirable to set this system on the heating cycle, compressor discharge gas flowing through the discharge line 8 is connected by means of a reversing valve 9 to the line 11 which carties the hot discharge gas to the indoor coil 13. This coil then acts as a condenser to give up its heat to the enclosure air. If it is desired to set the system for cooling the enclosure, the suction line 7 is connected tothe indoor coil 13 through a line 11, which then acts as an evaporator, while the discharge gas is carried to the outdoor coil 14 by the line 12.

During operation of the compressor, low pressure refrigerant is withdrawn from the suction line 7 which connects with the suction port (not shown) of the compressor unit 6. Low pressure refrigerant gas is compressed within the compressor unit to a relatively high pressure and temperature and is then discharged by the compressor through a suitable discharge passage 17 leading into the hermetic casing 3. For purposes of illustration, the discharge passage 17 is shown as a tube leading out of the hermetic casing and then back into the hermetic casing. However, this discharge passage could he a passage, such as that illustrated in the aforementioned Schulze application, which leads from the discharge port of the compressor unit through the main frame 18 and, thence, directly into the hermetic casing 6 without leaving the hermetic case. Included within the discharge passage is an aspirating means or venturi sec- =tion, generally designated by the reference numeral 21, through which hot discharge gas passes prior to entering the hermetic case. The passage 17 discharges the high pressure gas into the case below the motor and, after flowing upwardly over the motor 6, the high pressure gas is conducted out of the casing through the conduit 8 into the remaining portions of the system.

In order to cool the discharge gas flowing through the discharge passage sufficiently to maintain the motor within safe operating temperatures, cool liquid refrigerant from the heat exchanger operating as -a condenser is introduced into the high pressure discharge stream as it flows through the aspirating means. As may be seen in the drawing, the aspirating means contains a nozzle or gas accelerating section 22 and a diffuser or gas decelerating section 23 separated by a pinched or throat portion 24. As the high pressure discharge gas flows through the aspirating means, it drops in prmsure in the nozzle section 22 where its velocity is increased. Then, in the diffuser section of the aspirating means, the gas pressure increases to approximately its original pressure as the velocity of the gas decreases. Thus, a pressure drop or region of low pressure is created in the throat 24 of the aspirating means which is easily suflicient to overcome the pressure drop encountered in the case and tubing of one or the other of the heat exchanges. Thatis, the pressure in the throat 24 is normally less than the pressure in the latter stages of the heat exchanger operating as a condenser thereby causing liquid or condensed refrigerant to he siphoned through a passage connecting the aspirating means with the heat exchanger operating as a condenser. When liquid refrigerant is introduced into the throat or low pressure region of the aspirating means, it encounters the hot discharge gas and is vaporized or flashed into the gaseous form. Heat removed from the discharge gas, in vaporizing the liquid refrigerant, reduces the temperature of the discharge gas and the violent reaction created by the flashing of the liquid into vaporized form completely mixes the gases so that the resultant gas mixture issuing from the passage is at a uniform temperature and much cooler than the temperature of the original high pressure gas discharged from the compressor.

Liquid refrigerant is supplied from the heat exchanger operating as a condenser through the passage including a refrigerant supply conduit 26 which connects with a refrigerant bypass tube 27, which is in turn connected between the

heat exchangers

13 and 14 in parallel with the expansion means or capillary 16. The liquid refrigerant supply conduit 26 connects with the bypass tube 27 at some intermediate point 25 between the two heat exchangers. A pair of check valves, designated the first or indoor valve 28 and the second or outdoor valve 29, are arranged respectively on opposite sides of the connecting point 25 between the refrigerant bypass tube 27 and the condensed refrigerant supply conduit 26, and prevent the flow of refrigerant through the tube 27 in the direction away from the supply line 26. It may be seen, therefore, that during operation of the reversible cycle refrigeration system, refrigerant is permitted to flow through the check valve adjacent the heat exchanger operating as a condenser but is prevented from flowing through the check valve adjacent the heat exchanger operating as an evaporator. Thus liquid refrigerant is always supplied to the tube 27, and thereby to the refrigerant supply conduit 26 regardless of the direction of refrigerant flow through the system. As may be seen in the drawing, a. second capillary 36 is positioned in parallel with the check valve 28, or in parallel with the check valve 28 adjacent the indoor heat exchanger 13. It can be seen from the drawing that, when the system is operating on the cooling cycle, refrigerant flows through the check valve 29 into the liquid conduit 26 and thence into the discharge passage leading to the compressor. Liquid refrigerant also flows through the capillary 36 around the indoor check valve 28 into the indoor heat exchanger 13. Condensed refrigerant flowing through the capillary 36 is expanded to evaporator pressure in the same manner as refrigerant flowing through the first capillary 16. That is, when the system is operating on the cooling cycle, refrigerant flows through both of the

capillaries

16 and 36. However, when the system is operated on the heating cycle, and refrigerant flow is in the reverse direction, or from the indoor heat exchanger 13 toward the outdoor heat exchanger 14, it can be seen that, although refrigerant may flow through both of the

capillaries

16 and 36, only the flow through the capillary 16 is effective. Because of the check valve 29 there is no flow of refrigerant completely through the refrigerant bypass tube 27, to the outdoor heat exchanger 14 and the capillary 36 is effectively taken out of the system. It should be noted that, during the heating cycle when the indoor heat exchanger 13- is operating as a condenser, high prasure refrigerant is admitted to both ends of the capillary 36 thereby eliminating the effect of this capillary. Thus, greater restriction is inherently introduced into the systern during operation of the system on the heating cycle than during operation of the system on the cooling cycle, when both the

capillaries

16 and 36 are utilized for expanding refrigerant from condenser pressure to evaporator pressure.

Liquid refrigerant flowing through the conduit 26 is restricted to some extent by a restricting means or third capillary 31. The design of the restricting means or third capillary 31 should be such as to permit enough condensed refrigerant to flow through the conduit 26 to suf ficiently cool the discharge gas but still limit the flow sufficiently to eliminate short circuiting of the evaporator (or the heat exchanger operating as an evaporator) and eventual collection of refrigerant in liquid form within the case. Obviously, a capillary does not have to be used for this purpose. Other means, such as a needle valve or other type of restriction could easily be substituted for this capillary.

In operation, the venturi section or aspirating means 21 acts as a modulating device for supplying greater or lesser amounts of condensed refrigerant to cool the high pres sure discharge gas according to the flow of gas through the discharge passage from the condenser unit. Since the amount of liquid refrigerant flowing through the supply conduit 26 depends to a great extent upon the pressure recovery experienced in the diffuser section 23 from the throat 24 to the outlet of the diffuser and, since the amount of pressure recovery in the venturi or aspirating means is a function of the quantity of gas flowing therethrough, it is apparent that the amount of liquid refrigerant siphoned through the liquid refrigerant supply conduit 26 depends upon the quantity of discharge gas flowing through the discharge passage 17 leading from the compressor unit. Whenever the pressure of the suction gas is high, the temperature of the gas at the discharge outlet of the compressor 6 is, under normal conditions, correspondingly greater and the cooling requirement is, therefore, greater. However, when the suction pressure is high, a correspondingly greater quantity of gas is pumped which results in a greater flow of liquid refrigerant through the passage and through the throat 24 thereby increasing the flow of liquid refrigerant through the conduit 26 and supplying the neces' sary cooling of the high temperature discharge gas. Con

versely, when the suction pressure is low and the compressed discharge gas is at a relatively low temperature, the amount of gas being pumped through the discharge passage 17 is correspondingly less. This, consequently, produces a correspondingly smaller pressure difference between the throat 24 and the outlet of the aspirating means, thereby resulting in a diminished flow through the conduit 26 and a lesser amount of cooling of the discharge gas. Thus, under most conditions of operation, the aspirating means automatically modulates the amount of cooling of the discharge gas from the compressor, and automatically increases or decreases the cooling effect on this gas to maintain the motor within safe operating limits.

By the present invention there has been provided an improved arrangement in a reversible refrigeration system for providing injection cooling of a compressormotor unit regardless of the direction of refrigerant flow through the system which arrangement also serves to automatically increase the flow restriction in the system during operation on the heating cycle and to automatically reduce the flow restriction in the system during operation thereof on the cooling cycle.

While in accordance with the patent statutes there has been described what at present is considered to be the preferred embodiment of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, the aim of the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure comprising a motor-compressor unit, an indoor heat exchanger and an outdoor heat exchanger connected in reversible refrigerant flow relationship, a first capillary connected between said heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure, means for reversing the flow of refrigerant through said system thereby to operate each of said heat exchangers interchangeably as a condenser or as an evaporator, said motor-compressor unit being mounted in a hermetically sealed casing for containing a high pressure refrigerant gas, a discharge passage leading from said compressor into said casing for conducting compressed refrigerant from said compressor into said casing for cooling said motor, said discharge passage including an aspirating means for creating a low pressure region in said discharge gas stream as it passes through said aspirating means, a refrigerant bypass tube connected between said heat exchangers in parallel with said first capillary, a liquid refrigerant supply conduit connecting at one end with said refrigerant bypass tube and at the other end with said aspirating means for introducing liquid refrigerant into said discharge passage for cooling said high pressure refrigerant gas flowing through said discharge passage, check valves in said refrigerant bypass tube on opposite sides of the connection with said liquid refrigerant supply conduit for preventing flow of liquid refrigerant through said tube in the direction of said heat exchanger being operated as an evaporator during either cycle of operation of said system, and a second capillary means having one end connected to said refrigerant bypass tube at some point between said check valves and having its other end connecting with said indoor heat exchanger for introducing expanded refrigerant into said indoor heat exchanger during operation of said system on the cooling cycle when said indoor heat exchanger operates as an evaporator.

2. A reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure comprising a motor-compressor unit, an indoor heat exchanger and an outdoor heat exchanger connected in reversible refrigerant flow relationship, a first capillary connected between said heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure, means for reversing the flow of refrigerant through said system thereby to operate each of said heat exchangers interchangeably as a condenser or as an evaporator, said motor-compressor unit being mounted in a hermetically sealed casing for containing high pressure refrigerant gas, a discharge passage leading from said compressor into said casing for conducting compressed refrigerant from said compressor into said casing for cooling said motor, said discharge passage including an aspirating means for creating a low pressure region in said discharge gas stream as it passes through said aspirating means, a refrigerant bypass tube connected between said heat exchangers in parallel with said first capillary, a refrigerant supply conduit connecting at one end with said refrigerant bypass tube and at the other end with said aspirating means for introducing liquid refrigerant into said discharge passage for cooling said high pres sure refrigerant gas flowing through said discharge passage, a first check valve in said refrigerant bypass tube between said connection with said refrigerant conduit and said indoor heat exchanger, a second check valve in said refrigerant bypass tube between said connection with said refrigerant conduit and said outdoor heat exchanger, said first check valve preventing flow of liquid refrigerant through said refrigerant bypass tube in the direction toward said indoor heat exchanger and said second check valve preventing flow of liquid refrigerant through said refrigerant bypass tube in the direction toward said outdoor heat exchanger, and a second capillary means bypassing said first check valve and having one end connected to said refrigerant bypass tube and the other end connecting with said indoor heat exchanger for introducing expanded refrigerant from said refrigerant bypass tube into said indoor heat exchanger during operation of said system on the cooling cycle when said indoor heat exchanger operates as an evaporator.

3. A reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure comprising a motor-compressor unit, an indoor heat exchanger and an outdoor heat exchanger connected in reversible refrigerant flow relationship, a first capillary connected between said heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure, means for reversing the flow of refrigerant through said system thereby to operate each of said heat exchangers interchangeably as a condenser or as an evaporator, said motor-compressor unit being mounted in a hermetically sealed casing for containing a high pressure refrigerant gas, a discharge passage leading from said compressor into said casing for conducting compressed refrigerant from said compressor into said casing for cooling said motor, said discharge passage including an aspirating means for creating a low pressure region in said discharge gas stream as it passes through said aspirating means, a refrigerant bypass tube connected between said heat exchangers in parallel with said first capillary, a liquid refrigerant supply conduit connecting at one end with said refrigerant bypass tube and at the other end with said aspirating means for introducing liquid refrigerant into said discharge passage for cooling said high pressure refrigerant gas flowing through said discharge passage, check valves in said refrigerant bypass tube on opposite sides of said connection with said liquid refrigerant supply conduit for preventing flow of liquid refrigerant through said tube in the direction of said heat exchanger being operated as an evaporator during either cycle of operation of said system, a second capillary means having one end communicating with said refrigerant bypass tube at some point between said check valves and having the other end connecting with said indoor heat exchanger for introducing refrigerant into said indoor heat exchanger during operation of said system on a cooling cycle when said indoor heat exchanger operates as an evaporator, and a third capillary in said liquid refrigerant supply conduit for restricting the flow of liquid refrigerant therethrough toward said aspirating means and preventing short circuiting of refrigerant around said heat exchanger operating as an evaporator.

References Cited in the file of this patent UNITED STATES PATENTS Coyne Nov. 15, 1960