US3276221A

US3276221A - Refrigeration system

Info

Publication number: US3276221A
Application number: US430521A
Authority: US
Inventors: Ernest W Crumley
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-02-05
Filing date: 1965-02-05
Publication date: 1966-10-04
Anticipated expiration: 1983-10-04

Description

Oct. 4, 1966 E. w. CRUMLEY 3,276,221

REFRIGERATION SYSTEM Filed Feb. 5. 1965 INVENTOR EENE-$T W. Cxau M LE-Y ATTORNEY United States Patent M 3,276,221 REFRIGERATION SYSTEM Ernest W. Crumley, Apt. 502, Carlton Arms, Charleston, S.C. Filed Feb. 5, 1965, Ser. No. 430,521 7 Claims. (Cl. 62-197) This invention relates to refrigeration and more particularly to a refrigeration system of the type which operates at a relatively low compressor suction or back pressure.

In conventional refrigeration systems utilizing a motor driven compressor for compressing the gaseous refrigerant flowing in the system, there is a widespread, rapidly expanding use of what is referred to as a hermetic type compressor. As is well known, in the hermetic type compressor, the electric motor for driving the compressor is positioned together with the compressor in a common sealed enclosure. Suitable means are provided for bringing the motor leads through the casing in order to connect the motor to a source of power and refrigerant vapor flowing from the evaporator is conducted over the motor in heat transfer relationship therewith to the suction or intake side of the compressor. Thu the refrigerant vapor performs the vital function of cooling the motor and, in addition, this absorption of heat from the motor by the vapor raises the vapor temperature adding to the efficiency of the system. Such hermetic type compressors are not only efficient and relatively inexpensive but are characterized by an ease of maintenance as they may be easily and quickly replaced by a new unit when breakdown occurs.

It is customary in various refrigeration systems to design the system to operate at a selected level of suction pressure and to incorporate in such a system a compressor capable of operating efliciently at this selected suction pressure. For instance, compressors are commercially available today which are designed to operate at a low back pressure, a medium back pressure or a high back pressure .and each of these types of compressors may be of the hermetic type.

In systems where the compressor rating is relatively low, that is, where the compressor motor has a fractional horsepower rating or a rating of no more than a few horsepower, hermetic type compressors designed to operate at any of the aforementioned suction pressures are generally available. Although the gaseous refrigerant flowing from the evaporator to the compressor is quite small in a low back pressure system, the small size of such compressor motors requires only a limited amount of cooling. This limited cooling requirement in combination with heat loss produced by radiation from the motor-compressor housing permits adequatercooling to be obtained. Thus the hermetic type compressor is ideally suited for refrigeration systems of limited capacity and full advantage may be taken of its design.

However, as the refrigerating capacity of a refrigeration system increases, that is, where unusually low evaporator temperatures are required such as walk-in type meat refrigerators, large ice cream storage units, etc., there is an attendant increase in the size of the compressor and compressor motor. At the same time, there is an attendant increase in the cooling requirements of the compressor motor. In low suction or back pressure compressor refrigeration applications, the limited amount of gaseous refrigerant characteristic of a low back pressure system is not adequate for cooling a relatively large hermetic compressor motor. For this reason, the hermetic type compressor is not suitably employed in a large capacity, low suction pressure refrigeration applications as the lack of proper cooling produces motor burnout 3,276,221 Patented Oct. 4, 1966 with attendant maintenance and replacement costs. Instead, the common practice is to separate the compressor and compressor motor using individual units connected by a belt or by a direct drive. This separate compressor and motor arrangement is generally referred to as the open type compressor and as it provides adequate cooling for the separate motor, motor overheating and bumout is held to a minimum. 7

However, as can be understood, this separation of the compressor and compressor motor is more expensive from both the standpoint of initial cost as well as the installation. In addition, since such open type compressors must be serviced in place or shut down until the unit can be serviced at a remote location and since there are always delays even when maintenance is done in place, the maintenance cost of such open type compressors is quite high.

Accordingly, a primary object of this invention is to provide a new and novel improvement for a refrigeration system.

Another object of this invention is to provide a new and novel improved refrigeration system which permits the use of a hermetic type compressor having a relatively large rating.

A further object of this invention is to provide a new and novel improved refrigeration system utilizing a relatively low suction pressure which increases the cooling of a hermetic type compressor motor by the refrigerant flowing in the system.

The invention further contemplates the provision of a new and novel improvement for a refrigeration system which is accomplished by a simple modification of a conventional refrigeration system, which eliminates the need for a separate compressor and motor and their attendant initial and maintenance costs in large capacity refrigeration applications, which permits the use of a hermetic type compressor in low suction pressure refrigeration systerns of any capacity within a wide range and which may be controlled in a simple and easy manner.

A still further object of this invention is to provide a new and novel improved refrigeration system which virtually eliminates the possibility of motor burnout in low suction pressure systems utilizing hermetic type compressors.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawing.

The objects stated above and other related objects in this invention are accomplished by the provision of a conventional refrigeration system utilizing well known components serially interconnected by suitable conduits. These components include an evaporator, a hermetic type compressor which includes a compressor and motor arranged in .a common sealed enclosure, a condenser, a receiver and a thermal expansion valve having a bulb responsive to the temperature of the refrigerant flowing in the evaporator. A secondary conduit, preferably a capillary tube, in which a valve is positioned is included in the system and is connected so as to conduct liquid refrigerant contained in the receiver to the suction side of the compressor. .The valve in this secondary conduit is controlled by temperature responsive means positioned in heat transfer relationship with the windings of the compressor motor. ,The temperature responsive means controls the position of the valve to regulate the flow of refrigerant in the secondary conduit from the receiver to the compressor suction side wherein it expands to supplement the cooling action of the gaseous refrigerant from the evaporator on the compressor motor to thereby limit the operating temperature of the motor to a predetermined maximum.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation may be best understood by reference to the following description taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a diagrammatic view of the improved refrigeration system of the invention;

FIGURE 2 is an enlarged sectional view taken substantially along line 2-2 of FIGURE 1 in the direction of the arrows;

FIGURE 3 is a fragmentary view, partially in section, of a modification of the improved refrigeration system of FIGURE 1; and

FIGURE 4 is a fragmentary view of a second modification of the improved refrigeration system of FIGURE 1.

Referring now to the drawing and to FIGURE 1 in particular, there is shown a refrigeration system incorporating the basic components of a conventional refrigeration system together with certain features which, in combination, provide the refrigeration system of the invention. The conventional portion of the refrigeration system of FIGURE 1 includes an evaporator designated generally by the numeral formed from a tube or conduit 11 communicating with the suction or intake side of a hermetic type compressor designated generally by the numeral 12. The hermetic type compressor 12 is of the conventional type comprising an electric motor and compressor (not shown) arranged in vertically disposed relationship with the motor positioned above the compressor and connected thereto for direct drive preferably by a common shaft. The motor and compressor are contained within a common sealed enclosure 13 and the portion of conduit 11, indicated as conduit portion 11a is connected by suitable means such as a connector 14 in communication with the compressor intake through the enclosure 13. This gaseous refrigerant flowing within the conduit 11a passes over the motor contained within the upper portion of the housing 13 as shown diagrammatically in FIGURE 4 prior to entering the compressor contained within the lower part of the housing 13 in the well known manner.

By means of a suitable connection 16, a conduit 17 is connected with the enclosure 13 so as to communicate with the discharge or high pressure side of the compressor. The conduit 17 communicates with a condenser 18 which may be of the conventional type over which is circulated a heat transfer medium such as air in the well known manner by means such as a fan 19. The outlet of the condenser 18 is connected by means of a conduit 20 with the receiver 22 and the conduit 20 is provided with an open end 21 in communication with the interior of the receiver. As is well known, the receiver 22 is a reservoir for the refrigerant contained in the system in the liquid condition under high pressure. Another conduit is also connected to the receiver 22 and has an open end 24 communicating with the interior of the receiver as shown in FIGURE 1 for conducting liquid refrigerant out of the receiver in the well known manner.

The conduit 23 communicates at its other end with an intake opening 25 in a thermostatic expansion valve 26 of conventional construction. The valve 26 is provided with an interior 27 in which is positioned a flexible diaphragm 28. A valve stem 29 is suitably secured to one side of the diaphragm 28 and has a head 31 arranged to be moved into closing engagement with a valve seat 32. A spring 33 is also positioned around the pin 29 and urges the pin 29 and diaphragm 28 vertically upward to position the head 31 within the seat 32.

The other side of the diaphragm 28 is in communication with the end of a capillary tube 34 having at its remote end a bulb 36 secured in heat transfer relationship with the evaporator coil 11 in the conventional manner. The valve 26 is also provided with an outlet opening 37 which communicates with that end of the evaporator coil 11 remote from the compressor 12 as shown.

As specifically illustrative of the invention, a secondary conduit 41 is provided which communicates at one end with the interior of the receiver 22 and its other end with the conduit portion 11a preferably adjacent the connection 14 on the compressor enclosure 13 as shown in FIG URE 1. The conduit 41 is thus arranged to conduct liquid refrigerant from the receiver 22 to the compressor suction side and thereby supplement the cooling action of the gaseous refrigerant flowing in the conduit 11a on the compressor motor contained within the enclosure 13. Although the secondary conduit 41 may be provided with any desired inside diameter in accordance with the requirements of the system, the conduit 41 is preferably a capillary tube having a relatively small diameter such as /16, %2n or 1/64" Preferably an on-off valve 42 is provided in the conduit 42 by means of which the conduit 41 may be opened and closed manually. A strainer 43 is also preferably provided in the conduit 41 for blocking the passage of material other than pure refrigerant into the conduit portion 11a and subsequently into the suction side of the compressor.

In order to regulate the flow of refrigerant in the secondary conduit or capillary tube 41, means are provided which are preferably responsive-to the temperature of the compressor motor contained within the enclosure 13. More specifically, a solenoid type valve 44 of any conventional type including a solenoid 46 is positioned within the conduit 41. The solenoid 46 is connected by means of

conductors

47, 48 to a suitable source of power (not shown) and also to suitable means responsive to the temperature of the motor. More specifically, as shown in FIGURE 2, the

conductors

47, 48 are connected to strips 49, 51 of a thermostat designated generally by the numeral 52 which strips extend through an insulator plug 53 positioned within an opening 54 in the compressor enclosure 13.

The strips 49, 51 are contained within a thermostat housing 56 preferably embedded in the windings 57 of the compressor motor so as to be in heat transfer relationship therewith. Strip 49 is of the bi-metallic type which flexes in response to temperature rise so as to move its contact 58 into engagement with a contact 59 on the stationary strip 51.

FIGURE 3 shows a modification of the embodiment of FIGURES 1, 2 for regulating the flow of refrigerant in conduit 41. As shown in FIGURE 3, the valve 44 of FIGURE 1 is replaced in conduit 41 by a thermostatic expansion valve 61 similar in construction to the expansion valve 26 of FIGURE 1. A diaphragm 62 in valve 61 communicates on one side through a capillary tube 63 with a remote bulb 66 embedded in the motor windings 57. The capillary tube 63 extends through an opening in the compressor enclosure 13 as shown.

The conduit 41 communicates with an inlet 65 on the valve 61 and an outlet 68 in the valve 61 communicates through conduit 69 with the conduit 11a as shown. Similar to valve 26 of FIGURE 1, the expansion valve 61 is provided with a valve pin head 70, valve pin 71, a valve seat 72, and a spring 73.

As has been previously explained, the refrigeration system of the invention is particularly adapted to a system utilizing a relatively low suction or back pressure wherein the gaseous refrigerant flowing into the heremetic type compressor 12 is of a limited amount.

In the operation of the conventional portion of the system of FIGURE 1, high pressure liquid refrigerant flows from the receiver 22 to the expansion valve 26 wherein its flow is retarded. The refrigerant flowing into the evaporator coil 11 is controlled by the position of the diaphragm 28 under the control of the remote bulb 36. Movement of the diaphragm 28 moves the valve pin head 31 into and out of closing engagement with the valve seat 32. As the liquid refrigerant passes through the valve 26, its pressure is decreased and as it flows through the coil 11, it evaporates into gaseous form absorbing heat thereby accomplishing refrigeration.

The gaseous refrigerant then flows from the evaporator through conduit portion 11a as a cool, low pressure gas to the hermetic type compressor 12 over the compressor motor and into the compressor where its pressure and temperature are increased. After being compressed in the compressor 12, the gaseous refrigerant leaves the compressor at a much higher pressure and temperature and is conducted into the condenser 18 wherein it is cooled and condensed to a liquid, the air pumped by fan 19 removing heat from the refrigerant. Liquid refrigerant then flows into the receiver 22 through conduit As the low pressure gaseous refrigerant in such systems utilizing large hermetic type compressors 12 is not suflicient to cool the compressor motor, the motor windings 57 increase in temperature which temperature is sensed by the temperature responsive means such as the thermostat 52 of FIGURE 2. This increase in motor winding temperature moves the bimetallic strip 49 downwardly as viewed in FIGURE 2 moving its contact 58 in engagement with the contact 59 on stationary strip 51 completing a circuit. When the circuit is completed, the solenoid 46 is energized through

conductors

47, 48 opening valve 44 and permitting liquid refrigerant to flow from the receiver 22 through capillary tube 41 into conduit portion 11a communicating with the suction side of the compressor.

As the liquid refrigerant enters conduit portion 11a from conduit 41, it expands into gaseous for-m thereby supplementing the cooling action of the gaseous refrigerant flowing from the evaporator conduit 11. The supplementing eifect of the refrigerant in secondary conduit 41 is continued until the motor winding temperature is decreased causing thermostat 52 to open. Valve solenoid 46 is thereupon de-energized closing valve 44 and interrupting the flow of refrigerant in conduit 41. Thus the operating temperature of the motor is maintained below a predetermined maximum and motor burnout is avoided.

In the embodiment of FIGURE 3, the flow of liquid refrigerant in conduit 41 is under the control of the thermal expansion valve 61 instead of the solenoid valve 44 of FIGURES 1, 2. The position of the diaphragm 62 in valve 61 is controlled by the motor winding temperature detected by the remote thermal b-ulb 66 so as to move the valve pin head 70 in and out of engagement with valve seat 72.

As in the embodiment of FIGURES l, 2, when the temperature of the motor windings 57 reaches a predetermined :level as detected by the remote bulb 66, the diaphragm 62 of valve 61 moves downwardly to permit liquid refrigerant to flow from conduit 41 through the valve seat 72 and into the outlet conduit 69 of the valve 61 into the conduit portion 11a. Thus, the liquid refrigerant, as it expands into gaseous form in conduit portion 11a, is combined with the gaseous refrigerant flowing from the evaporator coil 11 to provide additional cooling of the compressor motor as in the embodiment of FIGURES 1, 2.

When the motor windings temperature has been reduced, the diaphragm 62 moves upwardly moving the valve pin head 70 into sealing engagement with the valve seat 72 interrupting the flow of liquid refrigerant in secondary conduit 41.

In still another modification of the refrigeration system of the invention as shown in FIGURE 4, a more simpli fied form of the invention contemplates dispensing with the motor temperature responsive means of FIGURES 1-3 and the substitution of a valve such as a solenoid valve 81 which is responsive to the operation of the compressor. As supplemental cooling of the compressor motor is needed only when the compressor is operated, although the system may be functioning, the valve 81 is designed to admit in the open position only that amount of addi- 6 tional refrigerant from receiver 22 through conduit 41 needed for proper cooling of the compressor motor when it is running.

As shown in FIGURE 4, solenoid valve 81 is positioned in conduit 41 and has its solenoid connected by one conductor 84 to a motor conductor lead 85 and by its other conductor 84 to a contact on a relay 83. In addition to lead 85, motor lead -86 is provided which is connected to relay 83 and both motor leads 85, 86 are in turn connected to any suitable motor control 87 connected to any suitable source of power in the manner shown in FIGURE 4. It should be understood that the arrangement of FIGURE 4 is representative only and any desired circuit may be employed for controlling the operation of the valve 81 in response to the operation of the motor M.

In the operation of the arrangement of FIGURE 4, when the motor M is energized through the motor control 87, relay 83 is energized to simultaneously energize both the motor M and the solenoid of valve 81. Thus refrigerant flows from the receiver 22 through conduit 41 into conduit portion 11a in the manner described above when the motor M is operated. When the motor M is de-energized to discontinue the operation of the compressor, the relay 83 is also de-energized opening the circuit to the solenoid of valve 81 so that the valve closes shutting off the flow of refrigerant in the conduit 41.

It should be understood that although the operation of valve 81 is controlled by the operation of the compressor motor M, other arrangements may be employed which permit the flow of refrigerant through conduit 41 only when the compressor 12 is operating. For instance, a suitable valve may be used for valve 81 which is responsive to the vacuum produced in conduit portion 11a when the compressor is operating.

With the novel construction of this invention, an improved refrigeration system has been provided which permits the utilization of a hermetic type compressor in refrigeration applications not heretofore possible without compressor motor burnout. By an extremely simple addition to a conventional refrigeration system, the gaseous refrigerant entering the suction side of the compressor is supplemented with refrigerant present in the system to provide proper cooling of the compressor motor in low suction pressure applications wherein the amount of gaseous refrigerant is insufficient for proper motor cooling. The open type compressor or separate motor and compressor installation common to large refrigeration units is no longer acquired in the system of the invention and the outstanding efliciency and low initial and maintenance costs common to the hermetic type compressor may be taken full advantage of. The controlling of the flow of refrigerant for supplementary cooling in the system of the invention may be easily accomplished by the outstanding arrangement of the invention and a wide variety of easily controlled valves or other control arrangements may be employed.

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

Having thus described the invention, what is claimed is:

1. In a refrigeration system having components including a hermetic type compressor having a suction side and a discharge side, a motor for driving said compressor positioned above said compressor in vertically disposed relationship, a common sealed enclosure for said compressor and motor, a condenser, a receiver, an expansion valve, an evaporator, conduits interconnecting said components serially in a closed system, a refrigerant in said closed system and wherein the refrigerant from said evaporator impinges on said motor in heat transfer relationship therewith prior to entering said compressor, the improvement of a secondary conduit directly communicating said receiver with the suction side of said compressor for conducting liquid refrigerant from said receiver to said compressor suction side to supplement the cooling action of the gaseous refrigerant from said evaporator on said compressor motor, means responsive to the operation of said compressor for regulating the flow of said refrigerant in said secondary conduit to maintain the operating temperature of said motor within a predetermined maximum.

2. In a refrigeration system having components including a hermetic type compressor having a suction side and a discharge side, a motor for driving said compressor positioned above said compressor in vertically disposed relationship, a common sealed enclosure for said compressor and motor, a condenser, a receiver, an expansion valve, an evaporator, conduits interconnecting said components serially in a closed system, a refrigerant in said closed system and wherein the refrigerant from said evaporator impinges on said motor in heat transfer relationship therewith prior to entering said compressor, the improvement of a secondary conduit directly communicating said receiver with the suction side of said compressor for conducting liquid refrigerant from said receiver to said compressor suction side to supplement the cooling action of the gaseous refrigerant from said evaporator on said compressor motor, means responsive to the temperature of said compressor motor for regulating the flow of said refrigerant in said secondary conduit to maintain the operating temperature of said motor below a predetermined maximum.

3. In a refrigeration system having components including a hermetic type compressor having a suction side and a discharge side, an electric motor for driving said compressor positioned above said compressor in vertically disposed relationship, a common sealed enclosure for said compressor and motor, a condenser, a receiver, an expansion valve, an evaporator, conduits serially interconnecting said components in a closed system, a refrigerant in said closed system and wherein the refrigerant from said evaporator impinges on said motor in heat transfer relationship therewith prior to entering said compressor, the improvement of a secondary conduit directly communicating said receiver with the suction side of said compressor for conducting liquid refrigerant from said receiver to said compressor suction side to supplement the cooling action of the gaseous refrigerant from said evaporator on said compressor motor, a valve in said secondary conduit, thermostatic means responsive to the temperature of said motor for controlling the position of said valve to regulate the flow of liquid refrigerant in said secondary conduit and thereby maintain the operating temperature of said motor below a predetermined maximum.

4. An improved refrigeration system in accordance with claim 3 wherein said valve is a solenoid valve and wherein said thermostatic means includes a source of electric power connected to said solenoid valve and a thermostat responsive to the temperature of the windings of said motor for controlling the position of said solenoid valve with said source of electric power.

5. An improved refrigeration system in accordance with claim 3 wherein said valve in said secondary conduit is a thermal expansion valve and wherein said thermostatic means includes a fluid pressure bulb responsive to the temperature of the windings of said motor for controlling the position of said thermal expansion valve.

6. In a refrigeration system having components including a hermetic type compressor having a suction side and a discharge side, a motor for driving said compressor, a common sealed enclosure for said compressor and motor, a condenser, a receiver, an expansion valve, an evaporator, conduits interconnecting said components in a closed system and a refrigerant in said closed system; the improvement of capillary tube means directly communicating said receiver with the suction side of said compressor for conducting liquid refrigerant from said receiver to said compressor suction side, said capillary tube means being adapted to expand and vaporize the liquid refrigerant entering said compressor suction side to supplement the cooling action of the gaseous refrigerant from said evaporator on said compressor motor and means responsive to the temperature of said compressor motor for regulating the flow of said refrigerant in said capillary tube means to maintain the operating temperature of said motor below a predetermined maximum.

7. In a refrigeration system having components including a hermetic type compressor having a suction side adapted for low back pressure operation and a discharge side, an electric motor for driving said compressor, a common sealed enclosure for said compressor and motor, a condenser, a receiver, an expansion valve, an evaporator, conduits interconnecting said components serially in a closed system and a refrigerant in said closed system, the improvement of capillary tube means directly communicating said receiver with the suction side of said compressor for conducting liquid refrigerant from said receiver to said compressor suction side, said capillary tube means being adapted to expand and vaporize the liquid refrigerant entering said compressor suction side to supplement the cooling action of the gaseous refrigerant from said evaporator on said compressor motor, a thermal expansion valve in said capillary tube means, a fluid pressure bulb communicating with said thermal expansion valve positioned in heat transfer relationship with the windings of said motor, said bulb being responsive to the temperature of the windings of said motor for controlling the position of said valve to thereby maintain the operating temperature of said motor below a predetermined maximum.

References Cited by the Examiner UNITED STATES PATENTS 2,746,269 5/1956 Moody 62505 2,967,410 1/1961 Schulze 62-505 3,088,042 4/ 1963 Robinson 62-505 3,122,894 3/1964 Bernhard 62-505 X 3,146,605 9/1964 Rachfal 62505 X MEYER PERLIN, Primary Examiner.