US2904971A

US2904971A - Superheat coil by-pass in refrigerating apparatus

Info

Publication number: US2904971A
Application number: US776945A
Authority: US
Inventors: Milton M Kosfeld
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1958-11-28
Filing date: 1958-11-28
Publication date: 1959-09-22
Anticipated expiration: 1976-09-22

Description

Sept. 22, 1959 'M. M. KOSFELD 2,

SUPERHEAT COIL BY-PASS IN REFRIGERATING APPARATUS Filed Nov. 28. 195a- FIG! FIG?! INVENTOR. MILTON M. KOSFELD H \S ATTORNEY United States Patent C) 2,904,911 SUPERHEAT con; BY-PASS" m anrnionmrmc APPARATUS= Milton M. Kosfeld, Louisville, Ky assignor to General Electric Company, a corporation of New: York,

Application November 28, 1958; Serial- N0. 776,945

3 Claims. (Cl- 62-196) The present invention. relates to a refrigerating; appa ratusand more particularly to a refrigerating apparatus utilizing a compressor of the type" commonly known as a high side case in which: the pressure within the compressor case isap'proximately the same as the P'I'CSSUTEOII" the high pressureside of the refrigerating system:

An object of the present invention is to provide" an improved refrigerating apparatus including a high side cornpressor and a compressor superheat" removal coil" and embodying-a means for preventing the hammering noise which sometimes occurs due" to the'pumping' of oil" and refrigerant in liquid form throughthe superheat removal coil.

more specific object of the present invention is to provide an arrangement for bypassing oil and refrigerant around the superheat removal coil directly into the corn pressor casing whenever oil and refrigerant in li'qui'd form is'pumped by the compressor; 7

Other objects and advantages of thepresent'invcnfiorr 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 toand forming a part of this specification.

In carrying out the present invention therei's provided in a refrigerating apparatus, a compressor and a cornpressor motor heremetica-Ily sealed within acasing: A discharge chamber is provided into which the compressed refrigerant gas from the compressor i s-discharged prior to being directed into a superheat' remov'ahcoil where it is-partially cooled prior to'ii'owing into the herrnetic car-- ing'. The partially cooled high pressure gas cools the compressor motor before flowing-out of the case into the remaining portions of the refrigeration system. In order to prevent hammering noise in thesuperhea-t removal coil, which sometimes results when refrigerant and oil in liquid form from the low pressure side'of the refrigeration systern is pumped by the compressor into thesuperheat re moval coil, a bypass passage is provided leading" directly from the discharge chamber into the casing through which oil and refrigerant in liquid form: is shunted around the" superheat' removal coil. The bypass passage contains a pressure responsive valve which is operable to permit flow of refrigerant and oil through the passage from thedischarge chamber to the casing in response to apredeter mined increase in pressure in the discharge chamber over thepressure in the casing. 1 i

For a better understanding of the invention, reference maybe had to the accompanying drawing in which:

Fig. l is an elevation view in cross section of the-pre fe'rred embodiment of the invention; 1

Fig. 2 is a horizontal; cross sectionrtak'en aiong line 2-2 of Fig: 1-; and I Fig; 3 is a diagrammatic illustration of a refrigeration system incorporating the present invention.

Referring now to the Fig. 1, there is shown a hermetic compressor including a hermetic casing 2 in which there is disposed a refrigerant compressor unit having an annnlar' chamber or compressionchamber 3" defined with-in a cylinder or housing 4. Disposed for rotation the chamber 3 is a rotor 6 which is driven by an eccentric 7 formed as an integral part of a drive shaft 8 which extends downwardly from the motor 9'. A hearing: 11', which, with the supporting main frame 12,1 defines the upper end wall of the annular compression chamberS', supports the shaft 8 above the eccentric 7 for rotation. by the motor. The main frame 12 also supports thc'coma prcssor within the casing. As may better be seen. in Fig, 2, Within the cylinder 4' there is provided a radial slot I3 having slidably disposed therein a blade or vane 14 is biased into engagement with the outer periphery of the rotor 6 thereby dividing, the chamber 3 into low and high pressure sides respectively designated 3a and3b. In the illustrated embodiment of the invention, the end of blade 14 is biased against the periphery of the rotor by means of a spring 16 arranged withinan enlarged opening13a forming partof the radial slot 13.

A compressor of this type is adapted to be connected. into a; refrigeration system in the manner indicated in Fig. 3'. During normal operation of the apparatus, low pressure refrigerant in gaseous form flows from the evaporator 17 through a suction line 19' which connects with. the suction port 21 (seen in Fig. 2) of the compressor. The suction port 21 delivers this suction or low pressure gas into the low pressure side 3a of the compression chamher 3 where it is compressed during rotation of the rotor 6' to a much higher pressure. and is discharged through a discharge port or outlet 22 into a discharge chamber 23; Mouted within the discharge chamber 23, is a suitable valve 24 for assuring, proper compression of the gases is suing from a discharge or outlet port 22 and for preventing reverse flow of gas back into the compression cham her 3.

During normal operation of the apparatus, high pressure gas flows from the discharge chamber 23 into a superheat removal coil 26, where the high pressure gas. is partially cooled. The outlet 25from the superhe-at removal coil 26 communicates with the inside of the casing 2 and discharges the partially cooled gas into the casing for cooling the motor. After cooling the motor, the high pressure gas discharges from the casing through the outlet or high pressure line 27 into the condenser 28 and the remaining portions of the refrigeration system. When. operating under normal conditions, most of the gas flow ing through the superheat removal coil 26 remains in the gaseous state; or, if a small amount of refrigerant liquifies in the coil, it is immediately carried out of the coil by the gas as it flows into the casing.

There are times during the operation of a refrigeration system of this type when refrigerant and oil are delivered to the suction inlet of the compressor from the evaporator almost entirely in the liquidstate. This occurs, under certain conditions, during the initial starting of the. compressor after the compressor has been off for a short period and liquid refrigerant and oil have collected in. the suction line 19. Also, even when the compressor has operated for a period of time, large slugs of liquid refrigerant are sometimes carried by the high velocity suction gas through the line 19 from the evaporator. The liquid refrigerant and oil is pumped through the compressor chamber 3, and. if means are not employed to prevent it, the liquid refrigerant is. forced through the frigerant through the coil 26 create a hammering noise,

7 somewhat in the same manner as a waterhamrner occurs in radiators of a steam heating system. In addition tothis hammering noise, the pressure in the discharge chamber suddenly becomes very great and the subsequently pumped liquid refrigerant and oil, which, for all practical purposes, is incompressible, causes bearing loads that likely to burn up the hearings or at least reduce the life of the bearings.

Some refrigerating systems employed an accumulator or large volume refrigerant trap in the suction line 19 to collect this liquid refrigerant and to prevent it from entering the compressor except in the gaseous state. However, to use an accumulator large enough to collect all of the liquid refrigerant that collects in the suction line 19 and the lower end of the evaporator 17, is not desirable in most of the present day appliances in which space is a premium. Further, when such an accumulator is used, during initial compressor start-up, as the suction pressure reduces in the suction line 19, the refrigerant in these accumulators begins to boil violently and causes large amounts of liquid refrigerant to be carried over into the suction inlet to the compressor. To prevent this from happening, these accumulators must be supplied with elaborate refrigerant trapping devices thereby making their cost rather high.

As will now be explained, the present invention is particularly concerned with an arrangement for eliminating the hammering noise which results from pumping of refrigerant and oil in the liquid state through the superheat removal coil thereby permitting the elimination of the liquid refrigerant accumulator, or at least permitting the use of an accumulator of very nominal size merely to stop the slugs of liquid which pass from the evaporator while the system is in operation. As may be seen in Figs. 1 and 2, there is provided a bypass passage 29, which leads directly from the discharge chamber 23 to the inside of the casing. A pressure responsive valve means 31 closes the bypass passage 29 and prevents the flow of refrigerant in gaseous form through the passage directly into the inside of the case. In the illustrated embodiment of the invention the valve means 31 comprises a leaf spring which is normally seated across the outlet side of the bypass passage 29. This spring must have sufficient strength to maintain the passageyclosed for small varitimes in pressure between the inside of the case and the discharge chamber. Since refrigerant gas normally flows freely through the superheat removal coil 26, the pressure within the casing 2 is approximately the same as that within the discharge chamber. intermittent discharging of high pressure gas from the chamber 3 into the discharge chamber 23 only raises the pressure within the discharge chamber, which is relatively large in comparison to the compression chamber, a couple of pounds above the pressure within the casing 2. In a tested embodiment of the invention using a valve means 31 that was capable of remaining closed under a pressure of approximately five pounds, the refrigerant in the gaseous state was normally directed into the superheat removal coil 26. However, the minimum pressure for the valve means is not a critical factor for reasons which will be explained later in this specification.

I From the above, it can be seen that in order to let refrigerant flow through the bypass passage 29, there must be a small pressure difference to open the valve means 31 depending on the characteristics of the valve. Under normal operation of the system when refrigerant in gaseous form is pumped by the compressor, the valve means 31 remains closed. However, when the compressor pumps refrigerant and oil in liquid form into the discharge chamber 23 and thence into the superheat removal coil 26, the pressure in the discharge chamber 23 rises rapidly and the pressure in the casing 2 drops. This is because the coil 26 restricts the flow of liquid to a certain extent and creates a substantial pressure drop in the coil. The pressure difierential between the casing 2 and the discharge chamber 23 very quickly exceeds the amount necessary to overcome the valve means 31. The liquid refrigerant in the discharge chamber, then seeks the path of least resistance and flows directly into the casing 2 through the bypass passage 29. Since the bypass passage permits the liquid refrigerant to shunt the v 4 superheat removal coil, the pulsations caused by the intermittent pumping of the liquid refrigerant into the chamber 23 are not transmitted, in any great degree, to the liquid in the superheat removal coil 26, because any subsequently pumped liquid flows directly through the bypass passage 29 into the casing 2.

It will be noted, that the diameter of the bypass passage 29, and therefore its cross-sectional area, is substantially greater than that of the tubing or coil 26. This, of course, assures that the restriction of the liquid flowing through this passage will be substantially less than the restriction of the liquid in the coil 26.

It has been found that the actual minimum pressure for the pressure responsive valve means 31 is not too critical as long as there is some pressure present. Even though a small amount of gaseous refrigerant escapes through the bypass passage directly into the casing without passing through the superheat removal coil the operaof the superheat removal coil 26 altogether.

By the present invention there has been provided a simple arrangement for eliminating the hammering noise which is prevalent in compressors utilizing a superheat removal coil whenever liquid refrigerant and oil is pumped through the compression chamber into the coil. Moreover, the arrangement greatly reduces the load -on the bearings of the compressor at such times when liquid refrigerant and oil is pumped through the compression chamber.

While in accordance with the patent statutes there has been described what at present is considered to be the preferred embodiment of the 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 intent 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:

1. In a refrigerating system, the combination comprising a hermetically sealed casing for containing a high pressure refrigerant gas, a compressor and a compressor motor mounted in said casing, a discharge chamber directly connected to the outlet of said compressor, a superheat removal coil having its inlet communicating with said discharge chamber and its outlet connecting with said casing thereby to cool the high pressure refrigerant gas from said compressor and to discharge said partially cooled gas into said casing to cool said compressor motor, a bypass passage connecting said discharge;

chamber directly with said case, and a pressure responsive valve in said bypass passage operable to admit refrigerant and oil from said discharge chamber to saidcasing in response to a predetermined increase in pressure in said discharge chamber over the pressure in said case due to oil and liquid refrigerant from the low pressure side of said refrigerating system being pumped through said superheat removal coil whereby hammeringnoise caused by said intermittent pulsations in said liquid refrigerant and oil in said superheat removal coil is prevented.

2. In a refrigeration system, the combination comprising a hermetically sealed casing for containing a high pressure refrigerant gas, a compressor and a compressor motor mounted in said casing, a discharge chamber directly connected to the outlet of said compressor, a superheat removal coil having its inlet communicating with said discharge chamber and its outlet connecting with said casing thereby to cool the high pressure refrigerant gas from said compressor and to discharge;

said partially cooled gas into said casing to cool said compressor motor, a bypass passage connecting said discharge chamber directly with said case, said bypass passage having a cross-sectional area substantially greater than the cross-sectional area of said superheat removal coil, and a pressure responsive valve in said bypass passage operable to admit refrigerant and oil from said discharge chamber to said casing in response to a predetermined increase in pressure in said discharge chamber over the pressure in said case due to oil and liquid refrigerant from the low pressure side of said refrigerat ing system being pumped through said superheat removal coil whereby hammering noise caused by said intermittent pulsations in said liquid refrigerant and said oil in said superheat removal coil is prevented.

3. In a refrigerating system, the combination comprising a hermetically sealed casing for containing a high pressure refrigerant gas, a compressor and a compressor motor mounted in said casing, a discharge chamber directly connected to the outlet of said compressor, a superheat removal coil having its inlet communicating with said discharge chamber and its outlet connecting with said casing thereby to cool the high pressure refrigerant gas from said compressor and to discharge said partially cooled gas into said casing to cool said compressor motor, a bypass passage connecting said discharge chamber directly with said case, said bypass passage having a cross-sectional area greater than the cross-sectional area of said superheat removal coil, a normally closed pressure responsive valve in said bypass passage, said pressure responsive valve being operable to open said passage upon a pressure increase in said discharge chamber over the pressure in said case approximately equal to the pressure drop of refrigerant gas flowing through said superheat removal coil so that refrigerant and oil in gaseous form is directed through said superheat removal coil While oil and refrigerant in liquid form is at least partially shunted directly into said casing due to the restriction on the liquid refrigerant and oil in the superheat removal coil and the resultant increase in pressure differential between said discharge chamber and said casing.

References Cited in the file of this patent UNITED STATES PATENTS 2,715,992 Wilson Aug. 23, 1955 2,738,657 Jacobs Mar. 20, 1956 2,794,323 Rataiczak et a1 June 4, 1957