US 2141715 A
Description (OCR text may contain errors)
Dec. 27, 1938. R. HlLGER 2,141,715
I REFRIGERATION MECHANISM Filed June 25, 1937 Patented Dec. 27,` 1938 UNITED STATES PATENT OFFICE 4 Claims.
'I'he invention relates to refrigeration mechanisms and more particularly to improvements in expansion-type refrigerating systems.
In Patent No. 1,601,445 issued to George Hilger on September 28, 1926, a three-pressure multistage expansion refrigeration system is disclosed in which high-pressure refrigerant isiexpanded into a single header maintained at a constant intermediate pressure and subsequently expanded again through separate thermally controlled valves into a plurality of low-pressure evapora-` tors. One object of the present invention is to provide an improved multistage expansion refrigeration system of this same general type but in which increased flexibility and effectiveness of operation of the systemv are had through the utilization of a novel arrangement for selectively maintaining an intermediate-pressure stage for the refrigerant flowing to a plurality of evaporators at either the same or different pressures for the several evaporators. i
Another object of the present invention is to provide a plural evaporator refrigeration systern including a multipressure expansion valve unit for each evaporator which successively decreases the pressure of the refrigerant in at least two stages but with the formation of a minimum ofilash gas in the intermediate stage or stages of such expansion.
A further object of the invention is to provide a plural evaporator refrigeration system embodying an improved arrangement for defrosting any selected one of the evaporators Without interrupting the operation of the other evaporators in the system and with a minimum loss in overall eiiiciency of the system.
The invention also resides in certain structural Y improvements in the expansion valve unit of the system.
Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specication.
For a better understanding of the invention, reference may be had to the accompanying drawing in which v Y Figure 1 is a diagrammatic illustration of a refrigeration system embodying the invention.
Fig. 2 is an enlarged` longitudinal sectional view of one of the expansion valve units included in the system shown in Fig. 1.
u Fig. 3 is an enlarged longitudinal sectional view (Cl. (i2- 115) of one of the three-way systems shown in Fig. 1.
The present invention is particularly applicable to plural evaporator systems and accordingly, has been illustrated as embodied in a system including two separate evaporators I0 and II. These evaporators may be mounted in separate heat insulated compartments or chambers and the system is such that they can be readily utilized to absorb heat loads of quantitative value but also loads which vary irregularly with respect to each other. Consequently, a high degree of exibility in the operation of the system may be had.
High-pressure liquid refrigerant may be sup- 15 plied in the system from any suitable source, the one illustrated herein being a conventional vcompressor-condenser unit including a compressor I2 driven by a belt-connected electric motor I3. Compressed liqueable gaseous refrigerant is dis- 20 charged from the compressor outlet I4 into a. conduit I5 through which it passes to an aircooled condenser I6 in which the compressed gaseous refrigerant is liqueed upon the diminution in temperature thereof by the cooling air 25 passing over the condenser. 'I'he refrigerant thus liquefied in the condenser I6 is accumulated by gravity flow in a receiver I1.
vSeparate expansion valve units erally by the numerals I8 and I9 are associated 30 with the respective evaporators I0 and II and serve to expandthe high-pressure refrigerant into the associated evaporators upon diminution of its pressure in successive stages. It will be noted that the expansion valve units I8 and I9 35 are connected to the high-pressure receiver I'I in parallel relation by a supply conduit 20 and branch conduits 2| and 22. The expansion valve units are substantially identical in construction and consequently, a description of one of these 40 units will suilice for both. l
Upon reference to Fig. 2, it-will be seen that the expansion valve unit I8 includes in general a main valve casing member 23 cored out to form a chamber 24, constituting an intermediate refrigerant pressure zone, and expansion valves 25 and 26 located respectively at the inlet and outlet of the chamber 24. The automatic expansion valve 25 throttles the high-pressure refrigerant from the receiver I 1 to a selected substantially 50 constant intermediate pressure in the chamber 24 while the valve 26 expands the intermediatepressure refrigerant from the chamber 24 into the evaporator I I) in accordance with the thermal requirements of the evaporator.
valves included in the designated gennot only different 10 in a suitable alined In the preferred construction illustrated, the expansion valve 25 includes a valve elementA 21 carried by a stem 28 and disposed in an inlet passage 29 formed in the casing 23. This valve element cooperates with a complemental seat formed in a. hardened wear-resistant bushing 38 threaded in a transverse partition in the valve casing 23 to control the flow of refrigerant from the inlet passage 29 to the chamber 24. A diskshaped pressure actuating member 3| exposed to the pressure of the refrigerant in the chamber 24 is secured tothe lower end of the valve stem 28 so that the pressure of the refrigerant in the intermediate-pressure zone is utilized to move the valve element 21 to its closed position, this action being supplemented by a small compression spring 32 interposed between the top of the valve element and a removable cap 33 threaded opening in the top of the casing 23. A second and larger compression spring 34 bears against the lower side of the pressure member 3| and tends to move the valve element 21 into open position. This latter spring 34 is mounted within a cup-shaped housing 35 detachably secured to the lower side of the casing 23 by cap screws 36, an imperforate flexible gasket 31 being interposed between the housing 35 and casing 23 to form a hermetic seal therebetween. The opening pressure exerted by the spring 34 on the valve element 21 may be varied by a suitable adjusting screw 38 threaded in the lower end of the housing 35 and bearing against a disk 39 seated in the lower end of the helical compression spring. A removable threaded cap 40 prevents accidental contact with or change of position of the adjusting screw 38. It will thus be seen that the pressure of the spring 34 may be varied through the medium of the adjusting screw 38 in such manner as to counterbalance the opposed spring 32 and the pressure exerted on the pressure actuating member 3l until the latter pressure reaches some predetermined minimum value at which point the spring 34 is overbalanced and the valve element 21 moved to closed position. The expansion valve 25 may thus be readily adjusted to admit refrigerant to the intermediate-pressure chamber 24 whenever the pressure therein falls below some selected minimum value so that the intermediate pressure prevailing within the chamber 24 is maintained substantially constant. It will also be understood that the intermediate pressures within the exparisien valve units |8 and I9 respectively may be maintained at diierent selected, though constant, values which are best suited to the particular requirements of the associated evaporator.
The thermally controlled expansion valve 26 includes in general a spherical valve element 4| cooperating with an annular wear-resistant valve seat member 42 threaded in a suitable partition in the casing 23 to control the iiow of refrigerant from the chamber 24 to an outlet passage 43. The spherical valve element 4| is mounted in a complemental recess in the top face of a disk 44 carried on the top of a helical compression spring 45 which normally biases the valve element to closed position. It will be noted that the spring 45 is disposed within a bore 46 in a. cylindrical extension 41 formed on the lower side of the valve casing 23 and surrounds a boss 48 on a -cylindrical plug 49 which is threaded in the lower end of the extension 41. An annular sheet metal spring retainer 50 surrounding the boss 48 in loose sliding engagement therewith maintains the lower end of the spring 45 in position. Adjustment of the spring pressure may be effected by shifting the retainer 50 axially through the medium of an adjusting screw 5| which contacts the bottom` of the spring retainer and is threaded in the plug 49. The escape of gaseous refrigerant ax ially of the adjusting screw 5| is prevented by packing washers 52 held in position by a, threaded gland 53. The outer end of the adjusting screw is protected by a cap 54 which is similar to the protective cap 46 and is threaded on the outer end of the plug 49.
The operating mechanism for the valve element 4| of the expansion valve 26 comprises in general a pair of oppositely acting pressure elements shown in the form of the disk-shaped ends of imperforate resilient metal bellows 55 and 56. The faces or ends of these bellows are connected by a spool-shaped actuating member or pin 51 made of thermal insulating material. It will be noted that the lower bellows 56 is exposed to the pressure of the refrigerant in outlet passage 43 while the upper bellows 55 is disposed in a separate chamber 58 formed within a separable housing 58 attached to the valve casing 23 by cap screws 60. Pressure `flluid is admitted to the chamber 58 through an opening 6| therein and the actuating pin 51 may thus be made to move axially in accordance with the differential between the refrigerant pressure prevailing in the valve unit outlet passage 43 and some external variable pressure which is transmitted to the chamber 58. In the construction illustrated the pressure in the chamber 58 is caused to vary in accordance with changes in'ternperature at the outlet of the associated evaporator. For this purpose, a feeler bulb 62 (Fig. 1) of conventional construction is clamped in heat exchange relation with the return line for the evaporator ||l and communication is had between the interior of the bulb and the chamber 58 through a feeler line 63. An inert gas is used to fill the bulb 62 so that its volume varies in accordance with changes in temperature in the refrigerant return line for the evaporator.
In order that the refrigerant in the passage 43 shall not aiect the temperature of the inert gas on the outer side of the bellows 55, a thermal barrier is placed between the chamber 58 and passage 43. For this purpose-an annular portion of heat insulating material 64, such as felt or the like, is interposed between the bellows 55 and 56, this portion of insulating material having a central opening through which the insulating spool 51 passes. In order to form a hermetic seal between the chamber 58 and the interior oi the valve casing 23 the bellows 55 and 56 are provided with annular laterally extending ange portions 55EL and 56, respectively, these flanges being clamped between the adjacent portions of the housing 59 and valve casing 23 with an annular spacer member 65 interposed therebetween. This spacer member may also be made of material having a low thermal conductivity, such as Bakelite. Thus, it will be seen that in the operl ation of the valve 26 the actuating spool 51 will be shifted axially downwardly when the pressure within the chamber 58 exceeds that Within the passage 43 by a predetermined amount which may be selectively varied by the adjustment of the balancing spring 45. movement of the actuating spool 51 causes an intermediate actuating member 4F* to move downwardly against the valve element 4| to shift the latter to open position. As the temperature at the outlet of the evaporator l0 decreases due Such a downward v to the admission of further refrigerant upon such opening of the valve 26, the pressure in the chamber 58 decreases correspondingly so that the valve element 4I is again permitted to move to its closed position under the bias of the spring From the foregoing, it will be seen that a simple and compact expansion valve unit has been provided in which a single casing member serves for both of the expansion valves and which is otherwise simplified. in construction. In addition, it will be noted that the intermediate-pressure chamber 24 is of comparatively small volume and length, thus minimizing the formation of flash gas therein as the refrigerant is throttled through the expansion valve 25. Thus, the advantages of accurate control of the temperature of the associated evaporator are had through the use of an intermediate-pressure stage but the disadvantages resulting from the use of a large volume intermediate-pressure header or the like are avoided. In addition, the use of separate preliminary expansion valves for each'evaporator makes possible a closer and more accurate control of the associated evaporator-lV temperature. In some installations, however, it is desirable to equalize the intermediate pressure in order to correlate the operation of the evaporator units in the system and for this purpose, a by-pass conduit 66 (Fig. 1) is provided which communicates with the intermediate-pressure chambers of the respective expansion valve umts I 8 and I 9. A manually operable shut-olf valve 66a is interposed in this conduit so that the intercommunication between the intermediate-pressure zones of the two umts may be cut off at will. It will be understood that the conduit 66 serves as an effective means for conveying intermediate-pressure refrigerant from one valve unit to the other in case one of the evaporators is heavily loaded so that insufflcient refrigerant is supplied through the initial expansion valve therefor or in the event that its initial i expansion valve becomes damaged or inoperative for any reason. f
In the operation of the system described above, high-pressure liquid refrigerant -from the receiver I1 is expanded into the evaporators III and II through their associated expansion valve units I8 and I9. 'I'he quantity of refrigerant supplied to the evaporator I0 is controlled in accordance with its return line temperature through the medium of the feeler bulb 62 as described above and a similar feeler bulb 62 disposed in thermal contact with the return line for the evaporator I I, connected through a feeler conduit 63a with the valve actuating mechanism in the unit I9, controls the ow of refrigerant to the evaporator I I in a similar manner. The refrigerant vaporized in the evaporators l0 and II then ows through the respective return lines 61 and 68 to the compressor inlet 69. This cycle is repeated and continued to maintain the evaporators at the desired respective temperatures.
An arrangement has also been provided for effectively defrosting one or more of the evaporators while maintaining the remainder of the evaporator units in the system in operation. For this purpose, a conduit 10 is arranged to convey hot gaseous refrigerant from the outlet of the compressor I2 to the respective outlets Il)n and IlEL of the evaporators I8 and I I. 'I'he outlets of the evaporators may be connected either to their return lines 61 and 68 or to the hot gas supply conduit 10 by three-way valves 1 I and 12, the details of one of these valves be.-
of this valve element frigerant is had in a with the conduit 16 through a slot 13 vin a rotatable valve element 14 movable by a manual operating handle 16. Upon clockwise rotation through an angle `of approximately 90 (as viewed in Fig. 3) the valve element cuts oil' communication between the conduit 1li-and the evaporator outlet I0 while connecting the latter to the, return line 61.
When the valve 1|, for example, is shifted to connect the evaporator I0 with the hot gas supply conduit-18 and disconnect it from its return line 61, a ow of compressed hot gaseous rereverse direction through the, evaporator, thus warming the same and effectively defrosting it. The refrigerant liquid forced out of the evaporator I0 due to this reverse ow of high-pressure gas may be utilized in the other evaporator II by transferring the same from the expansion valve unit I8 to the expansion valve unit I9 through conduit 66 upon opening the valve 66. It will be understood that the evaporator Il may be defrosted at will by a similar manipulation of its associated three-way valve 12. y l
Although a particular embodiment of the invention has been shown and described i'n some detail for Purposes of illustration, there is' no intention to thereby limit the invention to such embodiment but, on the other hand, the appended claims are Iintended to cover all modiiications within the spirit and scope of the invention.
I claim as my invention:
1. In a three-pressure refrigeration system the combination with a source of high-pressure compressed and liquefied vaporizable a plurality of low-pressure evaporators having inlets and outlets;
sociated with each of said evaporators and conof the valve illustrated in an expansion valve unit asrefrigerant, of
nected in series relationbetween said source and the associated evaporator; each of said units including a valve casing defining an intermediate refrigerant pressure zone chamber, an expansion valve for controlling the ow of refrigerant from said high-pressure source to said chamber to maintain a selected substantially constant pressure therein, and a second expansion valve for governing the flow of refrigerant from said Achamber into the associated evaporator in response to variations in the temperature of the refrigerant discharged from the evaporator; means connecting the outlets of said evaporatorslto said source in parallel relation, and means rendered operable and inoperable at will to equalize the pressures in said intermediate-pressure zone chambers.
2. A refrigeration system comprising, in combination, a compressor having an inlet and an outlet and supplying compressed vaporous refrigerant at a high pressure and temperature, a condenser in communication with said compressor outlet; a plurality of evaporators, means including separate expansion valve units associated one with each of said evaporators for supplying refrigerant from said condenser to said evaporators, each of said units including a valve casing defining an intermediate-pressure zone chamber having an inlet and an outlet passage and an independently operable pressure reducing valve element in each of said passages, means for returning vaporized refrigerant from the outlets of said evaporators to said compressor inlet, means operable at will for cutting ou cominunication-betweenv any selected one of said evaporator outlets and said cor'nprelssor inlet and for establishing communication between the selected outlet and said compressor outlet thereby' to direct' a .ilow' of hot gas reverselythrough the Vvevapora'lo,1r'to' defrost the same. and means operableat will@ A direct refrigerant from the intermdiatefpressurechamber yof the valve' unit 'associated -witrrsaid-one-ev'aporator to the in- 20 said source in a plurality of successive stages and supplying the same to the associated evaporators, and means operable at will to equalize the pressure of the refrigerant in a plurality of said valve means in an intermediate-pressure stage thereof.
4. In a three-pressure refrigeration system an expansion valve unit adapted to be interposed between a source of high-pressure liquid Vaporizable refrigerant and a low-pressure evaporator comprising a valve casing member cored out to form an intermediatelpressure refrigerant chamber of small volume having inlet and outlet passages, an expansion valve in said inlet passage, a throttling valve element in said outlet passage,V thermostatic means for moving said valve element in response to changes in temperature at a remote point, and means for thermallyinsulating said thermostatic element from the refrigerant flowing past said valve element.
RAYMOND G. HILGER.