US2669849A - Refrigerant flow control - Google Patents

Description

Patented Feb. 23, 1954 U N' IfiT ED- ES O-FIQE REFRIGERANT FLOW" CONTROL. Harold T. Lange, Webster Groves,..Mo;, assignor to Sporlan: valvetCot. Inc SttLouis, porationxoiMissouri Original, application October 9,. 1947,. Serial No..

This. invention relates: to improvementsxin re frigerant flow control, and: more particularly to improved meansrfor the regulation of refrigerant expansion valves as. employed in" systems of com pressor condenser evaporator type.

In the operation of refrigeration. systems there has "been accepted as inevitable, certain undesirable. irregularities in'the operation: of i the expan-- be'delayed, orif the valve be permittedto move only at a reduced rate under certain conditions.

Among the few successful structural'proposals which have been presentedfor the correction of this condition is the arrangement covered by a copending application of this applicant bearing Serial No. 778,814, filed October 9*, 1947-,now Patent' No: 2,573,151, granted October" 30; 1951, and en titled "Refrigerant 1 Expansion the instant app'lication is" a division. The elements therein disclosed and claimed offer an effectivearrangement toovercome the noteddifli culti'es, obtaining optimum results without the addition or"- moving parts, and at a'virtually negli gible increase in cost 'over certain prevailing systems. Accordingly, the present invention has as aaprincipal-object'to overcome; at least substantially, the; hunting andkcycling effects in asys temiofthe type noted, andto realize this result bya structure. which does not increase to any important extent. thetcost of prevalent systems and apparatus.

Another important: object is' attained through" the inclusion ofan improved. thermal sensing element, which is so: constructed as to; maintain a desirable character of response throughout normalopera'ting conditions of a compressoncondenser evaporator system, markedly differential rates of valve opening and closing response under abnormal operatingcon- The-foregoing and numerous other objects? will more clearly appear from the followingidetailed frequency of Valve, of which i and yet. afiord now PatentNo. 2,573,151, datedoctm ber 30,, 1951. Divided and gust2'0, 1951, Serial No.

this application- Au--- 242,657"

mu u J description of. a preferred embodiment, particnzlarly, when. considered in connectionwith the. accompanying drawing; in. which:

' Fig. 1.. is aschematic diagramv of: a refrigeration". system embodyingjthe novel thermal sensingele ment;

Fig. 2 isran enlarged side. elevation, partly section,.showingv a refrigerant. expansion valve.

suitablefor use;with1the. and

present improvements;

Fig; 3 is a side elevation, withportions broken away for clearness; of the novel thermal. respon sive element.

Referring now' by" characters of reference to a the drawing, a typical compressors-condenser evaporator system: is shown. diagrammatically by Fig. 1, principallyforcompleteness of disclosure;

and: includes a compressor C. serving to: dischargethecompressed refrigerant'to thecondenser CN the latter in turndelivering into a receiver R; from whichtheliquid is transferred to a thermostatic expansion valve TEV controlling the flowof' refrigerantto an; evaporator genera1ly-indi-- cated at. EVR, the evaporator being connected through-the: suction line- SL backto the'intake side of the compressor. 0, completing the closed system. A'thermal responsive element 1 l l is empioyed to control theexpansionvalve, and is 0p-- eratively connected. as through capillary tubing CT to a diaphragm chamber in'thevalve assem bly proper, as will. later appear;

The thermostatic'expansion valve-is ormay be ofitself of a known commercially successful type, and includes a' housing or'casing l I, enclosing aareciprocallymovable valve' guide I2, a valve member" l3 carried axially by the guide and operable to open and close a valve seat M, the seat being' formed" on .a. replaceable threaded element 15 provided Witha bore or flow passage there through. It isapparentthat throttling movemerits of the valve control the new of liquid through'theinlet tubing and a connection' I7; to an outlet fitting Iii" connected to the evaporator EVR: (See Fig. 2.)

As. is usual'in thermostatic expansion valve assemblies, there isprovided an expansible ele' mentsuch as a diaphragm. 2B, capable ofIfi'exing action in or adjacent a diaphragm chamber 21,

under the influences of. volume changes occurring by'reasomof thermal effects imparted to the sensingelement l H in'response to changesin superheat in;the suctionlineSL. A: follower plate 2 2. underliesrthevdiaphragm 20' as viewed in Fig. 2, th'e'di'aphragm being -peripherally positioned in wfiuid tight relation-as by aasuitable. metal-seal 23 aecasso between the companion parts of the diaphragm enclosure. Motion of the diaphragm and 01- lower is imparted to the guide l2, and hence to valve member 13, through a plurality of push rods, only one of which is shown, being indicated at 2d in dotted lines. Fluid pressure transmitted through the capillary tubing CT to the chamber 2| acts to urge the diaphragm and follower inwardly with a valve opening action, such action being opposed by the valve spring 25.

The foregoing description of the expansion valve is included principally for completeness, the structure as shown and described being substantially that of a unit of this type sold as the type L valve assembly of Sporlan Valve Company of St. Louis, Missouri. The valve structure further includes a portion of a so-called equalizer passage, although in certain installations this may be omitted without affecting the operation of the valve. When employed, the equalizer passage includes a bore 2% extended into a chamber 21 below the follower 22, the latter having plenary marginal clearance to assure that the diaphragm is affected by suction pressure. The equalizer passage is continued outwardly of the body of the valve by a short horizontal bore 36, through the tubing 35 communicating with the inlet end of the evaporator. It is now apparent that the chamber 21 below the follower and diaphagm is subject at all times to pressure conditions exist" ing at the evaporation inlet, which pressure, acting in conjunction with the spring 25, tends to bias valve l3 toward closed position against its seat 14, and in opposition to pressure above the diaphragm.

Referring now more particularly to the structure exemplifying the invention currently claimed, there is shown by Fig. 3 a thermal sensing element consisting of a number of adjacent spiral turns of capillary tubing wound upon and contiguous to an elongated core or mass, preferably formed or a material having a greater heat capacity than that of the material of the surrounding tubing, and indicated at H0. The several turns of tubing form, in effect, a bulb or cell, being indicated at iii. One end of the capillary tubing is indicated at H2, and may be utilized as a charging connection and sealed off after the fill of the chamber formed by the several turns H l, the opposite end of the tubing being connected to, or forming a continuation of the line CT. It is apparent that there is virtually only a line contact between the several turns of tubing Ill and the core us, highly restricting the thermal path between the suction line to which the sensing element is attached, and the core no.

The charge, particularly the fluid content of the turns of tubing HI, consists preferably of a fluid having characteristics approaching or iden tical with those of the refrigerant employed in the system, and will usually consist of Freon l2,

methyl chloride or any other of the refrigerants selected for the system according to preference and field of usage. It is assumed that the fluid charge of the coiled tubular element Ill and the tubing CT will, throughout the temperature range of the system, exist in greater part as vapor, and in lesser part of liquid.

The present improvement takes advanta e of the fact that the liquid will condense and that the vapor pressure within the sensing elementdiaphragm system will correspond to that of the coldest part of this fluid motor assembly. With the foregoing structure and principles in mind,

tin

d it is now apparent that when the temperature of the coiled tubing HI of the thermal sensing element, is rapidly reduced, as at the time of starting up the system or during a sudden reduction in load, the chamber thereof having a thin highly conductive wall, becomes rapidly cooled, effecting a condensation on the inside of the wall since its temperature is currently the lowest in the motor system, which correspondingly and quickly reduces the pressure.

The system is protected against sudden pressure increases by reason of the comparatively large mass or core H0 which has a greater heat capacity than the material of the sensing tubing Ill. Consequently, this mass no will for some time remain the coldest part of the system, causing the liquid to condense on the adjacent tubular wall surface, and will thus produce a distinct lag in the attainment of maximum vaporization with the motor system. The low pressure during this period of lag or damping effect, will result in a reduced pressure upon diaphragm 28, providing a distinctly delayed and minimized action of the valve incident to any unusual or rapid increase in suction line temperature or superheat. .From the foregoing operative description it is clear that there are produced difierential rates of action of the valve under opposite conditions.

During periods of normal or steady operation of the system, the mass H0 will attain a substantially steady temperature slightly lower than the temperature of the coiled tubular wall HI, inasmuch as the latter is influenced not only by the suction line temperature in response to superheat, but also by ambient air temperature. From this it follows that the mass llll, being substan tially enclosed or embraced by the tubular sensing element HI, will after some lag, be inlicenced by the suction line temperature, but will not be directly affected by the ambient air. if it be assumed as is preferred, that the ballast mass I!!! have the lowest temperature of the various parts of the motor system during normal running conditions, the pressure in the sensing element-diaphragm system will correspond to the temperature of the ballast mass 1 Ill, and will thus assure a steady or stable operation of the system.

From the foregoing it will be seen that this element permits the pressure of the vapor inthe motor system to decrease rapidly when the coiled tubular element ill becomes cooler than the thermal stabilizing mass IID encompassed thereby, but the vapor pressure will be pre eluded from increasing rapidly when the coiled element l l l is appreciably warmer than the mass H0. It will now be seen that the provision of the mass I In as a part of the motor system, serves also to raise the minimum point of the cycle by reducing at desired times the rate of refrig-- erant feed, and thereby overcomes the former tendency of a thermal responsive element to overregulate, resulting in feeding some of the liquid refrigerant over into the suction line.

Although the invention has been described by particular-icing the elements and principles of a preferred embodiment, the detail of description is not in any sense to be understood as restricting, numerous variants being possible within the scope of the claims hereunto appended.

I claim as my invention:

1. The combination in a compressor condenser-evaporator refrigeration system, of a thermostatic expansion valve arranged to control the flow of refrigerant to the evaporator, and comprising thermal responsive means arranged to act in accordance with suction line temperature for operating the expansion valve, said means including a thermal-sensitive container consisting of a coil of a thin-wall tubing, the coil being located and arranged to be heated and cooled from the suction line, said coil being charged with a volatile and expansive fluid, and a mass constituting a core within the coil and having restricted thermal communication with the coil tubing, the material of said mass possessing a greater heat capacity than the material of the coil, the mass being of such nature and so related to the coil as to effect markedly differential rates of valve opening and closing action in response, respectively, to increases and decreases of suction line temperatures.

2. The combination in a refrigeration system having an evaporator, of an expansion valve arranged to control the flow of refrigerant to the evaporator, a hollow, highly conductive thermal sensing element mounted to respond to variations in evaporator outlet line temperature, tubing connecting the expansion valve and the sensing element, a fluid charge in said tubing and said element under'a pressure such that at a temperature within the range of operating temperature of the evaporator some of the charge is in a liquid state, and a mass of solid material spaced from said evaporator outlet line in contact with the external surface of said element and bearing a thermal relation to the element such as to delay temperature equalization between said mass and said element upon changes in evaporator outlet temperature for producing a lag in the pressure increase of said charge in response to evaporator outlet temperature increases while permitting rapid pressure decrease of the charge in response to evaporator outlet temperature reductions.

3. The combination in a refrigeration system having an evaporator, of an expansion valve arranged to control the flow of refrigerant to the evaporator, a hollow, highly conductive thermal sensing element in the form of a coil mounted to respond to variations in evaporator outlet line temperature, tubing connecting the expansion valve and the sensing element, a fluid charge in said tubing and said element under a pressum such that at a temperature within the range of operating temperature of the evaporator some of the charge is in a liquid state, and a rod within said coil, spaced from said evaporator outlet line, and bearing a thermal relation to the element such as to delay temperature equalization between said mass and said element upon changes in evaporator outlet temperature for producing a lag in the pressure increase of said charge in response to evaporator outlet temperature increases while permitting rapid pressure decrease of the charge in response to evaporator outlet temperature reductions.

HAROLD T. LANGE.

References Cited in the file of this patent

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