US2282879A - Cooling unit - Google Patents

Description

Patented May 12, 1942 UNITED STATES PM cooLnvG UNrr I A Rollin H. Norris, Schenectady, N. Y., assignor to I f General Electric Co N ew York Y c mpany, ya corporation of 'Application February 27, loro, sei-iai No. 321,029'r A*icuiinefl(vital-12s)y j f' -My invention relates to cooling unit; Vand particularly to refrigerant distributingl arrangements for cooling units having a plurality vof evaporating elements or conduits.

Cooling units such as those employedin air conditioning systems commonly comprise a plurality of straight tubes provided with ns forextending the effective heat transfer surface thereof and connected'by suitable return bends to provide one or more continuous paths for the refrigerating uid. When a cooling'unit of vthis 5 type is connected in the circuit of a refrigerating machine as an evaporator, it frequently is desirable to supply refrigerant to the entire unitunder control of a single expansion valve. The several conduits maybe connectedto provide a single long conduit. However, this arrangement is objectionable since it results in a high pressure drop fromkthe inlet to the outlet of the conduit and, therefore, inelcient use of the major In general, the cooling unit asillustrated com- I.

portion of the conduit. One arrangement for avoiding long refrigerant conduits ina cooling unit is to connect'the `several turns in'vsuch a manner as to' provide a pluralityof parallel paths.-

arrangement,` however,` makes it 'necessary to providean additional distributing device for insuring equal distribution of both liquid and gaseous refrigerant to all the parallel paths. Furthermore, the results obtained yfrom the parallel arrangement of the conduits andV -the separate distributing device may notbe en.-

tirely satisfactory because 'the low velocities' pre'- vailing near the inlet ends vof the conduits re.

sult in relatively low coefficients of heat transfer between the refrigerant and the conduit near the inletend and consequently in less eective useof the heat transfer surface.

It is an object of my invention to provide a cooling unit for refrigerating systems which comprises a plurality of evaporating tubes vor conduits and an improved arrangement for facilitating the eicient use l'of the heat transfer surface of the entire unit. Y i

' Another object of my invention is to provide I a cooling unit lfor refrigerating systems having'a plurality of evaporator tubes or conduits and an improved arrangement for securing efficient use of the entire heat transfer surface of the `unit without the necessity of providing a distributing header orother device between theexpansion lvalve and the conduits.

. Further objects and advantages of my invention will become `apparent as the following description proceeds, and the features of novelty which' characterize my invention will be pointed 55 prises a plurality of conduits or tubes connected so that liquid vrefrigerant is admitted under control of a single thermostatic expansion valve and, after passing through one'tube, is'divided equallyandjdistributedto two other -tubes and after passing throughv each-of -thes'ewtwo' tubes l is again divided and distributed to additional tubes, the vaporized refrigerant being withdrawn through a suction manifold to which the lfinal group of tubes `is connected, This arrangement 'insures even distribution of refrigerant vat each dividing point-of the refrigerant' stream and;` furthermore, provides an increased 'cross-sectional area for facilitating the flow of gaseous l refrigerant as it is vaporized. I-Iigher` velocities of refrigerantiiow in the tubesnear the inlet end lof the cooling unit are obtained by this ar e rangement than would be obtained with all the tubes in parallel andv this arrangement,` therefore, uses more eectively the heat transfersurface of the unit.

Referring now to th'e drawing, in Figi-l lhave shown 'an airconditioning system'including 'a duct I0 provided witha fresh air inlet II and a room orvreturn air inlet I2 for withdrawing air from the room tobe conditioned. .A cooling unit I3-is arranged within thefduct I0 `to cool -f the air passing therethrough and a fan- I4 driven by a motor i5 is provided for circulating the air',

and returningit to theV room through-a discharge c duct I6,- The cooling unit I3 is connected'in the refrigerant circuit of a refrigerant machine including a compressor I1. driven by a motor `I8 and arranged to discharge compressed refrigerant into a condenserlil surrounded bya water cooling jacket 20 -through which cooling water flows as indicated by the arrows. vThe refrig- `erant is cooled and liquefied in the condenser I9 bythe circulation of water through the jacket 20 and is discharged into a liquidv receiver 2| from which it flows through a liquid line 22to` theccooling unit I3 under control of a thermostatic expansion valve 23. The valve ZSoperates ENT vvoFFICIE';

tomaintain a predetermined number of degrees of superheat of the vaporized refrigerant withdrawn fromthe cooling uriitv I6 through a suction line 24 and returned to the compressor, the

valve being provided with a thermal element or feeler bulb 25 securedin heat exchange relation -to the suction, line vadjacent the outlet of the evaporator. Y

` 'Ifhe cooling unit I3 comprises tubes or conduits numbered consecutively from` 26 'to 32 inclusively. Each of these tubes has been shown as comprising four straight runs or passes connected by suitable end turns tou prothe inlet to the outlet'of the evaporator to obtain Agreater velocities of ow in the nrst portion of the evaporating'path as represented .by

the conduit 23. The heat transfer coemcient along the portion of the evaporating path formed by the conduit 26 is therefore substantially greatvide al at sinuous coil. The planes of the sev- .The conduits 26 to 32, inclusive, are connected in such a manner thatthe middle conduit 26 receives the entire flow of liquid and gaseous refrigerant entering the evaporator from the expansion valve 23.` After passing through the conduit 29, the refrigerant stream is divided equally at a T-connection 34 and ows into the conduits 21 and 3i. After passing through the conduits 21` and 3|, the refrigerant streams are again divided equally by T- connections 35 and 30 liquid and -'gaseous components.. The vaporized 36 respectively, refrigerantthen flowing-through conduits 26, 28, 36 and 32 to the suction manifold 24. It is to be noted that thev two conduits receiving refrigerant from any one conduit are v arranged symmetrically with respect' to the one' conduit. The T-connect'ions 34, `35 and 36 are of identical construction, the 'I1-connection 34 being shown' in detail Vin Fig. 3. In order to facilitate the equal distribution of both liqiud and' gaseous refrigerant owing fromthe conduit 23 to the conduits 21 and 3l, a vertical ridge` or dividing element 31 is formed in the T-connection on the central axis of and in a direct line with the conduit 23. In order to neutralize any effect of gravity to produce uneven distribution of refrigerant, I prefer to arrange the 1 '-connec tions in a horizontal plane so that the entering and both the leaving streams ofthe refrigerant flow horizontally. Furthermore, it is'to be noted that each of the .T- connections 34, 35 and A36 receives refrigerant in a straightfline from a straight portion of the conduits 23, 21 and-3l reer than would be possible for a single tube if all the tubes were connected in parallel.

' During the operation oi the air conditioning' systems shown in l, air is circulated throughA the duct Ill by operation of the fan I4 and re.

lfrigeraknt is circulated through the cooling unit I3 by operation of the compressor I1. The ther-` mostatic expansion valve 23 maintains therate of ilow of vrefrigerant to the cooling unit such that the vaporized refrigerant in 4the suction l manifold\l4 .will have apredete'rmined numberof degrees of superheat. 'I'he mixture .ofliquivgiy and gaseous refrigerant entering the conduit '26. from the valve 23 absorbs heat from the air passing tnrougntne ductthereby increasing the gifs-p,`

eous component kin the `refrigerant -mixture lat the discharge end of the conduit 23 where mixture is divided equally. The refrigeranttherrl flows to the conduits 21 and 3| where further.y heat is absorbed and more of the liquid vaporized, the streamsbeing again divided equally atb the lf-connections .36 and 36 so that the streams of liquid and gaseous refrigerant flowing into the conduits 2s, :an and s2 contain erant velocities throughout the cooling unit are morel nearly equal,` and efficient use. is made of' a the entire evaporator surface.

y The variation in refrigerant velocities andin the coefilcients voi' heat ytransfer along each of the conduits 26 ,to

32inclusive, is minimized and as a result each -facilitating vthe even distribution of refrigerant of the conduits tends to carry its proportionate share of the load of thecooling unit. v Y

Itis apparent from the foregoing thatln'ha've provided a simple and effective arrangementfor among a plurality of conduits or tubes and for making effective use of the entire heat transfer lsurface of an evaporator` without the necessity of providing any distributing apparatus extern to the evaporator coils.

spectively. The refrigerant flowing from'the expansion valve and throughout the evaporating conduits comprises-a mixture of liquid and gaseous components, the vgaseous component-'increasing in volume throughout the length of the evaporator from the inlet to the outlet due to the vaporization ofthe liquid upon vabsorption of heat from the air flowing through the duct III.

Since the ,refrigerant entering anyv one .of the 'Vr-connections must first pass through a consid- .arable length of straight conduitwhich passes through the air stream, the velocity ei'fectsdue tothe passage of the refrigerant around a return bend are minimized at the T-connections and both the liquid and gaseous components of the mixture tend to be distributed evenly at the T-connections. It will be noted that the crosssectional area of the refrigerantpath is doubled at each of the Tconnections. It will be evident While I have shown my invention in connection with an air conditioning system, other applications will readilybe apparent to those skilled in the art. I do not.. therefore, desire my invention to be lirnitedtothe particular construction shownand described Vand I intend in the appended claim to cover all modifications within the spirit and scope of my invention. Y

What I claim as new and desire to secure LettersPatent'of the United States, is:y l

A cooling unit for a refrigerating system com-' prising an odd number of similar conduits dis.

tributedevenly over the path of a mediun'i to bel cooled and having straight portions arranged across the path of the medium, an inlet for admitting liquid refrigerant to the middleone of said conduits, a distributorat the outlet end-of that with the greater, cross-sectional area. there is' less pressure drop along the refrigerant path from the inlet to the outlet and consequently, it

' is possible for a given total pressure drop from said middle conduit for supplying substantially equal quantities` of -the refrigerant ydischarged therefrom to two others of said con'du'its located symmetrically on either side of said middle con',-

duit. and a distributor at the 'outlet of each' of said two conduits for again'dividing the refrigrically across the path of the mediumto be cooled, and means for collecting Vaporized re frigerant discharged from said further ones of said conduits and for removing the refrigerant 5 from said unit.

ROLLIN H. NORRIS.

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