US2405944A - Direct expansion chiller - Google Patents

Description

E. A. EDMoNDs DIRECT EXPANSION CHILLER Filed Nov 20, 1945 v E zimanzzis' Patented Aug. 20, 1946 DIRECT EXPANSION CHILLER,

Eugene A. Edmonds, Louisville, Ky., assignor to Henry Vogt Machine Co. Inc., Louisville, a corporation of Kentucky Application November 20, 1943, Serial No. l1148 This invention relates to a direct expansion chiller and proposes a construction in which the heat exchanging unit comprises a bundle of tubes generally connected serially, through which the liquid to be cooled flows, and a shell surrounding the tube bundle constituting the evaporator of a refrigeration system, containing liquid refrigerant. ihis arrangement avoids the use of stufiing glands which seal the ends of the individual refrigerant jackets in chillers of the double pipe type, and which are subject to leakage of refrigerant.

One of the objects of the invention is to provide a chiller of the type described, in which the tubes are secured adjacent their ends in tube sheets which constitute opposite ends of the chiller, the latter being provided with one or more expansible zones capable of contracting or expanding in the direction of the length of the tubes, thereby avoiding stresses, particularly in the joints between the tubes and tube sheets, and between the tube sheets and the surrounding wall of the shell, which would otherwise-be produced through differential thermal expansion between the tubes and shell.

Another object of the invention is to form the expansible Zone as a channel with drainage means at the lowermost point so that contaminating oil from the refrigerant may collect in the channel and from time to time be discharged.

Still another object of the invention is the provision of a direct expansion chiller as described, in which the individual tubes are provided with the customary scrapers, driven from one endof the apparatus, in which the tubes extend beyond the tube sheet at least at the end opposite the scraper drive, in a position exposed for inspection, each being provided with an end sight glass through which the end of the scraper shaft is visible so that breakage of a shaft can be readily discovered by observing the nonrotating condition of the end of the broken shaft through the sight glass.

Other objects of the invention will appear as the following description of a preferred and practical embodiment thereof proceeds.

In the drawing which accompanies and forms a part of the following specification and throughout the several figures of which the same reference characters have been used to. denote identical parts:

Figure 1 is a longitudinal vertical section through a chiller of the direct expansion type embodying the principles of the invention, two units being shown serially connected and in superposed relation;

Figure 2 is an end elevation of the left end of Fi ure 1;

Figure 3 is an end elevation of the right end of Figure 1;

-'-"Figure 4 is a longitudinal section on an'en- 4 Claims. (01. 62-114) 2 larged scale through the left chiller tubes and sight glass;

Figure 5 is a longitudinal section on an en larged scale of the right end of one of the chiller tubes, illustrating the packing for the scraper drive shaft;

Figure 6 is a'diagram illustrating the constant level liquid refrigerant controlled from a single fioat valve;

Figure '7 is a diagrammatic view illustrating the liquid level control of the refrigerant by independent float valves.

Referring now in detail to the several figures, the'numerals l and 2 represent direct expansion chiller units, each comprising a tube bundle consisting of a plurality of spaced parallel tubes 3, surrounded by a shell l having the cylindrical side wall 5 and the end walls 6 and I, said end walls being tube sheets'through which the tubes end of one of the 3 extend, and to which they are secured in fluid.

tight manner, as by welding. For the sake of eiilciency, the tubes 3 extend beyond the respective tube sheets only far enough to be serially interconnected by the transverse connections 8, and to receive the end adjuncts which on the lefthand side of the apparatus, as shown, consist of the sight glass mountings 9, and on the opposite side of the apparatus comprise the packing box for the scraper shafts.

One of the tubes 3, the first in the series, is provided. with the inlet coupling ll, while the last tube of the series is provided with the outlet coupling 12. Where two units are serially interconnected, as shown, the outlet 12 of the lower unit is coupled to the inlet H of the upper unit.

Since the inner tube system will ordinarily receive a liquid to be cooled while the shell will contain the refrigerant, there is a considerable temperature differential between the tubes and the wall of the shell which tends to differentially expand or contract these members. In the absence of some compensating provision, this would ordinarily create a strain at the joints between the tubes and tube sheet and along the joint between the tube sheet and shell. To avoid such strains, the invention provides the cylindrical wall 5 with an expansion joint l3 having the form of an outwardly extending channeled flange of sheet material capable of freely expanding or contracting to compensate for differential elongation between said surrounding wall and the chiller tubes. Said expansion joint is illustrated as being formed from pressed circumferential members welded together and to adjacent portions of the surrounding wall 5 between which itintervenes.

There may, of course, be one or more of these expansion joints to each unit. Only one for each unit is shown in the illustrated embodiment of the invention, and to. provide for the compact posi-j 3 tioning of the units, one is shown on the left side and the other at the right.

The tube bundles are intermediately supported within the shell by a suitable plate or bracin members, not shown. Each of the tubes 3 is provided in the customary manner with scrapers l 5, each comprising a shaft l6 with blades ll'supported. thereby and preferably inclined to the axis of said shaft, said blades engaging the inner wall of the tube with a scrapjournaled in a plat 43, which is pivoted eccentrically of the axis of said stub shaft at a point M to the support 36 so that the sprocket M can be tilted towards or away from the driving chain 38 which it engages. The plate 43 is provided with a threaded pin 45 extending through an 'arcuate slot 46 in the support 36 carrying a nut,

ing action which removes deposits from the liquid to be cooled, agitates the liquid to bring all parts of it into contact with the wall of the tube and increases the efliciency of the heat exchange by keeping the tube clean. The scraper shaft is carried in bearings 48, and by intermediate bearings, not shown. The scraper 3 shaft adjacent the driven end is provided witha lantern gland l9, slidably mounted within a cylindrical packing chamber formed in theend closure at. The packing chamber has a restricted inner end wall 2i for retaining inner packing rings 22 which surround the shaft [6 of the scraper. Sufficient of said packing rings are employed to maintain the gland in a definite zone of the bushing I9, in which zone said chamber is tapped by a drain 23 for collecting any liquid which may leak past the inner packing rings. Since the packing may be from time to time compressed to a greater or less degree, the gland is provided with an exterior channel 24 wider than the diameter of the drain 23, so as to remain in registry with said drain regardless of longitudinal shift in the position of i the gland due to the compression of the packing.

by means of which the plate 43 can be fixed in any position of adjustment. The support 33 has an arcuate slot 41, providing play for the stub shaft 42.

In the embodiment of the invention, as shown, in which two chiller unit are arranged in superposed relation, the liquid level of the refrigerant in each .unit may be regulated in various ways familiar to those skilled in the art, two of which are illustrated in Figures 6 and 7. In the former, an arrangement is shown in which a single float valve controls the level liquidrefrigerant in both units. In this form an overflow pipe 4-8 is provided, the upper end of which enters the upper shell at a point determining the desired liquid level in said shell, the lower end opening into the lower shell below the normal liquid level therein. Liquid refrigerant from a receiver is supplied by the pipes 49 and 5G to the upper shell, preferably above the liquid level therein, and fills the upper shell until it overflows by way of the pipe 48 into the lower shell, filling it to a level determined by A follower 25 is bolted to the bushing, having a skirt 26 entering the packing chamber and pressing against outer packing rings 22', which intervene between said follower and gland. The bolts have the form of studs 21 screwed into the flanged end wall of said packing chamber, and having nuts which press against said follower and by which the compression of the packing may from time to time be adjusted.

The extended ends of the tubes 3 at the left end of the unit have a flange collar 28 integrally attached thereto as by welding, and to the collar 2. plate 29 is bolted, which contains the bearin 38 for the adjacent end of the scraper shaft and has a central recess receiving the sight glass 3!, the latter being retained bysthe bezel 32, which is removably attached, as by the stud bolts 33. The shaft terminates in a nut 34 which thrusts against the bearing 38, the sight glass being slightly spaced from the nut by a spacer ring 34.

Referring again to the right side of the unit, the shafts l6 extend beyond the follower 25 having their ends journaled in bearings 35 carried by an upright support 33 mounted upon the floor or foundation. Between the follower 25 and bearing 35 the shafts [5 are provided with the sprockets 3'! disposed in the same vertical plane and surrounded by a driving chain 38, the" latter being driven by a sprocket 35 on an extended portion of one of the shafts l5, and which in turn is driven through the chain 30 from a motor, not shown. Since the tubes 3 are connected serially and the liquid therein flows alternately fromone end to the other of the chiller unit, the chain the position of the float in the float chamber 5!, the lower part of which is in communication with the liquid in the lower shell, while the upper part has a gas equalizing connection with the gas space in the upper shell. The float controls the feed valve 52. When the warm liquid to be cooled, or load, evaporates the refrigerant in the upper shell and the liquid level recedes, then the load will be shifted to the lower shell because the warm oil will come to the lower shell at a higher temperature. This increase of load on the lower shell evaporates the liquid refrigerant in the lower shell. The liquid level float control then functions by admitting liquid refrigerant to the upper shell until its overflows and refills the lower shell to the proper refrigerant level. Since the liquid to be cooled is warmer when it enters the upper shell 1 than when it enters the lower shell 2, the rate of ebullition of the refrigerant in the 3 upper shell will be greater than that in the lower drive is so disposed about the sprockets 3! as to shell, so thatthe level of liquid in the upper 'shell would at any time be lower than the liquid level in the lower shell. This means that the upper shell would operate at lower efficiency. In order to compensate for this greater rate of ebullition in the upper shell, a by-pass pipe 53 is provided which by-passes liquid refrigerant about the float controlled valve 52. The by-pas pipe is controlled by a valve 56. This valve may be adjusted to continuously admit a relatively small flow of refrigerant into the upper shell. The amount of additional liquid refrigerant thus supplied to the upper shell may be readily controlled, for if the valve 54 were opened too far, the result would be an increase in level in the upper shell until the level reached the overflow, whereupon, the level in the lower she'll would be raised by the overflow, preventing the ,valve 52 from opening and eventually flooding the'apparatus. However, the frequency of operation of the float controlled valve 52 can readily be determined and the valve 54 be adjusted to prevent overflow from theupper to the lower shell, due to the continuously added refrigerant.

In that form the invention shown in Figure 7, liquid refrigerant i independently fed to both the upper and lower shell by way of the branch pipes 55 and 56 from the main liquid feed pipe 51. Independent float valves 58 and 59 control the amount of refrigerant fed to each shell, the respective float chambers having their lower and upper portions connected to the lower and upper portions of the respective shells.

It is to be understood that the invention is complete in the use of a single unit, also that the arrangement of units where a plurality are employed is a matter of choice, the two arrangements herein disclosed being merely by way of example.

Each chiller unit is provided with a gaseous refrigerant outlet 65 at its upper part for connecting to the suction or low side of the refrigeration system. Where a plurality of units are combined, gaseous refrigerant outlets may discharge into a common stack, not shown, for multi-pressure operation. A bafile 6| is preferably mounted within the shell in the gas space therein, in confronting, spaced relation to the outlet 60 to prevent liquid refrigerant under conditions of ebullition from being drawn oil in the current of evacuating gas.

The construction of a direct expansion chiller with a single refrigerant chamber serving a plurality of tubes in which the tubes are integrally joined to the tube sheet through which they pass, and in which the longitudinal shell Wallis formed with an integral expansion joint, is an improvement both from the standpoints of simplification and efiiciency, over the conventional double pipe chiller having a refrigerant jacket individual to each tube, in that all packing joint for retaining the refrigerant are eliminated, and leakage of refrigerant which i inherent in all packing joints, is avoided.

The location of the ends of the tubes, on that side of the unit remote from the scraper drive, in an exposed position and the provision of lateral interconnections between the tubes which leave the ends of the latter unobstructed, together with the provision of the individual sight glasses forming closures for said ends, permits the operative condition of the scrapers to be ascertained by mere observation so that a broken scraper shaft can readily be detected through the fact that the observed end is not rotating. In the event of a broken scraper shaft, the affected scraper mechanism may be readily emoved by detaching the sprocket at the drive end, removing the plate 29 which carrie the sight glass and adjacent bearing and withdraw-- ing the entire scraper mechanism through the end of the tube thus opened.

While I have in the above described what I believe to be a preferred and practical embodiment of my invention, it will be understood to those skilled in the art that the specific details of construction and arrangement of parts are by way of illustration and not to be construed as limiting the scope of the invention a defined in the appended claims.

What I claim as my invention is:

1. In a direct expansion chiller, a shell comprising a longitudinal tubular wall and spaced tube sheets to which said wall is secured, forming end closures of said shell, the latter being the evaporator of a refrigeration system, a plurality of spaced tubes passing through said tube sheets and secured thereto with integral sealed joints, said tubes being serially interconnected externally of said tube sheets, having a liquid inlet and outlet respectively at the anterior and posterior ends of said series, a liquid refrigerant inlet communicating with said shell and a gaseous refrigerant outlet at the top of said shell.

2. In a direct expansion chiller, a shell comprising a longitudinal tubular wall and spaced tube sheets to which said wall is secured, forming end closures of said shell, the latter being the evaporator of a refrigeration system, a plurality of spaced tubes passing through said tube sheets and secured thereto with integral sealed joints, said tubes being serially interconnected externally of said tube sheets, having a liquid inlet and outlet respectively at the anterior and posterior ends of said series, a liquid refrigerant inlet communicating with said shell and a gaseous refrigerant outlet at the top of said shell,

said tubular wall having an integral expansible corrugation extending thereabout, concave on the inside of said 'wall and having a drain in its lower portion.

3. In a direct expansion chiller, a shell comprising a longitudinaI tubular wall and spaced tube sheets to which said wall is secured, forming end closures of said shell, the latter being the evaporator of a refrigeration system, a plurality of straight tubes passing through said shell and said tube sheets, extending therebeyond, lateral connections serially connecting said tubes externally of said shell, scraper shafts journaled in bearings in said tubes, terminating within said tubes at one end of said shell beyond said lateral connections and extending beyond said tubes at the opposite end of said shell, driving means on the extended ends of said shafts, closures for the ends of said tubes adjacent said driving means, each closure having means forming a cylindrical packing chamber through which the drive shaft passes, said packing chamber having a restricted inner end of wall, a lantern gland through which said shaft passes, intermediately located in said chamber, packing within said chamber on both side of said gland, and an axially adjustable follower extending into the outer end of said chamber in compressive relation to said packing, a drain communicating laterally with said chamber in the zone of said gland, the latter having an external circumfer ential channel wider than the opening of said drain whereby said channel remains in registry with said drain, regardless of longitudinal shift in the position of said gland due to compression of the packing.

4. In a direct expansion chiller, a plurality of units vertically tiered, each comprising a shell including a longitudinal tubular wall and spaced tube sheets to which said wall is secured forming end closures of said shell, the latter being the evaporator of a refrigeration system, a plurality of spaced tubes passing substantially horizontally through said tube sheets and secured thereto with integral sealed joints, said tubes of each unit being serially interconnected externally of said tube sheets, having a liquid inlet and outlet respectively at the anterior and posterior ends of said series, a conduit for supplying liquid refrigerant to the uppermost unit, a float valve responsive to liquid level in the lowermost unit controlling primary admission of liquid refrigerant to said uppermost unit, and an overflow conduit from a point in the uppermost unit determining the normal liquid refrigerant level therein, to the lower unit.

EUGENE A. EDMONDS.

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