US2346822A - Heat transfer apparatus - Google Patents

Description

G.QE. cLANcY HEAT TRANSFER APPARATUS` April 18, 1944.

, 1941 2 Sheets-Sheet l Filed Nov.

ff /f /f April 18, 1944. fcsjl-z. cLANAcY .HEAT TRANSFER APPARATUS Filed Nov. 8, 1941 2 Sheets-Sheet 2 I1-1V Eli-tbl" Gjfb Brt .5. Cf Mw# C117 CH fie Patented Apr. 18, 1944 i Taf.:

UNITED STATES HEAT TRANSFER APPARATUS Gilbert E. Clancy, Santa Fe, N. Mex., assignor to Drayer & Hanson, Incorporated, Los Angeles, Calif., a corporation of California Application November 8, 1941, Serial No. 418,341

4 Claims.

This invention relates generally to heat transfer apparatus, here llustratively disclosed in the form of water cooler apparatus, though not necessarily limited thereto. Considered in' its more restricted aspects, and particularly with reference to water coolers, the invention deals with refrigerated water coolers of the instantaneous type, as well as of the instantaneous type in combination with storage facilities..

A first and primary object of the invention is the provision of simple heat transfer apparatus having an exceptionally high rate of heat transfer.

A further object is to provide a simple, reliable water cooler of compact and inexpensive design, capable of satisfying the typical demands of restaurant or other like service, in which substantial demands for cooled drinking water are made.

Further and more particular objects include the provision of a water cooler in which the pressure drop of the water is comparatively low, in .which the thermal inertia is low, and in which the necessary refrigerant charge is exceedingly small.

Speaking generally, the heat transfer or cooling unit of the present invention comprises a, plurality of grouped tubes surrounded and closely confined by a tubular housing, with longitudinal uid passageways extending from end to end of the tubular housingformed betweentheindividual tubes, and between said tubes and the tubular housing. In the instance of a water cooler unit, the inside tubes may carry the refrigerant, and the longitudinal spaces in the tubular housing around the tubes may carry the water. This construction has several important advantages and accomplishments. First may be mentioned the relatively great area of the Contact between water and refrigerant tubes for given cross-sectional areas of refrigerant passages and water passages. 'Moreoven the cross sectional area of the longitudinal water passageways is relatively small, causing the velocity of water flow to be relatively high. And this high velocity water ow tends to reduce the thickness of the insulating water film that adheres to the refrigerant tubes. The construction may be characterized as affording a relatively high flow velocity for a given` quantity rate of flow, with attendant thinning of the water film on the tubes, and therefore increase in rate of heat transfer. Because of the high heat transfer rate gained by the novel construction described, the length of the water passagesy may be made relatively short, with at-v tendant 'reduction in over-all pressure drop.- As

lil

stated, the water velocity is made to be relatively high by utilizing water passages of small ycrosssectional area. This of course results in relatively great pressure drop per unit of length of the water passages, but-by making thefpassages of relatively short length, as is permitted by the high rate of heat transfer characteristic of the apparatus, the over-all pressure drop is made relatively low. 1

The water cooler of the present invention may be regarded as of an instantaneous type. However, the delivery rate of cooled water from any instantaneous cooler is ofcourse limited by the size and capacity of the unit, and as a further feature of the invention, there is preferably provided a storage tank, from which cooled water may periodically be drawn at a rate faster than the cooling rate of the unit. The features of this storage tank, and its novel association with the cooler unit, may however be discussed to better advantage in the course of the following detailed description.

The invention in all its aspects and details, as well as various specific objects and accomplishments not preliminarily mentioned, will appear and be described in the course of the following detailed description of certain present illustrative embodiments thereof, reference for this purpose being had to the accompanying drawings,V in y Fig. 1 is a, full scale longitudinal medial section, with parts in elevation, and intermediate sections broken out, of one preferred form of heat transfer unit in accordance with the invention;

Fig. 2 is a cross section on line 2 2 of Fig. 1;

Fig. 3 is a cross section on line 3 3 of Fig. l;

Fig. 4 is a cross section on line 4 4 of Fig. l;

Fig. 5 is a View similar to Fig. 1 but showingr a modification;

Fig. 6 is a longitudinal medial section, with parts in elevation, showing a cooling unit wrapped in a helical form about a storage tank;

Fig. 7 is a longitudinal section ofv a tank showing a group of further modified cooler units mounted therein.

Fig. 8 is a view similar to Fig. 1, showing a longitudinal section of the modified form of cooler unit shown in Fig. '7; y

Figs. 9, l0, ll and 1 2 are cross-sections taken. respectively, on lines 9 9, lm l, li-I l, and` l2 |2 of Fig. 8. K

Reference rst being had to Figs. 1 through 4, the heat transfer or cooling unit proper, designated generally by vthe numeral IIJ,l embodies, in its present preferred form, a plurality of reirigerant tubes II, typically formed of copper, or other suitable heat conductive metal, and preferably grouped or nested closely together in interengaging relation in a symmetrical pattern, for example vas indicated in Fig. 2. In the form shown in Fig. 2, there are six outside refrigerant tubes, grouped about a central refrigerant tube. The upper and lower ends of the group of tubes I I are itted into upper and lower tubular heads I5 and It, respectively, the upper head I5 receiving the end of a refrigerant supply pipe II, which will be understood to be connected to the usual expansion valve, not shown in Fig. 1, and which will be understood to receive refrigerant from a suitable source of supply. Lower head I5 is tted with a refrigerant outlet pipe I8 understood to lead back to the compressor or other refrigerating apparatus completing the cycle. The spaces between the several contacting tubes II, and between the outside tubes II and the surrounding tubular heads I5 and I6, are closed in a liquid tight manner at the upper and lower ends of the tubes, preferably lby filling in with solder, as indicated at I9 in Fig. 4. Thus the refrigerant `is confined to the two heads I5 and IB and to the connecting tubes II.

Tubes II are closely confined within a tubular housing 2D, also preferably formed of copper, and the upper and lower ends of which, in the present embodiment of the, invention, terminate somewhat short of the upper and lower ends of the tubes, as illustrated in Fig. l. Between the upper end of housing 2D and the head I5, and between the lower end of housing and the head I6, the outside refrigerant tubes II are spread outwardly somewhat, as at I I', thus providing water passages 2I therebetween. In the particular embodiment of the invention here illustrated, sleeves 23 and 24 are fitted over the upper and lower ends of housing tube 20 and the tubular heads I5 and I6, respectively, and confine the outwardly spread portions II of the tubes. These sleeves 23 and 24 may be regarded as enlarged extensions of the tubular housing 2i) that confines the refrigerant tubes.

The sleeve 24 is formed with a water inlet connection 26, which preferably has a restriction.. such as the orifice 21, and sleeve 23 is provided with a water discharge connection 28. The restriction here illustrated by the orice 2 may be of various types, or incorporated in the apparatus in various ways or locations, the function being simply to set or regulate the flow rate through the apparatus.

As has been described, the refrigerant is introduced to the cooler at I'I and flows downwardly through the tubes II to be finally discharged at I8. The water to be cooled is introduced to the cooler via water inlet connection 26, and rises within housing 2l) via the spaces between the refrigerant tubes to the water outlet 28. It will be understood that the rising water surrounds the refrigerant tubes on all sides, rising not only in the longitudinally extending spaces 3G between the outside tubes II and housing 2i), but also in the longitudinally extending spaces 3l between the outside tubes and the central tube. From what has already been described it will be evident how water introduced at 26 may pass through the spaces El between the spread sections of the lower end portions of the outside tubes to the spaces 3| and may pass from said spaces 3i through the spaces 2| between the spread sections of the upper end portions of the tubes to reach the water discharge outlet 28.

As will be evident, the construction described affords an extraordinarily large area of contact between the water in the longitudinal flow spaces 36 and 3l and the refrigerant tubes Il, as compared with the total cross-sectional area of the passages within the tubes Il, and of the spaces 3U and 3l.

Preferably, and as shown here, the outside refrigerant tubes i I are wrapped or twisted somewhat about the central tube, each tube being thus of helical form, and the several helically formed tubes nesting together in twisted cable fashion. This of course causes the longitudinally extending water passages Si] and 3I between the tubes to have a helical form. Several advantages are gained by this helical or twisted construction, among which may be mentioned greater ease of assembly, increase of turbulence, and therefore increase in rate of heat transfer, reduced strain on the apparatus in the event of freezing, and more uniform distribution both of the refrigerant flowing through the tubes and of the water in the water passages around the tubes.

Fig. 5 shows a modification, similar in many respects to the form of Figs. 1 through 4. Corresponding parts of the two embodiments are therefore identified by the same numerals but with the sub letter a added in the case of Fig. 5. In the embodiment of Fig. 5, the central refrigerant tube is extended downwardly through the lower head Ita, as indicated at 34, and serves as the inlet conduit for the refrigerant. In this instance, therefore, the refrigerant flows upwardly through the central refrigerant tube, is discharged from the upper end of the latter into head I 5a, and thence fiows downwardly through the outside refrigerant tubes, as indicated by the arrows. Aside from this modification, the form of Fig. 5 is the same as that of Figs. 1 through 4.

The described multiple refrigerant tube constructions result in a very high rate of heat transfer. It will be evident, as pointed out hereinbefore, that an exceptionally large area of refrigerant tube surface is presented to the water, which surrounds the several tubes of the group on all sides, and that this large area is gained with the use of a small total volume of refrigerant, as well as with a minimized cross-sectional area of water flow space. The rate of water flow through the unit is confined to what the unit can satisfactorily handle (the length of the unit being taken into account) by the restricted inlet orifice 21, which in any given case must be properly related to expected inlet Water pressure. As stated before, the relatively small cross-sectional area of the longitudinal water ow passages results in a relatively high velocity of flow through the unit and such relatively high flow velocity has the beneficial effect of substantial reduction in the thickness of the heat insulating water film known to adhere to the tube surfaces. This relatively high now velocity results in relatively high pressure drop per unit of length ofthe water passages, but because of the high rate of heat transfer gained by the apparatus, the unit may be relatively short for a given rate of heat transfer, and the over-all pressure drop accordingly becomes relatively low. The length of the unit is of course chosen to give the degree of cooling required, and may range from a foot or so to any number of feet, depending upon requirements. An advantage of the cooler that may be here mentioned is the fact that it is not injured by freezing. The water being in the spaces external of the tubes, they cannot be expansively injured as they might be by water freezing in them. And when water freezes in the helical passages around the tubes, the helical formation allows the tubes to creep locally with reference to the external sheath tube 20. And in the form of Fig. 7, where the lower ends of all the tubes are not anchored longitudinally with relation to the sheath tube 20a, the helical tubes may expand longitudinally to accommodate longitudinal expansion of water freezing in the helical passages. 'I'he thermal inertia of the cooler is very low, cold Water being delivered almost the instant the compressor starts.

Fig. 6 shows the combination of the described cooler unit with the storage chamber of the invention. The storage chamber, designated generally by numeral 40, embodies a cylinder 4I having a closed bottom 42 and a pressure tight removable cover 43, within which is slidably tted a longitudinally movable dividing wall or piston 45." In the particular construction illustrated, this piston 45 embodies a, cup leather 46 confined between washers 41 and 48 mounted on a bushing 49 which is slidable on a longitudinally extending guide rod 50 received at its ends in sockets I and 52 formed respectively in the bottom 42 of the cylinder and in the cover plate 43. Packing 53 carried by a packing nut 53 screwed onto bushing 49 prevents leakage of water along rod 50 from one side of the piston to the other. A coil compression spring 54 surrounding rod 41 above the piston seats upwardly against cover 43 and acts downwardly at all time aaginst piston 45.

Connected into the lower end of cylinder 4I is the water supply pipe 55, while the cooled water discharge pipe 56 is connected into the upper end of the cylinder through removable cover 43, as at 51.

In the particular embodiment of the invention shown in Fig. 6, the cooling unit I0 (for example, the unit of Figs. 1 through 4) is mounted in cooling relation to the cylinder 4 I, being in the present instance wrapped around said cylinder in direct contact with it. The entire cooling unit as seen in Fig. l is thus simply bent into a helical form and fitted directly onto the outside of cylinder 4I. The water inlet connection V26 leading into the lower end of cooler unit Ill is arranged to draw water from the lower end of cylinder 4I, as illustrated, and the cooled water discharge connection 28 of the cooler is arranged to discharge into the upper end of cylinder 4I- Further, the refrigerant return pipe I8 leading from the lower end of cooler unit I0 is shown as similarly helically wrapped about the cylinder 4I. Thus water which has been discharged from the cooler unit into the upper end of cylinder' 4| is further cooled, or maintained in a cooled condition, by the refrigerating effect of the tubes I I and the refrigerant return tube I8 wrapped about the cylinder 4I. l

Preferably, and as shown in Fig. 6, the storage unit 40 is enclosed within an exterior casing or jacket 60, having a removable cover 6I, a substantial layer of heat insulation material 62, such as rock wool, being packed within the jacket 60 entirely around the cooler and storage unit, as illustrated. The various water and refrigerant connections are suitably extended through the wall of this exterior jacket, as indicated.

Fig. 6 further illustrates the usual expansion valve 65, which receives the compressed refrigerant via supply line B6, and from which the refrigerant is released via connection I1 into the cooler unit.

The operation of the combined cooler and storage chamber of Fig. 6 is as follows: The refrigerant delivered via incoming refrigerant line 6,5 and expansion valve 65 to the upper end of the cooler unit III wrapped about the storage cylinder 4I ows downwardly via the refrigerant tubes II contained within the unit I0, and upon discharge from the lower end of the cooler unit, lows upwardly via pipe I8, similarly wrapped about the cylinder 4I, the upper end of the pipe I 8 extending outwardly through the casing 60 and being understood to connect with the return side of the compressor. Incoming water ows via connection 55 into the lower end of cylinder 4I, and water from the lower end of said Cylinder flows via connection 26 into the upwardly extending liquid passages 30 and 3| between the refrigerant tubes, as before described. This water then rises about the refrigerant tubes to the upper end of the cooler unit, being cooled by its contact with the tubes II as it rises, and the cooled water being finally discharged via connection 28 into the upper end of cylinder 4I. The rate of liquid flow upwardly through the cooler is determined, as before stated, by the diameter of the orifice 21 in the inlet connection 26, as well as by the inlet water pressure. Cooled water is thus discharged into the cylinder 4I from its upper end and so fills the cylinder. Piston 45 is normally in its lowermost position, as illustrated in Fig. 6. When water is drawn from service connection 56 at a rate greater than the maximum rate of liquid iiow through cooler Il), the charge of cooled water stored in the cylinder 4I above piston 45 is drawn upon. As this water flows outwardly via line 56, at a rate greater than the rate of inilow from cooler Ill, the pressure of the water below the piston causes the piston to rise, against the force of springl 54, followed up by incoming water from supply line 55. The piston 45 may thus rise to the upper end of cylinder 4I, at which time the stored volume of cooled water is of course exhausted, so that thereafter the delivery of cooled water from the unit is reduced to the restricted flow that can be obtained directly from the cooler. The supply chamber is of course designed to have such capacity, with relation to the periodic service calls expected to be made upon it, that normally the supply of cooled water contained within the upper portion of the cylinder 4I will not thus become exhausted, so that except for the possibility for an unanticipated extraordinarily heavy call upon the cooler, cooled water can always be drawn therefrom at the full ow rate.

When water ceases to be drawn from service line 56, the cooled water which has been taken from the upper end portion of storage cylinder 4l is then gradually replaced by ow received from the upper end of the cooler, spring 54 gradually returning piston 45 to its original lowered position.

Thus it will be seen that the cooled charge of water provided within the cylinder 4I above piston 45 is always availableto be drawn off as rapidly as desired. Ii this charge should become exhausted. cooled water may still be drawn from the apparatus, though at a somewhat reduced i'low rate, the rate of out-flow in this instance being restricted by the maximum flow rate of the lcooler unit I0, as determined by the orice 21.v Under such conditions the apparatus functions as an instantaneous cooler, but with reduced rate of supply. yAttention is called to the fact that under no conditions does the incoming uncooled make-up water mix with the cooled charge. And, as beiore described, the cooled charge of water contained within the storage cylinder Si is constantly being further cooled or maintained in its cooled condition, by heat transfer with the cooling unit and refrigerant return line i8 wrapped in intimate contact with the outside of the storage cylinder 4i.

In the event that the cooling unit lll of the form or apparatus shown in Fig. 6 should become frozen, thawing may be promoted by drawing off the cooled water from the upper end oi the cylinder 4l, and thus allowing relatively warm incoming water to rise in the cylinder below the ascending piston t5. This relativeli7 warm water warms the unit Iii in contact with the outside of the cylinder, and thus aids in thawing the cooler unit.

Fig. 7 shows how any desired number of the cooler units of the invention may be utilized in a parallel arrangement. Primarily, the arrangement disclosed permits cooling of water at relatively high flow rates, utilizing a number of relations projecting inside the tank. The units lila as seen in Fig. "I will be understood to be inverted top for bottom. as compared with the unit lila as seen in Fig. 5. As here illustratively shown, a threaded collar l2 welded to the housing tube 20a, just below the sleeve 24a at the upper end of each unit Ida is screwed into an internally threaded coupling tube 'I3 mounted in the head of the tank Il, though of course any other suitable coupling means may be employed if desired.

Tank 'il is `provided near its upper end with a water outlet i5. Tube 26a opening inside housing sleeve 24a is the water inlet, and the water so introduced passes between the upper spread portions of the tubes I la, thence downwardly via the passageways 30a formed between the tubes, and is discharged to the tank between the lower spread portions lla of the tubes. As appears in the drawing, the housing sleeve surrounding the lower spread portions of the tubes is in this instance omitted as unnecessary, the water discharging directly from the spaces between the ower spread portions of the tubes to the interior of the tank. In the particular embodiment illustrated in Figs. 7 to l2, the upper end of central tube 3s serves as the refrigerant inlet, and the refrigerant flows from the lower end thereof via the lower uid connection head |50. to the outside tubes ila, through which it then rises to upper head Ilia, in which the upper ends of the tubes are packed with the filling iQa and finally discharges via tube 18a. Of course, the direction of liquid flow could be reversed. For instance, the refrigerant could go in at iSd and out via the upper end of central tube 36; and the water might be introduced at l5, to enter the cooler units Illa at their low-er ends, and be discharged at 26a.

With either direction of water flow, the units main outside contact with the water within the tank constantly cool that water. In the case in which the water first passes through the cooler units and then into the tank, the .cooler units keep the temperature ofthe water down during subsequent storage periods. V'Ihe cooled water thus stored in the tank may if desired be drawn olf at a ow rate even greater than that at which the several units lila collectively are capable of suficiently cooling the water. The incompletely cooled water which is thus run into the tank is then reduced in temperature during the subsequent storage period by contact with the outsides of the units lila. And `in the case in which the water passes first through the tank and then through the cooler units, the water is precooled during the storage time in the tank, so that cooler water is delivered, or so that a quantity of sufciently cooled water, up to the capacity of the tank, may be drawn olf at a flow rate somewhat greater than the normal capacity. of the units Illa to cool.

In the above descriptionv the cooler has been described as a cooler for water; however, as will be recognized, the cooler may handle other liquids than water, and may have numerous applications in the heat transfer eld.

The invention has now been disclosed by way of specific illustration and description of certain present illustrative embodiments; it is to be understood, however, that this is for illustrative pur.- poses only, and that various changes in design, structure and arrangement may be made without departing from the spirit and scope of the invention or of the appended claims.

I claim:

l. In a heat exchange unit, the combination of a plurality of tubes having walls of heat conducting material closely interengaging each other throughoutJ a substantial portionof their lengths, a tubular housing of heat conducting material closely confining the interengaging portions of said tubes, the several tubes and housing being in close heat conducting Contact with each other, the housing having inlet and outlet fluid openings at its opposite ends, the outer surfaces of the interengaging tubes and the inner surface of the housing dening a plurality of laterally closed fluid passageways extending longitudinally within said tubular housing, the plurality of tubes having portions near their opposite ends, and beyond the ends of the closely confining housing, spread apart from each other to form fluid flow spaces to and from the laterally closed fluid passages between the tubes, a fluid connection head joined to each end of said plurality of tubes, said heads being spaced from the ends of the closely conning housing, and an enlarged tubular housing surrounding one of the spread-apart portions of the tubes between one end of the closely conning housing and one head and having a iiuid flow connection, one of said tubes having an end projecting beyond the corresponding ends of others of the tubes and projecting through the one said head to form a fluid flow connection.

2. In a heat exchange unit, the combination of a--plurality of tubes having walls of heat conducting material closely interengaging each other throughout a substantial portion of their lengths, a tubular housing of heat conducting material closely conning the interengaging portions of said tubes, the several tubes and housing being in close heat conducting contact with each other, the housing having inlet and outlet fluid openings at its opposite ends, the outer surfaces of the interengaging tubes and the inner surface of the housing dening a plurality of laterally closed fluid passageways extending longitudinally within said tubular housing, the plurality of tubes having portions near their opposite ends, and beyond the ends of the closely conning housing, spread apart from each other to form iluid flow spaces to and from the laterally closed fluid passages between the tubes, a iiuid connection head joined to each end of said plurality of tubes, said heads being spaced from the ends of the closely conning housing, and an enlarged tubular housing surrounding one of the spread-apart portions of the tubes between one end of the closely coniining housing and one head and having a iiuid iiow connection, said plurality of interengaging tubes being arranged in a cross-sectional formation which includes a central tube and surrounding tubes, the central tube having an end projecting beyond the corresponding ends of the surrounding tubes and projecting through the one said head to form a fiuid flow connection.

3. In a heat exchange unit, the combination of a plurality of tubes having walls of heat conducting material closely interengaging each other throughout a substantial portion of their lengths, a tubular housing of heat conducting material closely conning the interengaging portions of said tubes, the several tubes and housing being in close heat conducting contact with each other, the housing having inlet and outlet fluid openings at its opposite ends, the outer surfaces of the interengaging tubes and the inner surface of the housing dening a plurality of laterally closed fluid passageways extending longitudinally within said tubular housing, the plurality of tubes having portions near their opposite ends, and beyond the ends of the closely conning housing,

spread apart from each other to form uid flow spaces to and from the laterally closed fluid passages between the tubes, a uid connection head joined to each end of said plurality of tubes, said heads being spaced from the ends of the closely confining housing, and an enlarged tubular housing surrounding one of the spread-apart portions of the tubes between one end of the closely conning housing and one head and having a iiuid flow connection, said plurality of interengaging tubes being arranged in a cross-sectional formation which includes a central tube and surrounding tubes, the central tube having an end projecting beyond the corresponding ends of the surrounding tubes and projecting through the one said head to form a iiuid ilow connection, said central tube being straight, and the surrounding tubes being helically formed around the central tube.

4. In a heat exchange unit, the combination of a plurality of tubes having walls of heat conducting material closely interengaging each other throughout a substantial portion of their lengths, a tubular housing of heat conducting material closely confining the interengaging portions of said tubes, the several tubes and housing being in close heat conducting contact with each other, the housing having inlet and outlet iiuid openings at its opposite ends, the outer surfaces of the interengaging tubes and the inner surface of the housing defining a plurality of laterally closed fluid passageways extending longitudinally within said tubular housing, the plurality of tubes having portions near their opposite ends, and beyond the ends of the closely coniining housing, spread apart from each other to form uid flow spaces to and from the laterally closed uid passages between the tubes, a fluid connection head joined'to each end of said plurality of tubes, said heads being spaced from the ends of the closely confining housing, and an enlarged tubular housing surrounding one of the spread-apart portions of the tubes between one end of the closely coniining housing and one of the heads and having a fluid flow connection, one of said tubes having an end projecting beyond the corresponding ends of others of the tubes and projecting through the last mentioned head to form a fluid flow connection, the space between the other end of the closely conning housing and the other head being unhoused, for direct now of fluid from the spaces between the spread tubes at that end to a surrounding space,

GILBERT E. CLANCY.

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