US3011767A - Cold plate with conversion heater assembly - Google Patents

Description

Dec. 5, 1961 w. E. LAUTERBACH ETAL 3,011,767

com PLATE WITH CONVERSION HEATER ASSEMBLY Filed Aug. 5, 1959 @ff-EEA AV llnited rates Our invention relates -to an improvement in heat transfer plates and has for one purpose to provide ready means for converting a cooling plate to use as a heater.

Another purpose is to provide means for converting a cooling plate for heating use without any change or alteration whatsoever of the plate.

Another purpose is to provide a conversion unit which includes a heating element insertable into a cooling plate, and an associated heat responsivevelernent for controlling the actuating circuit of the heater in response to changes in the temperature of the plate or about the plate.

Another purpose is to provide removable heating means for a cooling plate which, when applied, is so related to the coil as to employ the entire coil as means for heating a surrounding heat storage body.

Another purpose is to provide a removable heating assembly for a cooling plate which can be applied to the cooling plate not only with no change of structure of the plate but without disconnection of the cooling plate or evaporator from the refrigerating circuit in which it is used. f

Other pumoscs will appear from time to time in the course of the specification and claims.

We illustrate our invention more or less diagrammatically the ccompanyingfdrawings wherein:

FIGURE l is a plan view of a plate embodying our y 3,011,767' lPatented Dec. 5, li

is secured to a transverse tube 1l or l2, which extends from edge to edge of the plate and terminates in a second fitting i3 or 14. Each such tube 1l or 12 is, therefore, connected at one end to one end of the coil A and is connected at the other end to a fitting at the opposite edge of the plate. As will be clear from the drawings, these tubes provide rectilinear passage all the way through, from edge to edge of the plate. In practice,

. eachcnd of each tube may be selectively closed either by invention, with parts in section and parts broken away;

FlGURE 2 is a partial side elevation on anenlarged scale; and

FIGURE 3 is a detail view of a variant connection for the heating element.

Lilie parts are indicated by like symbols throughout the specification and drawings.

Referring to the drawinffs, we illustrate a plate adapted to be connected in a conventional mechanical refrigeration circuit in which a compressor delivers a volatile rerigerant under compression, to a condenser, where the volatile refrigerant is changed to liquid fo .i the liquid, still under pressure, being delivered thence to a suitable evaporator. Our plate may be considered as an evaporator normally usable in such a system iu which the refrigerant is evaporated at a lowered pressure, and from which the evaporated refrigerant is withdrawn to the suction side of the compressor. Since the refrigeration system, as such, forms no part of the invention, it is not further described or shown herein.

The plate, as shown, includes generally plane, generally parallel plate side walls 1 and 2. The plate side wall 2 is shown as formed with circumferential edge walls 3, terminating in a circumferential flange 4, to which the plate side wall l may be welded or otherwise suitably secured. The result, when the walls are properly connected, is a gas-tight container, as will later appear.

Within the container', we illustrate a coil generally indicated as A, is formed of a plurality of generally parallel, generally rectilinear lengths 6, connected by bends 7. As it will later appear, it may, under some circumstances, be advantageous to form the coil A of rectangular tubing, in order to increase the heat transfer area of the coil surface.

Each end of the coil is shown as terminating in a fitting or lll. Fthese fittings are shown at one end of the plate but at opposite sides of the plate. Each such fitting a suitableclosure or plug or by a connection to the above described mechanical refrigeration circuit. in FlGURE l, the closure plugs are omitted, since the plate can be used vas a heater even when disconnected from its piping.

We nd it advantageous for many uses to employ a plate substantially thicker than the gauge or thickness of the pipe of which the coil A is formed. In that event, we find it advantageous to employ some suitable spacing means, such as the channels 15, which are more or less diagrammatically shown in FlGURES l and 2. These channels extend preferably substantially vfrom edge to edge of the plate, and contact the various straight lengths 6 of the coil A. When rectangular tubing is employed, there is thus a substantial heat contact area between the coil and the transversely extending channels or spacers l5. Any suitable means, not herein shown, may be employed for maintaining the channels 15 in predetermined spaced relationship.

We find it advantageous to provide a substantial body or filling of heat storage material in the plate. Where the plate is normally employed for cooling, it is practical substantially to till the interior of the plate with a brine or eutectic. 2li indicates a suitable filler assembly throuah which thereafter, is closed to prevent leakage.

lt is further advantageous to maintain all parts of the coil, the plate side walls, and the spacers in intimate contact. This intimate contact may normally be maintained by subjecting the interior of the plate to a less than atmospheric pressure. A partial vacuum may be drawn through the iitting 2l, which may, thereafter, be sealed to prevent unintended inliow of atmospheric air.

The heating system or conversion unit is shown in FIGURE l as including an outside fitting or contact box 25 shown, for convenience, with a removable lid 26. It is screw-threaded to, or otherwise secured to, a resistance element 27, the details of which do not of themselves form part or" the present invention and are therefore not illustra-ted. lt is preferable, however, that the member 27 be provided with a screw-threaded connection, as at 2S, which conforms to the internal screw threads with which the fittings i0, 13 and irl are provided. Tous the resistance element or heater 27 may enter and be secured to the appropriate end of either ofthe cross ducts 11 and 12. Where the plate is connected in the usual compressorcondenser circuit all that is needed, toadapt the plate for heating use, is to remove a closure plug and substitute foi' that plug. the screw-threaded connection 28 with the associated resistance heater 27. When the parts are in the position of FIGURE l it will be understood that the fitting 14 will receive a suitable inlet connection so that a volatile refrigerant is admitted in the direction of the arrow. In that event, the fitting lil will be closed with a suitable closure plug. The litting 9 -receives an outlet connection for the return of the evaporated refrigerant to the suction side of the compressor. The tlow is in the direction of the arrow, indicated in FGURE l. Were the heating conversion unit not in place, the litting 13 Would be closed by a closure plug. The only'change to be made, to change the plate for heating use, is to remove the plug or closure from the fitting 13 and to substitute the externally screwthreaded member 28 with its associated resistance heater 27. It will be understood, however, that the plate may the brine may be supplied, and which,

be used as a heater when disconnected entirely from a reirigerating system. In that event, it is not necessary to close the ttings 9, v and 14, although it may be advisable to employ closure plugs simply to prevent the entry of dust or other material into the coil in the plate.

We iind it advantageous to provide, generally, a thermostatic control for the heating conversion unit. In connection with FIGURE l, we illustrate a somewhat diagrammatic arrangement in which 30, 30, indicate conductive connections which enter the iitting 25 through any suitable flexible cable 31, and serve to connectthe resistance unit 27 with a suitable source of electric power. We illustrate diagrammatically two thermostatic control elements 32 and 33. One of these may be a conventional Y thermostat responsive to yroom temperature and the other may be a thermostatic controlV member, bulb or the like, wmch may be secured in some suitable way to or in contact with the plate. Thus we provide means for interrupting the supply of current to the resistance unit 27 either in response to a predetermined increase in the heat of the plate or in response to a predetermined increase in the ltemperature of the space surrounding the plate. We may control the heating unit by either or by both.

It will be realized that, whereas, we have Vdescribed and illustrated a practical and operative device, nevertheless, many changes may be made in the size, shape, nurnber and disposition of parts without departing from the spirit of our invention. We therefore wish our description and drawings to be taken as in a broad sense illustrative or diagrammatic ratherV than as limiting us to our precise showing. For example, it will be realized that, as shown in FGURE 3, the speciiic housing or iitting 25 may be omitted, andthe conductive connection may be made directly to the screw-threaded iitting 23a, through a flexible conduit, as shown at di). Also, whereas we have described andshown screw-threaded iittings and screwthreaded connections therefor, any suitable means for removably securing the plate into a cycling system, or for removably securing the conversion heating unit, may

V be employed.

The use'and operation of the invention are as follows:

We illustrate and describe a plate which is normally connected in a conventional compressor-condenser unit. We illustrate what may be vcalled a truck plate, a plate having a substantial body of a brine or eutectic in the space within the plate and about the coil. Under some circumstances, such as in the wintertime operation of a milk delivery truck, it becomes important to employ such a plate as a heating means. We provide a conversion unit which may be inserted in the plate with no change in the structure of the plate. In the plate herein shown two transverse tubes or ducts 11, 12 are shown, each of which is open at each end. Normally, in connecting the plate to a compressor-condenser unit the high pressure duct or tube from the condenser is connected to the fitting 10 or to thefitting 14. In either case the opposite fitting receives a closure plug. Similarly, the tube 11 is connected to the suction side of the compressor, this connection being ,made either to theiitting 9 orto the tting 13, with the opposite fitting closed by a plug or the like. Where it is desired to apply the conversion heater unit all that is necessary is to remove the closure plug from one of the ttings and to substitute the conversion unit. The conversionunit could be applied to the iitting 13 of the tube 11 or to the iittin g 14 of the tube 12 without in any way interfering with the normal flow of the refrigerant or without in any way interrupting the connection of the plate with the compressor-condenser unit. It is also possible, of course, to disconnect the plate from the compressorcondenser unit, in which case it may still be employed as a heater by the insertion of the conversion unit into either end of either of the tubes 11, 12. However, it is advantageous to be able to apply the conversion unit without even disconnecting the plate from the cycling connection.

Note that the length of the conversion unit 27 is such that when inserted in the'iitting 13 or 14 it will not quite reach to the connection between the tube 11 or the tube 12 and the coil.

The structure above described provides a singularly flexible unit for use in both summertime and wintertime. in the summertime operation, for example, of a milk truck, the eutectic solution is frozen by the refrigerant at night to provide a cold hold-over during the use of the milk truck the next day. yIn the wintertime, on the contrary, the eutectic solution is heated by the resistance heater at night and provides a warm hold-over during the use of the truck the next day. Thus, the present invention provides a plate which is universally practical and is useful for maintaining the desired temperature range in both summertime and wintertime use, without the necessity or modifying the plate structure or of substituting plates.

We claim:

l. A combined heating-refrigerating vacuum plate utilizable in or out of combination withV a Vmechanical refrigerating system, said plate including a top and a bottom wall, end walls, and sideV walls,l said walls being connected about their edges in gas tight relationship to form a iiuid tight enclosure, said top and bottom walls being substantially longer than they are wide, said side walls being substantially parallel to the long dimension of the top and bottomwvalls, a combination refrigerationheating iiuid coil of heat conductivermaterial within the plate, said coil being composed of a plurality of generally parallel runs joined by connecting bends, said runs being generally parallel to the side walls, said coil -terminating in an inlet and outlet opening into a iirst and a second header respectively, each header spanning the vacuum plate and being positioned substantially transverse to the parallel runs, each header having first and second openings in said side Walls, two of said openings one in each of the headers, being connectable to a .echanical refrigeration system, andl -another of said openings being closed, the space within the plate and around the coils and headers being largely illed, at all times, with a heat storage body, a vacuum connection opening into the plate for drawing a vacuum within the plate to thereby urge the coil into good heat exchange relationship'with at least one of the side walls, an electrical heater within one of said headers for defrosting the plate or raising the temperature of the heat storage body when the plate is used as a heating plate, said heater being secured to the remaining header opening and extending Vinto the header substantially the full length of the header and terminating short of the other end of the header, said heater lying in close fitting relationship to the wall of the header to thereby promote maximum heat exchange to the heat storage body surrounding the header, especially when the assembly is used as a heater plate assembly out of combination with a mechanical refrigeration system, and heat responsive means for regulating the current delivered by the heater to the heat storage body.

2. A combined heating-refrigerating vacuum plate utilizable in or out of combination with a mechanical refrigerating system, said plate including a top and a bottom wall, end walls, and side walls, said walls being connected about their edges in gas tight relationship toV form a fluid tight enclosure, said top `and bottom walls being substantially longer than they are wide, said side walls being substantially parallel to the long dimension of the top and bottom walls, a combination refrigeration-heating-duid coil of heat conductive material within the plate, said coil being composed of a plurality of generally parallel runs joined by connecting bends, said runs being generally parallel to the side walls, said coil terminating in an inlet and outlet opening into a first and a second header respectively, each header spanning the vacuum plate and being positioned substantially transverse to the parallel runs, each header having first and second openings in said side walls, two of said openings, one in each of the headers, being connectable to a mechanical refrigeration system, and another of said openings being closed, the space within the plate and around the coils and headers being largely filled, at all times, with a heat storage body, a vacuum connection opening into the plate for drawing a vacuum Within the plate to thereby urge the coil into good heat exchange relationship with at least one of the side walls, an electrical heater within one of saidheaders for defrosting Ithe plate or raising the temperature of the heat storage body when the plate is used as a heating plate, said heater being secured to the remaining header opening and extending into the header substantially the full length of the header and terminating short of the other end of the header, said heater lying in close fitting relationship to the wall of the header to thereby promote maximum heat transfer from the header to the heat storage body surrounding the header and from the coil to the heat storage body at locations remote from the header, especially when the assembly is used as a heating plate out of combination with a mechanical refrigeration system, and a heat control assembly for regulating the current delivered by the heater to the heat storage body, said heat control assembly comprising `a pair of thermostats connected to the heater, one thermostat being eiective to regulate the heater in response to the temperature of the plate and the other 10 in response to ambient temperature- References Cited in the le of this patent UNITED STATES PATENTS l 2,755,371 Jackson July 17, 1956 5 2,814,186 Kleist Nov. 26, 1957 2,859,945 Kleist Nov. 1i, 1958

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