Abstract: This specification relates to a heat exchanger (10) of the type wherein a plurality of elongated plates (12) are laminated together to define a plurality of passageways (14) for movement of a fluid therethrough. Each of the passageways (14) are formed by inwardly facing surfaces of a pair of laminated plates (12--12) which define a central fluid conducting section (34) located between reservoir sections (32--32) at each end thereof. Adjacent of the passageways (14--14) have heat transfer fins (18--18) located therebetween. Reservoir sections (32--32) of adjacent ones of the passageways (14--14) are interconnected so that a fluid may flow therethrough. The improvement of this invention is made to the laminated plates and it includes a plurality of beads formed on each of the pair of laminated plates (12--12). The beads formed on each of the plates are of two distinct varieties.

Abstract: A method for fabricating a solar energy collector assembly of the integral storage type is disclosed herein. This assembly utilizes a specifically designed storage arrangement which is expanded into its final shape from an initial collapsed configuration. In the specific embodiment disclosed, the storage arrangement includes many of its own design features apart from the overall collector assembly and serves as the main structural component of the entire assembly.

Abstract: A flat, very thin fluid heat exchanger of up to about 1/8 inch in thickness is formed from a pair of etched blanks. The blanks are provided with at least a pair of projecting tabs for locating the blanks relative to each other. The tabs are secured prior to brazing of the blanks and are thereafter removed. Posts are provided for facilitating securance of the heat exchanger to objects with which it is to be associated. A thin fluid flow passageway is provided between the blanks, and the heat exchanger provides fluid flow inlet and outlet openings communicating with the fluid flow passageway.

Abstract: A heat exchanger construction of the plate and fin type comprising a plurality of plate assemblies joined together in a stackable arrangement, each plate assembly being formed by a pair of similar plate members placed in mating face-to-face relationship with each other to form a central flow region therebetween. Each plate member includes a header portion located respectively adjacent each opposite end thereof, each header portion having at least one pair of spaced openings adaptable for receiving and discharging a fluid medium therethrough. A raised partitioning or pass rib is positioned extending between the pair of spaced openings associated with one of the header portions and depending upon the positioning of the respective pass ribs relative to one another when each respective pair of plate members are joined together either a single-pass or a double-pass flow system is formed therebetween.

Abstract: A cooling assembly for fuel cells having a simplified construction whereby coolant is efficiently circulated through a conduit arranged in serpentine fashion in a channel within a member of such assembly. The channel is adapted to cradle a flexible, chemically inert, conformable conduit capable of manipulation into a variety of cooling patterns without crimping or otherwise restricting of coolant flow. The conduit, when assembled with the member, conforms into intimate contact with the member for good thermal conductivity. The conduit is non-corrodible and can be constructed as a single, manifold-free, continuous coolant passage means having only one inlet and one outlet. The conduit has an internal coil means which enables it to be bent in small radii without crimping.

Abstract: A heat exchanger for indirect heat transfer between fluid media includes a duct member with the space in its interior divided by a separating wall extending transversely of the duct member axis into a pair of partial spaces. Webs located within the partial spaces and extending helically around the duct member axis form a pair of ducts in each partial space. One fluid medium is circulated through one duct and the other fluid medium through the other duct. The ducts in each partial space are interconnected by passages extending through the separating wall so that the fluid media flow through both partial spaces. The ends of the duct member spaced from the separating wall are closed by a combination seal and cover plate.

Abstract: Flexible container means for the warming or cooling of fluids. A preferred embodiment, useful for the warming of plasma following cryogellation techniques prior to its return to the patient, comprises container means formed by the heat sealing of polymeric materials thereby defining a winding passageway of tapered walls whereby the container becomes air self-evacuating.

Abstract: A transversally corrugated multi-luminal flat tube for circulating the refrigerant of an evaporator for an automotive air conditioner in indirect heat exchange relation with air is provided with one laterally marginal portion, being the one which faces inlet air flow in a transverse cross-flow system, that is so thick-walled about its outer perimeter, that inlet air, which is corrosive because it contains moisture and salt, will be prevented for a sufficiently long time from corroding pinholes through that part of the tube, the remaining part of the outer periphery of the flat tube, because it is less subject to corrosive attack being thinner walled, so as to maximize durability and mass flow rate, while minimizing weight and cost.

Abstract: Method and apparatus are disclosed for selectively clamping the edges of electronic modules into mechanical and thermal contact with a fluid coolant circuit. A stack of plural substantially parallel and generally planar fluid conduit-containing structures having spaced apart parallel legs jointly receive a stack of plural generally planar electronic modules disposed transversely therewithin. Each of the fluid conduit-containing structures includes mechanical/thermal contact pads disposed approximately perpendicular to its general plane on the inside edges of the parallel legs with the pads on some of the structures being directed one way and those on others of the structures being directed in an opposite way. At least one such set of structures is then collectively moved so as to selectively clamp the edges of the stack of electronic modules between opposingly directed contact pads.

Abstract: A solar heat collector is composed of a pair of solar collector panels welded by a laser beam along a plurality of spaced seams. A fluid under pressure is introduced between the solar collector panels to bulge them until a plurality of heat-transfer medium passages are defined between the welded seams. The welded seams have at their ends a plurality of circular or oblong welded seams which serve to prevent the ends of the spaced seams from being cracked or torn when the panels are bulged or the solar heat collector is in use, and also serve to uniformize the flow of the heat-transfer medium through the passages. A plurality of other circular or oblong welded spots may be provided in spaced relation to the circular or oblong welded seams in the longitudinal direction thereof to uniformize the shape of headers of the solar heat collector and increase the mechanical strength of the headers.

Abstract: A multiple-impingement cooled structure, such as for use as a turbine shroud assembly. The structure includes a plurality of baffles which define with an element to be cooled, such as a shroud, a plurality of cavities. Impingement cooling air is directed through holes in one of the baffles to impinge upon only the portion of the shroud in a first cavity. That cooling air is then directed to impinge again upon the portion of the shroud in a second cavity.

Abstract: A heat exchanger unit having opposed pan shaped sections with perimeter flanges which are folded one over the other to secure the sections together. The section having the inner flange is formed with a displaced flange portion or bead all along the perimeter flange portions, which bead is elastically displaced by the folded over flange to form a substantially leakproof joint.

Abstract: A charge air cooler is provided made up of a plurality of spaced generally parallel turbulators, each said turbulator comprising an outer channel member having a bottom wall and two transverse side edges, an inner channel member having a bottom wall and two transverse side edges, the side edges of the inner channel interfitting closely within the side edges of the outer channel member, an accordian shaped fin assembly between said channels having side edges of a plurality of accordian folds in contact with the bottom wall of both the inner and outer channel members, a transverse heat exchanger fin assembly between adjacent turbulators, frame means surrounding said turbulators and heat exchangers, header means at each end of said turbulators, and flange means around the periphery of each said header means forming therewith one of an inlet and outlet well whereby the turbulator ends may be operatively connected to a source of fluid to be cooled.

Abstract: In a hot water system, a receptor heat exchanger unit mounted in a wall with a flat surface exposed in a room. A refrigerator positioned in that room has a plate with a condenser coil thereon. The plate is exposed, and it extends outwardly beyond the wall of the refrigerator body and at the wall, and the plate is positioned in heat transfer engagement with the exposed surface on the receptor heat exchanger unit.

Abstract: Improvements in the condensing heat transfer surface of a condenser which handles organic working fluids whose surface tension is not more than 35 dyne/cm as gas mediums to be condensed. The improvements comprise the formation of a plurality of transversely spaced vertically extending grooves on the condensing heat transfer surface on which the gas medium condenses. The pitch of the grooves is about 1-2 mm and the depth is about 0.3-0.6 mm.

Abstract: A coiled heat exchanger utilizing a sandwich plate type construction with a plurality of spot welds equally spaced throughout, the plate being inflated to expand the passageways therebetween, has fluid tight connections feeding through the outside of the coil for accessing both passageways adjacent and opposite the center divider plate. One or more arcuate slots are punched in the center divider plate and surround a spot weld, with a larger hole punched in the adjacent outer plate and a tube welded against the divider plate to seal the arcuate slot and form a fluid connection between the passageway opposite the divider plate and the outside of the coil.

Abstract: A solar heat exchanger having a mesh sandwiched between two thin films for transfer of radiant solar energy to a fluid drawn through the mesh by suction.

Abstract: A plate-type heat exchanger having uniform surface temperature and improved structural strength is disclosed, which may be used as a structural support member for an object to be temperature controlled, and which provides a surface having an exceptionally uniform temperature for either heating or cooling the object. The heat exchanger includes a fin pad and a machined plate having a fluid passage therein, as well as other structural frame and support members. The major circuit flow direction of the fluid in the passage is perpendicular to the major longitudinal fin direction of the fin pad in the preferred embodiment. All components of the heat exchanger are of material having good thermal conductivity and structural strength, and the components are brazed or otherwise secured together to provide good thermal conductivity and structural reinforcement throughout.

Abstract: In a process for the production of a solar collector panel assembly, a pipe arrangement for carrying a heat exchange fluid and a carrier panel for carrying same and for absorbing solar energy are intimately jointed together as by soldering or brazing. The pipe arrangement has straight pipe sections and curved pipe sections connecting same. A joining agent such as solder is applied to the carrier panel along the lines of the pipe arrangement, and the pipe arrangement is then applied thereto. A filling material comprising a substance which repels the joining agent is disposed in the spaces defined between the pipe runs of the pipe arrangement. The intermediate assembly consisting of carrier panel, joining agent, pipe arrangement, filling material and possibly a heat barrier layer disposed on the side of the assembly remote from the carrier panel is fitted between two pressure plates which are clamped together.

Abstract: A method and means of exchanging heat in fluids is described herein. The heat exchanger device is comprised of a primary compartment which is separated into at least two longitudinal compartments by a vertically disposed heat exchanger plate. Each longitudinal compartment is divided into a plurality of sub-compartments by walls that extend outwardly from the heat exchanger plate to the sidewalls of the primary compartment. Fluid inlet means are provided at the lower portion and at opposite ends of each longitudinal compartment. Fluid outlet means are provided at the upper portion and at opposite ends of each longitudinal compartment. The sidewalls of each sub-compartment are shorter than the height of the heat exchanger plate to provide a common fluid flow way in each longitudinal compartment over the sub-compartments. The sidewalls of the sub-compartments are progressively lowered at their upper ends in the direction of fluid flow through the flow ways.

Abstract: A durable, low-cost, heat transfer panel of the type typically employed as a solar energy collector is disclosed. The panel includes a flow channel defining structure, preferably formed as a corrugated sheet and a superimposed flexible membrane, to which manifolds or headers are secured. The manifolds have mating corrugated surfaces that are interengaged with the corrugations on the panel sheet to provide transverse rigidity to the overall panel structure as well as distribution of heat transfer fluid to and from the panel. Modified forms of the panel are disclosed in which the panel includes a selective absorber and a venting structure. A method for blow-molding the manifold into mating interengagement with the corrugated support sheet of the panel is also disclosed.

Abstract: The present invention relates to a method of forming a solar collector, or absorber, panels or a heat storage tank, suitable for heating water using solar energy. It also relates to articles of manufacture so formed and to solar water heating apparatus using said articles. Three methods of forming the panel or tank from two sheets of uncured elastic material, such as EPDM rubber, by simultaneously bonding and curing such material around the peripheral edges of the two sheets and at spaced apart, discrete areas over most of the interior areas of the sheets. In one form of the method, one of the sheets is coated with a layer of release agent, over all areas except the discrete areas and the peripheral areas so that only such uncoated areas will bond during cure. In another form, a sheet of non-adherent plastic slightly smaller than the two sheets and having holes or holidays to form the discrete areas is bonded between the two sheets.

Abstract: Device for cooling semi-conductors wherein the cooler has an external surface for bearing against the cooled element. The cooler is characterized by an internal chamber having a plurality of spaced apart cooling studs.

Abstract: An intravenous fluid warmer includes an electrically heated warmer module receiving a low volume (10 ml.) disposable cartridge through which the fluid being heated flows. The module is configured as two spaced concentric elongated metallic heating elements having attached electric heaters and defining therebetween an elongated plenum adapted to receive the disposable cartridge. The temperature of the heating elements is individually monitored by separate sensors and an electronic temperature control module maintains the inner heating element at a slightly higher temperature (36.degree. C.) than the temperature (34.degree. C.) at which the outer heating element is maintained. The inner heating element is free floating through a limited range to accommodate manufacturing differences is the disposable cartridge. The cartridge, made of polystyrene or polycarbonate plastic, nests in the plenum in contact with the heating elements.

Abstract: The invention relates to a method and apparatus for heat exchange, especially for cooling at solid surfaces. At the solid surfaces, a locally uniform convective heat exchange is achieved. According to the invention, a sink flow is superimposed on a circular flow of a fluid in a flow chamber (1) at a surface of a heat-conducting solid wall (9) by means of a distributor, forming a vortex sink flow. The heat exchange surface of the component (9) to be cooled is at the same time the base plate (8) of a flow chamber (1).

Abstract: The sides of a heat exchanger unit are joined with perimeter flanges which are folded one over the other and then crimped tightly in such fashion as to cause adjacent portions of the perimeter to extend at different angles in different planes resulting in a scissor action therebetween effective to securely clamp the heat exchanger sides together and form a leak-proof chamber.

Abstract: A heating unit (10) transfers energy via vaporized working fluid exclusively. The unit operates at sub-atmospheric pressure and a unique heat transfer apparatus (84) is provided to serve as an energy absorber panel (12) and/or a heat exchange unit (44). Since vaporized working fluid is utilized to transfer energy several hundred times the amount of energy can be transferred per unit weight of working fluid as compared to systems which transfer energy via liquid working fluid. Thus, a minimal amount of working fluid can be utilized. The heating unit (10) is constructed so as to prevent the delivery of working fluid to the interior cavity (18) of the energy absorber panel (12) in response to the working fluid within the cavity (18) reaching a selected level. Vapor is conducted from a location in the cavity (18) above that selected level to the heat exchange unit (44).

Abstract: A counterflow evaporative heat exchanger employs parallel vertical uninterrupted coil containing sections having the sides thereof arranged to increase the area of liquid contact within the tubes, the smooth flow of a liquid film on the outside of the tubes, and to increase the impingement of gases against the outsides of the tubes thereby providing smooth liquid flow the full vertical length of each section and permitting the use of maximum air velocity with turbulence but with a minimum of liquid entrainment in the gas stream, thereby enhancing cooling of the internal liquid and reducing the space required for the coil assembly.

Abstract: A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet.

Abstract: A solar collector comprises a solar radiation absorbing surface, a transparent cover over but spaced from the absorbing surface, and a convection and heat radiation suppressing structure occupying at least part of the space between the absorbing surface and the transparent cover. The convection and heat radiating suppressing structure includes a self-supporting structure comprising at least two thin, corrugated transparent foils placed on top of each other in contiguous relationship such that they form a system of long narrow ducts between adjacent foils, the ducts extending substantially parallel to the absorbing surface. Provision is made for providing heat carrying fluid within the space between the absorbing structure, and the cover, including within the ducts between the foils.

Abstract: A solar heating roof shingle roof structure which combines the functions of a roof and a fluid conducting solar heating panel. Each shingle is a hollow body of the general size and configuration of a conventional shingle, and is provided with a fluid inlet and a fluid outlet. Shingles are assembled in a normal overlapping array to cover a roof structure, with interconnections between the inlets and outlets of successive shingles to provide a fluid path through the complete array. An inlet manifold is contained in a cap used at the peak of the roof and an outlet manifold is connected to the lowest row of shingles.

Abstract: A system for collecting solar heat energy includes a plurality of shingle members arranged in shingle fashion on the roof of a stucture or building. Each shingle member is formed of a web of waterproof material which is folded and seamed to define a flat, water-containing cavity therein. Each shingle member includes a flange extending on at least two sides thereof for securing the shingle member to the sub-roof by nails or the like. At least one fluid inlet coupling and fluid outlet coupling is secured to the shingle member in flow communication with the cavity. The fluid coupling members are disposed so that the shingle members may be partially overlapped and connected in open flow communication to the superjacent and subjacent shingle members.

Abstract: A solar heating panel utilizing an improved panel member construction to increase the strength and heat transfer capacity of the panel. The panel has upper and lower layers of individual interconnected panel members, with the panel members in the upper layer including a pair of spaced outwardly extending leg portions and a bight portion therebetween having a plurality of spaced longitudinal fins formed therein extending downwardly into the panel members of the lower layer. A sheet of transparent material overlies the upper layer of panel members. Air flowing in the channels of the lower layer of panel members absorbs heat collected from the sun in the upper layer of panel members, with the fins aiding in transferring heat from the panel members in the upper layer to the panel members in the lower layer, while rigidifying the entire panel structure.

Abstract: The invention relates to heat exchange devices for cooling the wall and the refractory of a blast-furnace. Such a device comprises a body shaped substantially as a body of revolution and having first and second end walls and a curved wall extending therebetween, the first end wall being a heat-transfer wall, a supply port and a discharge port for heat-transfer fluid, the ports being spaced-apart radially, the supply port being adapted for tangentially supplying the heat-transfer fluid into the body and the discharge port being adapted for tangentially discharging the heat-transfer fluid from the body, so that, in use, the fluid flows between the ports in a spiral path over the inner surface of the first end wall, the body having no internal obstacle to such flow. (FIG.

Abstract: Method and apparatus for evaporation cooling in metallurgical furnaces. In order to prevent the formation of heat-insulating layers of vapor, over a large area, between the heat exchange surface (14) and the cooling fluid supplied thereto, the cooling fluid is supplied at a plurality of positions which are distributed over the surface, and the amount of fluid supplied is so restricted that a closed film of fluid covering the entire heat exchange surface (14) can no longer be formed. The fluid is guided to the heat exchange surface (14) by fluid guide means which are in the form of pin members or plates, or by way of a loose filling of particles, which communicate with the heat exchange surface (14) (FIG. 2).

Abstract: A heat-transfer panel or sheet material comprises a woven wire mesh core of high thermal conductivity metal, for example copper or nickel, embedded in a closure layer of plastics material, for example a urethane, so that the mesh and the closure layer extend in the same longitudinal direction. The mesh core defines a nodal network and the nodes are located at or closely adjacent the outer surfaces of the closure layer so that satisfactory heat transfer between opposite sides of the panel is achieved over the whole outer surface area of the panel by virtue of heat conduction by the mesh core.

Abstract: A plate heat exchanger is provided which includes a plurality of plates mounted in abutting face-to-face relation. Interposed adjacent plates is a sealing gasket. The plates are held in assembled relation by an adjustable press. Each plate is provided with an extruded first section having second sections secured to opposite peripheral segments thereof. Each section is provided with broad opposed exterior surfaces. The first section has a plurality of internal passages formed therein defining first flow-paths for a first heat exchange medium. The opposed broad exterior surfaces of adjacent plates coact with the sealing gasket to define second flow-paths for a second heat exchange medium. The pressure exerted on the plates by the press to maintain same in abutting relation is determined by the maximum pressure generated by the second heat exchange medium within the second flow-paths during operation of the plate heat exchanger.

Abstract: A heat exchanger constructed from a plurality of stacked modules, each module having closed channels for high pressure flow and fins extending vertically up and/or down from the channels which form open channels suitable for low pressure flow when the modules are stacked parallel along their length.

Abstract: A heat exchanger module, such as a solar collector module, comprising a tube sheet (3) connected to a header (4). The tube sheet (3) passes through an opening in the header (4) so that the end of the sheet (5) protrudes a distance into the header (4), the header opening being united to the surface of the tube sheet (3) so that the tendency of the tube sheet (3) to burst or split open in the region of the junction of the tube sheet and header is minimized when the module is under fluid pressure. By the term "tube sheet" is meant a substantially planar sheet having an upper and a lower plastic membrane interconnected by a series of spaced division walls thereby forming a series of tubes arranged generally in a flat plane across the sheet, the tubes being continuous through the sheet and open at the two opposite ends of the sheet. The term also includes a sheet of circular tubes joined in side-by-side relationship.

Abstract: A protective device is provided for heat emitting structures including but not limited to exhaust manifolds for internal combustion engines. A protective device comprises a double-wall protective screen consisting of two metal sheets which are spaced apart and substantially parallel. The space between the metal sheets is bridged over to support these sheets against each other. The sheets are sealingly connected along their edges so that they enclose between the support points at least one coolant space connected to at least one coolant connection arranged on the edge of the protective screen.

Abstract: A heat pump for building-interior heating purposes comprises an outdoor heat exchanger with which heat is abstracted from air forced exclusively by wind currents through the heat exchanger. The heat exchanger comprises a spatial array of heat exchange elements forming a grid through which the wind-displacement can pass and around which the air is in contact with the elements, the grid being open in all compass directions to the air flow.

Abstract: The invention relates to a plate heat exchanger, which comprises a plurality of plates (1) arranged to the side of each other, each plate consisting of two metal sheets (2,3), which are welded one to the other along two parallel edges and have longitudinal bulgings in parallel with said edges. The invention has the object to produce a plate heat exchanger where the medium flowing within the plate is guided in a direction in parallel with the extension of the bulgings and back in the same direction. Each plate (1) is formed with a turning zone in that the bulgings in pairs meet in such a manner, that in the sheet plane two outermost bulgings meet along a semicircle line, thereafter the two bulgings next to the outermost ones, a.s.o., and the number of bulgings is an integer number.

Abstract: A welding seam back-up structure for mounting on the backside of the adjacently positioned edge margins of work members or workpieces that are to be joined by a weld seam, in which an elongate back-up tape of fiberglass or other suitable material is retained in a position bridging the backside of the edges to be joined, by means of an extrusion back-up tape holding structure having high heat conductivity characteristics and in one form is fabricated with at least one surface recess for receiving the back-up tape, the recess having a central longitudinal generally arcuate groove for conforming the backside weld bead, and longitudinally extending heat radiating fins. In another form, the extrusion is provided with a cover which coacts with the fins to provide a flow passage for a coolant fluid. In another arrangement the extrusion is reversible and has back-up tape receiving recesses on opposite sides.

Abstract: The collector comprises two thin stamped metal sheets, joined together by welding at their periphery, between which flows a heat-carrying liquid and is characterized in that said metal sheets are stamped with repetitive patterns whose concave surfaces are disposed opposite each other, but with staggering in their plane equal to approximately half a pitch, and in that the flat unstamped parts of said metal sheets are joined together by spot welds disposed substantially symmetrically and evenly in relation to said patterns.This collector is capable of resisting high pressures of the heat-carrying liquid.

Abstract: The present invention relates to a heat exchange unit for cooling oil or other fluids.

Abstract: A rigid, lightweight, base for a portable laser system, the base including a heat exchanger for dissipating heat conducted thereto from the laser system.

Abstract: A solar panel unit for heating circulating fluid has a plurality of preferably rectangular lenses for focusing and concentrating the sun's energy onto a heat-absorbing body through which a heat-exchange fluid is circulated.

Abstract: A condenser characterized in that a pair of heat transmitting surfaces having opposed longitudinal grooves are arranged with the ridges of the longitudinal grooves contacted with or closely adjacent to each other to define steam passageways by said opposed longitudinal grooves so that the condensate in the opposed longitudinal grooves is collected in the contacted regions or between the closely adjacent regions by surface tension and allowed to flow down.

Abstract: A hot water radiator intended mainly for heating domestic and office spaces. The radiator consists of two main components (10,20) with a first main duct (1) for introducing hot water and a second main duct (2) for removing cooled water as well as of a number of radiator ducts. The radiator ducts are formed and bounded by plane surfaces (11,21) and indentations (12-19,22,23) in the main components. These indentations are short both by comparison with the main ducts and with the distance between the main ducts. The main ducts with plane surfaces, indentations and main ducts can be produced by pressing or rolling plane metal sheets. The main components can be joined with one another by seam-welding and sportwelding. The hot water radiator is intended for connection (13,14) to a central heating system which supplies the heated water and removes the cooled water.

Abstract: A refrigerated shelf for a food display counter comprising a sheet of metal having an upper surface for supporting chilled food items and a cooling coil at the underside of the shelf, the coil being adapted for the flow of coolant therethrough for cooling the shelf. Heat transfer means in heat-exchange relation with the coil and the underside of the shelf is provided for effecting a substantially uniform temperature condition throughout the upper surface of the shelf.