Abstract: An economically formed tube of rectangular or oval-like cross section and with a corrugated internal fin includes spaced, relatively long side wall sections joined at their ends by relatively short end wall sections. An integral fin within the tube has crests and valleys defining a plurality of flow paths within the tube and is formed of a corrugated section of a strip employed to form one of the side walls and at least part of both of the end walls.

Abstract: A tube assembly for cooling an incoming fluid stream and destroying pollutants contained therein comprises a tube with a catalytic coating on its inner wall and an arrangement for disrupting laminar flow of the fluid stream as it transits the tube, thereby causing turbulence which increases mass transfer between the gas phase and the catalyst-coated inner surfaces. One embodiment comprises an axially inserted turbulator that is segmented by one or more axially directed cuts, each segment rotated by an offset angle with respect to an adjacent segment, and optionally coated with the catalytic coating. Another embodiment comprises sets of opposed dimples, each set separated from its adjacent set by a linear distance and an axial angle. Such tube assemblies may be advantageously employed in aircraft environmental control systems for conditioning cabin air.

Abstract: A folded multi-passageway flat tube is disclosed, which is made from a flat sheet metal strip and has folded webs and a longitudinal seam. Through-openings for improving the heat transfer and for generating transverse flow are provided in the folded webs. The through-openings are advantageously made by punching in the flat sheet metal strip, that is to say before folding, and are made congruent after folding. These folded multi-passageway flat tubes are preferably used for refrigerant condensers in motor vehicle air-conditioning systems.

Abstract: A flow translocator disposed within a conduit for transferring and separating laminar fluid flow during translocation of the fluid core to the outer perimeter of the conduit and the outer perimeter flow to the center of the conduit. The flow translocator includes a disk disposed transverse the length of a conduit and having an outer profile conforming to the inner profile of a conduit to form a sealed fit. Arrays of slots extend about the disk for simultaneously directing the fluid core to the inner profile of a conduit and the outer perimeter flow toward the fluid core. The slots are staggered to maintain separation of the fluid core and the outer perimeter fluid during translocation.

Abstract: A liquid-cooled heat sink for use in combination with a heat exchanger to cool electronic or electrical devices attached to said heat sink comprises a metal block having a plurality of circular passageways therethrough defined by cylindrical walls. An inlet is in fluid communication with one end of the passageways for receiving a cooling liquid, and an outlet is in fluid communication with an opposite end of the passageways for outputting the cooling liquid. At least one tape insert is mounted within at least one of the circular passageways, wherein the tape insert longitudinally bisects the circular passageway and further wherein edges of the tape insert abut cylindrical wall.

Abstract: A means for thermal maintenance of industrial pipe by virtue of a working medium passing through at least one prefabricated hollow element attachable to the outside surface of the pipe wall is disclosed. The hollow element comprises an outer cover defined by an inner portion, facing the external surface of the pipe wall, an outer portion, situated opposite the inner portion and facing outwardly and transition portions connecting the inner portion with the outside portion. The inner portion is provided with concave configuration defined by radius R1 and closely matching the curvature of the pipe. The inner portion encloses about 180 degrees of the pipe's external surface and the transition portions are rounded by radius r, wherein r<R1.

Abstract: A shell and tube type heat exchanger-evaporator for applications involving vapour-liquid separation and evaporation of refrigerants has a plurality of heat exchange tubes provided with an internal baffle that converts the straight tube channel of a standard heat exchange tube into two semi-circularly sectioned spiral channels. The two spiral channels define a spiralling flow path for the vapour generated in the heat exchange tube from a boiling liquid. The generated vapour flows through the two spiral channels with increasing velocity driving the unevaporated boiling liquid in a spirally rotating film of diminishing thickness over the whole internal wall of the heat exchange tube increasing the heat exchange capacity of the heat exchange tube.

Abstract: A thermoformed PVC, modified PVC, CPVC, metal or coated metal cover, covering system and method is provided for covering assemblies of pipe and pipe insulation, hangers, support rods and mechanical assemblies wherein the assembly is biocide treated, covered by and completely enclosed by the cover, the cover is sealed in order to prevent bacteria growth within the cover while allowing a smooth outside surface for biocide application. The cover can be modified to facilitate the application of biocide after the assembly is covered by providing resealable openings in said cover.

Abstract: The invention relates to a method for producing gilled metal pipes (1). According to said method, at least one continuous, gill-forming strip (4) is applied to a rotating pipe body (2) at a tangent and unwound onto the pipe body in an approximately helical line. The side of the strip facing towards the pipe body (2) is connected to the pipe surface by means of a welding device (8), using an additional material. The welding process is optimised and the finishing quality increased by moulding a web that is bent at right angles to the strip that forms the gills before said strip is unwound onto the pipe body (2). The strip is preferably bent into a U-shape and the web, which runs between the two limbs of the U-shape, is guided flatly on the pipe body.

Abstract: This invention relates to a pipe (1) having several internal ribs (2, 3, 4) having a spiral twist, where the ribs run with rotational symmetry with the longitudinal axis (5) of symmetry of the pipe (1). This invention creates a heat transfer pipe that will be characterized by a much better heat transfer in comparison with the previously known pipes having internal ribs, and to this end it guarantees not only an increase in the internal heat transfer surface area but also an effective cross-flow between the inside wall surface of the pipe and the core flow near the longitudinal axis of symmetry. To that end, the free ends (2c, 3c, 4c) of the internal ribs (2, 3, 4) are a distance (a) from the longitudinal axis (5) of symmetry of the pipe (1), which is in the range of 1:12 to 1:3 in relation to the inside diameter (d) of the pipe; and all the internal ribs (2, 3, 4) run in the same direction (arrow 6) and with the same spiral length (L) with a spiral twist to the longitudinal axis (5) of symmetry.

Abstract: A heat exchanger tube, having at least one twisted baffle therein, each of said twisted baffles extends in the inside of the heat exchanger tube along the axis thereof, said twisted baffles extends as long as at least a part of the entire length of said heat exchanger tube, and said twisted baffles are integrated with the inner surface of said heat exchanger tube. The twisted angle of said twisted baffles is between 100° to 360°. The ratio between the axial length of said heat exchanger tube with the twisted angle 180° of said twisted baffles and the internal diameter of said heat exchanger tube is 2 to 3. The thickness of said twisted baffles is approximated to that of said heat exchanger tube; in every cross section of said heat exchanger tube, the transition zone from the surface of said twisted baffles to the surface of said heat exchanger tube, and vice versa, is in the shape of a concave circular arc.

Abstract: A process for deposition and condensation and reaction and separation and distillation employing at least two chambers separated by a diaphragm with at least one separation wall and at least one orifice or flow duct or plurality thereof, said process providing a controlled and stationary conveyance capacity of an uncondensed intermediary phase for a product or by-product with a controlled concentration, structure or microstructure, for example, said conveyance capacity relying on a controlled pressure of an atmosphere in the at least two chambers on both side of said diaphragm and on a novel diaphragm and condenser technology and a temperature control of one or more chamber walls or said diaphragm or parts of said diaphragm being transversed by said uncondensed intermediary phase.

Abstract: A steam generator is formed by a plurality of similar heat accumulator units stacked vertically. Each heat accumulator unit of the stack has an orientation different than any adjacent heat accumulator unit so that multiple heat accumulator elements of the each heat accumulator unit align with respective open spaces of any vertically adjacent heat accumulator unit.

Abstract: The present invention relates to a device for the heat insulation of at least one underwater pipe (1) intended to be laid on the sea bed at great depth, comprising an insulating coating surrounding the latter and a protective envelope (3), characterized in that said insulating coating comprises a virtually incompressible liquid/solid phase change material (4) with a melting temperature T0 higher than that T2 of the medium surrounding the pipe in operation and less than that T1 of the effluents circulating in the pipe, and said material (4) preferably being impregnated in an absorbent matrix (2) surrounding the pipe (1), preferably nearest its outer surface, which protective envelope (3) is resistant and deformable and ensures a containment against and about said insulating coating.

Abstract: A fluid conveying tube for a vehicle cooler comprises at least two longitudinal ducts, each comprising two opposite, longitudinal primary heat exchange surfaces. At least one primary surface in each duct of the tube has a projecting surface structure. In a method of manufacturing such a tube, starting from a blank, use is made of a device, which has a feeder for feeding the blank through the device and a surface forming station for forming the surface structure on a portion of the blank surface. Furthermore, the device comprises an edge forming station for forming two opposite edges of the blank into two upright edge portions, which between themselves define an at least partly essentially flat web portion. In addition, the device comprises a duct forming station for making the edge portions abut against each other and against the web portion with a view to defining said ducts.

Abstract: A means for thermal maintenance of industrial pipe by virtue of a working medium passing through at least one prefabricated hollow element attachable to the outside surface of the pipe wall is disclosed. The hollow element comprises an outer cover defined by an inner portion, facing the external surface of the pipe wall, an outer portion, situated opposite the inner portion and facing outwardly and transition portions connecting the inner portion with the outside portion. The inner portion is provided with concave configuration defined by radius R1 and closely matching the curvature of the pipe. The inner portion encloses about 180 degrees of the pipe's external surface and the transition portions are rounded by radius r, wherein r<R1.

Abstract: An integral ceramic insert for a radiant tube. The insert has a helical shape and contains ceramic material; and it has a thermal expansion rate of less than 6.0×10−6 meters/meter/degree Celsius and a thermal conductivity of at least 0.2 calories/centimeter/second/degree Celsius. The diameter of the insert is from about 2 to about 10 inches, and it has a length such that the ratio of its length to its diameter is from about 2/1 to about 8/1. The helical shape of the insert contains one or more pitches of from about 2 to about 32 inches, each which defines a helix angle of from about 15 to about 80 degrees.

Abstract: A heat exchanger tube, having at least one twisted baffle therein, each of said twisted baffles extends in the inside of the heat exchanger tube along the axis thereof, said twisted baffles extends as long as at least a part of the entire length of said heat exchanger tube, and said twisted baffles are integrated with the inner surface of said heat exchanger tube. The twisted angle of said twisted baffles is between 100° to 360°. The ratio between the axial length of said heat exchanger tube with the twisted angle 180° of said twisted baffles and the internal diameter of said heat exchanger tube is 2 to 3. The thickness of said twisted baffles is approximated to that of said heat exchanger tube; in every cross section of said heat exchanger tube, the transition zone from the surface of said twisted baffles to the surface of said heat exchanger tube, and vice versa, is in the shape of a concave circular arc.

Abstract: A heat exchanger is constructed by tubes, corrugated fins and head pipes, which are assembled together. Herein, the tube is constructed by bending a flat plate whose surfaces are clad with brazing material to form a first wall and a second wall, which are arranged opposite to each other with a prescribed interval of distance therebetween to provide a refrigerant passage. Before bending, a number of swelling portions are formed to swell from an interior surface of the flat plate by press. By bending, the swelling portions are correspondingly paired in elevation between the first and second walls, so their top portions are brought into contact with each other to form columns each having a prescribed sectional shape corresponding to an elliptical shape or an elongated circular shape each defined by a short length and a long length.

Abstract: A process solution supplying mechanism for supplying a process solution to a wafer, comprises a source for containing the process solution, a pipe for introducing the process solution from the source to the wafer, a process solution supply driving system for supplying the process solution from the source to the wafer, and a process solution supplying/stopping mechanism for carrying out apply and stop of the process solution, wherein the pipe and the process solution supply driving system are provided separately and the process solution supplying/stopping mechanism is provided to a portion other than the pipe.

Abstract: A new flash tube device adapted specifically for use with hot erosive flow streams is provided. This flash tube uses an extension cone fixed to the outlet of a choke to create an extension choke to insure that the shock wave occurs within the extension choke, thereby decreasing the flow velocity to a subsonic level, reducing the kinetic energy of the flow as it leaves the extension choke. By moving the shock wave into the extension choke, this device dramatically improves the working life of the flash tank, allowing for easier separation of fluid/solids and vapor in the flash tank.

Abstract: In the method and apparatus of making a header pipe, the end faces of the edge portions of a flat plate, which have been respectively cut into a given shape according to a trimming operation, are then respectively face-struck into a linear shape. Also, in the trimming operation, each of the edge portions of the flat plate is cut into a shape having a larger dimension than that of a finally required shape thereof, and the thus produced excess length portions of the edge portions are worked by compressing when a pair of semidivided cylindrical portions are butted against each other. Since a connecting portion situated between the pair of semidivided cylindrical portions is always pressed with a given pressure, the working properties of the connecting portion in the molding operation are prevented from being revived.

Abstract: The present invention provides a system and method for actively manipulating and controlling aerodynamic or hydrodynamic fluid flow over a surface. More specifically, the present invention provides a system and method to control aerodynamic or hydrodynamic fluid flow behavior of a ducted fluid flow using very-small-scale effectors. The system and method for actively manipulating and controlling fluid flow over a surface includes the placement of arrays of very-small-scale effectors on ducted surfaces bounding the ducted fluid flow. These very-small-scale effectors actively manipulated the boundary layer manipulated to control the flow behavior of the ducted fluid flow and suppress or prevent flow separation within the primary fluid flow.

Abstract: A multichannel flat tube for a heat exchanger has a plurality of parallel flow channels aligned in a row, side by side, along a transverse axis of the tube. At least the inner flow channels have oval cross-sections, and major semiaxes of the inner flow channels are inclined relative to the transverse axis of the tube at an acute angle. The flat tube can be designed for high operating pressures with relatively low weight and relatively high heat exchange capability. The construction may be used, for example, in CO2 air conditioners in motor vehicles.

Abstract: A method and an apparatus for heating or cooling material having poor thermal conductivity, especially medium-consistency fiber suspensions. The material is directed, substantially as a plug flow, at a velocity below 5 m/s (e.g. 0.1-1 m/s) through an apparatus formed by a flow channel provided with heat exchange surfaces. The flow of the material is throttled at a throttling point by a more than 30% reduction in the cross-sectional area of the channel. After throttling, the material is discharged from the throttling point in such a manner that another portion of the material contacts the heat exchange surfaces.

Abstract: The present invention relates to heat exchange elements and heat exchange assemblies and water heaters containing such heat exchange elements. The inventive heat exchange elements include an elongated support member or spine, from which extends either a single vane which is the length of the support member of a series of vanes. The heat exchange element is able of be positioned parallel to the longitudinal axis of a flue. The heat exchange element may impart helical motion to the flue gases in one embodiment, but in another embodiment no helical motion is imparted to the flue gases. The embodiment of the invention includes several methods of manufacture of the heat exchange elements. The embodiments of the water heater and heat exchange assembly also disclose the use of a baffle for use in association with the elements, to improve the efficiency of the elements at the upstream end of the water heater.

Abstract: A heat exchanger tube, having at least one twisted baffle therein, each of said twisted baffles extends in the inside of the heat exchanger tube along the axis thereof, said twisted baffles extends as long as at least a part of the entire length of said heat exchanger tube, and said twisted baffles are integrated with the inner surface of said heat exchanger tube. The twisted angle of said twisted baffles is between 100° to 360°. The ratio between the axial length of said heat exchanger tube with the twisted angle 180° of said twisted baffles and the internal diameter of said heat exchanger tube is 2 to 3. The thickness of said twisted baffles is approximated to that of said heat exchanger tube; in every cross section of said heat exchanger tube, the transition zone from the surface of said twisted baffles to the surface of said heat exchanger tube, and vice versa, is in the shape of a concave circular arc.

Abstract: A profiled tube (50b) comprising a high carbon content alloy (greater than 0.3%), superalloy or other high creep strength material, has a fluted bore with internal fins (52b) and intervening valleys or troughs (56b). Such a tube is made by centrifugal casting and subsequent electrochemical machining by drawing of an electrode (104) along the tube while at the same time passing electrolyte along the tube and around the electrode and also applying an electrical current between the tube and electrode, so that material of the tube passes into solution in the electrolyte.

Abstract: A flow conduit includes surface-enlarging members for cooling fluid in the flow conduit. The surface-enlarging members include cooling blades that extend outwards and downwards from the surface of the flow conduit.

Abstract: In the reaction process, at least two educts A, B are divided by a system, assigned to each of them, of slit-like microchannels 1a, 1b into spatially separate fluid lamellae, which then emerge into a common mixing and reaction space 4. The fluid lamellae here have a thickness <1,000 &mgr;m, preferably <100 &mgr;m, at a width thickness ratio of at least 10. It is essential here that educts A, B can emerge as thin fluid lamellae 6a, 6b into the mixing/reaction space 4, each fluid lamella 6a of an educt A being led into the mixing/reaction space 4 in the immediate vicinity of a fluid lamella 6b of another educt B. The adjacent fluid lamellae 6a, 6b then subsequently mix by diffusion and/or turbulence. As a result, the mixing operation is accelerated substantially compared with conventional reactors. In the case of rapid chemical reactions, the formation of undesirable by-products or secondary products is largely prevented in this manner.

Abstract: An insert for a radiant tube comprised of an oxidation resistant metal alloy or a refractory material.

Abstract: A water heater includes a water tank, a combustion chamber below the tank and communicating with the flue tube, and a flue system. The flue system includes a flue tube, and a cruciform fin metallurgically bonded to the flue tube wall and dividing the flue tube into four flue chambers extending substantially parallel to the longitudinal axis of the flue tube. The flue system also includes a removable baffle hanging in each flue chamber. The baffles include adjustable turbulation surfaces to control the quality of combustion in the water heater.

Abstract: A microstructures lamellae mixer comprising a guide component for supplying fluids to be mixed to a mixing chamber, the guide component being composed of a plurality of foils which are layered one above the other and into which microchannels are incorporated such that separate fluids supplied to the guide component are formed into spatially separated microstreams which then emerge adjacent to each other in a mixing chamber.

Abstract: A heat pipe has an elliptical cross-section. Heat exchange fins are mounted to the heat pipe at the condenser end. The fins are galvanized on the heat pipe. Spacer pins can be used to support and space the heat exchange fins from each other. Internal spacers can be provided within the heat pipe to add support to the heat pipe structure for longer heat pipes.

Abstract: The invention concerns a device for limiting the bending radius of a flexible duct comprising at least a bend stiffener arranged around one length of the flexible duct and fixed by a rear part on a fixed end support, characterized in that it further comprises an element for maintaining the bend stiffener arranged between the flexible duct and the bend stiffener and comprising at least a portion capable of flexural bending extending over one length of the flexible duct located at least between the rear part and the end of the bend stiffener.

Abstract: A flow duct for the passage of a two-phase flow which has a liquid and a gaseous phase is described, comprising an inner wall completely enclosing the two-phase flow radially to the direction of flow. The invention is distinguished by the fact that raised contours are provided on the inner wall of the flow duct, and these raised contours are attached to the inner wall essentially perpendicularly to the direction of flow and are at a distance from one another in the direction of flow.

Abstract: A mold insert for an injection molding machine has a circumferential liquid conduit groove and a plurality of liquid-receiving bores extending inwardly from the groove. Baffles are removably inserted into the liquid-receiving bores and have heads located in locking engagement with the sidewalls, including the undercut portions thereof, to retain the baffles in their respective liquid-receiving bores. Each baffle has a blade that fits snugly within a liquid-receiving bore to separate the liquid-receiving bore into a liquid inlet passageway and a liquid outlet passageway. Fins project outwardly from opposite faces of the blade to create turbulence in liquid flowing into and out of the liquid-receiving bore, which enhances cooling (or heating) of the mold insert. The baffle is also useful with other solid components having a liquid conduit for cooling purposes and a transverse liquid-receiving bore intersecting the liquid conduit.

Abstract: Safety-enhanced steam tracing includes a metallic tube with a thin jacket of polymeric material, such as silicone rubber. The polymeric jacket is typically about 40 mils to about 60 mils thick. The safety-enhanced steam tracing provides a substantially lower risk of burn injury than bare metal steam tracing, yet its conductance performance is about the same as that of bare metal steam tracing.

Abstract: A heat exchanging device is disclosed. The device includes a fluid flow tube having a turbulator which includes a plurality of coil sections. Each of the coil sections includes a number of coil members of uniform diameter. The coil sections are spaced apart by a predetermined number of other coil members having smaller diameters and different heights than the coil members in the coil sections. These coil configurations force fluid flowing around them into heat exchanging contact with the tube walls.

Abstract: A device for enhancing the mixing and uniform distribution of fluids within a conduit. The device includes a core pipe which can optionally receive a first fluid and series of helically wound vanes wrapped about the core pipe employing the core pipe as a mandrel. Fluids entering the conduit are mixed by virtue of passing over and about the helically wound vanes while heat transfer can be effected by heat passing between the mandrel and the fluid passing over the vanes. Ideally, the vanes are wrapped about the mandrel at an angle of approximately 45.degree. thereto and adjacent layers of vanes are wrapped about the mandrel at opposite signs so that interstices are ideally created between vanes of approximately 90.degree..

Abstract: A counterflow evaporator for refrigerants, in particular for zeotropic refrigerants, where elongated inner members are inserted in the elongated tubular members of the evaporator to form an annular passage through which the refrigerant can flow. Resilient support members maintain the elongated inner members in position within the elongated tubular members.

Abstract: A process for mounting lugs or projections on a thin metal sheet, by forming the lugs and/or projections out of the thin metal sheet by way of massive forming. Such a thin metal sheet in the form of a thin sheet metal strip is used preferably for forming rectangular tubes for an exhaust gas heat transfer device which, for guiding the exhaust gas, is provided with a bundle of these rectangular tubes.

Abstract: The heat exchanger tube comprises a cylindrical, smooth walled outer tube (1) of steel into which a profiled insert (2) of aluminium is inserted. The profiled insert is constituted by two half shells (3,4) which engage in one another at their longitudinal edges with groove-shaped recesses (7) and rib-like projections (8). Both half shells (3,4) carry longitudinally extending ribs (5) on their internal surface which are so aligned that each half shell with its ribs constitutes a profile which is open on one side.

Abstract: The present invention provides apparatus, systems, and methods related to the manufacture of integrated circuits. Specifically, embodiments of the present invention include apparatus designed to provide thorough and reliable fluid mixture for gases used in a semiconductor processing system. In one embodiment of the invention, the gas mixing apparatus comprises a gas mixer housing having a gas inlet, a fluid flow channel, and a gas outlet. The fluid flow channel is fluidly coupled to a plurality of gas sources. The majority of the gas mixture occurs in the fluid flow channel which comprises one or more fluid separators for separating the gas into two or more gas portions and one or more fluid collectors for allowing the gas portions to collide with each other to mix the gas portions. This separation and collection of the gas portions results in a thoroughly mixed gas.

Abstract: The invention concerns a process for manufacturing ribbed tubes, wherein a stainless steel tube is provided with ribs by helicoidally winding a copper strip around it, and a ribbed tube thus manufactured. In joining the tube and rib, the unmelted copper strip is set on the tube surface edgewise into a melted area produced by a laser beam exclusively on the tube surface, thereby bonding the strip onto the tube by the solidification of the melted tube material. In this manner ribbed tubes can be provided, featuring an internal tube made of corrosion-resistant stainless steel and a helicoidal rib made of copper for increasing the heat exchange surface of the tube, which is distinguished by high thermal conductivity.

Abstract: A process for fabricating a low cost high efficiency liquid cold plate is described. The process uses a metal extrusion designed with internal fluid channels. A simple process for fabricating fluid inlet and outlet manifolds, creating turbulent flow inside the fluid channels, a method for capping the extrusion ends, and a method for improving the surface contact with heat generating components is described.

Abstract: A stationary material mixing apparatus for mixing various components in a fluid stream. The mixing apparatus is in the form of a cone-shaped module containing a plurality of openings therethrough where within the openings are located mixing elements which induce a rotational angular velocity to the fluid stream. As preferred embodiments, the mixing apparatus, located within a conduit, can also contain a biscuit with further mixing elements and a series of either helically wound tubes or vanes further enhancing the mixing operation.

Abstract: A multilayer metal sheet-polymer composite wherein the multilayer metal sheet side provides heat resistance and heat protection for the polymer side. The multilayer metal sheet component preferably comprises aluminum or stainless steel foils bonded to the polymeric component to form articles such as, conduits, panels, equipment housings and cooking devices.

Abstract: Stiffener designed for fitting to a piping consisting of a flexible conduit for use in a marine environment, carying a hot fluid, the said stiffener comprising a flexible casing located at least partially over the said flexible conduit, having structure (15) for dissipating the heat at the interface between the stiffener and the flexible conduit (3).

Abstract: Heat-exchanging conduit tubes for a laminated heat exchanger made of aluminum material containing aluminum alloy having a brazing material claded and formed by folding one plate or overlaying two plates and brazing to connect edge joints of the folded plate or the overlaid plates, wherein the folded plate or the overlaid plates have projections protruded from one or both faces of the opposed plates toward the other plate, the projections are joined in contact with a flat face of the other plate or the projections of the other plate, and the edge joints of the folded plate or the overlaid plates are joined, and the height of the edge joint of the each plate is smaller than those of the projections. Thus, the heat-exchanging conduit tubes can be securely brazed to provide flat tubes having a satisfactory pressure resistance, and a method for producing them can be attained.