Abstract: A heating apparatus for use in heating a substrate comprises an electric heater and a power supply part. The electric heater is made up of an approximately columnar body which is made of graphite, and this columnar body has a top with a flat surface part on which the substrate is placed and a pair of legs which extend downwardly from the flat surface part. The legs are defined by an opening in the columnar body. The power supplying part is coupled to the electric heater and supplies a voltage across the legs of the columnar body so that a current flows from one leg to the other, thereby generating heat at the flat surface part to heat the substrate.

Abstract: In a semiconductor device such as hybrid IC, thermal heads, etc., a thick film resistor of the semiconductor device contains a boride particle of a metal dispersed in a glass matrix, the particle having a particles size of 0.005 to 0.1 .mu.m. Generation of a thermal stress can be suppressed and the electroconductive particles themselves form isotropic electroconductive passages by such dispersion, and the semiconductor devices can have a distinguished electroconductivity. Preferable boride of a metal is LaB.sub.6, which gives distinguished resistor characteristics.

Abstract: A flat resistance for a blower control unit of an automobile air conditioner, and a blower control unit using the same. The flat resistance includes: a porcelain enameled metallic substrate including a flat head portion, having an edge and one surface, and parallel terminal supporting portions projecting outwardly from the edge of the head; a resistance circuit printed on the one surface of the head portion, the resistance circuit including a plurality of resistances electrically connected in series; a temperature fuse, interposed in the resistance circuit, for being tripped to break the resistance circuit when the porcelain enameled metallic substrate becomes overheated; and terminals, printed on both the head portion and the terminal supporting portions, each terminal being connected to one end of a corresponding one of the resistances.

Abstract: Improved, edge compensated capacitors and a method for making the same are presented. The present invention arranges individual cells of capacitors and uses passive dummy cells so as to achieve a ratio between the length of the exposed perimeters of the cells of the two capacitors that is equal to the desired capacitance ratio between the two capacitors. By doing so, the edge shrinkage effects on both cells are taken into account, and accurate capacitor ratios are maintained. In one embodiment of the invention the number of intersections between exposed edges of the cells of the two capacitors are also adjusted to conform to the capacitor ratio to achieve additional edge shrinkage compensation.

Abstract: A sheet-like ceramic substrate for tip parts is provided which can effectively prevent occurrence of a crack thereof. The ceramic substrate comprises a ceramic sheet 7 having first and second primary dividing grooves 2a and 2b and first and second secondary dividing grooves 3a and 3b formed at mutually corresponding locations of the opposite faces thereof. The depth of the dividing grooves 2a, 2b, 3a and 3b is comparatively small, and while the opposite ends of the first primary dividing grooves 2a and on one face of the ceramic sheet 7 extend to a pair of opposing sides 7b of the ceramic sheet 7, the opposite ends of the second primary dividing grooves 2b on the other face of the ceramic sheet 7 are spaced from the opposing sides 7b, and the opposite ends of the first and second secondary dividing grooves 3a and 3b are spaced from the other pair of opposing sides 7a of the ceramic sheet 7.

Abstract: A potentiometer includes a rotatably mounted lever which acts as a follower member adapted to lie in contact with a moveable finger, the movement of which the lever is to follow, the lever being biassed at all times towards the finger by resilient return means.The lever is in the form of a fork having two arms whereby it is adapted to embrace the finger. Whichever one of these arms is in the trailing position with respect to the direction of rotation in which the lever is biassed by the return means is longer than the other arm. In the embodiment described, the longer arm is an active arm, the shorter arm being a security arm.

Abstract: A nonlinear resistive surface mount device for protecting against electrical overvoltage transients which includes a pair of conductive sheets and a quantum mechanical tunneling material disposed between the pair of conductive sheets. This configuration serves to connect the conductive sheets by quantum mechanical tunneling media thereby providing predetermined resistance when the voltage between the conductive sheets exceeds a predetermined voltage.

Abstract: In a recording head for use in a recording apparatus for effecting recording on a recording medium, having a plurality of heat generating elements and electrodes for applying energy to the heat generating elements, when the effective width of the heat generating elements is Wr and the width of the electrodes connected to the heat generating elements is We, 1/10.ltoreq.We/Wr.ltoreq.1/2, and when the length, in the direction of an electric current, of the portion of the heat generating elements in which the current distribution becomes roughest and the portion of the heat generating elements in which the current distribution becomes finest is L, the condition that 1/4.ltoreq.L/Wr.ltoreq.3/2 is satisfied wherein the junctions between said heat generating elements and said electrodes overlap each other.

Abstract: A reflection-free termination of a TEM waveguide, in which a TEM wave is conducted through an inner conductor (4) and an outer conductor (1) and is absorbed at one end of the TEM waveguide by an RF absorber (5) for absorbing a field energy and by an ohmic line termination (7) for absorbing a conductor-guided energy of the TEM wave, is constructed in such a manner that the line termination (7) is located in a plane determined by the inner conductor (4) and located in the wave direction. The line termination (7) is constructed as an ohmic resistance which produces a gradual, serial damping on the inner conductor (4) and locally compensates for a capacitance loading additionally produced at the line termination (7) by the RF absorbers.

Abstract: A high-precision and high-stability resistor element, which exhibits zero, or close to zero, resistance deviation during time and in given temperature and power ranges, includes a bonded sandwich of several substrates of inorganic insulating material having a substantially zero coefficient of thermal expansion with one or more R (Resistance) and TCR (Temperature Coefficient of Resistance) trimmed resistive metal foil patterns which can be retrimmed in two directions during periodic verifications.

Abstract: Small easily removable insert designed for placement in the battery compartment of a battery powered device (becoming part of the circuit of the device when in place) which includes a current/voltage control means and may have sidewalls and dimensions which allow the replacement of a battery or batteries standard to the device by smaller sized batteries.

Abstract: An electrical resistance device includes a conductive metal pattern carried on an insulating surface. A portion of the conductive metal pattern includes a two-dimensional array of areas devoid of conductive material ("voids") within a mesh of conductive material. Typically, the voids are hexagonal and are arranged such that the adjacent edges of adjacent hexagons are parallel to each other and spaced apart a distance not more than about 0.10 in. The hexagonal voids typically are arranged so that the centers of sets of three adjacent voids lie on the corners of equilateral triangles.

Abstract: A high-speed high temperature electrical resistance heater and method of making the same, said heater being in the form of a uniquely configured composite, non-homogeneous body having an esentially electrical-conducting material and an essentially electrically insulating material, wherein one of the materials is constituted as a porous matrix, and the other of the materials permeates the matrix of the one material. The electrically-conducting material has nodes and connective threads interconnecting the nodes, and electrical connections can be made to different places on the electrically-conducting material. The method involves forming a sintered matrix and impregnating the same with a ceramic substance, then sintering the impregnated matrix.

Abstract: An overvoltage resistor formed in the substrate semiconductor material of an integrated circuit. The overvoltage resistor is formed from a resistive layer formed over a well of a semiconductor material having a conductivity type which is opposite to the conductivity type of the substrate material. The overvoltage resistor is not connected to the voltage supplies of the integrated circuit, thereby eliminating the virtual pn-diode which would otherwise be formed between the well and the substrate and allowing the overvoltage resistor to protect the integrated circuit from voltages outside the range of supply voltages.

Abstract: A coiled heating element is manufactured by providing a coiled element of bare resistance wire in which the coil pitch is not greater than twice the cross-sectional dimension of the wire. The element is stretched by an amount permitting recovery to its original configuration and an electrically insulating particulate material is applied to the stretched element. The stretched element is then allowed to return towards its original configuration thus trapping particulate material between adjacent coils of the element and the element is heated so as to oxidize the surface of the wire.

Abstract: An improved thermal ink jet printhead has a plurality of heating elements in ink channels selectively addressable by electrical signals to eject ink droplets from nozzles located at one end of the ink channels on demand. The heating elements each have a passivated layer of resistive material that has non-uniform sheet resistance in a direction transverse to the direction of ink in the channels. The non-uniform sheet resistance provides a substantially uniform temperature across the width of the resistive layer, so that the power required to eject a droplet is reduced and the droplet size dependence on electrical signal energy is eliminated.

Abstract: A thermal ink jet printhead is improved by using heating element structures which space the portion of the heating element structures subjected to the cavitational forces produced by the generation and collapsing of the droplet expelling bubbles from the upstream electrode interconnection to the heating element. In one embodiment this is accomplished by narrowing the resistive area where the momentary vapor bubbles are to be produced so that a lower temperature section is located between the bubble generating region and the electrode connecting point. In another embodiment, the electrode is attached to the bubble generating resistive layer through a doped polysilicon descender. A third embodiment spaces the bubble generating portion of the heating element from the upstream electrode interface, which is most susceptible to cavitational damage, by using a resistive layer having two different resistivities.

Abstract: A thermal ink jet head incorporates bubble-generating resistors, each with a relatively thick layer of unpassivated resistive material, such as TaAl. The thermal ink jet head includes an ink source, ink channels, respective orifices, and circuitry for providing the electrical energy which the resistors convert to heat to form bubbles which expel ink through respective orifices. A range between 3,000 .ANG. and 5,000 .ANG. is preferred for the resistive material to minimize failure rate while avoiding thermal, electrical and manufacturing limitations of passivated resistors.

Abstract: A surface mount wirewound resistor having a conventional wirewound resistor embedded in a plastic body member with terminal axial leads of the resistor being severed at the opposite ends of the body member. A U-shaped metallic terminal pad and clip is secured to the ends of the body member and is in electrical contact with the severed ends of the axial leads. The upper and lower portions of the terminal pad are in coplanar relationship with the upper and lower surfaces of the body member. An alternate surface mount wirewound resistor has metallic tabs that extend from the resistance element embedded in the plastic body member, with the tabs being bent upwardly from the ends thereof and into coplanar relationship with the upper surface of the body member.

Abstract: A thick film resistor (TFR) is provided that is capable of being compensated for impedance variations related to the TFR laser-trimming process. According to the invention, a thick film capacitor (TFC) metallization is provided in parallel with the thick film to compensate the RF impedance. A method is also provided for calculating the exact length of the TFC metallization necessary to compensate the RF impedance. Once this length (L) is known, the TFC metallization can be laser-trimmed to obtain the desired length.

Abstract: With the deployment of ISDN within a building, a resistor box is usually required, at each distribution frame, between the first and second set of cross-connect connectors in order to maintain a balanced loop. In the present invention, a quick connect terminating resistor for use with cross-connect type of connectors is disclosed. It is used for eliminating the use of the resistor box. The quick connect terminating resistor is comprised of a body having a connecting end, conductor portions on said body at said connecting end adapted to mate with a pair of terminals of said cross-connect type connector and resistor means connected to said conductor portions for providing a terminating resistance across said pair of terminals of said cross-connect type connector.

Abstract: A resistor for the treatment of materials, such as for the production of monocrystals by the planar resistor method includes an electrically conductive thin plate having a zone with a plurality of holes. With respect to an electric current flowing in the plate substantially parallel to its faces, the plate has lower electrical resistance in a peripheral area of said zone than in the central portion thereof.

Abstract: Heating devices, in which a semi-conductor pattern is carried on an insulating surface and a pair of spaced apart electrodes are electrically connected to the semi-conductor pattern, are characterized in that the semi-conductor pattern in at least one heating area of the device defines a two-dimensional array of areas that are devoid of semi-conductor material ("voids") within a continuous "mesh" of semi-conductive material. Preferably, the voids are hexagons arranged with the sides of adjacent hexagons parallel to each other, the centers of adjacent hexagons are at the corners of equilateral triangles, and the overall direction of current flow in the device is not parallel to any of the sides of the triangles.

Abstract: An electric resistance heating element for heating fluids includes a plurality of ring-shaped members made of a ceramic material having a positive temperature coefficient (PTC) disposed in concentric generally coplanar relationship, one around the other, and spaced apart from each other to form through passages for fluid flow therebetween. Electrode layers are formed at the two opposite ends of each ring and a pair of electrically conductive securing ring members are each securely soldered to a respective one of the electrode layers. Each securing ring member is integrally formed with two diametrical cross members soldered to each ceramic ring-shaped members and with each cross member having spaced grooves radially engaging and positioning the ring-shaped ceramic members. The outer periphery of each securing ring member incorporates a plurality of radially extending lugs for mounting the heating element for use and for making electrical connection between the securing ring member and a power supply.

Abstract: A resistor is provided with a plurality of turn parts whose corners have an obtuse flexional angle in order to improve the relative resistance precision. A ladder resistor can be formed with a plurality of such resistors connected in series, and various electronic devices are formed employing the ladder resistor.

Abstract: A high density resistor array mounted on a substrate is used in a balanced array. Each circuit element in the array is terminated with a resistor and with each terminating resistor being located at a uniform electrical and physical distance from its respective circuit, resulting in uniform impedances.

Abstract: A distributed wye resistor network fabricated on an integrated circuit substrate includes a resistive body coupled between two terminal elements. The resistive body includes a plurality of slots extending therethrough between the terminal elements to form a plurality of discrete resistive links. The resistive body therefore has characteristics of an artificial anisotropically conducting medium. The resistive links have a parabolic length profile. The links can be continuously cut, starting with the shortest link, until parameters of the integrated circuit are brought within desired specifications.

Abstract: Zinc oxide surge arresters are used to replace capacitive elements for voltages below the pick-up voltage of the surge arrester. Advantageously, the surge arresters may be provided in an alternating current network to provide a high degree of protection against transient disturbances without increasing cost.

Abstract: A ceramic heater for regenerating a fine particle collecting filter which is exposed to exhaust gases at elevated temperatures. This ceramic heater comprises two electrode potions, a heat generation portion connected to the two electrode portions and a holding projection portion of a ceramic heater connected to the side of the heat generating portion. The two electrode portions, the heat generating portion and the holding projection portion are formed integrally.

Abstract: A planar heat generating resistor has a heat generating resistor layer formed on or above a support member and a pair of opposing electrodes formed on the heat generating resistor layer, such that a width of the heat generating layer at the electrode area is larger than a width of the electrodes and a voltage is applied across the electrodes, in which a ratio of a maximum value of a gradient of .phi., .sqroot.(.differential..phi./.differential.x).sup.2 +(.differential..phi./.differential.y).sup.2 to a value of .sqroot.(.differential..phi./.differential.x).sup.2 +(.differential..phi./.differential.y).sup.2 at a center of the resistor is no larger than 1.4 when a Laplace equation .differential..sup.2 /.differential.x.sup.2 +.differential..sup.2 .phi./.differential.y.sup.2 =0 is solved for the heat generating resistor when an orthogonal coordinate system X-Y is defined on the resistor surface, a potential at a point (x,y) on the resistor surface is represented by .phi.

Abstract: A surface contact electrical component having two cylindrical, exposed, conductive end caps and a plastic body therebetween. The body has substantially planar upper and lower faces. The separation of the upper and lower faces is slightly less than the diameter of the end caps so that a layer of glue may be placed between the body and a printed circuit board when the end caps are in contact with the printed circuit board.

Abstract: An electrical resistor having a negative temperature coefficient for incremental resistance values has a resistance wafer with solderable coatings on opposite sides thereof and current lead elements soldered to the coatings, with the soldered ends of the lead elements being each coiled to form an annular eye, the soldering covering only the region of the eye and leaving the remainder of the coatings outside of the eye free of solder.

Abstract: An improved high frequency selecting switch terminal comprising two conductor pins which are coaxial. When a conductor pin from a cable is inserted into the terminal, it pushes the front end of the first conductor pin forward into the front end of the second conductor pin. At the front ends of the first and second conductor pins are first and second sliding blocks which force the pins forward. Thus, input signals are transmitted from the cable to the switch. The terminal further comprises a thick film resistor which connects the front end of the second conductor pin and a conductor ring which is disposed on the front surface of the second sliding block. When the cable is removed, the first and second sliding blocks move to the original position and the conductor ring contacts with the rim of the terminal housing. In this way, the terminal absorbs undesirable signals from the surroundings so as to prevent interference.

Abstract: A heating device of the present invention has a heating element of a substantially V-shape and is made of a ceramic material having electric conductivity. Electrode plates are respectively mounted at both ends of the heating element for energizing the heating element. Further, the heating device has a holder for holding the heating element by interposing both ends of the heating element therebetween. This holder is composed of a pair of insulating plates made of an electric insulating material. Both ends of the heating element are formed with projections. One of the insulating plates is formed with recesses for receiving both ends of the heating element in coincidence with the shape of both ends of the heating element.

Abstract: An attenuator is in the form of a pad comprising a coating of resistive material which connects an input port, an output port and a pair of linked constant potential ports. The regions of the pad adjacent to the outer edges of the input port are provided with outwardly pointing cusps with curved boundary edges. These reduce current crowding at the edges of the input port, and avoid localized overheating of the adjacent regions of the pad, which could result in pad failure.

Abstract: An electrical heating device comprises a substrate, a pair of parallel, spaced apart elongated conductors extending longitudinally of the substrate, and a semi-conductor pattern carried on the substrate and electrically connected to and extending between the conductors. The semi-conductor pattern produces a thermal image for an infrared target. In some embodiments, the thermal image is irregular or circular in shape and the semi-conductor pattern includes a plurality of transversely-spaced bars having relatively wide portions outside, and relatively thin portions within, the area producing the thermal image.

Abstract: Current sensing resistance apparatus in the form of a single piece, unitary, U-shaped conductor fabricated from thin flat ribbon material to provide two parallel leg portions terminating in opposite bifurcated ends each pair of which are dissimilarly sized thereby forming electrical circuit connecting elements.

Abstract: An apparatus relating to a voltage divider having one or more Kelvin connection taps, including first and second spaced terminals and a current carrying resistor between the first and second terminals. A third terminal is spaced from the resistor and the resistor has at least one conductive but non-current-carrying peninsula extending from a junction on the side of the resistor and connecting with the third terminal to produce a Kelvin connection tap. A cut is made only in the non-current-carrying peninsula along the path having a component parallel to the side of the resistor from which the peninsula extends and shading the junction of said peninsula and the side from the third terminal, to adjust the interconnection of the third terminal with the resistor and vary the voltage output without varying the resistance of the resistor. An extension of this cut may be made parallel to the edge of the peninsula to further increase the adjustment.

Abstract: An apparatus relating to a voltage divider having one or more Kelvin connection taps, including first and second spaced terminals and a current carrying resistor between the first and second terminals. A third terminal is spaced from the resistor and the resistor has at least one conductive but non-current-carrying peninsula extending from a junction on the side of the resistor and connecting with the third terminal to produce a Kelvin connection tap. A cut is made only in the non-current-carrying peninsula along the path having a component parallel to the side of the resistor from which the peninsula extends and shading the junction of said peninsula and the side from the third terminal, to adjust the interconnection of the third terminal with the resistor and vary the voltage output without varying the resistance of the resistor. An extension of this cut may be made parallel to the edge of the peninsula to further increase the adjustment.

Abstract: The heating element has an outer connector assembly including a cylindrical threaded portion adapted to be threaded into a boss on the heater water tank and a sheathed continuous electric resistance heating rod which has both ends secured to the connector assembly and which extends generally perpendicular to the heater tank centerline when installed. The heating rod is formed in a serpentine, generally W-shaped pattern with respect to the centerline of the cylindrical threaded portion, which provides the heating rod with an effective length greater than the inside diameter of the water tank, permits the heating rod to be inserted and withdrawn through the bore of the tank boss and permits the heater rod to be rotated, as the connector assembly is being threaded into and out of the tank boss, without striking any obstructions inside the water tank, such as the cold water dip tube, the hot water pipe and the anticorrosion anode.

Abstract: A Hybrid Integrated Circuit package (11) typically includes a circuit substrate or article (12) on which are formed thin film components (17, 18, 19) of a circuit (22) and to which is bonded at least one semiconductor chip (21). Prior to bonding the chip (21) to the article (12) the circuit (22) undergoes various tests and adjustment operations. An electric element, preferably a resistance element (36), is formed on the article (12). The element (36) is functionally independent of the circuit (22) on the article (12). A first, initial value of the element (36) marks the article (12) as belonging to a first group of articles having first circuit characteristics. The initial value of the element (36) is selectively altered to a second value upon a determination that the article (12) has circuit characteristics other than those of the first group. In the described preferred embodiment the first group is a group of electrically acceptable articles (12), while other characteristics are those of defective articles.

Abstract: A precision resistor for use in electrical circuits arranged on printed circuit boards is produced from a band of thermally conductive alloy. The band is selectively surface treated with a conductive coating to improve solderability in the region of the resistor where it is connected to conductors of the circuit board.

Abstract: A disc type composite part for use in electrical and electronic equipment which includes a disc substrate of ceramic dielectric material having a through-opening formed at its central portion, a first electrode and a second electrode respectively provided adjacent to the outer periphery and around the through-opening on one surface of the substrate, a third electrode provided on the other surface of the substrate, a shortcircuiting member for selectively shortcircuiting the third electrode with the first or second electrode, resistor elements connected for bridging between the first and second electrodes so as to extend over the one surface of the substrate without following the diametrical direction of the substrate, and an electrically insulating covering layer formed at least on the one surface of the substrate.

Abstract: A film type resistor especially suitable for use on planar electronic circuit substrates. The resistor is capable of being adjusted or trimmed to provide resistance values over a substantially wide range. The resistor can also be trimmed while actively functioning in a circuit including one or more other components, so as to provide a desired operating parameter for the circuit.

Abstract: A resistor particularly useful as a self-regulating fluid heater has passages extending through a body of ceramic resistance material of positive temperature coefficient of resistivity (PTC) and has ohmic contact coatings formed on the inner walls of the passages. The passage walls define thin webs of the resistance material between adjacent passages and are of uniform thickness end to end. Slits located in the walls at the ends of selected passages accommodate electrically conducting means which interconnect the contacts in selected pairs of the passages. In that way, predetermined groups of the contacts are interconnected at respective ends of the resistor so that when the groups of contacts are connected in a circuit, electrical current is directed through the thin webs of resistance material between contacts of opposite polarity in adjacent passages, thereby to heat the resistor to self-regulate its temperature to efficiently generate heat for transfer to a fluid directed through the passages.

Abstract: A fixed attenuator for microwave band comprising of a dielectric substrate, with a resistance film and a conductor film attached on said substrate so as to form an attenuation circuit. The substrate further comprises of at least one hole provided through the dielectric substrate. The attenuator is mounted on a metallic board or a printed circuit board by a screw inserted in said hole. Thus, the cooling effect of the resistance film has been improved while keeping the low manufacturing cost and stable structure, by fixing the dielectric substrate on a metallic board by screws inserted in the mentioned holes.

Abstract: A resistance ladder having a plurality of resistance branches in an integrated circuit chip, including a layer of resistive material defining a plurality of discrete linear segments and a plurality of connector tabs extending from each of the linear segments at predetermined intervals for defining each resistance branch: wherein the layer of resistive material further defines a number of curvilinear segments for connecting the linear segments to provide a continuous resistive material layer for defining said resistance ladder. Each curvilinear segment is approximately a segment of a circle. The resistive material layer also defines a plurality of connector tabs extending from each curvilinear segment; with the angular separation of the tabs being approximately defined by.theta.=(R/.rho.)ln(r.sub.2,/r.sub.1),wherein R is the resistance required for each leg of the resistance ladder;.rho. is the sheet resistance of the resistive material;r.sub.1 is the inner radius of said circle; andr.sub.

Abstract: A porcupine wire coil of electric resistance wire is positioned in a tube having an electrically insulating inside in which the peaks or looped ends of the coil convolutions are embedded so as to hold the coil convolutions spaced from each other. When the coil is energized, fluid flowed through the tube can be heated.

Abstract: A body of ceramic material of positive temperature coefficient of resistivity is molded so that a plurality of passages extend between opposite ends of the body. In molding the body, lands or abutments of resistor material are formed around the ends of alternate body passages at one end of the body and around the ends of the other passages at the opposite end of the body. A band of masking material is applied to the sides of the body and the body is then immersed in a coating bath for simultaneously coating the inner walls of the body passages, the ends of the body, and the unmasked bands of the body side surface with an electrically conductive ohmic contact material. Preferably, the ohmic contact and masking materials are selected to be impervious to reducing atmospheres and the ends of the body are treated for coating at least the unmasked bands of the body side surfaces with a material characterized by low electrical contact resistance.

Abstract: A compact resistor device comprises a body of ceramic material of positive temperature coefficient of resistivity having a large number of passages extending through the body between opposite ends of the body, thereby forming very thin webs of the resistor material between adjacent passages. Coatings are formed on the resistor material along the inner walls of the passages to serve as ohmic contacts. The coatings in alternate passages are connected together at one end of the resistor device and the coatings in the other passages are connected together at the opposite end of the device to serve as device terminals. When the device terminals are connected to a power source, current flows through very thin webs of resistor material between ohmic contacts in adjacent body passages. The resistor device is particularly useful in current limiting applications requiring low, room-temperature resistance and in heat-exchanger applications where a fluid to be heated is directed through the passages.