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WO2000042360A1 - Chauffage de fluide par resistance electrique - Google Patents

Chauffage de fluide par resistance electrique Download PDF

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Publication number
WO2000042360A1
WO2000042360A1 PCT/IL2000/000022 IL0000022W WO0042360A1 WO 2000042360 A1 WO2000042360 A1 WO 2000042360A1 IL 0000022 W IL0000022 W IL 0000022W WO 0042360 A1 WO0042360 A1 WO 0042360A1
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WIPO (PCT)
Prior art keywords
fluid
flow
heated
plates
discrete
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PCT/IL2000/000022
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English (en)
Inventor
Pessach Seidel
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Individual
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Individual
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Priority to AU19992/00A priority Critical patent/AU1999200A/en
Publication of WO2000042360A1 publication Critical patent/WO2000042360A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
    • F24H1/10—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium
    • F24H1/101—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium using electric energy supply

Definitions

  • the present invention relates generally to the heating of fluids, and, more particularly, to the heating of fluids by use of electrical resistance heating.
  • FIG. 1 This form of resistance heating is illustrated in Fig. 1, wherein there is illustrated an electrically conductive tube a, to extreme portions of which, referenced b and c, is attached an electrical circuit d.
  • This tube functions as an electrical resistor when an electrical current flows therethrough, thereby providing a predetermined thermal power output, of which a portion is transferred to the liquid flowing in the tube.
  • This type of system has not been found to be particularly efficient, and thus has not been implemented commercially.
  • Flat plate heat exchange systems are known, and are used widely, inter alia, for pasteurizing milk and juices, as well as for other purposes. While heat exchange systems have various advantages, a major drawback thereof is the lack of accuracy in obtaining target temperatures. For example, a juice that it may be desired to heat to 90°C, may end up being heated to within 5°C of that temperature. While for some purposes this may be satisfactory, for others, such as the pasteurization of milk or water, heating to beyond a target temperature may give rise to undesirable effects, such as change in color or taste, in the case of milk. In the case of water, heating above 60°C may give rise to limescale deposition within the heat exchange system, thereby causing a narrowing of the flow paths and a change in the heat exchange characteristics.
  • the present invention seeks to provide an improved electrical resistance heater for fluids flowing therethrough in thermally conductive association therewith, which is considerably more efficient than known liquid electrical resistance heaters. While the present invention is particularly exemplified with the use of liquids, this is not intended to exclude the heating by the present invention, of gases.
  • the present invention further seeks to provide a hybrid heater for heating a fluid by a combination of electrical resistance heating and heat exchange.
  • the present invention seeks to provide an electrical resistance heater for a fluid, which employs pressed, typically textured metal plates, for improved heat transfer, for use in place of known heat exchange pipes.
  • a system for heating fluids which includes: a flow-through heating element, having inlet and outlet ports for a fluid to be heated, and having one or more discrete flow-through portions extending therebetween, and formed of an electrically conductive material which is operative to emit thermal energy when connected to an electrical power source; and electrical connection apparatus for connecting the one or more discrete flow-through portions to an electrical power source; wherein the one or more discrete flow-through portions are configured so as to impart turbulence to a fluid flowing therethrough.
  • each discrete flow-through portion has one or more inward-facing surfaces having a surface texture configured to impart turbulence to a fluid flowing therealong.
  • the system also includes apparatus for regulating the amount of electrical power supplied to the discrete flow-through portion; and one or more temperature sensors for providing to the control apparatus an indication of the temperature of the fluid being heated.
  • the one or more inward-facing surfaces includes a pair of textured surfaces facing each other, and defining therebetween a fluid flow path.
  • the one or more flow-through discrete portions of the flow-through heating element includes a plurality of pairs of textured surfaces facing each other, and defining therebetween fluid flow paths.
  • the apparatus for regulating is operative to selectably change the supply power level to each discrete flow-through portion in response to the fluid temperature indication.
  • the one or more discrete flow-through portions are a stack of thermally conductive flat plates spaced apart by a corresponding plurality of intervening sealing gaskets, operative to define a fluid tight seal with the plates, wherein the flat plates and the intervening sealing gaskets are operative to define a labyrinthine flow path for the fluid to be heated, along which the fluid to be heated flows in heat transfer association with the textured surfaces, and the electrical connection apparatus is connected only to specific ones of the plurality of the stack of flat plates, such that they emit and transfer thermal energy to the fluid flowing therebetween along the labyrinthine fluid flow path.
  • the flat plates are electrically connected in parallel.
  • two or more of the flat plates may be connected in electrical series.
  • the stack of plates is connected in a closed electrical circuit, and is employed as a core element in an electrical transformer
  • the flow-through heating element further has inlet and outlet ports for a heat exchange medium, and wherein the plurality of flat plates and sealing gaskets defines an additional flow path which is separated from the labyrinthine flow path, and which is arranged in heat exchange association with the fluid to be heated, such that, when the temperature of the heat exchange medium is greater than the temperature of the fluid to be heated, a heat transfer is effected through the plates, from the heat exchange medium to the fluid to be heated.
  • At least a predetermined portion of the labyrinthine flow path for the fluid to be heated, and at least a predetermined portion of the additional flow path for the heat exchange medium are mutually parallel and define therebetween a heat exchange interface.
  • the predetermined portion of the labyrinthine flow path includes substantially the entire length thereof, and the predetermined portion of the additional flow path includes substantially the entire length thereof.
  • a predetermined non-heat exchange portion of the labyrinthine flow path is not parallel to the additional flow path, and the electrical connection apparatus is connected to the flat plates defining the predetermined non-heat exchange portion only, such that a fluid to be heated enters the system and, along a first portion of the labyrinthine flow path is heated by heat transfer with the heat exchange medium, and, subsequently flows along a second portion of the labyrinthine flow path whereat it is heated by heat emitted from the plates to which the electrical connection apparatus is connected.
  • the one or more discrete, flow-through portions include a tubular member, and the one or more inward-facing textured surfaces are formed on an inward-facing wall portion of the tubular member.
  • a method of heating fluids which includes the following steps: conducting a fluid to be heated through a flow-through heating element having one or more discrete flow-through portions formed of an electrically conductive material which is operative to emit thermal energy when connected to an electrical power source; connecting the one or more discrete flow-through portions to an electrical power source such that it emits thermal energy, thereby to heat a flow of fluid through the one or more discrete flow-through portions; and imparting turbulence to the fluid as it flows through the one or more discrete flow-through portions.
  • the step of regulating includes selectably varying the electrical power level supplied to each of the one or more discrete flow-through portions in response to a sensed fluid temperature.
  • the step of conducting a heat transfer medium heat transfer medium in heat transfer association with the fluid simultaneously with the step of connecting the one or more discrete flow-through portions to an electrical power source.
  • the one or more discrete flow-through portions includes first and second flow-through portions through which flows the fluid to be heated, and wherein the step of conducting a heat transfer medium is performed in association with the first of the two flow-through portions only, and the step of connecting to an electrical power source includes connecting to an electrical power source the second flow-through portion only.
  • the fluid to be heated is a liquid.
  • Fig. 1 is a diagrammatic representation of an electrical resistance fluid heater constructed in accordance with the PRIOR ART
  • Figs. 1A-1F are pictorial views of textured heat transfer plates for use in various embodiments of the present invention, having different respective distributions of fluid ports;
  • Fig. 2A is an exploded view of a heat transfer plate and sealing gasket for use therewith, wherein the gasket is configured so as to confine a fluid flow through the plate ports only;
  • Fig. 2B is a pictorial view of a sealing gasket for use with a heat transfer plate, wherein the gasket is configured so as to confine a fluid flow between a first predetermined pair of plate ports only;
  • Fig. 2C is a pictorial view of a sealing gasket for use with a heat transfer plate, wherein the gasket is configured so as to confine a fluid flow between a second predetermined pair of plate ports only;
  • Fig. 3 A is an exploded view of a textured plate electrical resistance fluid heating system, constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig. 3B is an enlarged schematic view showing fluid flow through a portion of the system of Fig. 3 A;
  • Fig. 4 is an exploded view of a hybrid, electrical resistance and heat exchange, textured plate, fluid heating system, constructed and operative in accordance with an alternative embodiment of the invention, wherein a fluid is heated simultaneously by fluid heat transfer and electrical resistance heating;
  • Fig. 5 is an exploded view of a hybrid, electrical resistance and heat exchange, textured plate, fluid heating system, constructed and operative in accordance with a further embodiment of the invention, wherein a fluid is heated by fluid heat transfer and electrical resistance heating, in series;
  • Fig. 6 is a partially cut away, schematic side view of an electrical resistance, textured tube, fluid heating system, constructed and operative in accordance with yet a further embodiment of the present invention;
  • Fig. 7 is a view similar to that of Fig. 3 A, but wherein the plates are connected in electrical series;
  • Fig. 8A is a diagrammatic, enlarged view showing the superposition of a portion of one plate over an adjacent plate portion;
  • Fig. 8B is a cross-sectional illustration of the plate portions seen in Fig. 8A, taken along line B-B therein, showing an example of mutual electrical isolation of the plates;
  • Fig. 9 is a schematic view of an electrical heat exchanger in which a stack of heat exchanger plates functions as a transformer core.
  • the present invention provides a novel electrical resistance fluid heating system, in which heat transfer is improved by as much as five times or more when compared with known devices.
  • a basic improvement which the present invention provides lies in the provision of textured heat transfer surfaces across which a fluid, which may be a fluid or a gas, to be heated, flows. The inventor has found that the provision of textured heat transfer surfaces so as to cause highly turbulent flow of the fluid to be heated, provides a desired heat transfer coefficient of the device, and a corresponding improvement in heat transfer efficiency.
  • a preferred form of electrical resistance heat transfer device is as formed from flat, corrugated heat transfer plates, such as known, by way of example, to be used in flat plate heat exchangers. Examples of such devices, constructed in accordance with various embodiments of the present invention, are shown and described hereinbelow in conjunction with Figs. 3A-5. As will be appreciated from the description of the various embodiments shown in Figs. 3 A-5, a further advantage of using a flat plate heater is the ability to control very precisely the temperature to which a fluid is heated.
  • the present invention also provides a textured surface, tubular heating device. This type of device is illustrated and described below, in conjunction with Fig. 6.
  • the flat plate heating devices are formed of a stack of flat, heat conductive, preferably metal plates, referenced 10, which are formed with one or more fluid ports formed at corner locations, respectively referenced 12a, 12b, 12c and 12d. Plates 10 are arranged in a stack and are spaced apart by sealing gaskets, referenced 14, located therebetween. The sealing gaskets 14 define together with the flat plates 10, various labyrinthine fluid flow paths, along which heat is transferred from or across the flat plates 10, as described hereinbelow.
  • flat plates 10 are typically as used in flat plate heat exchangers.
  • Each flat plate 10 has a textured central portion, referenced 16, illustrated herein, by way of example, as having herringbone corrugations, bounded at the four corners 12a-12d, by fluid ports 18 and/or port impressions 20.
  • a flattened edge portion, referenced 22, extending along the entire periphery of plates 10 is configured to seat generally rectangular sealing gaskets 14, so as to surround fluid ports 18 and port impressions 20.
  • the port impressions 20 are locations whereat an impression of a port has been pressed into the plates 10, which are made of metal, but without actually opening thereat a port. Accordingly, fluid passage across a plate 10 can occur only through one of ports 18.
  • both the plates and the sealing gaskets are variously configured, so as to define different flow paths, depending on requirement, as will be appreciated from the description of various embodiments of the invention in conjunction with Figs. 3A-5, below.
  • the provision of plates having different combinations of ports 18 and impressions 20, is as listed in the table below, in conjunction with Figs. 1A-1F, and respectively labeled as types S, T, V, W, X, and Y.
  • a flow channel unit referenced generally 24, which is a combination of a plate 10, and a sealing gasket 14.
  • plate 10 is of type S, having four fluid ports 18.
  • Each of these units may be considered a “discrete flow-through portion,” which, depending on the precise embodiment of the invention, may have provided thereat electrical resistance heating, exchange heating, or both.
  • the equivalent of the flow channel unit in the embodiment of Fig. 6 hereinbelow, provided as a single “discrete, flow-through portion,” is the entire inner tube wall 124.
  • Sealing gasket 14 has an exterior element 26, formed of elongate side portions
  • the exterior element serves, when the gasket is sealingly disposed between a pair of plates 10, to define therewith an interior, sealed volume.
  • the gasket 14 further has up to four, corner-located, cross ribs, respectively referenced 30a, 30b, 30c and 30d, and formed integrally with exterior element 26. These ribs are operative to cooperate with the exterior element 26 so as to isolate an associated fluid port 18 from the remainder of the interior volume provided between two adjacent plates, thereby to prevent fluid flowing through the associated fluid port 18, from entering the remainder of the interior volume between two plates. Conversely, the absence of any of ribs 30a-30d in association with a fluid port 18, permits fluid communication between the portion of the interior volume in registration with textured central portion 16 and the associated fluid port.
  • the gasket 14a is provided with all four ribs 30a-30d, such that, in combination with a pair of plates of type S, fluid flow is permitted through the fluid ports 18 only, and no flow between ports, across the textured central portion 16 of plate 10, is permitted.
  • each of the illustrated gaskets has only a pair of cross ribs.
  • the illustrated gasket, referenced 14b has ribs 30b and 30d. Accordingly, when used in combination with a pair of plates having fluid ports at corner locations 12b and 12d, fluid flow is permitted therebetween, in isolation from fluid flowing through ports 18 at either of corner locations 12a and 12c.
  • the illustrated gasket, referenced 14c has ribs 30a and 30c. Accordingly, when used in combination with a pair of plates having fluid ports at corner locations 12a and 12c, fluid flow is permitted therebetween, in isolation from fluid flowing through ports 18 at either of corner locations 12b and 12d.
  • FIGs. 3A-5 there are provided various electrical resistance fluid heating systems employing flat plates 10 interspersed with sealing gaskets 14, thereby to define fluid flow paths.
  • each flow unit 24 is denoted by a two letter code, such as, AT, CT, and so on.
  • Each such code refers to the particular type of gasket, A, B or C, shown and described above on conjunction with Figs. 2A-2C, respectively; and to the particular type of plate, S, T, V, W, X or Y, shown and described above on conjunction with Figs. 1A-1F, respectively, used in combination therewith.
  • each unit is identified by its position in an exemplary stack of nine such units, the units being labeled 24-1, 24-2, 24-3, 24-4, 24-5, 24-6, 24-7, 24-8 and 24-9, respectively.
  • this labeling refers to the position of a flow channel unit being described, only, it being appreciated that the precise configuration of the unit at each position is identified by the above-mentioned two-letter codes.
  • plates 10 and gaskets 14 are indicated in Figs. 3 A, 4 and 5 with suffixes 1, 2,..., 9, thus denoting their positions in the stack.
  • the plate and gasket of unit 24-1 are referred to in the description hereinbelow, as plate 10-1 and gasket 14-1, respectively.
  • an electrical resistance fluid heating system referenced generally 40, constructed in accordance with a preferred embodiment of the present invention.
  • System 40 is formed of a stack of flat plates 10, interspersed with gaskets 14, bounded at either end by first and second end plates, respectively referenced 42 and
  • Plates 10, gaskets 14 and end plates 42 and 44 are connected in a sealed stack by any suitable elongate fastening elements (not shown), as known in the field of flat plate heat exchangers.
  • First end plate 42 has formed therein an inlet 46 for a fluid to be heated, and an outlet 48 for the heated fluid.
  • Second end plate 44 is "blind,” having no inlet or outlet ports, and just acting to seal the stack of plates at the end distal from first end plate 42.
  • first flow unit 24-1 is formed of an A type gasket and a T type plate. The use of a type T plate provides for plate 10-1 having a fluid port 18 at each of corners 12b and 12d, and for flow through these ports in communication with inlets 46 and 48, respectively, but with no flow between the fluid ports, across the textured central portion 16 of plate 10-1.
  • the remaining flow units 24-2 through 24-9 all employ type T plates, but in combination with type C gaskets.
  • This enables fluid entering between plates 10-1 and 10-2 to flow not only through fluid port 18 so as to enter into the space between plates 10-2 and 10-3, but also to flow across the downstream facing textured central portion 16 of plate 10-2, and the upstream facing textured central portion 16 of plate 10-3, thereafter exiting the intra-plate space via fluid port 18 of plate 10-1, prior to exiting the system 40 via outlet 48.
  • this flow pattern repeats itself throughout the stack, as indicated by double arrows 50 associated with fluid ports 18 at corner locations 12d, and single arrows 52 associated with fluid ports 18 at corner locations 12b.
  • a further gasket 14 (not shown) is provided between the second end plate 44, thereby permitting fluid flow through fluid port 18 at corner location 12d of plate 10-9, and return of the fluid, after flowing across textured central portion 16 of the plate, through fluid port 18 at corner location 12b thereof.
  • Fluid passing through the system 40 is heated by application to the plates of an electrical current, either AC or DC, thereby providing the well known resistance heating effect.
  • a suitable voltage typically in the range 0 > 50V, although not limited thereto, is supplied across the stack. The precise voltage selected depends on the desired heating effect in any particular situation.
  • Application of an electrical current to the plates causes a heating thereof, such that, upon a flow of a relatively cool fluid in contact therewith, a thermal gradient is created, causing a heat transfer from the heated plates to the fluid.
  • textured surfaces in resistance heating of a fluid, a turbulent flow is provided adjacent to the heating surfaces, thereby causing a continuous mixing of the fluid, so as to maximize heat transfer to the fluid, for as long as there is a temperature gradient between the plates 10 and the portion of fluid flowing in contact therewith.
  • An example of a particularly suitable type of textured surface is that of the herringbone type surface as illustrated in the drawings, and as found in known flat plate heat exchangers.
  • Fig. 3B there is seen a plurality of plates 10, between which fluid is flowing, as in system 40. It is particularly notable that the direction of flow constantly varies, due to the perturbations in the plate configuration. This ensures a turbulent flow, and continuous mixing of the fluid while flowing.
  • a further advantage of the present embodiment is the fact that the intra-plate fluid stream has a relatively narrow cross-section, indicated as 'd', typically no more than 2-5 mm, and that it is heated from two directions.
  • the present invention possesses a number of advantages over the known smooth pipes. Among these advantages are the fact that the system of the present invention has a heat transfer coefficient which is at least five times as much as that known in the art. This provides that, for a given thermal energy input over a given area, the temperature difference between the wall of the heat exchanger structure and the fluid can be reduced by a corresponding amount.
  • Fig. 3 A in order to suitably monitor the heating effect in device 40, there are provided one or more temperature sensors, indicated schematically at 41, which provide a suitable controller, referenced 54, with temperature data feedback. Preferably, at least two such sensors are provided, in association with the inlet 46 and outlet 48.
  • the controller 54 is configured so as to regulate the current supply to the plate stack in accordance with a desired heating effect, and in accordance with the feedback received for the temperature sensors.
  • the use of a highly efficient system such as provided herewith, allows for a high degree of regulation in the amount of heating to be provided.
  • all the plates 10 may be connected in a parallel arrangement in a single electrical circuit, such that each plate is provided with the same current.
  • Fig. 7 it is also envisaged that all or several of the plates 10 may be advantageously grouped together by connection in electrical series, in order to increase the electrical resistance, and thus inherently changes the required electrical voltage of the system.
  • the plates 10 are seen to be grouped together, by way of example only, in three such groups, referenced generally, A, B and C. This enables matching of circuit resistance to voltage and power supply of the system.
  • implementation of the system in series, as described enables such a system to be designed such that its performance as a heat exchange system can be matched with a transformer of given maximum output and voltage.
  • each plate In order to connect the plates in series, it is necessary to electrically isolate each plate from its adjacent plates. As seen in Figs. 8A and 8B, the illustrated herringbone plates contact each other at discrete locations only, typically at junction points of opposing ridges.
  • isolation of such plates can be provided by any means preventing contact at the junction points, such as providing, for example, in every second plate, referenced A, perforations 200 having placed therein suitable electrically insulating plugs 202, as shown in the drawing.
  • the plates may be coated with a substrate formed of a suitable electrical insulator, or by any other suitable means.
  • Figs. 4 and 5 there are seen, in exploded view, two hybrid, electrical resistance and heat exchange, textured plate, fluid heating systems, constructed and operative in accordance with alternative embodiments of the invention.
  • Figs. 4 and 5 A main difference between the respective systems of Figs. 4 and 5 is that the system of Fig. 4, referenced generally 60, is a parallel system, in which both the exchange heating and the electrical resistance heating are provided in parallel or simultaneously, whereas, the system of Fig. 5, referenced generally 80, is a linear system, in which a fluid to be heated is subjected first to exchange heating, and subsequently to electrical resistance heating.
  • parallel system 60 is formed of a stack of flat plates 10, interspersed with gaskets 14, bounded at either end by first and second end plates, respectively referenced 62 and 64.
  • Plates 10, gaskets 14 and end plates 62 and 64 are connected in a sealed stack by any suitable elongate fastening elements (not shown), as known in the field of flat plate heat exchangers.
  • First end plate 62 has formed therein a heat exchange medium inlet 66 and a corresponding outlet therefor, referenced 67; and an inlet 68 for a fluid to be heated, and a corresponding outlet therefor, referenced 69.
  • Second end plate 64 is "blind.”
  • first flow unit 24-1 is formed of an A type gasket, and an S type plate, having four fluid ports 18, thereby to communicate and separate thereat the various flows associated with the inlets and outlets, 66, 67, 68 and 69.
  • the remaining flow units 24-2 through 24-9 all employ type S plates, as used in unit 24-1.
  • the types of gaskets employed are also alternated; units 24-2, 24-4, 24-6 and 24-8 are provided with type C gaskets, so as to permit flow across textured portions 16 of plates 10 between ports 18 from corner 12d to corner 12b; and units 24-3, 24-5, 24-7 and 24-9 are provided with type B gaskets, so as to permit flow across textured portions 16 of plates 10 between ports 18 from corner 12a to corner 12c.
  • the resulting flow pattern of the heat exchange medium through the stack is indicated by double arrows 70 associated with fluid ports 18 at corner locations 12a, of plates 10-3, 10-5, 10-7, and 10-9; by first single arrows 72 associated with fluid ports 18 at corner locations 12a of plates 10-1, 10-2, 10-4, 10-6, and 10-8; and by second single arrows 73 associated with fluid ports 18 at corner locations 12c of all the plates 10-1 through 10-9.
  • the resulting flow pattern through the stack of the fluid being heated is indicated by double arrows 74 associated with fluid ports 18 at corner locations 12d, of plates 10-2, 10-4, 10-6, and 10-8; by first single arrows 76 associated with fluid ports 18 at corner locations 12d of plates 10-1, 10-3, 10-5, 10-7, and 10-9; and by second single arrows 77 associated with fluid ports 18 at corner locations 12b of all the plates 10-1 through 10-9.
  • the heat exchange medium enters the system through inlet port 66 at a temperature ti, and exits the system through outlet port 67 at a lower temperature t 2 , wherein ti - 1 2 equals ⁇ i.
  • Fluid being heated enters the system through inlet port 68 at a temperature t 3 , and exits the system through outlet port 69 at a higher temperature t 4 , wherein t 4 - 1 3 equals ⁇ 2 .
  • ⁇ 2 and ⁇ i are approximately equal, wherein the thermal energy lost by the heat exchange medium is transferred to the fluid being heated.
  • this will be provided both to the heat exchange medium and to the fluid being heated, such that the working temperature of the entire system is raised by ⁇ .
  • the electrical resistance heating of the present system is very accurate, having a typical margin of error of approximately ⁇ 0.1 °C. Accordingly, for any given temperature to which it is desired to heat a fluid, the difference in initial temperatures ti and t of the heat exchange medium and fluid to be heated, should be so as to ensure that the maximum temperature to which the fluid will be heated by virtue of the heat exchange only, should equal the target temperature minus the maximum margin of error.
  • the electrical resistance heating can then be operated by the computer/controller 54, receiving input from suitably placed temperature sensors, so as to ensure an exit temperature t of the heated fluid having a margin of error of only ⁇ 0.1 °C, equal to 2% of the margin of error achieved in the prior art.
  • linear system 80 is formed of a stack of flat plates 10, interspersed with gaskets 14, bounded at either end by first and second end plates, respectively referenced 82 and 84.
  • Plates 10, gaskets 14 and end plates 82 and 84 are connected in a sealed stack by any suitable elongate fastening elements (not shown), as known in the field of flat plate heat exchangers.
  • First end plate 82 has formed therein a heated fluid inlet 86, there being formed in second end plate 84 a heated fluid outlet, referenced 87. Further provided, in first end plate 82, is an inlet 88 for the heat exchange medium, and a corresponding outlet therefor, referenced 89.
  • the system includes a heat exchanging stage, referenced generally 100, in which a fluid is heated via heat exchange with the heat exchange medium; and a resistance heating stage, referenced generally 102, in which the fluid is further heated by resistance heating.
  • Heat exchanging stage 100 typically includes flow units 24-1 through 24-6, and resistance heating stage 102 typically includes flow units 24-7 through 24-9. It will be appreciated, however, that many more than the illustrated exemplary nine flow units may be provided, and that the heat exchanging and resistance heating stages may overlap.
  • first flow unit 24-1 is formed of an A type gasket, and a V type plate, having three fluid ports 18, at corners 12a, 12b and 12d, thereby to communicate with while separating the respective flows associated with inlets 86 and 88, and outlet 89.
  • the remaining flow units are clearly illustrated in the drawing, and are described herein only with regard to the flow.
  • the flow units 24-1 and 24-2 are configured so as to direct the fluid to be heated through fluid ports 18 in the corner portions 12a of plates 10-1 and 10-2, as seen by arrows 102. Subsequently, the heated fluid flow divides, as indicated by double arrow 104, passing through plate 10-3 via port 18 in corner portion 12a thereof, and, at the same time, flowing across textured central portion 16 of plate 10-3, as indicated by arrow 106, so as to also pass through port 18 formed in corner portion 12c of plate 10-3.
  • the two portions of the heated fluid flow pass in parallel through ports 18 formed in corners 12a and 12c of plate 10-4.
  • the combination of a type B gasket with a type W plate causes both branches of the flow emerging into the space between plates 10-4 and 10-5 to be forced through a single port 18, formed in corner portion 12c of plate 10-5.
  • the flow passes through a corresponding port 18 in plate 10-6, so as to emerge into the resistance heating stage 102 of the system 80.
  • the described labyrinthine path of the heated fluid is complemented by the path followed by the heat exchange medium.
  • This path alternates with that of the heated fluid, and is indicated by double arrows 90 associated with fluid ports 18 at corner locations 12d, of plates 10-2, and 10-4; by first single arrows 92 associated with fluid ports 18, also at corner locations 12d, of plates 10-1, 10-3, and 10-5; and by second single arrows 93 associated with fluid ports 18 at corner locations 12b of all the plates in the heat exchanging stage 100, namely, 10-1 through 1-5.
  • the heat exchange medium flow emerging through port 18 of corner portion 12d of plate 10-5 is forced to return through port 18 of corner portion 12b of the same plate, eventually discharging from system 80 via heat exchange medium outlet 89.
  • the flow pattern of the heated fluid through resistance heating stage 102 is indicated by a first double arrow 110 associated with port 18 at corner location 12c of plate 10-7, and a second double arrow 111 associated with port 18 at corner location 12a of plate 10-8; by first single arrows 112 associated with fluid ports 18 at corner location 12a of plates 10-7 and 10-9, and by a second single arrow 114, indicating the flow emerging through port 18 of corner portion 12c of plate 10-8, which is directed across textured central portion 16 of plate 10-9 to port 18 at corner location 12a of plate 10-9, so as to exit therethrough, and discharge from system 80 via outlet 87.
  • the heat exchange medium enters the system through inlet port 88 at a temperature ti, and exits the system through outlet port 89 at a lower temperature t 2 , wherein ti - 1 2 equals ⁇ i.
  • Fluid being heated enters the system through inlet port 86 at a temperature t 3 , and exits the system through outlet port 87 at a higher temperature t , wherein t - t 3 equals ⁇ 2 .
  • ⁇ 2 is composed of a first heating increment, provided by heat exchange in stage 100 of system 80, and a second heating increment, provided by electrical resistance heating in stage 102.
  • the particular advantage provided by this system is that, whereas the increase in temperature provided merely by the heat exchange between the two working fluids may have, a margin of error of up to ⁇ 5 °C, the electrical resistance heating of the present system is highly accurate, having a typical margin of error of approximately ⁇ 0.1 °C.
  • ⁇ i should be equal to (t 4 - 5), such that, in the event that the margin of error is equal to minus 5 °C, the required heat increment ⁇ in the resistance heating stage 102 equals + 10 °C; and in the event that the margin of error is equal to plus 5 °C, the required heat increment ⁇ in the resistance heating stage 102 equals 0 °C.
  • an electrical resistance flow-through heating system referenced generally 120.
  • system 120 includes a tube 121, which has an exterior insulating layer 122, formed of a suitable thermally and, preferably, electrically insulative material, and an inner tube wall 124.
  • Inner tube wall 124 is formed of any suitable, electrically conductive material, such as aluminum, across which an electrical voltage is applied, as via terminals 126 and 128, thereby to provide resistance heating of the inner tube wall 124.
  • Inner tube wall 124 has a corrugated or otherwise textured surface, which is adapted to provide impart to a fluid flowing therethrough, a flow that is turbulent enough so as to provide a desired mixing and heating of the fluid, generally as described above in conjunction with Fig. 3 A.
  • system 120 also includes an electrical power supply, temperature sensors, and controller, as shown and described above in conjunction with Figs. 3A-5, and which are thus neither shown nor described herein.
  • a pack 310 of heat exchanger plates such as shown and described above in conjunction with any of Figs. 1B-5 and 7-8B, and connected in a closed electrical circuit, as illustrated, serves as the core of the secondary "winding" of an electrical transformer, seen enclosed by a primary winding 302.
  • the present construction benefits from advantages similar to those described hereinabove, in conjunction with other embodiments of the present invention.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Instantaneous Water Boilers, Portable Hot-Water Supply Apparatuses, And Control Of Portable Hot-Water Supply Apparatuses (AREA)

Abstract

L'invention concerne un système de chauffage de fluides comprenant un élément (40) de chauffage à flux traversant, comportant des orifices d'entrée (46) et de sortie (48) destinés au fluide à chauffer, et une ou plusieurs portions (10) discrètes à flux traversant s'étendant entre ces orifices. Ledit système est constitué d'un matériau électroconducteur capable d'émettre de l'énergie thermique lorsqu'il est connecté à un source d'alimentation électrique. L'invention concerne également un appareil de connexion électrique destiné à connecter les parties (10) discrètes à flux traversant à une source d'alimentation électrique, ces parties discrètes à flux traversant étant configurées de manière à créer une turbulence dans un fluide s'écoulant entre elles.
PCT/IL2000/000022 1999-01-11 2000-01-11 Chauffage de fluide par resistance electrique Ceased WO2000042360A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU19992/00A AU1999200A (en) 1999-01-11 2000-01-11 Electrical resistance heating of liquids

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IL12800899A IL128008A0 (en) 1999-01-11 1999-01-11 Electrical resistance heating of liquids
IL128008 1999-01-11

Publications (1)

Publication Number Publication Date
WO2000042360A1 true WO2000042360A1 (fr) 2000-07-20

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IL2000/000022 Ceased WO2000042360A1 (fr) 1999-01-11 2000-01-11 Chauffage de fluide par resistance electrique

Country Status (3)

Country Link
AU (1) AU1999200A (fr)
IL (1) IL128008A0 (fr)
WO (1) WO2000042360A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2249099A4 (fr) * 2008-01-23 2016-11-30 Cmtech Co Ltd Dispositif de chauffage de fluide

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4343988A (en) * 1978-02-04 1982-08-10 Firma Fritz Eichenauer Electrical resistance water heating device, particularly for beverage preparation machines
US5438642A (en) * 1993-07-13 1995-08-01 Instantaneous Thermal Systems, Inc. Instantaneous water heater
US5729653A (en) * 1995-06-07 1998-03-17 Urosurge, Inc. Fluid warming system
US5872891A (en) * 1996-05-24 1999-02-16 Son; Jae S. System for providing substantially instantaneous hot water

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4343988A (en) * 1978-02-04 1982-08-10 Firma Fritz Eichenauer Electrical resistance water heating device, particularly for beverage preparation machines
US5438642A (en) * 1993-07-13 1995-08-01 Instantaneous Thermal Systems, Inc. Instantaneous water heater
US5729653A (en) * 1995-06-07 1998-03-17 Urosurge, Inc. Fluid warming system
US5872891A (en) * 1996-05-24 1999-02-16 Son; Jae S. System for providing substantially instantaneous hot water

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2249099A4 (fr) * 2008-01-23 2016-11-30 Cmtech Co Ltd Dispositif de chauffage de fluide

Also Published As

Publication number Publication date
AU1999200A (en) 2000-08-01
IL128008A0 (en) 1999-11-30

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