Patent Description:
A vehicle generally includes a heater for heating air to be supplied to a passenger compartment. Alternatively, the heater is used to supply heated air to demist or defrost the windscreen. In some cases, the heater is used to supply hot air or hot coolant for cold starting the engine. With the emergence of the electric vehicles, the heater is also applicable for battery thermal management. The heaters can be used for efficient thermal management of the batteries used for powering the electric motor, thereby drastically enhancing the service life of the batteries. The air to be heated is generally passed through a heat exchanger, which includes a heating element such as for example, heat exchange flow pipes through which a heated fluid circulates in case of thermal heater or an electrical resistive element supplied with current in case of an electrical resistive heater. Particularly, the air to be heated circulates across the heat exchanger and extracts heat from the heating element.

The electrical heater includes a plurality of heating elements arranged with respect to fluid heating spaces configured with respect to the heating elements for heat exchange between the fluid flowing through fluid heating spaces and the heating elements. Each heating element includes a tube that receives an electrical core therein. Specifically, the tube together with the electrical core forms the heating element. The electrical core for example comprises PTC (Positive Temperature Coefficient) resistors. Each tube may have several electrical cores, which may be arranged one after the other in a direction of the tube. Each heating element includes electrodes on both sides of the at least one electrical core for power supply through the heating element. The electrodes and electrical cores are comprised in heat generation portions of the heating elements. Further, the heating elements include electrically insulating and thermally conductive material layers. The layers being located between one of the electrodes and walls of the tube. In this way, the tube is electrically insulated from the electrodes and the electrical core but thermally in contact with them.

Documents <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose such electrical fluid heaters, according to the preamble of claim <NUM>.

The fluid heating spaces are either defined by a housing enclosing the heating elements or by a plurality of modular elements, particularly, plates that are assembled to define the fluid heating spaces with respect to the heating elements. The fluid heating spaces are in fluid communication with an inlet and an outlet. Particularly, the fluid entering the electrical heater through the inlet flows through the fluid heating spaces configured adjacent to the heating elements and in the process extracts heat from the heating elements. The fluid after extracting heat from the heating elements egresses through the outlet. However, the fluid flowing through the fluid heating spaces so configured fails to directly contact the heating elements. Further, air pockets that detrimentally impact the efficiency and performance of the electric heater. Indeed, air is acting as a thermal isolator and hot spots on the heating elements can arise. In case the fluid heating spaces are defined by joining a plurality of plates, the brazing of the plates is an issue.

Accordingly, there is a need for an electric heater that ensures uniform distribution of the heat exchange fluid along the surface of the heater element even when the heater element is of substantially large size. Further, there is a need for an electric heater configured with fluid heating spaces that ensures sufficient heat exchange between the heater element and the fluid flowing through the fluid heating spaces, thereby improving efficiency and performance of the electric heater. Still further, there is a need for an electric heater that ensures convenient brazing connection between the plates configuring the fluid heating spaces with respect to the heating element by homogenizing the brazing temperature and avoiding thermal stresses.

An object of the present invention is to provide an electrical fluid heater that obviates the problems faced by conventional electrical fluid heaters due to non-uniform fluid distribution with respect to the heating element.

Still another object of the present invention is to provide an electrical fluid heater that ensures homogeneous fluid distribution and fluid filling in all the fluid flow passes to achieve improved efficiency and performance.

Yet another object of the present invention is to provide an electrical fluid heater that prevents formation of air pockets within the electric heater.

Still another object of the present invention is to provide an electrical fluid heater that ensures convenient brazing connection between plates configuring fluid flow passes with respect to the heating element by homogenizing the brazing temperature and avoiding thermal stresses.

An electrical fluid heater includes a fluid inlet and a fluid outlet, at least one heating elements and a plurality of plates. The plurality of plates are stacked to form a fluid flow path between the fluid inlet and the fluid outlet for the fluid to be heated by the at least one heating element. The at least one heating element being sandwiched between adjacent plates thereby defining fluid heating spaces from either sides of the at least one heating element to permit heat exchange between the fluid flowing through the fluid heating spaces and the at least one heating element. Each of the plates includes at least one opening, in particular formed on a substantial portion thereof, such that the fluid flowing through the fluid heating spaces is in direct contact with the heating elements.

Generally, the plates includes fluid circulation sections, at least one section formed with a corresponding opening.

Further, the electrical fluid header includes a first end plate and a second end plate. The first end plate includes a first portion and a second portion. The first portion of the first end plate is corresponding to first fluid circulation sections of the plates and is formed with the inlet, whereas, the second portion of the first end plate is corresponding to the second fluid circulation sections of the plates and is formed with the outlet. The first fluid circulation sections of the plates define fluidly coupled first fluid flow passes that receive fluid from the inlet for heat exchange with the heating elements and the second fluid circulation sections of the plates define fluidly coupled second fluid flow passes that delivers fluid to the outlet after heat exchange with the heating elements.

Generally, the electrical fluid header includes a plurality of heating elements. Each heating elements being sandwiched between adjacent plates thereby defining fluid heating spaces from either sides of the at least one heating element.

Preferably, at least one heating element includes a heat generation portion enclosed inside a tube and a wall for the tube is also defining the fluid flow spaces and is in direct contact with the fluid flowing through the fluid heating spaces.

Generally, the tube is a metal extruded tube and an electrical isolating material electrically isolates the heat generation portion from the tube.

Generally, the periphery of the at least one opening formed on the plate is brazed on the tube wall on one side of the heating element and the periphery of the opening formed on the adjacent plate is brazed on the tube wall on another side of the heating element, thereby sealing closing the fluid heating spaces.

Preferably, the first opening and the second opening of the plate are separated and in fluid isolation with respect to each other by means of a rib, the rib cooperates with another adjacent plate, thereby defining the different fluid circulation sections of the plate.

Specifically, the at least one opening covers at least <NUM> percent, in particular <NUM> percent and preferably <NUM> percent of the plate.

Particularly, the first openings on adjacent plates forming the fluid heating spaces with respect to the corresponding heating element are aligned with respect to each other.

Similarly, the second openings on adjacent plates forming the fluid heating space with respect to the corresponding heating element are aligned with respect to each other.

Further, the first openings and the second openings on adjacent plates include rib portions formed along periphery thereof to facilitate brazing connection between the adjacent plates.

The present invention envisages an electrical fluid heater, particularly, a high temperature coolant heater, hereinafter, simply referred to as a fluid heater. The fluid heater includes a fluid inlet and a fluid outlet, at least one heating element and a plurality of plates. The plurality of plates are stacked to form a fluid flow path between the fluid inlet and the fluid outlet for the fluid to be heated by the at least one heating element. The at least one heating element being sandwiched between adjacent plates thereby defining fluid heating spaces from either sides of the at least one heating element to permit heat exchange between the fluid flowing through the fluid heating spaces and the at least one heating element. Each of the plates includes at least one opening, in particular formed on a substantial portion thereof, such that the fluid flowing through the fluid heating spaces is in direct contact with the heating elements. Although, the present invention is explained in the forthcoming description and the accompanying drawings, with the example of high temperature coolant heater, however, the present invention is applicable for any other heat exchanger, for use in vehicular or non-vehicular applications and where it is required to arrange the plates and heating elements with respect to each other to configure fluid flow pass between the fluid inlet and the fluid outlet and fluid heating space to permit heat exchange between the fluid flowing through the fluid heating spaces and the at least one heating element and where high thermal efficiency is required to be achieved by improving fluid contact with the heating element and convenient to configure brazing connection is required between the various elements configuring the high voltage coolant heater.

<FIG> illustrates an isometric view of an electric fluid heater <NUM>, hereinafter referred to as fluid heater <NUM>, in accordance with an embodiment of the present invention. In accordance with an embodiment, the electric fluid heater is a high voltage coolant heater and the electric fluid heater of the present invention is explained in the forthcoming description and drawings with the example of the high voltage coolant heater. The fluid heater <NUM> includes a pair of end plates <NUM> and <NUM>, at least one heating element <NUM>, preferably a plurality of heating elements <NUM> and a plurality of plates <NUM>, wherein each plate <NUM> is formed of different sections 40a and 40b. <FIG> illustrates an exploded view of the fluid heater <NUM> and the arrangement in which the different elements of the fluid heater <NUM> are arranged and assembled with respect to each other.

<FIG> illustrates an isometric view of the first end plate <NUM> of the pair of end plates <NUM> and <NUM>. The first end plate <NUM> is defined by the opposite longer walls <NUM> and <NUM> and the pair of opposite shorter walls <NUM> and <NUM>. The opposite longer walls <NUM> and <NUM> are also referred to as first and second longer walls <NUM> and <NUM>. The opposite shorter walls <NUM> and <NUM> are also referred to as first and second shorter walls <NUM> and <NUM>. The opposite longer walls <NUM> and <NUM> and the opposite shorter walls <NUM> and <NUM> define the periphery of the first end plate <NUM> and at least a portion of the fluid flow pass corresponding to the first end plate <NUM>. The first end plate <NUM> of the pair of end plates <NUM> and <NUM> includes a first portion 10a formed with an inlet 12a for ingress of fluid into and a second portion 10b formed with an outlet 12b for egress of fluid out of the fluid heater <NUM> from same side of the electrical fluid heater <NUM>. The first portion10a and the second portion 10b are separated by a groove <NUM> and are in fluid isolation with each other. Such configuration of the inlet 12a and the outlet 12b formed on the same side of the electric fluid heater <NUM> causes the fluid to follow a U-turn trajectory between the inlet 12a and the outlet 12b. Further, the first portion 10a of the first end plate <NUM> is corresponding to the first fluid circulation sections 40a of the plates <NUM> whereas, the second portion 10b of the first end plate <NUM> is corresponding to the second fluid circulation sections 40b of the plates <NUM>. The first portion 10a of the first end plate <NUM> distributes fluid received from the inlet 12a to a portion of the first fluid flow pass defined by the first fluid circulation sections of the plates <NUM> for heat exchange with the corresponding portion of the heating elements <NUM>. The second portion 10b collects the fluid that had passed through second fluid flow pass and undergone heat exchange with the corresponding portion of the heating elements <NUM> and directs the fluid to the outlet 12b for egress of the fluid. The first fluid flow pass defined by the first portion 40a of the plate <NUM> and the second fluid flow pass defined by the second portion 40b of the plate <NUM> together define a fluid flow path between the inlet 12a and the outlet 12b. Such configuration of the inlet 12a and the outlet 12b formed on the same side of the fluid heater <NUM> provide several advantages. For example, configuring the inlet 12a and the outlet 12b on the same side of the fluid heater <NUM> provides compact configuration to the fluid heater <NUM> and addresses packaging issues. Further, such configuration also addresses routing issues associated with routing of inlet and outlet conduits connected to the inlet 12a and the outlet 12b for supplying and delivering out fluid from the fluid heater <NUM>.

The cross section of the first portion 10a is increasing from the inlet 12a towards the first fluid flow passes defined by the first fluid circulation sections 40a. Referring to the <FIG>, the inlet 12a is disposed at the center of the first portion 10a and proximal to the longer walls <NUM> of the first end plate <NUM>. Such strategic placement of the inlet 12a ensures even distribution of the coolant to the portion of the fluid flow passes defined by the first fluid circulation sections 40a. Similarly, the second portion 10b corresponding to the second fluid circulation sections 40b of the plates <NUM> and is converging from the second fluid circulation sections 40b to the outlet 12b in the fluid flow direction. Specifically, the cross section of the second portion 10b is decreasing from the second fluid flow passes defined by the second fluid circulation sections 40b towards the outlet 12b. Further, again referring to the <FIG> and <FIG>, the outlet 12b is also disposed at the center of the second portion 10b and proximal to the longer walls <NUM> of the first end plate <NUM>. In accordance with another embodiment of the present invention, the outlet 12b is disposed at the corner of the first end plate <NUM> defined at the intersection of the first longer wall <NUM> and the first shorter wall <NUM>. Specifically, the outlet 12b is farthest from the groove <NUM>. Such strategic placement of the outlet 12b ensures that the portion of the fluid flow passes defined by the second fluid circulation sections 40b of the plates <NUM> is filled before the fluid egresses through the outlet 12b. More specifically, such strategic placement of the outlet 12b ensures even distribution of the coolant in the fluid flow passes defined by the second fluid circulation sections 40b before egressing through the outlet 12b. Such configuration of the outlet avoids trapping air in the area beneath the second portion and the fluid flow passes defined by the second fluid circulation sections 40b by scavenging the fluid evenly underneath the second portion 10b of the first end plate <NUM>. In another embodiment, the outlet 12b can be disposed horizontally instead of being disposed vertically the to reduce back-pressure and improve flow path. However, the present invention is not limited to any particular configuration of the first end plate <NUM> with the inlet 12a and the outlet 12b in any particular position. The inlet and the outlet can be positioned on the first and the second potions so as to avoid air trapping by scavenging the fluid evenly underneath the first and second portions 10a and 10b respectively based position of the openings <NUM> a and 41b formed on the plates <NUM>. The openings 41a and <NUM> b are generally disposed beneath and aligned to the inlet 12a and the outlet 12b respectively. Similar to the first end plate <NUM>, the second end plate <NUM> is formed with different portions 20a and 20b. The first portion 20a and the second portion 20b of the second end plate <NUM> is corresponding to the first fluid circulation sections 40a and the second fluid circulation sections 40b of the plates <NUM> and the first portion 10a and the second portion 10b of the first end plate <NUM>.

The second end plate <NUM> is formed with different portions 20a and 20b that are in fluid communication with each other unlike the first and the second portions 10a and 10b of the first end plate that are in fluid isolation with each other. Particularly, the second end plate <NUM> fluidly couples the first and the second fluid flow passes formed adjacent to the respective heating elements <NUM> and in fluid communication with the inlet 12a and the outlet 12b respectively.

<FIG> illustrates an isometric view of the heating element <NUM> of the plurality of heating elements <NUM>. The plurality of heating elements <NUM> extend along the end plates <NUM> and <NUM>. Each of the heating elements <NUM> is sandwiched between adjacent plates <NUM>, thereby defining fluid heating spaces from either sides of the at least one heating element. The fluid heating spaces are configured either on one side of the heating element <NUM> or one both sides of the heating element <NUM>. The at least one heating element <NUM> includes a heat generation portion <NUM> enclosed inside a tube <NUM>. The tube <NUM> is a metal extruded tube and an electrical isolating and thermally conductive material layer <NUM> electrically isolates the heat generation portion <NUM> from the tube <NUM>. Each heating element <NUM> includes electrodes <NUM> on both sides for power supply through the heating element <NUM>. The layers <NUM> being located between one of the electrodes <NUM> and walls 32a and 32b of the tube <NUM>. In this way, the tube <NUM> is electrically insulated from the electrodes <NUM> and the electrical core <NUM> but thermally in contact with them. The walls 32a and 32b of the heating element <NUM> is in direct contact with the fluid flowing through the fluid heating space.

Each plate <NUM> includes a pair of opposite longer walls <NUM> and <NUM>, a pair of opposite shorter side portions <NUM> and <NUM>, at least one rib <NUM>, a first opening 41a and a second opening 41b.

Each plate <NUM> is formed into different sections 40a and 40b corresponding to the different portions 20a and 20b of the second end plate <NUM> and the different portions 10a and 10b of the first end plate <NUM>. The first fluid circulation sections 40a of the plates <NUM> defines fluidly coupled first fluid flow passes. In the assembled configuration of the plates <NUM>, the first fluid flow passes receive fluid distributed thereto by the first portion 10a of the first end plate <NUM> from the inlet 12a for heat exchange with at least a portion of the heating elements <NUM> sandwiched between the plates <NUM>. Also, the second fluid circulation sections 40b of the plates <NUM> define fluidly coupled second fluid flow passes. The second flow passes deliver fluid to the second portion 10b of the first end plate <NUM> for egress through the outlet 12b after heat exchange with the heating elements <NUM> in the assembled configuration of the plates <NUM>. The plates <NUM> are positioned and assembled to each other by using first positioning elements 42b, 44b and corresponding second positioning elements 42c, 44c formed on the adjacent plates <NUM>.

<FIG> illustrates isometric views of the adjacent plates <NUM>. <FIG> illustrates an isometric view of the plate <NUM> of a pair of adjacent plates defining at least a portion of a fluid flow pass. <FIG> illustrates an isometric view of the adjacent plate of the pair of adjacent plates, wherein the adjacent plate in conjunction with the other plate of the pair of adjacent plates arranged in axial direction with respect to each other defines at least a portion of the fluid flow pass. Each plate <NUM> includes a pair of opposite longer walls <NUM> and <NUM>, hereinafter referred to as the first and the second longer walls <NUM> and <NUM> respectively, a pair of opposite shorter side portions <NUM> and <NUM>, hereinafter, referred to as first and second shorter side portions <NUM> and <NUM> respectively. The pair of opposite shorter side portions <NUM> and <NUM> in conjunction with the pair of opposite longer walls <NUM> and <NUM> define the periphery of the plate <NUM> that defines at least a portion of the fluid flow pass defined by the adjacent plates <NUM>. Each longer wall <NUM>, <NUM> of the pair of opposite longer walls <NUM> and <NUM> is formed with separate portions corresponding to the first and second fluid circulation sections 40a and 40b of the plate <NUM>.

The pair of opposite longer walls <NUM> and <NUM> are formed with portions corresponding to the first and the second fluid circulation sections 40a and 40b of the plate <NUM>. The portions of the plate <NUM> proximal to opposite longer walls <NUM> and <NUM> formed with fluid inlet or outlet manifolds that are fluidically in communication with a corresponding fluid heating space defined by openings 41a and 41b formed on the plate <NUM> and the corresponding heating element <NUM>. Either one of the fluid inlet or outlet manifolds being formed with apertures 42a and 44a for either one of ingress in a corresponding fluid inlet manifold defined by the plate <NUM> in conjunction with the adjacent plate <NUM> and egress of fluid from a corresponding fluid outlet manifold defined by the plate <NUM> in conjunction with the adjacent plate <NUM>. The apertures 42a or 44a that are configured on the first plate adjacent to the first end plate 10a are in fluid communication with the inlet 12a. The pair of opposite shorter side portions <NUM> and <NUM> in conjunction with the pair of opposite longer walls <NUM> and <NUM> define the periphery of the plate <NUM> that define at least a portion of the fluid flow pass corresponding to the plate <NUM>.

Again referring to the <FIG>, the plurality of the plates <NUM> are so stacked with respect to the heating elements <NUM> that a pair of adjacent plates <NUM> form at least a portion of fluid flow path. The pair of adjacent plates are separated with respect to each other by at least one heating element <NUM> to define fluid heating spaces. More specifically, the pair of adjacent plates <NUM> form at least a portion of the fluid flow path configuring fluid communication between the inlet 12a and the outlet 12b and also define the fluid heating spaces in conjunction with the corresponding heating element <NUM>. The fluid heating spaces permit heat exchange between the fluid flowing through the fluid heating spaces and the at least one heating element <NUM>, More specifically, the pair of adjacent plates <NUM> in conjunction with walls 32a of the corresponding tube <NUM> of the heating element <NUM> defines the fluid heating spaces between the tube <NUM> and one of the adjacent plates <NUM>. Particularly, the walls 32a of the tube <NUM> defines and is in contact with fluid heating spaces disposed adjacent to the tube <NUM>.

For positioning the adjacent plates <NUM> with respect to each other, one of the adjacent plates <NUM> is formed with first positioning element 42b, 44b that engage with corresponding second positioning elements 42c, 44c formed on the adjacent plates <NUM> to position and assemble the plate <NUM> with respect to the adjacent plates <NUM>.

Further, each of the plates <NUM> includes at least one corresponding opening 41a, 41b. In particular, each of the plates <NUM> includes sections 40a and 40b, wherein at least one section 40a, 40b is formed with a corresponding opening 41a, 41b. The first opening 41a and the second opening 41b are separated and in fluid isolation with respect to each other by means of the rib <NUM>, the rib <NUM> cooperates with another adjacent plate <NUM>, thereby defining the different sections 40a and 40b of the plate <NUM>. The rib <NUM> also supports the heating element <NUM> sandwiched between the adjacent plates <NUM>. The corresponding opening 41a, 41b is formed on a substantial portion of the corresponding section 40a, 40b of plate <NUM>. More specifically, the at least one opening 41a, 41b covers at least <NUM> percent, in particular <NUM> percent and preferably <NUM> percent of the plate <NUM>. However, the size of the openings 41a, 41b is not limited to be equal to any particular proportion of the plate <NUM> and the openings 41a, 41b can be as big as possible to improve heat transfer to the coolant while still considering minimum brazing area requirements to achieve a proper sealing/contact. The first openings 41a on adjacent plates <NUM> forming the fluid heating spaces with respect to the corresponding heating element <NUM> are aligned with respect to each other. Similarly, the second openings 41b on adjacent plates <NUM> forming the fluid heating space with respect to the corresponding heating element <NUM> are aligned with respect to each other. Generally, the first openings 41a formed on the first fluid circulation sections 40a of the plates are aligned with respect to each other and the second openings 41b formed on the second fluid circulation sections 40b of the plates <NUM> are aligned with respect to each other. Further, the first opening 41a and the second opening 41b are symmetric about the rib <NUM>.

The first openings 41a and the second openings 41b on adjacent plates <NUM> are in fluid communication with the corresponding apertures 44a and 42a formed on the first and second fluid circulation sections 40a and 40b of the adjacent plates <NUM> respectively. Generally, the apertures 44a and 42a are formed alternately on the opposite longer walls <NUM> and <NUM> of each pair of the adjacent plates <NUM> to define zigzag fluid flow path between the inlet 12a and the outlet 12b and permit fluid communication between the fluid heating spaces defined by the adjacent plates <NUM>. With such configuration, the fluid flowing through the fluid heating spaces is in direct contact with the heating elements <NUM>, thereby preventing formation of air pockets or dead zones within the electric fluid heater <NUM> and improving the thermal efficiency of the electric fluid heater <NUM>.

Again referring to the Figures, at least two of the plates <NUM> define the fluid flow path or circulation path for circulation of the fluid adjacent to the at least one heating element <NUM> while still allowing direct contact of the fluid with the heating element <NUM> through the at least one opening 41a, 41b formed on the plate to hold the at least one heating element <NUM>. The at least two plates cooperate to hold the at least one heating element. Such configuration of the first and second fluid circulation sections 40a and 40b of the plates <NUM> configured with the openings 41a and 41b that are in fluid communication with the apertures 44a and 42a configures fluid heating spaces that permits efficient heat exchange between the fluid flowing through the fluid heating spaces and the heating element <NUM> by causing the fluid in the fluid heating spaces to be in directly contact the heating elements <NUM>. The plates <NUM> are configured with ribs around the openings 41a and 41b to conveniently configure brazing connection between the adjacent plates <NUM> and between the plates <NUM> and the corresponding heating element <NUM> by homogenizing the brazing temperature and avoiding thermal stresses. Particularly, the periphery of the at least one opening 41a, 41b is brazed on the tube <NUM> on one side thereof and the periphery of the opening 41a, 41b formed on the adjacent plate <NUM> on another side thereof.

Claim 1:
An electrical fluid heater (<NUM>) comprising
• a fluid inlet (12a) and a fluid outlet (12b);
• at least one heating element (<NUM>)
• a plurality of plates (<NUM>) stacked to form a fluid flow path between the fluid inlet (12a) and the fluid outlet (12b) for the fluid to be heated by the at least one heating element, the at least one heating element (<NUM>) being sandwiched between adjacent plates (<NUM>) thereby defining fluid heating spaces from either sides of the at least one heating element to permit heat exchange between the fluid flowing through the fluid heating spaces and the at least one heating element (<NUM>),
characterized in that each of the plates (<NUM>) comprise at least one opening (41a, 41b), in particular formed on a substantial portion thereof, such that the fluid flowing through the fluid heating spaces is in direct contact with the heating elements (<NUM>).