JP2015152218A - fluid heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid heating device which makes damage such as cracks less likely to occur when used under conditions where a temperature is repetitively increased and decreased and achieves excellent reproducibility and high reliability.SOLUTION: A fluid heating device includes: a passage formation body 1 including a passage C for a heated fluid therein and having a substantially rectangular parallelepiped shape; and a heater unit 2 contacting with at least one surface of the passage formation body 1. The heater unit 2 and the at least one surface of the passage formation body 1 are not bonded to each other. It is preferable that the heater unit 2 is composed of a heating element 21 and two electric insulation layers 22a, 22b sandwiching the heating element 21 from both sides. It is preferable that the fluid heating device further includes a pressing plate 3 which presses the heater unit 2 to the passage formation body 1.

Description

  The present invention relates to a fluid heating apparatus that heats a fluid using a heating element.

  The process of heating fluids such as process fluids and cleaning liquids to a predetermined temperature is not limited to industrial applications such as chemical plants and food factories, but leads to hand dryers installed in commercial facilities, etc., and hot water cleaning toilet seats in general households. Widely used in various fields. In such a fluid heating process, when a high-temperature fluid for heat exchange cannot be used, a heating method using a resistance heating element capable of heating the heated fluid to a desired temperature relatively quickly may be employed.

  For example, in Patent Document 1, a layered heating element and an insulating layer covering the layered heating element are fired on one surface of a ceramic substrate, and then a zigzag channel is formed on the other surface. A ceramic heater that can efficiently heat the liquid flowing through the pipe is disclosed. Patent Document 2 discloses a ceramic heater in which a ceramic sheet having a heating element is wound around an outer peripheral surface of a pipe-shaped ceramic member via an adhesive layer and then integrated by firing. .

JP 2002-151236 A JP 2005-183371 A

  Due to the recent increase in interest in environmental conservation and power saving, fluid heating devices using heating elements such as those described above are required to be able to heat fluid efficiently with low power consumption. Needless to say, reliability is required. However, in the structure in which a heating element or an insulating layer is baked or bonded to the surface of the ceramic substrate as shown in Patent Documents 1 and 2 described above, a slight thermal expansion coefficient between the ceramic substrate and the heating element or the insulating layer is obtained. Thermal stress was generated due to the difference, and cracks occurred at the interface during repeated heating and cooling, thereby impairing reliability.

  The present invention has been made in view of such conventional problems, and is a highly reliable fluid heating device that is less likely to be damaged, such as cracks, even when used under conditions where the temperature rise and fall is repeated, and has excellent reproducibility. The purpose is to provide.

  In order to achieve the above object, a fluid heating apparatus provided by the present invention includes a substantially rectangular parallelepiped-shaped flow path forming body having a flow path of a fluid to be heated inside, and a heater that contacts at least one surface of the flow path forming body. A fluid heating apparatus having a unit, wherein the heater unit and the flow path forming body are not bonded to each other.

  ADVANTAGE OF THE INVENTION According to this invention, even if it uses on the conditions where temperature raising / lowering is repeated, it is hard to damage and can provide the highly reliable fluid heating apparatus excellent in reproducibility.

It is a disassembled perspective view which shows one specific example of the fluid heating apparatus of this invention. It is a top view which shows the state which attached the short tube to the entrance / exit of the flow path of the fluid heating apparatus of FIG. It is a top view which shows the other specific example of the flow path provided in the fluid formation body of the fluid heating apparatus of this invention. It is a top view which shows the specific example of the circuit pattern of the heat generating body which the heater unit of the fluid heating apparatus of this invention has. It is a front view which shows the specific example of the coupling | bonding method of the fluid heating apparatus of this invention. It is a front view which shows the other specific example of the fluid heating apparatus of this invention.

  First, embodiments of the present invention will be listed and described. A fluid heating apparatus according to an embodiment of the present invention includes a substantially rectangular parallelepiped-shaped flow path forming body provided with a flow path of a fluid to be heated inside, and a heater unit that contacts at least one surface of the flow path forming body. The apparatus is characterized in that the heater unit and the flow path forming body are not bonded to each other. With such a configuration, it is possible to provide a highly reliable heating apparatus that is not easily damaged even when used under conditions where the temperature rise and fall is repeated, and that is excellent in reproducibility.

  In the fluid heating apparatus of the embodiment of the present invention, it is preferable that the heater unit has a heating element and two electric insulating layers sandwiching the heating element from both sides. Thereby, it becomes possible to use an electroconductive material for a flow-path formation body and the pressing plate mentioned later. In the fluid heating apparatus according to the embodiment of the present invention, a pressing plate that presses the heater unit toward the flow path forming body is further provided, and the pressing plate and the flow path forming body are fastened. It is preferable. Thereby, much higher heat transfer efficiency can be achieved.

  In the fluid heating device according to the embodiment of the present invention, the thermal conductivity of the electrical insulating layer on the side in contact with the flow path forming body out of the two electrical insulating layers is that of the other electrical insulating layer. It is preferably larger than the thermal conductivity. Thereby, it is possible to suppress a loss of heat generated by the heating element. Moreover, in the fluid heating apparatus of the embodiment of the present invention, the heater units are arranged one by one on two surfaces located on opposite sides of the flow path forming body, and each of these heater units has. It is preferable that the shortest distance from the heating element to the flow path is substantially the same. This makes it possible to heat the heated fluid very quickly.

  Next, a specific example of the fluid heating apparatus of the present invention will be specifically described with reference to FIG. The fluid heating apparatus shown in FIG. 1 has a rectangular plate-like flow path forming body 1 provided with a flow path C of a fluid to be heated inside, and has substantially the same plan view shape as the flow path forming body 1, The heater unit 2 has a rectangular plate shape that substantially contacts the heated surface 1 a of the flow path forming body 1, and has substantially the same planar view shape as the flow path forming body 1 and the heater unit 2. And a rectangular plate-like pressing plate 3 that presses the channel toward the flow path forming body 1.

  The heater unit 2 includes a layered resistance heating element 21 formed in a predetermined circuit pattern, and a first insulating layer 22a and a second insulating layer 22b that sandwich the resistance heating element 21 from both sides to ensure electrical insulation. Consists of. The fluid heating device including the flow path forming body 1, the heater unit 2, and the pressing plate 3 can be used in a state of being coupled by a coupling means such as a bolt, which will be described later. It can be used in a state of being stored in the protective means.

  Hereinafter, each component of the heating device described above will be specifically described. The material of the flow path forming body 1 is appropriately selected in consideration of the type of fluid that mainly flows in the flow path, the operating conditions such as temperature and pressure, the installation environment of the fluid heating device, etc. From the viewpoint of thermal efficiency, it is preferable to use a material having high thermal conductivity. Examples of such a material having high thermal conductivity include metals such as copper and aluminum, ceramics such as silicon carbide and aluminum nitride, or ceramic composites such as Si-SiC and Al-SiC containing at least one of these. The body can be mentioned.

  Among these, metals are general-purpose and easy to produce, and have a high thermal conductivity compared to ceramics, so they are excellent in cost performance. However, since the Young's modulus of metal is lower than that of ceramics, depending on the operating temperature, the metal flow path forming body 1 may be heated by heat or thickened to maintain the flatness of the surface on which the heater unit is disposed. In order to maintain good adhesion to the heater unit 2 even when warping occurs, it is preferable to interpose a flexible electrical insulating sheet between the flow path forming body 1 and the heater unit 2 as will be described later.

  On the other hand, ceramics are excellent in machining accuracy and excellent in rigidity (Young's modulus), so that the flatness of the surface on which the heater unit 2 abuts can be kept good. In addition, since it does not deform even if the plate thickness is reduced, the flow path forming body 1 can be reduced in size, thereby reducing the heat capacity of the device itself, so that the set temperature can be changed when starting up the fluid heating device in the shutdown state. Can quickly transition to steady state.

  In particular, by selecting a ceramic material having a high thermal conductivity, the heat transfer performance to the fluid to be heated is improved while maintaining the flatness and small heat capacity of the surface on which the heater unit 2 abuts as described above. Even if a thermal shock occurs due to a rapid temperature change, problems such as cracks, cracks, and deformation are less likely to occur. In the case of ceramics, it is more preferable to select a material having a low thermal expansion coefficient in consideration of resistance to thermal shock.

  The size of the flow path forming body 1 and the number and shape of the flow paths C provided therein are appropriately determined according to the operating conditions such as the physical properties, flow rate, inlet and outlet temperatures of the heated fluid flowing in the flow path C. It is done. FIG. 1 shows an example in which two channels C having the same inner diameter extending in the longitudinal direction pass through the central portion in the thickness direction of the rectangular plate-shaped channel forming body 1. As shown in FIG. 2, it is preferable to form an inlet / outlet (also referred to as a tap) by connecting joints such as a Teflon short pipe 4 by welding or the like at both openings of each flow path C. Therefore, the pipe from the supply source of the heated fluid and the pipe up to the use point of the heated fluid can be easily connected to the flow path C.

  The flow path of the flow path forming body 1 is not limited to the linear shape shown in FIG. 1, but, for example, as shown in FIG. 3, the flow path forming body 11 snakes on a surface parallel to the surface to be heated. A single channel C may be formed. For example, two meandering flow paths C having substantially the same shape and the same material are prepared, and a groove having a rectangular cross section is formed on one of the surfaces, and this groove forming surface is formed. What is necessary is just to overlap and join another plate-shaped member so that it may cover. Thereafter, the inlet / outlet of the channel C can be formed by attaching short pipes and joints to both openings of the channel in the same manner as the channel forming body 1 described above. Thus, by providing the meandering flow path C, the length of the flow path can be made longer than that in FIG. 1, so that the fluid to be heated can be heated to a higher temperature. In addition, it becomes possible to make the to-be-heated fluid flow in a turbulent state in a flow path by roughening the processing roughness of the wall surface of a flow path, and it becomes possible to further improve thermal efficiency.

  Returning again to FIG. 1, it is desirable that the heat generated in the resistance heating element 21 be quickly transferred to the flow path C of the flow path forming body 1, so that the first contact with the heated surface 1 a of the flow path forming body 1 is performed. It is preferable to use a material having high thermal conductivity for the one insulating layer 22a. Specifically, the thermal conductivity of the first insulating layer 22a is preferably 1 W / (m · K) or more, and more preferably 3 W / (m · K) or more. It should be noted that the thermal conductivity can be further increased by adding a filler such as boron nitride, aluminum nitride, alumina, or silica having a high thermal conductivity. It is preferable that the material used for the first insulating layer 22a has further flexibility. Even if the flow path forming body 1 is warped due to thermal expansion or contraction, the flexible first insulating layer 22a is freely deformed to form a gap between the flow path forming body 1 and the heater unit 2. It is because it can prevent.

  The resistance heating element 21 generates Joule heat by flowing electricity supplied through the electrode portions at both ends to the conductive wire, and is manufactured by patterning stainless steel or nickel-chrome foil by etching or the like. Can do. FIG. 1 shows a resistance heating element 21 having a circuit pattern that meanders uniformly between a pair of electrodes, but the resistance heating element is not limited to the circuit pattern shown in FIG. The circuit pattern may meander irregularly as shown in FIG.

  Further, as shown in FIG. 4B, the heat generation density in the plane may be made higher on the inlet side than on the outlet side of the fluid to be heated by making the circuit pattern asymmetrical. As a result, the amount of heat generated from the resistance heating element 21 can be increased on the inlet side where the fluid to be heated flows at a temperature lower than that on the outlet side, so that heating can be performed efficiently. Such a design of locally different heat generation densities may be performed by changing the pitch of the conductive wires or changing the cross-sectional area of the conductive wires in one heating element circuit as described above. As in the side region and the outlet side region, a heating element circuit having a different calorific value may be provided for each region by dividing the surface into a plurality of regions. When dividing into a plurality of areas as described above, it is preferable to perform temperature control individually by providing a temperature sensor to be described later for each divided area. 4A and 4B show circuit patterns formed so as to avoid the installation location of the temperature sensor indicated by the alternate long and short dash line.

  A plurality of resistance heating elements may be provided instead of a single layer. For example, when there are restrictions on the electrical specifications of the control equipment or space restrictions such as the size of the device being small, two layered resistance heating elements are stacked with an electrical insulation sheet sandwiched between them, and their one ends are connected to each other In addition, one series circuit can be formed by using the other end as a power supply terminal. In this way, for example, a plurality of heating element layers can be disposed within a thickness of less than 1 mm, and matching with the electrical specifications of the control device is also possible.

  The electrical insulating sheet interposed between the two heating element layers described above is provided between the layers in contact with each other so that heat can be transferred quickly during heating and cooling, similar to the first insulating layer 22a described above. It is important to arrange so that no voids are generated. If there is a gap between the above-mentioned layers, the air in the gap expands when the heating element layer is heated, which may cause peeling of the heating element layer or dielectric breakdown, and the fluid to be heated is not flowing. The same condition may occur and cause abnormal heat generation.

  The amount of heat generated by the resistance heating element 21 is preferably temperature-controlled based on a temperature sensor (not shown) provided in the flow path forming body 1. It is preferable to use a resistance temperature detector for the temperature sensor. The resistance temperature detector is formed by, for example, depositing a platinum resistor on the plane of an insulating ceramic substrate by vapor deposition, etc., adjusting the obtained platinum resistor to a predetermined resistance value, and then bonding the electrode pad portion by means such as bonding. It can be produced by connecting lead wires and covering the platinum resistor and the pad portion with an insulating film. With this structure, the temperature measuring element can be reduced in size, so that the heat capacity of the element can be reduced and the temperature responsiveness can be improved.

  The temperature sensor may be bonded using an adhesive. As such an adhesive, a material mainly composed of an organic resin such as silicone or epoxy, or a combination of an inorganic material such as ceramic particles and a binder component can be used. In particular, the adhesive mainly composed of silicone resin has heat resistance and elasticity to withstand the temperature range required for fluid heating, and thus absorbs a slight difference in thermal expansion between the temperature measuring element and peripheral members. It is suitable for obtaining.

  When installing the temperature sensor, it is desirable to install the temperature sensor so that the flat surface portion of the temperature measuring element is in contact with the flat surface portion of the flow path forming body over the entire surface. Temperature response is obtained. From the viewpoint of cost, it is preferable not to process the flow path forming body, but to provide a cutout with a shape and a size suitable for the temperature measuring element on the heater unit and the holding plate side arranged on the heated surface.

  If the amount of heat that escapes slightly through the lead wire connected to the resistance temperature detector becomes a problem, a part of the lead wire is brought into contact with or close to the surface of the flow path forming body or holding plate using an adhesive or the like. Is preferred. As a result, the amount of heat escape from the lead wire can be reduced, so that the difference between the detected temperature and the actual temperature can be prevented from adversely affecting the measured value of the temperature measuring element unit having a small heat capacity. In the above contact or proximity, it is preferable to make the contact or proximity distance as long as possible.

  Since it is desirable that the amount of heat generated in the resistance heating element 21 be supplied to the heated fluid with as little loss as possible, the second insulating layer 22b is made of a material having a lower thermal conductivity than the first insulating layer 22a, that is, thermal resistance. It is preferable to select a material. Specifically, as described above, when selecting an electrically insulating sheet having a thermal conductivity of 1 W / (m · K) or higher as the first insulating layer 22a, the second insulating layer 22a is selected. For 22b, an electrical insulating sheet having a heat insulating property with a thermal conductivity of less than 1 W / (m · K) is selected.

  Examples of such an electrically insulating sheet having heat insulation include silicone resin, fluorine resin, polyimide resin, mica, and the like. Since the silicone resin is flexible, abnormal heat generation due to voids can be avoided as described above. In addition, fluororesin, polyimide resin, and mica function as a heat insulating material against heat transfer to the holding plate side opposite to the flow path side, and there is no particular problem even in a temperature range exceeding 200 ° C. Can be used. Furthermore, in the case of a sheet made of fluororesin, polyimide resin, or mica, in addition to low thermal conductivity, the surface has excellent releasability, so that relative to the surface direction due to the difference in thermal expansion coefficient described later Can be slid during a typical movement.

  The material of the pressing plate 3 is preferably a general-purpose and inexpensive metal. In this case, the same material as that of the flow path forming body 1 is preferable because the thermal expansion coefficient matches. In the heater unit 2 having the first insulating layer 22a, the resistance heating element 21, and the second insulating layer 22b, the flow path forming body 1 and the pressing plate 3 are coupled by a coupling means such as a bolt and a nut. Integrate with. Specifically, a through hole penetrating in the thickness direction is provided in both the flow path forming body 1 and the pressing plate 3, and a bolt 5 is inserted into each through hole and tightened by tightening the tip end with a nut 6. Can do. When the shape of the heater unit 2 in plan view is substantially the same as that of the flow path forming body 1 and the pressing plate 3, it is necessary to provide a through hole at a position corresponding to the heater unit 2.

  Alternatively, as shown in FIG. 5, a through hole that penetrates in the thickness direction is provided in one of the pressing plate 3 and the flow path forming body 1, and a female screw corresponding to the through hole is provided in the other, You may fasten by inserting the male screw 7 in each through-hole, and screwing it in a female screw. As described above, in the case of coupling by a coupling means such as a screw or a bolt and nut, the contact surface direction depends on the difference in thermal expansion coefficient between the flow path forming body 1 and the holding plate 3 or the temperature gradient in the thickness direction at the time of start-up. Therefore, it is preferable that the above-mentioned inner diameter of the through-hole is set to have a sufficient size in consideration of this relative movement. Thereby, problems, such as a deformation | transformation and a crack, can be prevented.

  In the fluid heating apparatus of one specific example of the present invention, the flow path forming body 1 having the flow path described above, the heater unit 2 that comes into contact with the surface thereof, and the pressing plate 3 that comes into contact with the heater unit 2 are mutually connected. The contact surface is not bonded. Here, not being bonded includes not only the case of bonding via an adhesive layer such as an adhesive, but also means of chemical bonding such as welding, fusion, and fixation by firing. That is, when the heater unit 2 and the flow path forming body 1 or the heater unit 2 and the pressing plate 3 are integrated by bonding, the interface is gradually increased and lowered due to the difference in thermal expansion coefficient and the temperature gradient in the thickness direction. This may cause problems such as peeling and cracking, and may reduce the ability to heat the fluid.

  On the other hand, if the structure is such that the flow path forming body 1 and the heater unit 2 or the holding plate 3 and the heater unit 2 are simply overlapped without being bonded to each other, the difference in thermal expansion between the flow path forming body 1 and the heater unit 2 Even if a force that moves relatively in the direction of the contact surface is applied, the member can be slid freely without being restricted by the abutting member. As a result, even if the temperature rise and fall is repeated, breakage such as cracks does not occur due to thermal stress, and it is possible to provide a highly reliable fluid heating apparatus with excellent reproducibility.

  As mentioned above, although the specific example was given and demonstrated about the fluid heating apparatus of this invention, this invention is not limited to the specific example which concerns, It can implement in the various aspect of the range which does not deviate from the main point of this invention. For example, as illustrated in FIG. 6, the heater unit 2 including the first insulating layer 22 a, the resistance heating element 21, and the second insulating layer 22 b may be disposed on both surfaces of the flow path forming body 1.

  When the heater unit 2 is disposed only on one side as shown in FIG. 1, there is a concern that the heat efficiency may be deteriorated due to heat dissipation to the outside air or peripheral members depending on the installation environment of the fluid heating device, but the heater unit 2 on both sides. Is heated from both sides of the flow path forming body 1, the heated fluid can be heated extremely efficiently. In this case, by arranging the heater units 2 having the same configuration on the front and back surfaces of the flow path forming body 1 in symmetry, a heating device with high thermal efficiency can be manufactured at low cost without increasing the types of components.

  In addition, gaps are likely to occur between adjacent conductive lines in the circuit pattern, and these gaps can cause thermal resistance. Therefore, the gap and between the insulating sheet and the resistance heating element are filled with an adhesive component if necessary. May be. This gap is only required to be filled with the above-described flexible insulating sheet. However, the denser the line and space of the pattern, the more difficult it becomes.

  As the adhesive component, a film or varnish containing a thermoplastic or thermosetting polyimide resin is effective. By arranging these between the insulating sheet and the pattern and thermocompression bonding under optimum temperature and pressure conditions, a heater layer maintaining good thermal contact can be manufactured. In this case, the heater layer is covered with an insulating film of the same material, and unevenness along the heat generation pattern path is slightly formed on the surface. Therefore, a flexible heat conductive sheet is placed between the flow path forming body and the pressing plate. It is preferable to arrange a sheet for heat insulation.

  Further, when a planar resistance heating element is manufactured by, for example, etching a metal foil, the metal foil between adjacent conductive wires is not completely removed, but is electrically insulated from the circuit of the heating element. You may leave it in the state. This is preferable because the gap can be filled with the same material and the same thickness as the circuit of the resistance heating element. In addition, when the flow path forming body and the pressing plate are mechanically coupled by screwing or the like, a metal foil layer that is electrically insulated from the circuit as described above is provided around the screwing through hole. Since the thickness of the resistance heating element layer can be made uniform over almost the entire surface, deformation of the flow path forming body and the pressing plate due to the axial tightening force at the time of screwing can be prevented.

[Example 1]
A fluid heating apparatus as shown in FIG. 1 was produced and a test for heating water as a fluid to be heated was performed. Specifically, first, as a material for the flow path forming body, a plate-like member having a length of 30 mm × width of 90 mm × thickness of 8 mm formed of copper (Cu), aluminum nitride (AlN), and silicon carbide (SiC), respectively. Three sheets were prepared, and a flow path was formed by penetrating two flow paths with an inner diameter of 3 mm extending in the longitudinal direction at the center of each thickness direction. Short pipes were attached to both openings of each channel to provide fluid inlets and outlets.

  As a heater unit to be brought into contact with one side of each of the three types of flow path forming bodies thus obtained, the first insulating layer has the same vertical and horizontal length as the flow path forming body and a thickness of 0.5 mm. Using a silicone sheet with a filler, a resistance heating element using a heating element layer having a uniform heating density etched into a 20 μm-thick stainless steel foil so as to form a circuit pattern with no roughness difference in the surface, For the insulating layer, polyimide having a thickness of 50 μm was used. In addition, a stainless steel plate having the same vertical and horizontal length as the flow path forming body and a thickness of 1 mm was used as the pressing plate. These were superposed in the order shown in FIG. 1 and fastened with bolts and nuts.

  Next, a temperature sensor was fixed to the surface of the flow path forming body using an adhesive, and power feeding cables were attached to both ends of the resistance heating element. In this manner, fluid heating devices of Samples 1 to 3 were produced. For comparison, Sample 1 was used except that a silicone sheet containing no filler was used for the first insulating layer, a silicone sheet was used for the second insulating layer, and the flow path forming body and the heater unit were adhered to each other. Sample 2 was prepared in the same manner as Sample 2, except that the first insulating layer was not used, glass was used for the second insulating layer, and the flow path forming body and the heater unit were bonded together. A fluid heating apparatus of Sample 5 produced in the same manner was produced. Table 1 below shows main equipment specifications of the fluid heating devices of Samples 1 to 5.

  While introducing water at a temperature of 20 L as a fluid to be heated into the flow path forming body of the fluid heating apparatus of Samples 1 to 5 at a flow rate of 0.5 L / min, the temperature at the temperature sensor is room temperature. After the power was supplied to the resistance heating element so that the temperature was raised from 100 to 100 ° C., the power supply was stopped and the temperature was lowered by heat exchange with 20 ° C. water as it was. This heat cycle was set as 1 cycle, and 1000 cycles were repeated. And after repeating 1000 cycles, water was heated on the same conditions as the 1st cycle. During this heat cycle test, the water temperature at the entrance and exit of the fluid heating device and the appearance of the device after 1000 cycles were confirmed from the viewpoint of the presence or absence of fatal defects. The results are shown in Table 2 below.

  As can be seen from Table 2 above, in Samples 4 and 5, which are comparative examples, the thermal conductivity of the plate-like channel forming body is higher in Sample 4, but the heat capacity is smaller in Sample 5, and the temperature rise is Sample 5 gave faster results. In addition, the water temperature on the outlet side was higher in the sample 5. Further, when the appearance after the heat cycle elapsed was confirmed in detail, deformation of the plate-like flow path forming body, peeling of the adhesion interface between the flow path forming body and the insulating sheet (coat), and cracks were confirmed. As a result of performing the same temperature increase test again in this state, the results were inferior to the performance results at the time of temperature increase confirmed before the heat cycle.

  This is because the abutting members are bonded to each other, so even if the same material is used, the adhesive interface peels off or cracks occur due to the slight difference in thermal expansion caused by the temperature difference depending on the installation environment. As a result, it is considered that the amount of heat generated by the resistance heating element could not be transferred well to the heated fluid of the flow path forming body.

  On the other hand, in Samples 1 to 3, no abnormality in the appearance was observed even after 1000 heat cycles, and the performance was the same as the initial value, which proved to be a highly reliable fluid heating device. . In addition, from the relationship between the thermal conductivity of the first insulating layer and the second insulating layer, for example, Sample 1 and Sample 4 are generated when the amount of heat generated by the heating element is transferred to the flow path forming body side instead of the holding plate side. As can be seen from the initial performance difference, the energy-saving fluid heating device with less heat loss was also demonstrated.

[Example 2]
For the fluid heating devices of Samples 1 to 3 of Example 1 described above, each heater unit was replaced with one side of the flow path forming body and contacted on both sides and tightened with bolts and nuts, and was the same as Example 1. Thus, fluid heating devices for Samples 1a to 3a were respectively prepared. And the heat cycle test similar to Example 1 was done with respect to the fluid heating apparatus of these samples 1a-3a. The results are shown in Table 3 below.

  As can be seen from Table 3 above, it was found that the initial performance was improved in Example 2 as compared to Example 1, and that the same performance as in the initial stage was obtained even after 1000 heat cycles. As mentioned above, it is predicted that there will be a heat loss in which the amount of heat generated by the resistance heating element is partially dissipated to the outside air by heating from only one side, but the heating is performed from both sides and the configuration is made symmetrical. This is probably because the amount of heat generated can be efficiently transferred to the channel side.

[Example 3]
Compared with the fluid heating device of the samples 1a to 3a of Example 2 described above, the heat generation density distribution from the center to the fluid inlet side of the circuit pattern of the resistance heating element is compared with the heat generation density distribution from the center to the fluid outlet side. The fluid heating devices of Samples 1b to 3b were respectively produced in the same manner as in Example 2 except that the circuit pattern was produced and incorporated so as to be 1.5 times. And the heat cycle test similar to Example 1 was done with respect to the fluid heating apparatus of these samples 1b-3b. The results are shown in Table 4 below.

  It was found that the initial performance was further improved in Example 3 as compared to Example 2, and that the same performance as in the initial stage was obtained after 1000 heat cycles. By designing the heat generation density at the low fluid inlet side higher than the heat generation density at the fluid outlet side where the temperature increases due to heat reception, the difference between the fluid temperature on the fluid inlet side and the heater temperature is increased, resulting in higher thermal efficiency. Is considered to have improved.

DESCRIPTION OF SYMBOLS 1, 11 Flow path formation body 1a Heated surface 2 Heater unit 3 Holding plate 4 Short pipe 5 Bolt 6 Nut 7 Male screw 21 Resistance heating element 22a 1st insulating layer 22b 2nd insulating layer C Flow path

Claims (5)

  A fluid heating apparatus having a substantially rectangular parallelepiped-shaped flow path forming body provided with a flow path of a fluid to be heated, and a heater unit that contacts at least one surface of the flow path forming body. A fluid heating apparatus in which at least one surface of a path forming body is not bonded to each other.   The fluid heating apparatus according to claim 1, wherein the heater unit includes a heating element and two electric insulating layers sandwiching the heating element from both sides.   The fluid according to claim 1, further comprising a pressing plate that presses the heater unit toward the flow path forming body, wherein the pressing plate and the flow path forming body are fastened. Heating device.   The fluid according to claim 2, wherein, of the two electric insulating layers, the heat conductivity of the electric insulating layer on the side in contact with the flow path forming body is larger than the heat conductivity of the other electric insulating layer. Heating device.   The heater units are arranged one by one on two surfaces located on opposite sides of the flow path forming body, and these heater units have substantially the same shortest distance from the heating element to the flow path. The fluid heating apparatus according to any one of claims 1 to 4.

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