JP2015152219A - fluid heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid heating device with enhanced heat efficiency.SOLUTION: A fluid heating device heats fluid, and includes: a tabular flow channel formation body 1 provided with one or a plurality of flow channels C for fluid to be heated inside; a heater unit 2 contacting at least one surface of the flow channel formation body; and a cover material 3 covering the heater unit 2. Here, the flow channels C extend parallel to the contact surface with the heater unit 2, and when a distance from the contact surface to the flow channel C located at the shortest distance is denoted by t1, a thickness of the cover material 3 is denoted by t2, a heat conductivity of the flow channel formation body 1 is denoted by c1, and a heat conductivity of the cover material 3 is denoted by c2, a relation of c1/t1>c2/t2 is satisfied.

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 high melting point metal that becomes a resistance heating element is applied to one side of a ceramic sheet by a printing method, and this is wound so that the resistance heating element is on the outer peripheral surface of a ceramic pipe material. A ceramic heater is disclosed that is integrated by bonding and firing after being applied.

JP 2005-183371 A

  Due to the recent increase in interest in environmental conservation and power saving, fluid heating devices using heating elements as described above are required to be capable of heating fluid efficiently with low power consumption. However, in the structure shown in Patent Document 1 described above, since the material of the sheet covering the resistance heating element is the same as the material of the pipe member around which the sheet is wound, it is generated in the resistance heating element sandwiched between them. The amount of heat generated could not be transferred efficiently to the fluid flowing inside the pipe-shaped member.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a fluid heating apparatus with improved thermal efficiency by suppressing the loss of heat generated in the resistance heating element.

  In order to achieve the above object, a fluid heating device provided by the present invention is a fluid heating device for heating a liquid, and is a plate-like channel forming body provided with one or a plurality of channels for a fluid to be heated inside. And a heater unit that contacts at least one surface of the flow path forming body, and a cover material that covers the heater unit, and the flow path extends in parallel with the contact surface with the heater unit, The distance from the contact surface to the channel located at the shortest distance is t1, the thickness of the cover material is t2, the thermal conductivity of the channel forming body is c1, and the thermal conductivity of the cover material is c2. In this case, c1 / t1> c2 / t2.

  According to the present invention, since the loss of heat generated in the resistance heating element can be suppressed, a fluid heating device with extremely high thermal efficiency can be provided.

It is a disassembled perspective view which shows one specific example of the fluid heating apparatus of this invention. It is a longitudinal cross-sectional view which shows the other 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 longitudinal cross-sectional view which shows the other specific example of the fluid heating apparatus of this invention. It is sectional drawing which shows the distance to the flow path located in the shortest distance from the contact surface of the heater unit and flow path formation body in the fluid heating apparatus of this invention, and the thickness of a cover material. 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.

  First, embodiments of the present invention will be listed and described. A fluid heating apparatus according to an embodiment of the present invention is a fluid heating apparatus that heats a liquid, and includes a plate-shaped flow path forming body including one or a plurality of flow paths of a fluid to be heated therein, and the flow path formation. A heater unit that contacts at least one surface of the body and a cover material that covers the heater unit, and the flow path extends in parallel with the contact surface with the heater unit, and is shortest from the contact surface. When the distance to the channel located at the distance is t1, the thickness of the cover material is t2, the thermal conductivity of the channel forming body is c1, and the thermal conductivity of the cover material is c2, c1 / t1> It is characterized by c2 / t2. With this configuration, it is possible to suppress the loss of heat generated in the resistance heating element, and thus it is possible to provide a fluid heating device with extremely high thermal efficiency.

  In the fluid heating apparatus according to the embodiment of the present invention, it is preferable that the c1 is 100 W / (m · K) or more. This makes it possible to provide a fluid heating device with higher thermal efficiency.

  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, Two heater units 2 each having a rectangular plate shape, which are substantially in contact with both surfaces 1a and 1b, which are heated surfaces of the flow path forming body 1, and substantially the same plane as the flow path forming body 1 and the heater unit 2 A rectangular plate that has a visual shape and presses the heater unit 2 toward the flow path forming body 1 and covers substantially the entire surface of the heater unit 2 opposite to the surface that contacts the flow path forming body 1. The cover material 3 is shaped.

  As described above, the amount of heat transfer per unit time to the fluid heating device can be increased by bringing the heater units 2 into contact with both surfaces of the flow path forming body 1, but the amount of heat transfer may be small. If there is no room for installation, the heater unit 2 and the cover material 3 may be provided only on one side of the flow path forming body 1 as shown in FIG.

  The heater unit 2 includes, for example, a layered resistance heating element formed in a predetermined circuit pattern, and a first insulating layer and a second insulating layer that sandwich the resistance heating element from both sides to ensure electrical insulation. The The 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, but avoiding contact with a high temperature portion. Is necessary, it is preferably used in a state of being housed in a heat insulation means including air insulation or a protection means such as a container. In addition, when the flow-path formation body 1 and the cover material 3 are formed with a nonelectroconductive material, the direction which contact | abuts the nonelectroconductive material side among a 1st insulating layer and a 2nd insulating layer can be eliminated.

  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, operating conditions such as temperature and pressure, the installation environment of the fluid heating device, and the like. For example, when corrosion resistance is required, copper, brass, phosphor bronze, and aluminum (A3003 material), which are relatively excellent in corrosion resistance, are preferable. When strength is required, ceramics such as SiC, AlN, and SiSiC are selected. It is preferable to do. Moreover, when importance is attached to high heat transfer performance, copper, aluminum, SiC, AlN, and SiSiC, which are materials having high thermal conductivity, are preferable. In particular, the thermal conductivity is more preferably 100 W / (m · K) or more.

  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. 3, it is preferable to form an inlet / outlet (also referred to as a tap) at both openings of each flow path C by connecting joints such as a short tube 4 made of Teflon by welding or the like. 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 wall surface in the flow path may be roughened so that the fluid to be heated flows in a turbulent state in the flow path. This makes it possible to further increase the thermal efficiency. Further, as shown in FIG. 4, the flow path C may meander on a surface parallel to the heated surface of the flow path forming body 11. Thereby, since a flow path can be lengthened, the to-be-heated fluid can be heated up to higher temperature. 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.

  The number of flow paths C is not limited to one or two as shown in FIGS. 1 and 2, but may be three or more as shown in FIG. 5 (a). When a plurality of flow paths C are provided in this way, as shown in FIG. 5A, the flow path forming body 21 is arranged so that all the central axes of the flow paths C are aligned in the central portion in the thickness direction. Alternatively, as shown in FIG. 5B, several pieces may be arranged at different positions in the thickness direction of the flow path forming body 31. As shown in FIG. 2, when the heater unit 2 is provided only on one surface of the flow path forming body 1, the flow path C is disposed at a position closer to the heater unit 2 than the central portion in the thickness direction of the flow path forming body 1. It is preferable to arrange them.

In the above-described fluid heating apparatus according to a specific example of the present invention, as shown in FIG. 6, the distance from the contact surface of the heater unit 2 to the flow path C located at the shortest distance in the flow path forming body 1 described above. Is t1, the thickness of the cover material 3 is t2, the thermal conductivity of the flow path forming body 1 is c1, and the thermal conductivity of the cover material 3 is c2, the following equation 1 is satisfied.
[Formula 1]
c1 / t1> c2 / t2

  By satisfying the relationship of c1 / t1> c2 / t2 as described above, the fluid to be heated that flows in the flow path C of the fluid heating device can be efficiently heated. That is, in order to evaluate the thermal efficiency of the fluid heating device, to what extent the heat generated by the heating element in the fluid heating device contributes to the heating of the heated fluid flowing in the flow path C of the flow path forming body 1, and However, it is necessary to know how much heat is dissipated outside the system through a cover material for fixing the heating element. As a result of intensive studies on the movement of heat generated in the heater unit 2 provided on one side, it was found through experiments that it can be easily evaluated by using the parameters of the above-described formula 1.

  That is, the heat transfer from the resistance heating element contributing to the heating of the fluid to the flow path C of the flow path forming body 1 increases if the thermal conductivity of the flow path forming body 1 is large. If the shortest distance to one channel C is large, it becomes a heat transfer resistance and it takes time for heat transfer. On the other hand, if the thermal conductivity of the cover material is large, the amount of heat dissipated outside the system through the cover material increases, and if the cover material is thick, it becomes a heat transfer resistance and heat dissipation can be suppressed.

  The cover material 3 is not limited to one sheet, and the heater unit 2 may be covered with two or more different cover materials. For example, you may make it make the role which presses the heater unit 2 toward the flow-path formation body 1, and the role of heat insulation to each bear a different member.

  For example, examples of the member that imparts heat insulation include fluororesin, polyimide resin, and mica. These are also preferable in that they can be used without any problem even in a temperature range exceeding 200 ° C. As a member that plays the role of a pressing plate, a general-purpose and inexpensive metal is preferable. In this case, the same material as that of the flow path forming body 1 is preferable because the thermal expansion coefficient matches. However, in this case, in order to electrically insulate the resistance heating element, it is necessary to sandwich both sides of the resistance heating element between the first insulating layer and the second insulating layer.

As described above, when the heater unit 2 is covered with two or more different cover materials, c2 and t2 in the above equation 1 may be replaced with cn and tn in the following equations 2 and 3, respectively.
[Formula 2]
cn = Σ (ci × ti) / Σti, i = 1 to n
[Formula 3]
tn = Σti, i = 1 to n

  A resistance heating element generates Joule heat by flowing electricity supplied through electrode portions at both ends to a conductive wire, and can be manufactured by patterning stainless steel or nickel-chrome foil by etching or the like. it can. The circuit pattern of the resistance heating element may be a meandering pattern uniformly between a pair of electrodes, or may be a circuit pattern meandering irregularly as shown in FIG. Alternatively, as shown in FIG. 7B, 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 can be increased on the inlet side where the fluid to be heated, which is lower in temperature than the outlet side, can be heated 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. 7A and 7B 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 has a gap between the layers in contact with each other so that heat can be transferred quickly during heating and cooling, as in the case of the first insulating layer described above. It is important to arrange so that no occurs. 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 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.

  The flow path forming body 1, the heater unit 2, and the cover material 3 are integrated by being coupled by a coupling means such as a bolt nut and screw fastening. Specifically, a through hole penetrating in the thickness direction is provided in both the flow path forming body 1 and the cover material 3, and a bolt 5 is inserted into each through hole and tightened with a nut 6 at the tip thereof. Can do. If 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 cover member 3, it is necessary to provide a through hole at a position corresponding to the heater unit 2.

  Alternatively, a through hole penetrating in the thickness direction is provided in one of the cover material 3 and the flow path forming body 1, and a female screw corresponding to the through hole is provided in the other, and a male screw is provided in each through hole. You may fasten by inserting and screwing 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 is determined by the difference in thermal expansion coefficient between the flow path forming body 1 and the cover material 3, the temperature gradient in the thickness direction at the time of start-up, or the like. 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.

  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.

[Example 1]
Eleven types of 20 mm long x 100 mm wide x 9 mm thick made of Cu, SiC, AlN, SiSiC, Al (A3003), brass, phosphor bronze, carbon steel, Al ₂ O ₃ , SUS304, and SUS316, respectively. These plate-shaped members were prepared, and two through-holes extending in the longitudinal direction with an inner diameter of 3 mm as flow paths were provided in the center of the plate-shaped member in the thickness direction. Thereby, the shortest distance t1 to a flow path will be 3 mm in any of the front and back of a plate-shaped member.

  And the short pipe was attached to both opening parts of each flow path, and it was set as the inlet / outlet of the to-be-heated fluid. One heater unit was brought into contact with the front and back surfaces of the flow path forming body thus obtained, and each heater unit was covered with a plate-shaped cover material. In the heater unit, a heating element obtained by forming a circuit pattern by etching on a stainless steel foil having a thickness of 20 μm has the same vertical and horizontal sizes as the flow path forming body and has a thermal conductivity of 5 W / (m · K). A silicon insulating sheet sandwiched between and electrically insulated was used.

  A feeding cable was attached to both ends of the stainless steel heating element, and a temperature sensor was fixed to the surface of the flow path forming body by bonding. As the cover material, a plate-like member made of SUS304 having a thickness t2 of 1.5 mm, a length of 20 mm, and a width of 100 mm was used. And the fluid heating apparatus of the samples 1-11 piled up in order of a cover material, a heater unit, a flow path formation body, a heater unit, and a cover material by fastening using six stainless steel M3 bolts and nuts. Produced.

  15 ° C. tap water as a fluid to be heated is introduced into the fluid heating device of each sample at a flow rate of 0.5 L / min, and the heating element is set so that the temperature of the temperature sensor installed on the surface of the flow path forming body becomes 100 ° C. After heating, the temperature rise ΔT of the liquid to be heated was measured. The results are shown in Table 1 below together with the materials used for the flow path forming body and the cover material, their thermal conductivities c1 and c2, and c1 / t1 and c2 / t2 which are values obtained by dividing these by t1 and t2, respectively.

  As can be seen from Table 1 above, in samples 1 to 8, the temperature rise ΔT of the liquid to be heated exceeds 10 ° C., and the water supply is more efficient than samples 9 to 11 in which the temperature rise ΔT is less than 5 ° C. The water could be heated.

[Example 2]
Three types of plate members (20 mm long × 100 mm wide) made of brass having a thickness of 5 mm, 9 mm, and 22 mm are prepared as flow path forming bodies, each having a through-hole with an inner diameter of 3 mm in the central portion in the thickness direction as in Example 1. Two were provided. Thereby, the shortest distance t1 from the front and back surfaces of the plate member to the flow path is 1 mm, 3 mm, and 10 mm, respectively. As the cover material, a SUS304 plate having a thickness t2 of 1 mm was used. Thereafter, the fluid heating devices of Samples 12 to 14 were produced in the same manner as in Example 1. The temperature rise ΔT was measured in the same manner as in Example 1 for the fluid heating devices of Samples 12-14. The results are shown in Table 2 below.

  As can be seen from Table 2 above, in Samples 12 to 13, the temperature rise ΔT of the liquid to be heated exceeded 10 ° C., and tap water could be heated more efficiently than Sample 14.

[Example 3]
Three types of plate members (length 20 mm × width 100 mm) made of SiC having a thickness of 5 mm, 9 mm, and 27 mm were prepared as flow path forming bodies. Two were provided. As a result, the shortest distances t1 from the front and back surfaces of the plate-like member to the flow path are 1 mm, 3 mm, and 12 mm, respectively. The cover material was the same as in Example 2. Thereafter, in the same manner as in Example 1, fluid heating devices of Samples 15 to 17 were produced. The temperature rise ΔT was measured in the same manner as in Example 1 for the fluid heating devices of Samples 15 to 17. The results are shown in Table 3 below.

  As can be seen from Table 3 above, in Samples 15 to 16, the temperature rise ΔT of the liquid to be heated exceeded 10 ° C., and the tap water could be heated more efficiently than Sample 17.

[Example 4]
As the flow path forming body, three plate members (20 mm long × 100 mm wide) made of Al (A3003) are prepared every three, and each of the through holes having an inner diameter of 3 mm is formed in the central portion in the thickness direction in the same manner as in Example 1. Book provided. Thereby, the shortest distance t1 from the front and back surfaces of the plate member to the flow path is 2 mm. Each of the cover material SUS304, brass, and the thickness t2 consisting _Al 3 003 were used three kinds of plates 2 mm. Thereafter, in the same manner as in Example 1, fluid heating devices for Samples 18 to 20 were produced. The temperature rise ΔT was measured in the same manner as in Example 1 for the fluid heating devices of Samples 18 to 20. The results are shown in Table 4 below.

  As can be seen from Table 4 above, Sample 18 was able to heat tap water more efficiently than Samples 19-20.

1, 11, 21, 31 Channel formation body 1a, 1b Heated surface 2 Heater unit 3 Cover material 4 Short tube 5 Bolt 6 Nut C Channel

Claims (2)

A fluid heating apparatus for heating a liquid, a plate-shaped flow path forming body provided with one or more flow paths of a fluid to be heated inside, a heater unit that contacts at least one surface of the flow path forming body, A cover material covering the heater unit;
The flow path extends parallel to the contact surface with the heater unit, and the distance from the contact surface to the flow path located at the shortest distance is t1, and the thickness of the cover material is t2. A fluid heating device in which c1 / t1> c2 / t2 where c1 is a thermal conductivity of the path formation body and c2 is a thermal conductivity of the cover member.   The fluid heating device according to claim 1, wherein c1 is 100 W / (m · K) or more.

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