JP6252347B2 - Fluid heater - Google Patents

Description

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

  Technology that heats 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 and hot water cleaning toilet seats in general households. Widely applied in various fields. In the heating of such a fluid, a method of exchanging heat between a low-temperature side fluid that is a fluid to be heated and a high-temperature side fluid such as steam or a heat medium is often used. When it 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. Patent Document 2 discloses a fluid heating element formed by providing a resistance heating element on the other surface of a flat ceramic substrate whose one surface is a liquid contact surface, and further covering an insulating layer thereon. A ceramic heater is disclosed.

JP 2005-183371 A JP 2002-151236 A

  Due to the recent increase in interest in environmental conservation and power saving, a fluid heater using a resistance heating element is required to have a low power consumption and can efficiently heat a fluid. 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. Heat could not be efficiently transferred to the fluid flowing inside the pipe-shaped member. Further, in the structure shown in Patent Document 2, cracks are likely to occur at the bonding interface due to a slight difference in thermal expansion coefficient between the ceramic substrate and the insulating layer while the temperature change is repeated, and the reliability may be impaired.

  The present invention has been made in view of the problems of the conventional fluid heater, and an object thereof is to provide a highly reliable fluid heater excellent in thermal efficiency and reproducibility.

  In order to achieve the above object, a fluid heater provided by the present invention includes a flow path unit having a flow path of a fluid to be heated inside, and an electric insulating material accommodated in the flow path and having substantially the same thickness. The linear heating element is spirally wound at a pitch at which the insulating coating materials do not adhere to each other, and the extending direction of the spiral axis is substantially in the direction of the flow path. It is characterized by matching.

  ADVANTAGE OF THE INVENTION According to this invention, the highly reliable fluid heater excellent in thermal efficiency and reproducibility compared with the conventional fluid heater can be provided.

It is a longitudinal cross-sectional view which shows one specific example of the fluid heater of this invention. It is a top view which shows one specific example of the linear heating element which the fluid heater of this invention has. It is a perspective view which shows one specific example of the comb-tooth shaped member around which the linear heating element which the fluid heater of this invention has is wound. It is a perspective view which shows the plate-shaped member which comprises the comb-tooth shaped member of FIG. It is a front view which shows a mode that the outgoing side heat generating body and the back side heat generating body are wound around the comb-tooth shaped member of FIG. 3 via the spacer.

  First, embodiments of the present invention will be listed and described. A fluid heater according to an embodiment of the present invention includes a flow path unit having a flow path of a fluid to be heated inside, and a linear heating element that is accommodated in the flow path and covered with an electrical insulating material, The linear heating element is spirally wound at a pitch at which the insulating coating materials are not in close contact with each other, and the extending direction of the spiral axis substantially coincides with the direction of the flow path. With this configuration, it is possible to provide a highly reliable fluid heater that is superior in thermal efficiency and reproducibility compared to conventional fluid heaters.

  In the fluid heater according to the embodiment of the present invention described above, the linear heating element includes an outward heating element and a return heating element that reciprocate at least once in the flow path. It is preferable that the heating element is coaxial and the spiral winding directions are opposite to each other. This makes it possible to cancel the magnetic field generated by the spiral linear heating element.

  In the fluid heater according to the embodiment of the present invention described above, two or more flow paths containing the linear heating elements are provided in the flow path unit, and the flow paths extend in parallel to each other. It is preferable. As a result, it is possible to select a flow method of the heated fluid to be flown through the two or more flow paths from parallel and series, and to increase the degree of freedom in designing the flow path unit.

  In the fluid heater according to the above-described embodiment of the present invention, a heated fluid supply port is provided at the bottom of the flow path, and a heated fluid discharge port is provided at the top of the flow path. It is preferable. As a result, the entire linear heating element can be immersed in the fluid to be heated, so that extremely high thermal efficiency is ensured and the linear heating element can be prevented from being overheated locally.

  In the fluid heater according to the above-described embodiment of the present invention, it is preferable that the linear heating element is spirally wound around a comb-like member and accommodated in the flow path. In particular, when the linear heating element is composed of an outward heating element and a return heating element, the outward heating element is spirally formed at the back of the gap between adjacent tooth portions of the comb-like member. It is preferable that the return side heating element is spirally wound around the outside of the gap. As a result, the linear heating element can be accommodated in the flow path at a very high density.

  In the fluid heater according to the above-described embodiment of the present invention, it is preferable that a spacer for separating the forward heating element and the backward heating element is fitted to each tooth portion of the comb-like member. As a result, even when the linear heating elements are accommodated in the flow path at an extremely high density, it is possible to avoid the linear heating elements from coming into contact with each other and being locally overheated. Furthermore, it is preferable that the tip part of each tooth part of the comb-like member protrudes outward from the outermost peripheral part of the spiral of the return side heating element. As a result, even when the linear heating element is accommodated in the flow path at an extremely high density, it is possible to avoid the linear heating element from contacting the wall surface of the flow path unit and being overheated locally. .

  Next, a specific example of the fluid heater of the present invention will be specifically described with reference to FIG. A fluid heater 1 according to an embodiment of the present invention shown in FIG. 1 includes a substantially rectangular parallelepiped channel unit 10 having a channel through which a fluid to be heated flows, and a fluid to be heated flowing through the channel. It consists of a linear heating element 20 covered with an electrical insulating material that is heated to a temperature. More specifically, the flow path unit 10 includes a heated fluid supply port 11 and a discharge port 12 at both ends in the longitudinal direction, and a flow channel 13 communicating with the supply port 11 and the discharge port 12. Is formed inside.

  The flow path 13 is composed of two upper flow paths 13a and a lower flow path 13b extending in parallel with each other, and the heated fluid introduced into the flow path unit 10 via the supply port 11 is supplied. After entering through the port 11 and branching immediately and flowing through these two flow paths in parallel, they merge together immediately before the discharge port 12 and are discharged from the discharge port 12. The shape of the flow path 13 is not limited to this, and may be configured by a group of three or more parallel flow paths, or may be configured by only one flow path from the supply port to the discharge port. Also good. In the case of only one flow path, it may extend in a straight line, or may meander in the horizontal direction or the vertical direction. In the case of a plurality of flow paths, they may be communicated in parallel as shown in FIG. 1 or may be communicated in series.

  A flow path unit having a flow path as described above is formed by, for example, digging a groove having a desired pattern to be a flow path by machining on one surface of a solid block having a rectangular parallelepiped shape, and then performing this machining. It can be produced by covering a surface with a rectangular plate-shaped lid and adhering them by welding or brazing, etc., and perforating openings that respectively serve as supply ports and discharge ports at both ends of the flow path.

  Alternatively, a solid cylindrical member is provided with a flow passage penetrating in the axial direction thereof, and then a disc-shaped lid provided with openings for supply ports or discharge ports is adhered to both ends. Is also possible. In this case, the use of the pipe material saves the trouble of processing the through hole for the flow path, and therefore it can be more easily manufactured. The flow path of the fluid to be heated may be such that the processing roughness of the inner wall surface is roughened so that the fluid flowing inside tends to be turbulent, or a baffle plate is provided to lengthen the flow path. Thereby, the heat transfer efficiency from the covered linear heating element 20 can be improved.

  When producing the flow path unit, it is preferable to install the supply port and the discharge port so that the fluid to be heated enters from the lower side and exits from the upper side. Specifically, as shown in FIG. 1, it is preferable to provide the supply port 11 at the bottom of the flow path 13 and provide the discharge port 12 at the top of the flow path 13. Thus, when the fluid to be heated is introduced into the flow path 13, the fluid to be heated can be filled in the flow path 13 from the bottom to the top, and when the fluid to be heated is a liquid, the flow path 13. The liquid can be filled without generating an air pocket. As a result, since all the coated linear heating elements 20 can be immersed in the fluid to be heated, extremely high thermal efficiency can be realized.

  On the other hand, if the position of the discharge port 12 is not at the top of the flow path 13, the heated fluid is discharged from the discharge port 12 before all of the coated linear heating elements 20 are immersed in the heated fluid. When the fluid to be heated is liquid, the upper part of the coated linear heating element 20 is exposed on the liquid surface of the fluid to be heated, and heat cannot be efficiently transferred. Moreover, in the exposed portion, the coated linear heating element 20 is likely to be abnormally overheated, which may cause problems such as dissolution of the coating material.

  Various materials such as metal and resin can be used as the material of the flow path unit 10, and can be appropriately selected depending on the nature of the fluid to be heated, its operating temperature range, the installation environment of the flow path unit 10, and the like. In the case of a metal, for example, copper, aluminum, stainless steel or the like can be used. These metals are versatile and cost-effective, and can be easily manufactured by machining, brazing, welding, and other processing techniques, so depending on the location of the heater and the size and shape of the heater required It becomes possible to design relatively freely. In addition, metals have the advantage that they have a higher heat resistant temperature and superior mechanical strength compared to resins, and stainless steel is more excellent in environmental resistance.

  On the other hand, in the case of resin, for example, acrylic, fluororesin or the like can be used. These resins are general-purpose and have excellent cost performance, and can be easily produced by machining techniques such as machining and welding. In particular, in the case of a resin, since the melting point is lower than that of a metal, there is an advantage that shape processing such as welding can be easily performed at a relatively low temperature. In addition, the resin has the advantage of being lightweight and excellent in environmental resistance, and in particular, a fluororesin represented by Teflon has extremely high environmental resistance. For this reason, it can be suitably used for applications where there is a weight limit or for which the environmental load is particularly high.

  A metal heating wire can be used for the linear heating element 20 covered with the electrical insulating material housed in the flow path 13. As the material of the metal element wire, stainless steel, nickel-chromium, an alloy containing chromium, or the like can be used. For example, vinyl, polyethylene, polyimide, silicone, fluororesin, or the like can be used as an electrical insulating material that covers the entire surface of the metal strand with substantially the same thickness. Specific materials can be appropriately selected depending on the type of fluid to be heated and the operating temperature range thereof. When heat resistance and environment resistance are required, it is desirable to use a fluororesin such as Teflon. In other cases, cost advantage can be obtained by using general-purpose vinyl, polyethylene, polyimide, or silicone.

  The linear heating element 20 covered with the electrical insulating material is spirally wound and accommodated in the flow path 13. At that time, as shown in FIG. 1, the extending direction of the spiral axis and the direction of the flow path 13 are made substantially parallel. Further, the linear heating element 20 is wound spirally at a pitch at which the insulating coating materials do not contact each other. Thereby, the linear heating element 20 can be accommodated in the flow path 13 with high density, and all the surfaces of the linear heating element 20 can be brought into contact with the fluid to be heated, so that extremely high thermal efficiency is achieved. can do. On the other hand, if the insulating coatings are in contact with each other, the area in contact with the fluid to be heated is reduced and the thermal efficiency is lowered. In addition, the heat generation density is increased at that portion, causing local abnormal overheating. It is not preferable.

  The linear heating element 20 is preferably reciprocated in the flow path 13 at least once. Thereby, the linear heating element 20 can be accommodated in the flow path 13 with a higher density. When reciprocating once in the flow path 13, as shown in FIG. 2, the forward heating element 21 and the backward heating element 22 are coaxial and spiral so that the spiral winding directions are opposite to each other. It is preferable to wind. For example, when the forward heating element 21 is clockwise, the backward heating element 22 is preferably left-handed. By reversing the spiral winding direction in this way, the magnetic field generated by each coil can be canceled out, and the influence of magnetism on the periphery by the heater can be suppressed. FIG. 2 shows a state where the return side heating element 22 is spirally wound at a pitch P at which the insulating coating materials do not contact each other.

  As described above, when the linear heating element 20 is housed in the flow path 13 in a spirally wound state, it is preferable to use a comb-like member in order to ensure that the insulating coating materials do not adhere to each other. . For example, the comb-like member 30 of one specific example shown in FIG. 3 has a three-dimensional structure in which four rectangular pieces having substantially the same shape having comb teeth are radially formed in a cross-section with the comb-tooth side facing outward. By winding the linear heating element 20 along the comb teeth, it can be spirally wound at a desired pitch. Then, the extending direction of the spiral axis can be made to coincide with the direction of the flow path 13 by inserting the comb-like member 30 into the flow path 13 while the linear heating element 20 is still wound.

  The comb-tooth shaped member 30 of FIG. 3 can be produced by combining two substantially identical rectangular plate-like members 31 having comb teeth as shown in FIG. 4 on both side surfaces, for example. That is, two rectangular plate-like members having the same shape are prepared, comb teeth are provided on both side surfaces extending in the longitudinal direction, and a notch is formed from one end portion in the longitudinal direction to the central portion in the longitudinal direction. The comb-like member 30 can be formed by fitting the notches into each other. The material of the comb-like member 30 is preferably the same as the material of the flow path unit 10.

  When the forward heating element 21 and the return heating element 22 that reciprocate the linear heating element 20 once are formed, the depth of the gap 33 between adjacent tooth portions 32 of the comb-like member 30 shown in FIG. It is preferable that the forward heating element 21 is spirally wound on the side and the return heating element 22 is spirally wound on the outer side of the gap 33. At that time, a spacer 34 for separating the forward heating element 21 and the backward heating element 22 is provided at each tooth portion 32 of the comb-like member 30 so that the outward heating element 21 and the backward heating element 22 do not contact each other. It is preferable to fit.

  Furthermore, it is preferable that the front end portion of each tooth portion 32 of the comb-like member 30 protrudes outward from the outermost peripheral portion of the spiral of the return side heating element 22. FIG. 5 shows a state in which the distal end portion of each tooth portion 32 of the comb-like member 30 protrudes outward by a length L from the outermost peripheral portion of the spiral of the return side heating element 22. As a result, it is possible to avoid the linear heating element 20 from coming into contact with the wall surface of the flow path unit 10 and being locally overheated.

  The flow path unit 10 is provided with a temperature sensor 14 for controlling the temperature of the linear heating element 20. It is preferable to use a resistance temperature detector for the temperature sensor 14. The resistance temperature detector is formed by, for example, forming a platinum resistance element on the flat surface portion of the insulating ceramic substrate as a temperature measuring element portion by means such as vapor deposition, and adjusting the resistance value to a predetermined value, and then the electrode pad portion. It can be obtained by bonding the lead wires to each other by means such as bonding. The platinum resistor and the electrode pad are preferably covered with an insulating film. With this configuration, the temperature measuring element unit can be reduced in size, and the temperature responsiveness can be improved.

  The resistance temperature detector can be installed on the outer wall surface or the inner wall surface of the flow path unit 10, or in the flow path (space) or on the surface of the insulating coating portion of the linear heating element. The specific installation location is appropriately selected in consideration of the part to be measured and matching with the control device. During installation, the lead wire of the resistance temperature detector is covered with a metal sheath or a resin pipe, passed through the insertion hole provided in the wall surface of the flow path unit 10, and then welded to maintain the sealing performance with the outside. The temperature in the flow path unit 10 can be measured as it is.

  When measuring the fluid temperature inside the flow path unit 10, in order to avoid mechanical damage due to pressure from the heated fluid, and depending on the type of heated fluid, the temperature of the resin pipe is measured in consideration of environmental resistance. It is preferable that the element portion is covered and the tip portion is filled with a resin substantially the same material as the resin pipe and sealed. Further, when measuring the temperature of the linear heating element, the temperature measuring element is brought into contact with the surface of the electrical insulating material covering the linear heating element and then covered with the resin pipe as described above. It is preferable to seal by the means.

  When installing on the inner and outer wall surfaces of the flow path unit 10, it can be fixed using an adhesive. As the adhesive, an adhesive 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 that can withstand the temperature range required for fluid heating and elasticity, so it absorbs a slight difference in thermal expansion between the temperature measuring element and peripheral members. This is preferable.

  As mentioned above, although the specific example was given and demonstrated about the fluid heater 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. That is, the technical scope of the present invention extends to the claims and their equivalents.

  A solid rectangular solid block having a width of 50 mm, a height of 50 mm, and a length of 100 mm made of PTFE was prepared, and four through-holes with an inner diameter of 20 mm extending in the longitudinal direction were provided therein as flow paths. Space portions communicating with these four flow paths were provided at both ends in the longitudinal direction of the solid block so that the fluid to be heated flows in parallel with these four flow paths. As a coated linear heating element housed in the four flow paths of the flow path unit thus produced, a thickness of a metal strand made of SUS304 soft wire having an outer diameter of 0.45 mm and a length of about 10 m is obtained. What coated 0.5 mm PTFE was prepared.

  Each of the coated linear heating elements was spirally wound around four PTFE comb-like members as shown in FIG. At that time, as shown in FIG. 5, first, a right-handed spiral is wound around the inner side of the comb-like member, and then a PTFE annular spacer is fitted to each tooth part, and the left-handed outside of the comb-like member. Wound in a spiral. As a result, the forward heating element and the return heating element could be wound coaxially. Moreover, the front-end | tip part of the tooth part of the comb-tooth shaped member was able to protrude from the outer side of the outermost periphery part of a return side heating element.

  The four comb-like members, each of which the coated linear heating elements manufactured in this way were wound one reciprocally from end to end, were accommodated in the four flow paths, respectively. Further, the resistance thermometer is brought into contact with the covering portion on the linear heating element, and in this state, a part of the linear heating element in contact with the resistance thermometer is covered with the resistance thermometer with a pipe, The tip of the pipe was welded and sealed so that the heated fluid did not enter the inside. Further, rectangular lid members were welded to both ends of the flow path unit, and through holes were provided on one side at a position communicating with the lowermost part of the flow path and on the other side at a position communicating with the uppermost part of the flow path. And the pipe made from PTFE was attached to these through holes by welding, and it was set as the supply port and the discharge port, respectively. In this way, a fluid heater of Sample 1 was produced.

  For comparison, instead of the configuration of the fluid heater of the sample 1 in which the coated linear heating element is spirally wound around four comb-like members, the heat generation is made of SUS304 soft wire having an outer diameter of 0.45 mm. The body is inserted into a sheath tube made of SUS304 having an outer diameter of 2.4 mm and an inner diameter of 2.0 mm, and a sheath type heating wire filled with MgO is spirally wound between the inner wall surface of the sheath tube and the heating element. 4 were prepared. These four sheath type heating wires are respectively accommodated in the four flow paths of the flow path unit produced in the same manner as the fluid heater of the sample 1 described above, and thereafter the same as the fluid heater of the sample 1 described above. A fluid heater of Sample 2 was produced.

  With each of the fluid heaters of Samples 1 and 2 thus prepared, water heated at a temperature of about 22 ° C. as a fluid being passed at a flow rate of 1.0 L / min, the linear heating element The temperature of water was raised by applying about 2 kW of power to the metal wire. After about 520 seconds, the power supply to the metal element wire of the linear heating element was stopped, and the temperature was lowered by heat exchange by passing water. This heat cycle was repeated 1000 times. Thereafter, a water temperature increase test was performed under the same conditions as in the initial stage. At this time, it was confirmed that there were no fatal defects in the water entrance / exit temperature accompanying the temperature increase and the appearance after the heat cycle.

  As a result, in the fluid heater of sample 1, the water inlet / outlet temperature difference was 25 ° C. in the initial evaluation, and even when the heat cycle was repeated 1000 times, no appearance abnormality or local overheating was observed, and the performance was also initial. The numerical value equivalent to was shown. On the other hand, in the fluid heater of Sample 2, the water inlet / outlet temperature difference in the initial evaluation is 15 ° C., and in the performance evaluation after 1000 heat cycles, the water inlet / outlet temperature difference is 9.7 ° C. And worsened. After disassembling and inspecting the inside, it was confirmed that the fluid heater of Sample 2 was cracked in the SUS304 sheath tube.

  Sample 1 was suitable for outer diameter and material as compared with sample 2, so it was found that sample 1 could be placed densely in the flow path, and extremely high thermal efficiency was obtained. Moreover, it was found that Sample 1 has fewer contact interfaces between the heating element and the fluid than Sample 2, and is excellent in heat transfer. Furthermore, it was found that Sample 1 is superior to Sample 2 in terms of long-term stability resulting from stress in a spirally wound state. Thus, it has been found that according to the present invention, a fluid heater having high thermal efficiency and high reliability can be obtained.

DESCRIPTION OF SYMBOLS 1 Fluid heater 10 Flow path unit 11 Supply port 12 Discharge port 13 Flow path 13a Upper flow path 13b Lower flow path 14 Temperature sensor 20 Linear heating element 21 Outward heating element 22 Return heating element 30 Comb-like member 31 Plate member 32 Teeth 33 Gap 34 Spacer P Pitch L Projection length

Claims (5)

A flow path unit having a flow path of a fluid to be heated inside, and a linear heating element housed in the flow path and covered with an electrical insulating coating material, the linear heating element being the electrical insulating coating The material is spirally wound around the comb-like member at a pitch at which the materials do not adhere to each other, and the extending direction of the spiral axis substantially coincides with the direction of the flow path, and the linear heating element is disposed in the flow path. The forward heating element and the return heating element that reciprocate at least once, and the outward heating element and the return heating element are coaxial, and the spiral winding directions are opposite to each other. A fluid heater in which a spacer for separating the forward heating element and the return heating element in a direction intersecting the spiral axis is fitted to each tooth portion of the member . The fluid heater according to claim 1, wherein two or more flow paths containing the linear heating elements are provided in the flow path unit, and the flow paths extend in parallel to each other. And the supply port of the heated fluid is provided at the bottom of the channel, the outlet of the heated fluid at the top of the channel is provided, the fluid heating according to claim 1 or claim 2 vessel. The forward heating element is spirally wound around the gap between adjacent teeth of the comb-like member, and the return heating element is spirally wound outside the gap. The fluid heater according to claim 1 , wherein the fluid heater is provided. 5. The fluid heater according to claim 4 , wherein a tip end portion of each tooth portion of the comb-like member protrudes outward from an outermost peripheral portion of the spiral of the return side heating element.

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