JP2004028524A - Floor heating mat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently transmit heat to a floor finishing material from a heat radiation pipe by certainly closely sticking a top part of the heat radiation pipe to the floor finishing material, and to suppress wasteful heat quantity radiated under a floor or the like. <P>SOLUTION: This floor heating mat 3 has a body base material 12 of a synthetic resin foam, and the heat radiation pipe 13 of a synthetic resin stored in a groove part 23 formed in the body base material 12. The top part of the heat radiation pipe 13 is projected from a surface of the body base material 12, and a bottom part of the groove part 23 is formed with two projection parts 24 extending along the groove part 23 and supporting the heat radiation pipe 13. Thereby, the top part of the heat radiation pipe 13 is certainly closely stuck to the floor finishing material 16 with the floor finishing material 16 constructed on the body base material 12, and a contact area between the heat radiation pipe 13 and an inner circumferential part of the groove part 23 can be reduced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floor heating mat, and more particularly, to a floor heating mat configured to efficiently transfer heat from a radiating pipe through which hot water flows to a floor finishing material.
[0002]
2. Description of the Related Art Conventionally, a hot water type floor heating system in which hot water is circulated in a floor heating mat laid below a floor finishing material and the floor finishing material is heated by the heat of the hot water has been put to practical use. ing. Here, various types of floor heating mats have been proposed or put into practical use. Among them, a plate-shaped main body made of a synthetic resin foam (for example, styrofoam) and a main body have been proposed. Floor heating mats provided with a radiating pipe made of synthetic resin (for example, cross-linked polyethylene) for providing warm water to heat the floor finishing material are provided.
[0003]
As shown in FIG. 9, in such a floor heating mat, generally, the radiator tubes 101 are housed in grooves 102 formed in the main body 100, and are provided on the upper surfaces of the main body 100 and the radiator tubes 101. Then, a sheet-like thin film member 103 made of metal (for example, aluminum) having a high thermal conductivity is attached, and the heat of the hot water in the radiator tube 101 is transmitted to the floor finishing material via the thin film member 103. However, in such a floor heating mat, the contact area between the heat radiating pipe 101 and the inner peripheral portion of the groove 102 is large, and a large amount of waste heat is radiated from the heat radiating pipe 101 to the bottom of the floor via the main body 100. Had occurred.
[0004]
Therefore, in the floor heating mat described in Japanese Patent Application Laid-Open No. 2002-81661, a plurality of protrusions are formed at predetermined intervals in the length direction of the groove on the inner peripheral portion of the groove, and the radiator tube is housed in the groove. In this state, the heat radiating pipe is supported by the plurality of protrusions, but the heat radiating pipe does not come into contact with the groove between the plurality of protrusions, so that an adiabatic gap is formed in which air with low thermal conductivity is interposed. Will be. Therefore, the contact area between the heat radiating tube and the inner peripheral portion of the groove is reduced, and the amount of heat radiated from the heat radiating tube to the main body is reduced.
[0005]
In the conventional floor heating mat, the floor finishing material applied on the main body is made to rattle so that the top of the heat radiating tube does not protrude from the surface of the main body. Although it is necessary to prevent this, it is difficult to manufacture the groove of the main body so that the surface of the main body and the top of the heat radiating tube are substantially flush with each other. Becomes larger than the outer diameter of the radiator tube, and the radiator tube is completely accommodated in the groove. In such a state, the radiator tube and the floor covering material do not adhere to each other, so that heat cannot be efficiently transmitted from the radiator tube to the floor covering material. Further, in the floor heating mat described in the above-mentioned publication, since the protrusions are formed at predetermined intervals in the length direction of the groove, the state of close contact between the radiator tube and the floor finish material is not provided where there is no protrusion. Poorly, the heat transfer efficiency is deteriorated.
An object of the present invention is to ensure that the heat radiating pipe is in close contact with the floor finishing material to efficiently transfer heat from the heat radiating pipe to the floor finishing material, to minimize the amount of waste heat radiated to the floor or the like, and the like. .
[0006]
According to a first aspect of the present invention, there is provided a floor heating mat which is housed in a main body made of a synthetic resin foam, and is housed in a groove formed in the main body base and allows hot water to flow therethrough. And a radiating pipe made of synthetic resin for heating the radiating pipe, wherein a top portion of the radiating pipe is configured to protrude from a surface of the main body base material.
[0007]
This floor heating mat is laid below the floor finishing material, and heats the floor finishing material by circulating hot water. The main body substrate is a member formed of a synthetic resin foam such as styrene foam having a high heat insulating property. The main body substrate includes a rectangular plate, a panel, or an elongated plate for installation between joists. And various types having a planar shape. On the other hand, the heat radiating tube is formed of a synthetic resin such as cross-linked polyethylene, and is housed in a groove formed in the main body base material. Hot water supplied from an outdoor heat source device is passed through the radiator tube, and the heat of the hot water is transmitted to the floor finishing material to heat the floor surface.
[0008]
Here, since the top of the heat radiating pipe projects outward from the surface of the main body base material, when the floor finishing material is applied on the main body member, the heat radiating pipe surely contacts the floor finishing material, and Heat can be efficiently transferred from the pipe to the floor covering. Further, even when there is some manufacturing error in the groove portion, the outer diameter of the resin tube, and the like, the heat radiating tube and the floor finish material are easily adhered to each other.
[0009]
A floor heating mat according to a second aspect of the present invention is the floor heating mat according to the first aspect, wherein a plurality of protrusions extending along the groove and supporting the radiation pipe are formed at the bottom of the groove. . Therefore, a portion other than the projection portion of the bottom of the groove does not contact the radiator tube, and the contact area between the radiator tube and the inner peripheral portion of the groove decreases. That is, the amount of heat radiated from the heat radiating tube to the main body substrate can be suppressed. Further, since the plurality of protrusions extend along the groove, the close contact state with the floor finishing material over the entire length of the radiator pipe is better than that of the floor heating mat described in JP-A-2002-81661. Therefore, heat can be efficiently transmitted from the radiator tube to the floor finishing material.
[0010]
The floor heating mat according to claim 3 is configured such that in the invention according to claim 2, the height of the protrusion from the bottom of the groove is higher than the protrusion amount of the radiating tube from the surface of the main body base material, and When the floor finishing material is applied on the base material, the projections are deformed and the top of the heat radiating pipe is in close contact with the floor finishing material, so that the top of the heat radiating pipe and the surface of the main body are substantially flush with each other. It is characterized by that. As described above, the top of the heat radiating tube is in a state protruding from the surface of the main body base material. In this state, when the floor finishing material is pressed against the main body base material to apply the floor finishing material, the main body base material is pressed. The radiating tube whose top is protruded from is also pressed toward the groove by the floor finishing material. At this time, the projections supporting the heat radiating tubes are deformed, and the heat radiating tubes are pushed into the grooves in a state where the heat radiating tubes are in close contact with the floor finishing material, so that the heat of the hot water is efficiently transmitted from the heat radiating tubes to the floor finishing material. Will be able to do it.
[0011]
Here, since the height of the protrusion from the bottom of the groove is configured to be higher than the amount of protrusion of the heat radiating tube from the surface of the main body base material, the heat radiating tube is positioned inside the groove when the floor finishing material is applied. Even when the heat sink is pushed into the heat sink and the top of the heat sink becomes almost flush with the surface of the main body substrate, the heat sink does not contact the bottom of the groove, and the thermal conductivity falls below the heat sink in the groove. Since a heat-insulating gap in which low-temperature air is interposed is formed, it is difficult to dissipate heat from the radiator tube to the main body.
Furthermore, in a state where the floor finishing material is constructed so as to be substantially in close contact with the main body base material, the top of the heat radiating pipe and the surface of the main body base material are substantially flush with each other, so that the floor finishing material is loose. Nothing.
[0012]
The floor heating mat according to claim 4 is the invention according to any one of claims 1 to 3, wherein the heat-dissipating pipe is formed of a tape-like film material having a high thermal conductivity in a spiral shape so that substantially half of the width thereof overlaps. It is characterized by being wound. First, since the tape-like film material is wound around the heat radiating pipe, heat is easily transmitted from the heat radiating pipe to the floor finishing material. Furthermore, since the tape-shaped film material is spirally wound around the heat radiating tube so that approximately half of its width overlaps, the thickness of the film material wound around the heat radiating tube becomes uniform, and the surface of the heat radiating tube becomes Since no irregularities are formed on the floor, the adhesion between the heat radiating tube and the floor finish is not impaired.
[0013]
Embodiments of the present invention will be described. In the present embodiment, the present invention is applied to a hot-water floor heating system that heats a floor finishing material in a room with hot water supplied from a heat source device.
As shown in FIG. 1, the floor heating system 1 includes a heat source device 2 that is provided outside and supplies hot water, and a floor heating mat 3 that is laid below the floor finishing material (see FIG. 2). .
[0014]
Although not shown, a burner, a heat exchanger for heating hot water with the combustion gas from the burner, a pump for circulating hot water, and the like are arranged inside the heat source unit 2. A header box 10 is provided below the heat source unit 2, and a plurality of cross-linked polyethylene hot water pipes 11 are branched from a hot water header provided in the header box 10. , Hot water circulates between the heat source device 2 and another heating terminal such as a floor heating mat 3 or a hot water type air conditioner (not shown).
[0015]
Next, the floor heating mat 3 will be described.
As shown in FIGS. 2 to 4, the floor heating mat 3 is made of polystyrene foam and has a substantially rectangular main body 12 in a plan view, and is accommodated in a groove 23 formed in the main body 12 and allows hot water to flow therethrough. And a radiating tube 13 made of cross-linked polyethylene for heating the floor covering 16.
As shown in FIGS. 2 and 3, the floor heating mat 3 is composed of a base plywood 15 disposed on a plurality of joists 14 and a wooden floor finishing material 16 having a floor surface 16 a formed on the surface thereof. A heat insulating material 17 made of polystyrene foam is provided between the plurality of joists 14. Further, around the floor heating mat 3, dummy plywoods 18 and 19 having substantially the same thickness as the main body base material 12 and keeping the surface on which the floor finishing material 16 is placed horizontal are also laid.
[0016]
On the surface of the floor heating mat 3, a metal (for example, aluminum) sheet-like thin film member 20 having high thermal conductivity for uniformly transmitting heat to the floor finishing material 16 is attached.
As shown in FIGS. 2 to 4, a plurality of wooden joists 21 are integrally provided on the main body 12, and the groove portions 23 are formed continuously and meandering between these joists 21. ing.
[0017]
On the other hand, the heat radiating pipe 13 is also formed in a meandering shape like the groove 23, and the hot water supply pipe 11a and the hot water return pipe 11b (see FIG. 1) disposed in the hot water pipe 11 are connected to the heat radiating pipe 13, respectively. Have been. Further, as shown in FIG. 5, a metal foil (for example, aluminum foil) with an adhesive is provided on the heat radiating tube 13 in order to easily transfer heat from the heat radiating tube 13 made of cross-linked polyethylene to the floor covering 16. , A tape-like film material 22 having high thermal conductivity is wound. Here, the tape-shaped film material 22 is radiated in a spiral shape so that substantially half of its width overlaps in order to make the wound thickness uniform so as not to cause irregularities on the surface of the heat radiating tube 13. Wound around tube 13.
[0018]
As shown in FIGS. 6 and 7, two projections 24 extending along the groove 23 and supporting the heat radiation tube 13 are formed at the bottom of the groove 23 that accommodates the heat radiation tube 13. The portion of the bottom of the groove 23 other than the protrusion 24 is not in contact with the radiator tube 13. Here, the projections 24 are formed such that the depth L from the surface of the main body 12 to the tip of the projections 24 is smaller by about 0.5 to 1.0 mm than the outer diameter of the heat radiating tube 13. ing. That is, as shown in FIG. 6, the top of the heat radiating tube 13 projects from the surface of the main body 12. Further, the height of the protrusion 24 from the bottom of the groove 23 is configured to be higher than the amount of protrusion of the heat radiation tube 13 from the surface of the main body 12.
[0019]
Therefore, as shown in FIG. 7, when the floor finish 16 is applied on the main body 12, the radiator tube 13 is pushed into the groove 23 by the floor finish 16, but at this time, the protrusion 24 Is deformed so that the heat radiating tube 13 comes into close contact with the floor finish material 16, and the top of the heat radiating tube 13 and the surface of the main body 12 are formed on substantially the same plane. In addition, since the height of the protrusion 24 from the bottom of the groove 23 is configured to be higher than the amount of protrusion of the radiator tube 13 from the surface of the main body 12, the radiator tube 13 is located in the groove 23. Even when the top portion of the heat radiating tube 13 and the surface of the main body base material 12 are substantially flush with each other, the heat radiating tube 13 does not contact the bottom of the groove portion 23, and the lower side of the heat radiating tube 13 in the groove portion 23. A heat insulating gap 25 in which air with low thermal conductivity is interposed is formed.
At the lower end of the main body 12, a plurality of recesses 12 a for reducing the contact area between the main body 12 and the base plywood 15 are also provided.
[0020]
Next, the operation of the floor heating mat 3 will be described.
As shown in FIG. 6, since the depth L from the surface of the main body 12 to the tip of the protrusion 24 is smaller than the outer diameter of the radiator tube 13, the floor L is placed on the main body 12 of the floor heating mat 3. Before the finishing material 16 is applied, the top of the heat radiating tube 13 is in a state of protruding from the surface of the main body 12.
[0021]
From this state, as shown in FIG. 7, the floor finishing material 16 is placed on the floor heating mat 3, and then the floor finishing material 16 is fixed to the small joists 21 with nails or the like, and The floor finishing material 16 is constructed. At this time, the floor finish 16 pushes the top of the protruding radiator tube 13 into the groove 23. At this time, the protrusion 24 formed at the bottom of the groove 23 is deformed, and the radiator tube 13 is The top of the heat radiating tube 13 and the surface of the main body 12 are configured to be substantially flush with each other in a state of being in close contact with the floor finishing material 16.
[0022]
Therefore, heat is efficiently transmitted from the radiator tube 13 to the floor covering 16 via the thin film member 20. At this time, a heat insulating gap 25 is also formed in the groove 23 below the heat radiating pipe 13, and air having a low thermal conductivity is interposed in the heat insulating gap 25. The amount of heat radiated to the heat is suppressed.
[0023]
Next, the radiation efficiency on the floor between the conventional floor heating mat as shown in FIG. 9 and the floor heating mat 3 of the embodiment (the amount of heat transmitted to the floor and contributing to heating with respect to the amount of hot water supplied to the floor heating mat) ) Will be described with respect to results obtained by experiments. First, in a conventional floor heating mat, the inner diameter of the radiator tube is 5 mm (outer diameter is 7.2 mm), the thickness of the main body is 12 mm, the thickness of the thin film member is 40 μm, the supply hot water temperature is 60 ° C., and the thickness of the floor finishing material is 12 mm. When the thickness of the base plywood was 12 mm and the thickness of the heat insulating material was 50 mm, the average temperature of the floor surface was about 33 ° C., and the heat radiation efficiency on the floor at this time was about 73%.
[0024]
On the other hand, in the floor heating mat 3 of the embodiment, each specification of the heat radiating pipe 13, the main body base material 12, the floor finishing material 16, the base plywood 15, and the heat insulating material 17 is the same as that of the conventional floor heating mat. When an aluminum foil having a thickness of 25 μm and a tape-shaped film material 22 made of a film made of PET (polyethylene terephthalate) are wound and the supply hot water temperature is set to 50 ° C., which is 10 ° C. lower than the conventional temperature, the average temperature of the floor surface 16a is The temperature was about 33 ° C., which is almost the same as the conventional case, but it was confirmed that the heat radiation efficiency on the floor at this time was about 82%, and the amount of heat dissipated wastefully under the floor was reduced by nearly 10%.
[0025]
According to the floor heating mat 3 described above, the following effects can be obtained.
1) Since the depth L from the surface of the main body 12 to the tip of the projection 24 is smaller than the outer diameter of the heat radiating pipe 13, the top of the heat radiating pipe 13 projects from the surface of the main body 12, and When the finishing material is applied on the main body member, the heat radiating pipe 13 is securely adhered to the floor finishing material 16 and heat is efficiently transmitted from the heat radiating pipe 13 to the floor finishing material 16 via the thin film member 20. As a result, the temperature rise on the floor immediately after the start of heating is increased, and the immediate warming property is also improved. Furthermore, even when there is some manufacturing error in the groove 23, the outer diameter of the heat radiating tube 13, and the like, the heat radiating tube 13 and the floor finishing material 16 can easily adhere to each other.
[0026]
2) Since the two protrusions 24 are formed at the bottom of the groove 23 so as to extend along the groove 23 and support the radiator tube 13, portions of the bottom of the groove 23 other than the protrusion 24 are formed. The contact area between the heat radiation tube 13 and the inner peripheral portion of the groove 23 is reduced without contact with the heat radiation tube 13. That is, the amount of heat radiated from the radiator tube 13 to the main body 12 can be suppressed.
[0027]
3) When the floor finishing material 16 is applied on the main body 12, the projections 24 are deformed, and the top of the heat radiating tube 13 adheres to the floor finishing material 16, and the top of the heat radiating tube 13 and the main body 12 And the top surface of the heat radiating pipe 13 is securely adhered to the floor finishing material 16 and heat is efficiently transmitted from the heat radiating pipe 13 to the floor finishing material 16. It can be constructed so that it does not rattle. Further, the height of the protrusion 24 from the bottom of the groove 23 is configured to be higher than the amount of protrusion of the heat radiation tube 13 from the surface of the main body 12, and the heat radiation tube 13 is pushed into the groove 23. When the top of the heat radiating pipe 13 and the surface of the main body 12 are substantially flush with each other, a heat insulating gap 25 in which air with low thermal conductivity is interposed is formed below the heat radiating pipe 13 in the groove 23. Therefore, it is difficult to dissipate heat from the radiator tube 13 to the main body 12, and it is also possible to reduce the running cost of the heat source device 2.
[0028]
4) Since the tape-like film material 22 having high thermal conductivity is wound around the heat radiating tube 13, heat is easily transmitted from the heat radiating tube 13 to the floor finishing material 16, and the tape-like film material 22 has a width corresponding to the width of the tape-like film material 22. Since the wrapping is wound spirally so that approximately half overlaps, the thickness of the film material 22 wrapped around the radiator tube 13 becomes uniform, and the surface of the radiator tube 13 does not have unevenness. The heat radiation pipe 13 can be reliably pushed into the groove 23 when the floor finish 16 is applied.
[0029]
Next, modified embodiments in which various modifications are made to the above-described embodiment will be described. However, the components having the same configuration as the above embodiment are denoted by the same reference numerals, and the description thereof will be appropriately omitted.
1] As shown in FIG. 8, a concave groove 30 is formed so as to be continuous with the bottom of the groove 23A of the main body 12A and extend along the groove 23A, and a depth L ′ from the surface of the main body 12A to the bottom of the groove 23A. May be smaller than the outer diameter of the heat radiating tube 13. Also in this case, as in the above-described embodiment, in the state before the floor finishing material 16 is installed, the top of the heat radiation pipe 13 projects beyond the surface of the main body 12A, and the floor finishing material is placed on the main body 12A. When the step 16 is constructed, the concave groove 30 is deformed, and the heat radiating tube 13 is brought into close contact with the floor finishing material 16, so that the top of the heat radiating tube 13 and the surface of the main body 12A are substantially flush with each other. Further, a heat insulating gap 25A is also formed below the radiator tube 13 in the groove 23A. Therefore, substantially the same effects as in the above embodiment can be obtained.
[0030]
2] The upper surface of the small joist 21 may be configured to be slightly lower (for example, about 0.5 to 1.0 mm) than the upper surface of the main body 12. With this configuration, before the floor finishing material 16 is applied, the top of the heat radiating pipe 13 projects beyond the small joist 21, and the floor finishing material 16 is fixed to the small joist 21 to finish the floor. When the material 16 is applied, the top of the heat radiating tube 13 will surely adhere to the floor finish material 16.
[0031]
3] The main body 12 is made of a material having elasticity such that the bottom of the groove 23 is easily deformed by the heat radiating pipe 13 when the heat radiating pipe 13 is pushed into the groove 23 when the floor finishing material 16 is applied. In this case, the protrusion 24 may be omitted by making the depth of the groove 23 itself smaller than the outer diameter of the radiator tube 13.
4] As the main body substrate 12, various types can be used as long as they have a planar shape such as a sheet shape, a panel shape, or an elongated plate shape for installing a joist.
[0032]
According to the first aspect of the present invention, since the top of the heat radiating tube is configured to protrude from the surface of the main body base material, when the floor finishing material is applied on the main body member, the heat radiating tube is surely formed. As a result, the heat can be efficiently transferred from the radiator tube to the floor finish. Furthermore, the temperature rise of the floor finishing material immediately after the start of heating is increased, and the immediate warming property is improved. Further, even when there is some manufacturing error in the groove portion, the outer diameter of the resin tube, and the like, the heat radiating tube and the floor finish material are easily adhered to each other.
[0033]
According to the second aspect of the present invention, since a plurality of protrusions extending along the groove and supporting the radiator tube are formed at the bottom of the groove, the portion of the bottom of the groove other than the protrusion and the radiator tube are formed. Are not in contact with each other, and the contact area between the heat radiating tube and the inner peripheral portion of the groove is reduced. That is, the amount of heat radiated from the heat radiating tube to the main body substrate can be suppressed.
[0034]
According to the third aspect of the present invention, when the floor finishing material is applied on the main body base material, the projections are deformed, and the heat radiating tube is brought into close contact with the floor finishing material, and the top of the heat radiating tube and the surface of the main body base material. Is constructed on the substantially same surface, so that the radiator tube adheres firmly to the floor finish material, heat is efficiently transmitted from the radiator tube to the floor finish material, and the construction is performed so that the floor finish material does not rattle. You can also. In addition, since the height of the protrusion from the bottom of the groove is configured to be higher than the amount of protrusion of the radiator tube from the surface of the main body of the main body, the radiator tube is pushed into the groove at the time of floor finishing material construction. When the top of the heat radiating pipe and the surface of the main body base material are substantially flush with each other, a heat insulating gap is formed on the lower side of the heat radiating pipe in the groove, where air having a low thermal conductivity is interposed. It becomes difficult to radiate heat from the radiator tube to the main body base material, and it is also possible to reduce the running cost of the heat source device.
[0035]
According to the invention of claim 4, since the tape-like film material having a high thermal conductivity is wound around the heat radiating pipe, heat is easily transmitted from the heat radiating pipe to the floor finishing material. Since it is spirally wound so that approximately half of the width overlaps, the thickness of the film material wound around the heat radiating tube becomes uniform, and no irregularities are generated on the surface of the heat radiating tube. In addition, the heat radiation pipe can be reliably pushed into the groove when the floor finishing material is applied.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a floor heating system according to an embodiment of the present invention.
FIG. 2 is a perspective view of a floor heating mat and various floor materials around the mat.
FIG. 3 is a partially enlarged sectional view of FIG. 2;
FIG. 4 is a schematic plan view of a floor heating mat.
FIG. 5 is a perspective view of the heat radiating tube in a state where the sheet-like film material is wound.
6 is a partially enlarged cross-sectional view of FIG. 4 (before floor finishing material is applied).
FIG. 7 is a partially enlarged cross-sectional view of FIG. 4 (after floor finishing material has been applied).
FIG. 8 is a diagram corresponding to FIG. 6 of a modified embodiment.
FIG. 9 is a partially enlarged sectional view of a conventional floor heating mat.
[Explanation of symbols]
3 Floor heating mats 12, 12A Body base material 13 Heat radiating pipes 16 Floor finishing materials 22 Tape-like film materials 23, 23A Grooves 24 Projections

Claims (4)

Floor heating including a synthetic resin foam body main body, and a synthetic resin radiator tube housed in a groove formed in the body base material and allowing warm water to flow to heat the floor finishing material On the mat
A floor heating mat, wherein a top portion of the radiator tube is configured to protrude from a surface of a main body substrate. The floor heating mat according to claim 1, wherein a plurality of protrusions extending along the groove and supporting the radiator tube are formed at a bottom of the groove. The height of the protrusion from the bottom of the groove is configured to be higher than the amount of protrusion of the heat radiating tube from the surface of the main body base material, and when a floor finish is applied on the main body base material, the protrusion The floor heating mat according to claim 2, wherein the portion is deformed so that the top of the heat radiating tube is in close contact with the floor finishing material, and the top of the heat radiating tube and the surface of the main body are substantially flush with each other. The floor heating according to any one of claims 1 to 3, wherein a tape-like film material having a high thermal conductivity is spirally wound around the heat radiating tube so that substantially half of the width thereof overlaps. mat.

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