JPS5947809B2 - Electric heating device for heating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric heating device for space heating that is compact and always provides a uniform temperature distribution.

Figure 1 is a sectional view showing a conventional tubular heating electric heating device.
is a cylindrical sealed container made of copper or steel pipe with a plurality of heat dissipation fins 2 formed on the outer circumferential surface, and an insulating bushing 3 is provided on both end plates 1a and b at approximately the center of the sealed container 1.
A heating element 4 made of a nichrome wire or the like whose both ends are supported via ay3b is housed, and the space inside this sealed container 1 is filled with powdered magnesha or alumina, etc., which has a heat conductive function and an electrically insulating function. It is filled with a heat medium 5 consisting of.

6a and 6b are connectors that electrically connect both ends of the heating element 4 and power feeding lead wires 7a and 7b to each other.

Since the conventional tubular electric heating device is configured as described above, when the heating element 4 is energized by power supply from the lead wires 7a and 7b, the heat of the heating element 4 is transferred from the heating medium 5 through the closed container 1. The heat reaches the heat radiation fins 2, exchanges heat with the outside air, heats it, and becomes a heat source for heating.

However, as described above, the heat of the heating element 4 is transferred to the heat medium 5.
In the case where heat is conducted to the closed container 1 and the heat dissipating fins 2 through the heat transfer medium 5, the heat conductivity of the heat medium 5 is poor, so the conduction loss relative to the calorific value of the heating element 4 is extremely large.

Now, assuming that the heating element 4 is disposed approximately at the center of the closed container 1, the radius of the heating element 4 is r 1 = 1 mm.

Inner wall radius r2 of airtight container 1 = 10 mm, and heat medium 5
Thermal conductivity K = 0.3 kcal/mhr
'C, the thermal resistance R is as follows.It can be seen that when a high thermal resistance occurs between the heating element 4 and the inner wall of the closed container 1 and the thermal conductivity is poor.

Also, at this time, the heating element 4 naturally becomes extremely hot, so
The insulating bushings 3 a t 3 b require a material with good electrical insulation as well as thermal insulation, which causes an increase in cost.

Furthermore, in order to reduce the thermal resistance, the distance between the heating element 4 and the inner circumferential wall of the closed container 1 may be narrowed, but if this is done, the diameter of the closed container 1 will become smaller, which inevitably The heat transfer area of the heat dissipation fins 2 formed on the outer periphery of the heat dissipation fins 2 is also small, and a predetermined amount of heat dissipation cannot be achieved, resulting in the drawback that the electric heating device cannot have a large capacity.

The present invention has been made with attention to this point, and an object thereof is to provide an electric heating device for heating that is small in size and can always provide a uniform temperature distribution.

That is, FIGS. 2 and 3 show an embodiment of the present invention, and numeral 8 denotes a cylindrical sealed container made of copper or steel pipe with a plurality of heat dissipation fins 16 formed on the outer circumferential surface. Approximately in the center of the container 8 are these end plates 8a +
A sheathed heating element 9 is housed airtightly passing through 8b.

Thus, this sheathed heating element 9 includes a heating wire 10 made of a nichrome wire or the like, which is inserted through the approximate center of the small diameter tube 12;
A heating medium 11 made of powdered magnesia or alumina is filled in the space of the small diameter tube 12, both ends of the heating wire 10, and a power supply lead wire 13a.

13b and a connector 14a that electrically connects them to each other.

14b.

Reference numeral 15 is designed to immerse the sheathed heating element 9 in a refrigerant such as R-113J, which is sealed in the airtight container 8 leaving a space 17 at the top.

Reference numeral 18 denotes condensing fins protruding from the upper part of the inner circumferential surface of the sealed container 8, and the condensing fins 17 are used to condense and liquefy the gas refrigerant that has been heated to boiling by the sheathed heating element 9 and evaporated in the space 11. It was established in

Since the heating electric heating device of the present invention is constructed as described above, the liquid refrigerant 15 is heated to boiling due to the heat generated by the sheathed heating element 9 supplied with electricity, and then evaporated into the space 17.

Then, the evaporated gas refrigerant is cooled and condensed by contacting the condensing fins 17, and the liquefied liquid refrigerant flows into the lower part of the closed container 8 and is heated and boiled again by the sheathed heating element 9. The cycle is repeated. .

Note that the heat transferred to the radiation fins 16 of the closed container 8 by exchanging heat with the evaporated gas refrigerant exchanges heat with the outside air and heats it, thereby becoming a heat source for heating.

As mentioned above, the heating electric heating device of the present invention has a refrigerant 15
The heat of the heating element 9 is transferred to the closed container 8 by repeated boiling and condensation.
Because the heat is conducted through the heat dissipating fins 16, its thermal resistance is extremely small compared to conventional heat transfer media made of powdered magnesia or alumina.

That is, now using [R-113J as the refrigerant 15, boiling thermal conductivity hB = 5000 kcal/mhr'c condensing thermal conductivity hC = 400 kcal/rrt hr'
C, it can be seen that in the shape used in the calculation of equation [1] above, the radius of the small diameter tube is r1'-3 mm, and the thermal resistance is greatly reduced.

Also, the radius of the small diameter tube 12 of the sheathed heating element 9 and the heating wire 1
Since the radius ratio of 0 is close to 1, the thermal resistance between the heating wire 10 and the small diameter tube 12 is equal to the outer diameter r1' of the small diameter tube 12 -
It can be set to approximately 3 mm, and the overall thermal resistance is R'1+R1=0.634<1.222 R.

Therefore, according to the present invention, since the thermal resistance between the heating element 9 and the sealed container 8 is reduced, the temperature difference between the heating element 9 and the sealed container 8 is also reduced, and the same amount of electric power as the conventional one is required. If there is, an electric heating device for heating with a large amount of heat dissipation can be obtained, and if the amount of heat dissipated is the same, the amount of heat generated by the heating element 8 can be lower, which not only simplifies insulation measures, but also
This has the excellent effect of allowing miniaturization as an electric heating device.

FIG. 4 shows another embodiment of the present invention, in which the condensing fan 18 of the above embodiment is arranged in a crescent shape extending in the circumferential direction on the inner peripheral surface of the closed container 8. In contrast, this other embodiment is arranged extending in the axial direction on the inner circumferential surface of the closed container 8, and its operation and effect are exactly the same as those of the above-mentioned embodiment.

FIG. 5 shows an example of the use of the electric heating device of the present invention, in which a plurality of electric heating devices are arranged parallel to each other on a plate 18 at a predetermined interval, and a blower 19 is used to force heat exchange. This shows the case where it is configured as a large-capacity heating device.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional electric heating device, FIGS. 2 and 3 each show an embodiment of the present invention, FIG. 2 is a sectional view, and FIG. [It is a sectional view taken along the I-■ line. Further, FIG. 4 is a sectional view showing another embodiment of the present invention. Further, FIGS. 5A and 5B show an example of the use of the electric heating device of the present invention, with FIG. 5A being a front view and FIG. 5B being a side view. In the drawing, 8 is a closed container, 9 is a sheathed heating element, 10 is a heating wire, 11 is a heat medium, 15 is a refrigerant, 16 is a heat radiation fin,
17 is a space, and 18 is a condensing fin. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A closed container having heat dissipation fins formed on the outer peripheral surface and condensing fins formed on the upper inner peripheral surface, a heating element attached to the bottom of the closed container, and a heating element inside the closed container. The container is sealed with a space left in the upper part, and is equipped with a refrigerant in which the heating element is immersed, and the refrigerant that is heated to boiling by the heating element and evaporated in the space is condensed and liquefied by condensing fins to form a closed container. An electric heating device for heating, characterized by circulating air inside the device. 2. The heating electric heating device according to claim 1, characterized in that a sheathed heating element is used as the heating element. 3. The electric heating device for heating according to claim 1, characterized in that [R-113J is used as the refrigerant.