JPS59157439A - Circular tube type solar heat collector - Google Patents

Abstract

PURPOSE:To save cost of material for producing a reflecting mirror by a method wherein the semicylindrical reflecting mirror is formed by mirror-finishing the outer surface or the inner surface of a glass cylinder so that the glass cylinder serves also as the reflecting mirror and a glass tube in which it is sealed. CONSTITUTION:One half of the outer or the inner peripheral surface of the circular glass tube is mirror-finished as shown by Numeral 4 and a heat collecting plate 12 having a width of about half the inner diameter of the glass tube is arranged within the glass tube in such a manner that the plate 12 extends between the center of the tube and the center of that part of the inner surface of the tube which corresponds to the mirror-finished part 14. Further, the mirror- finished part 14 is covered with a heat insulating material 15 of a suitable configuration to thereby prevent the releasing of heat out into the atmosphere from the glass tube and a gas such as carbonic acid gas, xenon or the like having a heat transfer efficiency lower than air is sealed into the glass tube so that the heat loss of the solar heat collector is reduced and the heat collecting characteristic of the solar heat collector is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to a cylindrical thick FLtS heater that aims to reduce heat loss by utilizing specular reflection.

One of the goals of developing solar collectors is to supply 1 [Rusheat] in factories, and the idea that this is particularly important in Japan has been rapidly gaining strength recently. The temperature range for factory heat treatment is 100℃ to 250℃.
There are many examples of usage up to this level. If heat in this temperature range could be supplied by solar heat at 4T, Japan's energy situation would be greatly improved.

Most of the solar collectors developed from this standpoint are non-tracking, stationary types, and moreover, they succumb to low concentration ratio tights where the concentration ratio does not significantly exceed 1.

The problems with such a thick heat collector will be discussed below.

The basic format of a non-tracking type solar collector using a glass circular tube and a reflecting mirror is one in which a reflecting mirror 2 is enclosed in a glass circular tube as shown in Fig. 1, and the reflecting mirror shown in Fig. 2. In some cases, the sunlight reflected and concentrated by the heat collecting tube 6 is received by the surface of the heat collecting circular tube 6 which is held concentrically inside the glass circular tube in a high vacuum state. In the former case, especially the pressure inside the pipe is 10 11111
111 (L or less) In order to achieve high vacuum insulation, baking at approximately 400°C is required during vacuum evacuation during manufacturing. Therefore, due to heat resistance restrictions, a metal reflector must be used. Material costs increase.Furthermore, a process of encapsulating the I-mirror in a glass tube is required. On the other hand, in the latter case, in addition to the need for a reflective mirror material, a protective transparent cover 7 is required to prevent the reflective mirror surface from being directly exposed to the outside air, which increases the material cost. This results in weakening the intensity of sunlight reaching the heat collector plate.

The present invention is intended for cases where the condensing ratio is 1 or slightly less than 1. First, due to the action of the semi-cylindrical reflecting mirror 80 shown in FIG. This principle itself is a well-known fact, and in this case, the condensing ratio is 1.

The present invention realizes a semi-cylindrical diameter of 111 m by mirror-finishing the outer or inner surface of a glass cylinder, and eliminates the drawbacks of the conventional cylindrical solar collectors described above, resulting in a high-performance, safe cylindrical solar collector. The purpose is to obtain a vessel.

Firstly, according to the present invention, the reflector base material is the glass tube itself, which saves material costs related to anti-gF1m. Secondly, the step of encapsulating the reflecting mirror is eliminated, which simplifies the manufacturing process. Third, the pressure of the gas sealed inside the tube is 10.
-'w+m When creating a high vacuum where the thermal conductivity of the gas is negligible at 11 g or less, mirror finishing using conventional technology can be applied to the outer surface of the glass tube after completing vacuum evacuation during manufacturing, which requires baking at about 400°C. , it is freed from restrictions on heat resistance conditions during manufacturing regarding reflective mirror materials. Of course, it is also possible to apply a mirror finish to the inner surface of the tube if the heat resistance conditions during manufacturing can be met. Furthermore, the fourth effect is that the mirror surface is not exposed to the outside air and is superior in terms of weather resistance and durability.If the outer surface of the tube is processed with an M surface, the mirror surface is also isolated from the vacuum inside the glass tube. Therefore, it may not have any effect on the degree of vacuum inside the tube.

Now, Fig. 4 shows a cross-sectional view of a conventional circular tube solar collector that is a non-concentration type and does not use surface reflection, and explains the differences from the circular tube solar collector according to the present invention. . Although the optical efficiency of the cylindrical solar collector according to the present invention is slightly reduced due to mirror surface irregularities, the area of the heat collecting plate is half that of the conventional evacuated tube solar collector. Therefore, under the same conditions, the heat loss is approximately halved, and the circular tube type solar collector of the present invention has a high heat collection efficiency in the a% filtration range, which is advantageous.

Next, the pressure of the gas sealed inside the glass arm was set to 10'mm and 11g.
~ Atmospheric pressure also results in a similar reduction in heat loss due to specular reflection. This pressure IIi! Compared with a pressure range of 410 mm1 la or less, baking at a high temperature during vacuum evacuation during manufacturing is inconvenient, the evacuation time is extremely short, and it is also extremely easy to maintain a vacuum seal and 'R air. There are many benefits such as. However, in this case, the heat conduction of the gas existing between the heat collector plate and the glass tube wall cannot be ignored, and the WA of the part of the glass tube near the heat collector plate
The temperature is considerably higher than that of the outside air, and the heat loss from the glass tube to the outside air increases significantly. In order to prevent this, the mirror-finished portion 14 is covered with a heat insulating material 15 of an appropriate shape, as shown in a cross-sectional view in FIG. , 4L In the type of vacuum tube solar collector, the heat conduction of the gas existing between the heat collecting plate and the glass cylinder wall is 1o-2 mmHg which cannot be ignored.
In the pressure range from ~atmospheric pressure, the amount of heat dissipated through the enclosed gas and the glass tube to the outside air was large, and it was impossible to cover the glass tube with an insulating material because it would impair the transmission of sunlight. In other words, the method of covering a glass tube with a heat insulating material became possible for the first time with the structure of the present invention. In addition, when the pressure inside the tube is in the range of 210 mm1a to 10 mmHaPia(r), the convection of the gas sealed inside the tube is slow and weak, and the tube is in an almost stationary state, so the heat loss is extremely small. Note that heat loss can be greatly reduced by providing a small gap between the inner surface of the glass tube and the end of the heat collecting plate.

Generally, the sealed gas in thick S* heaters is air, but #IF/
By using a gas having a lower thermal conductivity than air, such as 1 gas or xenon, as the enclosed gas, the heat loss of the solar collector can be reduced and the heat collection characteristics can be improved. For example, Kihinone, whose thermal conductivity is 1/42 or less that of air, is expensive, but
If it is sealed in a glass tube at a pressure range of about 1 ml, the required q is approximately proportional to the pressure, so a green mold can be used, and it can be used economically.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a concentrating solar collector in which a reflector is enclosed in a glass tube whose pressure is kept below I O -4 mmHg. Figure 3 is a diagram of the principle of a solar collector with a heat collecting plate installed in the center of a semi-cylindrical cylinder, and Figure 4 is a diagram of a conventional vacuum tube solar collector. FIG. 5 is a cross-sectional view of a circular tube type solar collector according to an embodiment of the present invention. 12・・・・・・・・・ Heat collection plate, 13・・・・・・・・・
・Glass tube, 14... Mirror surface, 15...
...Insulation material. Patent applicant Toshiyuki Hashimoto

Claims (4)

[Claims] (1) Half of the outer or inner surface of the glass circular tube is polished to a mirror finish, and a heat collecting plate with a width approximately half the inner diameter of the glass tube is placed between the center of the tube and the inner surface of the glass tube at the center of the mirror-finished part. A circular tubular solar collector that is characterized by its ability to tighten. (2) The circular tube type solar collector according to claim 1, wherein the pressure inside the glass tube is set to 10 −4 mmHg or less, and a slight gap is provided between the end of the heat collecting plate and the glass tube wall. (3) The internal pressure horn of the glass tube is 10-10-2II1~
A circular tube solar collector according to claim 1, which is set to atmospheric pressure and has a mirror-finished portion of the glass tube covered with a suitable heat insulating material from outside the tube; (4) The circular tube solar collector according to claim 3, wherein the gas sealed in the glass tube is air, carbon dioxide gas, xenon, etc., which have a lower thermal conductivity than air.