JPS59229138A - Vacuum glass tube type solar heat collector - Google Patents

Abstract

PURPOSE:To obtain the high heat collecting efficiency for a heat transferring fluid by a method wherein a heat resistance between a light-heat conversion body and a heat transferring fluid is made to be a heat resistance of a heat pipe action due to a heat transferring medium inside of a sealed tube. CONSTITUTION:An outer glass tube 3 and a sealed tube 2 are sealed by the heat fusing for keeping a space 5 formed between the sealed tube 2 and the outer glass tube 3 under vacuum condition. The sealed tube 2 is provided with a light-heat conversion body 1 such as a selective absorbing film and the like on the outer surface thereof, and a heat transfering medium 7 is enclosed inside thereof. The transparent outer glass tube 3 covers the sealed tube 2. Also, a part of the sealed tube 2 is contacted with a heat transferring fluid 9, while the inside of the sealed tube 2 is made to be a heat pipe, that is, the sealing of the vacuum portion is made by the heat fusing of each glass, consequently, the stress generated by the temperature variation at the heat fused part is small. Therefore, the reducing of a vacuum degree caused by the damage of the sealing can be prevented, and the heat resistance produced between the light-heat conversion body and the heat transferring fluid is the heat resistance of the heat pipe action due to the heat transferring medium inside of the sealed tube, accordingly, the high heat collecting efficiency for the heat transferring fluid can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a solar heat collector for converting sunlight into heat and using it as a heat source for hot water supply, heating and cooling, etc.

<Conventional structure and its problems> In the conventional vacuum glass tube type solar heat collector, a metal heat collection tube is placed inside a transparent glass tube, and the space between the glass tube and the heat collection tube is In a vacuum state, the glass tube and the heat collecting tube are sealed with a heat-sealing compound or the like to reduce loss due to heat conduction to the outside air. However, when the temperature of the heat collecting tube changes, the temperature of the glass tube at the part connected to the heat collecting tube by the heat fusion compound also changes.
Since the thermal expansion coefficients of metal and glass are greatly different, large stress is generated in the heat-sealing compound part, the seal is broken, and the degree of vacuum in the space between the glass tube and the heat collecting tube is reduced.
The disadvantage was that heat loss increased.

In addition, as another form of vacuum glass tube type solar heat collector, an inner glass tube with a photothermal converter such as a selective absorption film on the outer surface is placed inside a transparent outer glass tube. The space between the glass tube and the inner glass tube is evacuated, the outer glass tube and the inner glass tube are sealed by heat fusion, and the outside air is released.
In order to reduce heat conduction loss, a metal heat exchanger for heat exchange between the light-to-heat converter and the heat transfer fluid was inserted inside the inner glass tube to serve as a solar heat collector.

In this form, since the vacuum sealing is done between the glass tubes, large stress is not likely to occur in the cough heat welding part due to changes in humidity, the degree of vacuum is maintained, and there is no increase in heat conduction loss to the outside air. It can be prevented. However, since there is a heat exchanger between the photothermal converter and the heat transfer fluid, there is a large thermal resistance between the photothermal converter and the heat transfer fluid, which has the disadvantage of low heat collection efficiency. Furthermore, since the heat transfer fluid is circulated within the heat exchanger, there are disadvantages in that the water head loss during circulation is large and the power consumption of the circulation pump is large.

<Object of the Invention> The present invention eliminates the above-mentioned conventional drawbacks, eliminates the increase in heat conduction loss due to a decrease in the degree of vacuum, and improves heat collection efficiency by minimizing the thermal resistance between the photothermal converter and the heat transfer fluid. The purpose of the present invention is to provide a vacuum glass tube type solar heat collector that has a high heat transfer fluid and has a small water head loss during circulation of a heat transfer fluid, so that the power consumption of a circulation pump is low.

<Structure of the Invention> The vacuum glass tube type solar collector of the present invention includes a sealed tube provided with a light-to-heat converter such as a selective absorption film on the outer surface and sealed with a heat transfer medium inside, and a sealed tube that covers the sealed tube. The outer glass tube and the sealed tube are sealed by heat fusion so as to maintain a vacuum in the space between the outer glass tube and the transparent outer glass tube, and the end of the sealed tube is brought into contact with a heat transfer fluid. thereby transferring solar heat to the heat transfer fluid.

<Description of Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a longitudinal cross-sectional view of a heat collector according to the present invention, and FIG. 2 shows a cross-sectional view taken along line A-A in FIG. 1. 2 is a sealed tube in which a heat transfer medium made of a material with high latent heat such as fluorocarbon is enclosed; 10 is a wick for the heat transfer medium 7, which is attached to the inner surface of the sealed tube. 7 indicates a liquid heat transfer medium, and 6 indicates a space within the sealed tube. Preferably, the entire surface of the sealed tube 2 is coated with the photothermal converter 1, except for the portion that comes into contact with a heat transfer fluid, which will be described later. The photothermal converter 1 functions to convert sunlight into heat. An outer glass tube 3 is recessed in the sealed tube 2 so as to cover the photothermal converter 1.
The seal @ 2 and the outer glass tube 3 are heat-sealed while the space 5 between the outer glass tube 3 and the outer glass tube 3 is evacuated. The part where this heat r7A is attached is indicated by reference numeral 4. Photothermal converter 1 in sealed tube 2
The uncoated portion, preferably the end 8 of the sealed tube 2, is fitted into the hole of the support tube 11, and the gap between the hole of the support tube and the sealed tube 2 is sealed by an appropriate method. do. It is preferable that the coefficients of thermal expansion of the sealed tube 2 and the support tube 11 are as equal as possible. A heat transfer fluid 9 is supplied into the support tube 11 from a utilization device (not shown). The arrow in Figure 2 indicates sunlight.

Next, the operation of the vacuum glass tube type solar collector according to the present invention will be explained. Solar radiation passes through the outer glass tube 3 and is converted into heat in the photothermal converter 1.
As a result, the photothermal converter 1 reaches a high temperature and imparts heat to the heat transfer medium 7 through the sealed tube 2. At this time, the heat of the photothermal converter 1 is also radiated to the outside air through the space 5 and the outer glass tube 3, but no large stress is generated in the heat-sealed part 4 even due to changes in humidity, and the space 5 maintains a vacuum. Since it is sagging, there is little heat dissipation to the outside air. Therefore, most of the heat of the photothermal converter 1 is transferred to the heat transfer medium 7 through the sealed tube 2,
The heat transfer medium 7 reaches a high temperature and evaporates. This vapor reaches the end 8, imparts heat to the heat transfer fluid 9, condenses and the heat transfer medium 7 is circulated by the wick 10. In other words, the heat transfer medium 7 acts as a heat pipe.

<Effects of the Invention> As is clear from the above explanation, the present invention has the following advantages:
The vacuum part is sealed by the heat rALA between the glasses, and the stress generated in the heat part due to temperature changes is small, so there is no decrease in the degree of vacuum due to the breakage of the seal, and there is no heat transfer to the photothermal converter. The thermal resistance between fluids is the thermal resistance of the heat pipe action due to the heat transfer medium inside the sealed tube. Therefore, high heat collection efficiency can be obtained for the heat transfer fluid.

Furthermore, the head loss during circulation of the heat transfer fluid is small because it is only the head loss due to the end of the inner glass tube, and the power consumption of the circulation pump for circulating the heat transfer fluid can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a vacuum glass tube type solar collector according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view thereof. 1... Light-heat converter 2... Sealed tube 3... Outer glass tube 4... Heat fusion part 5... Space 6... Space
7... Heat transfer medium 8... End 9... Heat transfer fluid 10... Wick 11... Piping patent applicant Satoru Yoshimura, patent attorney representing Matsushita Electric Co., Ltd.

Claims (1)

[Claims] A space between a sealed tube in which a light-to-heat converter such as a selective absorption film is provided on the inner and outer surfaces and a heat transfer medium is sealed inside, and a translucent outer glass tube that covers the sealed tube. The outer glass tube and the sealed tube are sealed by thermal bonding so as to maintain a vacuum, a part of the sealed tube is brought into contact with a heat transfer fluid, and the inside of the sealed tube is used as a heat pipe. Vacuum glass tube type solar heat collector. (2) The vacuum glass tube type solar heat collector according to claim (1), characterized in that glass wool is used as the wick of the heat pipe inside the internally sealed tube. (3) The vacuum glass tube type solar heat collector according to claim (1), characterized in that the heat pipe inside the inner sealed tube is a gravity heat pipe that does not use a wick.