JPS5924143A - Overheat preventing mechanism for solar heat collector - Google Patents

Abstract

PURPOSE:To obtain a highly reliable method of the titled device, in which an electric motor is not employed, for the overheat preventing mechanism, reducing the rate of incidence of solar beams to prevent the overheat of a heat collecting tube, by a method wherein a spiral spring of bimetal or the like is equipped at the part of a vacuum sealing plug having a temperature near the same of the heat collecting tube to move an external reflection mirror automatically. CONSTITUTION:The temperature of the vacuum sealing plug 5 of the heat collecting tube 2 at the inside of a vacuum glass tube 1 becomes equal to the same of the heat collecting tube approximately, therefore, the spiral spring 6, consisting of bimetal or a shape memory alloy is equipped at the periphery of the plug to move the external reflection mirror 4 upon the overheating and reduce the rate of incidence of solar beams. A considerable distance exists between the external reflection mirror 4 and the spiral spring 6, therefore, a connecting rod 7 is necessary. In case the heat collecting tube is a heat pipe, the temperature of a header 8, in which heat exchange of a heat medium is effected, becomes near to the temperature of the plug, therefore, the spiral spring is provided at the header, but the length of connecting rod therebetween is elongated. The temperature of the heat collecting tube is risen to a temperature near 300 deg.C when it is heated in an empty condition in the conventional method, however, the temperature thereof may be controlled to a temperature below 200 deg.C by this mechanism.

Description

[Detailed Description of the Invention] The present invention relates to a vacuum tube type solar collector with an external reflector, and particularly relates to a mechanism for preventing overheating of the collector tube in a dry firing state where no coolant (water, etc.) is supplied. be.

The cross section of a conventional heat collector is shown in Figure 1, with a vacuum glass tube 1
, a heat collecting tube 2 (such as a heat pipe), an internal reflecting mirror 3 (replaced if omitted), an external reflecting mirror 4 (made of thin metal), and a vacuum-sealed cap.

Since the external reflector was fixed, the heat collection tube was
The temperature reached close to 0°C, which caused the internal vapor pressure (of water, etc.) to become high, resulting in a rupture.

An object of the present invention is to provide a highly reliable method that does not use an electric motor as an overheat prevention mechanism that reduces the incidence of sunlight so that the heat collection tube does not overheat.

In order to achieve the above object, we invented a method for automatically moving the external reflector by installing a mainspring made of bimetal or the like in a vacuum-sealed mouthpiece that is close to the temperature of the heat collecting tube. In this case, the temperature of the heat collecting pipe will be lower than the temperature of part of the header (mouthpiece etc.) even when the heating is empty.
We focused on the point where Ic is approximately equal.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. Since the temperature of the vacuum-sealed cap 5 of the heat collecting tube 2 inside the vacuum glass tube l is approximately equal to that of the heat collecting tube, a mainspring 6 made of bimetal or shape memory alloy is installed around the cap to prevent it from overheating. The external reflecting mirror 4 is moved to reduce the incidence rate of sunlight. As shown in FIG. 3, since the distance between the external reflecting mirror 4 and the mainspring 6 is considerable, a connecting rod 7 is required. If the heat collecting tube is a heat pipe, the temperature of the header 8 that exchanges heat with the heat medium will be close to the temperature of the base, so a senmai can be installed in the header, but the connecting rod with the reflector will be longer. .

FIG. 4 shows the effect of this embodiment. When the heat collection pipe is in an empty firing state, the temperature conventionally rose to nearly 300°C, but according to the present invention, it can be controlled to 200°C or less. 1 FIG. 5 shows another embodiment of the present invention, in which when the external reflecting mirror 4 is also located at the bottom of the vacuum glass tube 1, an overheating prevention mechanism for moving the reflecting mirror all the way down is installed.

FIG. 6 shows a similar modification, in which a spring made of bimetal or the like is used to push down the circular reflecting mirror in order to move the entire lower part thereof.

According to the present invention, the external reflector is fully moved by the force of a spring made of bimetal or the like without using an electric motor as an overheating prevention mechanism for the solar heat collector, thereby improving reliability and economy. When moving the external reflector of the collector with an electric motor,
Although a temperature detector and a power source are required, the present invention operates mechanically, so the reliability is more than twice that of the conventional method.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a conventional vacuum tube type heat collector with an external reflector.
Fig. 2 is an explanatory diagram of a heat collector showing an embodiment of the present invention, Fig. 3 is an explanatory diagram of the present embodiment, Fig. 4 is a comparison diagram of the conventional Karamoto embodiment at dry firing temperature, Fig. 5 , FIG. 6 is an explanatory diagram showing another embodiment. DESCRIPTION OF SYMBOLS 1... True wall glass tube, 2... Heat collecting tube, 3... Internal reflecting mirror, 4... External reflecting mirror, 5... Vacuum sealed cap,
6... Mainspring (bimetal or shape memory alloy), 7
... Connecting rod, 8... Header. Kaya 3 (2) To the 4th figure 'The missing space! 9th place

Claims (1)

[Claims] 1. In a solar heat collector consisting of a vacuum glass tube, a heat collector tube, an external reflector, and a vacuum-sealed cap, the external reflector is moved to prevent the heat collector tube from overheating when the collector is idle. An overheating prevention mechanism for a solar heat collector, characterized in that a bimetal or shape memory alloy is installed in a vacuum-sealed cap part and connected to an external reflector.