Method for controlling stagnation temperature of solar vacuum tube

Abstract

The invention provides a method for controlling a stagnation temperature of a solar vacuum tube. The method controls the stagnation temperature of the solar vacuum tube by changing emissivity of a back surface of a heat absorbing body of the solar vacuum tube. The inventive method can effectively control the stagnation temperature of a vacuum heat collecting tube, and make the stagnation temperature lower than a bearable set temperature of a solar vacuum heat collecting tube system, to thereby prolong the service life and lower manufacture cost of the system.

Description

technical field [0001] The invention relates to the application field of solar energy, and in particular relates to a method for controlling the air drying temperature of a solar vacuum tube. Background technique [0002] At present, the uncontrolled heating of solar vacuum tubes is the primary consideration in the manufacture and system design of solar thermal utilization devices. Due to the high absorption rate of the solar spectrum selective absorption coating and the low emissivity of the coating (the absorption rate is greater than 96%, and the emissivity is less than 6%), although the vacuum tube collector using this type of solar spectrum selective absorption coating The efficiency is relatively high, but the air drying temperature is also very high. When the solar irradiance is 800W / m2, the air drying temperature can reach above 300°C. The air drying temperature of the solar vacuum tube collector is too high, which makes the system have the following problems: [0...

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Problems solved by technology

[0003] 1. The temperature is high, and high temperature resistant materials need to be selected, resulting in high cost;

[0004] 2. High temperature causes high pressure inside the system, which makes it necessary to increase the pressure bearing capacity of the system, resulting in high cost

[0005] 3. High temperature and high pressure, resulting in short system life, reduced reliability, increased maintenance costs, etc.

[0006] How to maintain the high efficiency of the vacuum tube collector at low temperature, and lower the efficiency at the set high temperature section, so as to reduce the air drying temperature at no load (heat sink) is a problem that needs to be solved at present

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