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What is used to absorb heat in a flat-plate solar collector

Views:5     Author:Site Editor     Publish Time: 2019-08-25      Origin:Site

Flat plate solar collectors are almost a tool that everyone has used. It is an important medium for converting solar energy into heat. It is often used in solar water heaters, heating of houses, and so on. I believe many of its users are curious about how flat plate solar collector absorbs heat. When I was young, I was very curious about how solar water heaters can heat water. I believe you can read this article to solve this problem when your child asks you questions.


If the explanation you want to explain is clear, you need to know the following points:

  • The Composition Of The Flat Plate Solar Collector

  • How Flat Panel Solar Collectors Work

  • Introduction of endothermic materials

  • Flat Panel Solar Collectors Features

 

A  The Composition Of The Flat Plate Solar Collector

The flat plate solar collector is composed of a heat absorbing core, a casing, a transparent cover, a heat insulating material and related components. After adding the circulating pipe and the insulated water tank, it becomes able to absorb the solar radiant heat and raise the water temperature.

B  How Flat Panel Solar Collectors Work

Simply put, flat panel solar collectors is the radiant energy generated by absorbing sunlight, and heats the water to form hot water. So how is it absorbed? Then look down.


Sunlight consists of visible and invisible light of different wavelengths. Different substances and different colors have different absorption and reflection abilities for different wavelengths of light. Black has the strongest ability to absorb sunlight, so you feel warmer when you wear black or dark cotton. White has the strongest ability to reflect sunlight, so people in the summer are mostly wearing light or white clothing. By using the black heat collecting property, the parallel sunlight can be collected by a focusing lens at a point, a line or a small area, and the heat collecting purpose can also be achieved. Place a piece of paper in the sun, no matter how strong the sun, even in the hot summer, the paper will not be lit by the sun. However, if the concentrator is used to collect sunlight on the paper, it can be ignited.


The sunlight is irradiated onto the surface of the heat absorbing body coated with the absorbing layer through a transparent cover plate, and most of the solar radiation energy is absorbed by the absorber, converted into heat energy, and transmitted to the working fluid in the fluid passage. In this way, the cold working fluid from the bottom of the collector is heated by the solar energy in the fluid passage, the temperature is gradually increased, and the heated hot working fluid is discharged from the upper end of the collector with the useful heat energy. The use of water in the tank is a useful energy gain. At the same time, due to the increase in temperature of the heat absorbing body, heat is dissipated to the environment through the transparent cover and the outer casing, thereby constituting various heat losses of the flat panel solar collectors.


C  Introduction of endothermic materials 

In order for the heat absorbing plate to absorb solar radiation energy to the maximum extent and convert it into heat energy, the heat absorbing plate should be covered with a dark coating, which is called a solar absorbing coating.


Solar absorbing coatings can be divided into two broad categories: non-selective absorbing coatings and selective absorbing coatings. A non-selective absorbing coating refers to an absorbing coating whose optical properties are independent of the wavelength of radiation; a selective absorbing coating refers to an absorbing coating whose optical properties vary significantly with different wavelengths of radiation.


a, non-selective absorption coating

In general, it is not very difficult to achieve a high solar absorption ratio simply. It is difficult to achieve a high emissivity ratio while achieving a low emissivity. For selective absorbing coatings, as the solar absorption ratio increases, the emissivity tends to increase. For the commonly used blackboard lacquer, the solar absorption ratio can be as high as 0.95, but the emissivity is also around 0.90. Therefore, it belongs to non-selective absorption coating.


b, Selective absorption coating

The selective absorbing coating can be prepared by various methods such as a spraying method, a chemical method, an electrochemical method, a vacuum evaporation method, a magnetron sputtering method, and the like. Most of the selective absorption coatings prepared by these methods can achieve a solar absorption ratio of more than 0.90, but the range of emissivity they can achieve is significantly different. From the performance point of emissivity, the order of the above various methods should be: magnetron sputtering method, vacuum evaporation method, electrochemical method, chemical method, spraying method. Of course, each method has a range of emissivity values, and the actual emissivity value of a coating depends on the degree to which the coating process is optimized.


D  Flat Panel Solar Collectors Features

a) the structure is simple, flexible and easy to maintain;

b) the form is changeable, easy to integrate with the building;

c) long life and stable performance;

d) Anti-freezing and anti-scaling, defrosting and snowing;

e) The water quality is clean and conducive to health.

 

Flat panel solar collectors are often used throughout our lives, not only for solar water heaters, but also for house heating. And the low price, safe and reliable, simple operation is really a good helper in life. Knowing how this helper works, you can use it more flexibly to bring more convenience to your life.


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