Views:0 Author:Site Editor Publish Time: 2019-07-31 Origin:Site
With the extensive development and use of solar energy, flat panel solar collectors are now more widely used in our lives. Solar water heaters in daily life, solar air conditioners in the south, solar heating in the north, etc. Different application locations have different requirements for flat panel solar collectors. Therefore, flat panel solar collectors have also made different changes. This article aims to introduce a comparative study of flat panel solar collectors.
You will understand the following points:
1.Single glaze structure
2.Double glaze structure
3.Comparison of advantages and disadvantages between the both
Since the temperature of the heat absorbing surface of the collector is higher than the ambient temperature, some of the heat that it can absorb is inevitably lost to the surrounding environment. This part of the heat loss includes heat absorption from the heat absorbing surface to the transparent cover and from the outer transparent cover to the surrounding environment due to radiation and convection; heat conduction from the back and edge of the collector and the outer surface Convection (radiation accounts for a small fraction) heat loss. The design of the collector should minimize these heat losses.
The transparent cover is a plate-shaped member that covers the heat absorbing plate in a flat panel solar collector and is composed of a transparent (or translucent) material. It has three main functions: one is to project it on the heat absorbing plate through solar radiation; the other is to protect the heat absorbing plate from dust, rain and snow; the third is to form a greenhouse effect and prevent suction. The hot plate dissipates heat to the surrounding environment by convection and radiation after the temperature rises. According to different flat panel solar collectors requirements, it is divided into a single glaze structure and a double glaze structure.
The single glaze structure means that the number of layers of the transparent cover is one layer. Generally used in domestic solar water heaters. The solar energy absorbed by the single glaze structure can meet the needs of general household use. In addition to this, the number of layers of the transparent cover depends on the operating temperature of the flat panel solar collectors and the climatic conditions of the area in which it is used. Most of them have a single-layer transparent cover without special needs, and the single glaze structure can absorb more solar radiation.
The double glaze structure appears to reduce the heat loss at the top, and the two-layer cover effectively reduces the convection and radiant heat loss of the collector. Generally used in the north of solar heating, southern solar air conditioning and other needs.
When the second layer cover is close to the heat absorbing plate, the natural convection heat transfer between the interlayer air and the heat absorbing plate can be effectively hindered, and the instantaneous efficiency of the heat collector is effectively improved, but the upper surface temperature of the cover plate is also high. It will intensify the natural convection of the air interlayer between the double-glazed cover plates; when the transparent heat-insulating plate is about 18 mm away from the heat-absorbing plate, the collector efficiency reaches the maximum value; when the double-glazed cover plates are far apart At the time, the natural convection phenomenon of the air interlayer inside the collector cannot be effectively weakened, thus causing the instantaneous efficiency of the collector to be lowered.
The single glaze structure is low in cost and functions to meet general needs. However, its heat loss is severe and solar energy utilization is low.
When the ambient temperature is lower than 18 degrees Celsius, the collector of the double glaze structure has an advantage. When the ambient temperature is 10 degrees Celsius, the instantaneous efficiency of the double-layer glass cover collector is 0.26 higher than that of the ordinary flat collector; the inlet water temperature And the increase of solar radiation intensity can cause the internal temperature of the collector to rise. At this time, the heat preservation effect of the double-layer glass cover is more obvious. When the inlet water temperature is 50 degrees Celsius, the double-layer glass cover collector is more than the single-layer glass cover. 678。 The instantaneous efficiency of the flat panel solar collector is 0. 27; when the lower glass cover is 18 mm above the heat absorbing plate, the instantaneous efficiency of the collector is up to 0. 678. However, the addition of a cover plate somewhat reduces the actual effective solar transmittance and is relatively costly.
In short, if there is no high requirement for the flat panel solar collectors, the single glaze structure can be chosen. After all, it is relatively inexpensive, the performance also meets the demand, and the cost performance is very high. However, if you are pursuing a higher conversion rate or you need a higher conversion rate, you can choose a double glaze structure. According to your own needs, the most suitable is the best.
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