Abstract
In the current study, we developed and tested a new type of solar collector named W-shape solar collector. It is a solar collector with single air pass between the transparent cover and the absorber. The cover has double glass whereby the upper glass is flat and the lower glass is w-shape. The absorber is also W-shape. This combination gave rise to an undulatory airflow circulation in the new collector. This modular solar collector allowed the functioning of several configurations of flat plate solar thermal collector. After realization of the prototype, an experimental characterization was done during a natural period of sunshine in the town of Ngaoundere between November and December 2016. It consisted in characterizing the solar radiation, the input/output temperatures of the solar collector, the temperature of the absorber and the air velocity profile. During the experiments, the solar collector was directed facing the south and tilted either by 45°or by 30° compared to the horizontal plan. Temperature profile analysis showed at noon sun and air velocity of 0.3 m/s, the outlet air temperature of the w-shape solar collector gives 75°C while that of the flat collector gives only 60°C. Nevertheless, the temperature of the flat absorber was higher than that of the W-shape absorber. This allowed us to conclude that the convection heat transfer coefficient of the W-shape solar collector improved than the flat solar heat collector. Also the efficiency profiles highlight the positive contribution of the W-shape in the improvement of the thermal performances of a solar collector.
Highlights
Flat plate solar air heaters are simple in design and construction
We have focused our attention on design and experimental characterization of the thermal performance of a new solar collector with a Wshape cover form
A box made of local wood with a thickness of 15 mm, dimensions of 1000×450×170 mm, opened on the side exposed to solar radiation, on the lateral side, are openings for input and output of air
Summary
Flat plate solar air heaters are simple in design and construction. He transforms solar radiation into thermal energy extracted by the fluid which circulated inside the collector. In agro-industries these collectors are frequently used in the field for drying, cooking or distillation process These converters have a low convection heat transfer coefficient between the absorber plate and flowing air inside the collector. This is essentially due to the low thermo-physical properties of air (Amer et al, 2010). The performances of these systems can be improved, firstly, by optimizing the convective heat transfer coefficient between the plate absorber and the air, secondly, by reducing heat losses through the various components of the solar collector and thirdly by using artificial roughness and in various configurations to create turbulence airflow near wall
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