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ISSN Печать: 1065-5131
ISSN Онлайн: 1563-5074
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OVERALL HEAT LOSS FROM BOTH SIDES OF A TILTED UNGLAZED SOLAR COLLECTOR UNDER INDOOR CONDITIONS USING FLOW CALORIMETRY AND THERMOGRAPHY
Краткое описание
An experimental investigation of the overall heat loss on a flat plate absorber solar collector in the natural convection regimen from both sides of the plate is presented in terms of the heat transfer coefficient, UL. The study considers variations of the inclination angle with respect to the horizontal axis and the input-ambient temperature difference. The experiments were based on the steady-state energy balance under controlled indoor conditions, using heat flow calorimetry and infrared imaging. The UL value was determined in the range of 0°–90° for the tilt angle and 3.3–34.1°C for the input-ambient temperature difference. It can be seen that the UL value changes by 9.7% due to the plate tilt angles and 16.8% due to the input-ambient temperature difference over the working range. The maximum UL value was found at a 45° flat plate tilt angle, slightly decreasing as it changes its position vertically or horizontally. The UL value varies nearly linearly with the input-ambient temperature difference, with a slope of 0.035 W/m2K/K. The two-variables correlation was obtained of the UL value, which agrees well with a root-mean-square error of 0.12 W/m2K (R2 = 0.97). Therefore, with a non-considerable wind effect on unglazed solar collectors, the UL value is affected as the tilt angle and input-ambient temperature difference change with regard to the characterization parameters.