Determination of the Proper Distance between the Absorber Plate and One-layer Cover in Flat-plate Solar Collectors Using Numerical Method

The Maximum energy loss in flat-plate solar collectors is due to top heat loss. The variables of absorber plate temperature, ambient temperature, wind speed, the distance between the absorber plate and the cover, collector length, and tilt angle are effective. In this research, considering the long-term meteorological data and developed relations for the top loss in flat-plate solar collectors in previous researches, including convection, conduction and radiation losses, calculations were performed in the form of Fortran codes. Results showed that the proper value for the distance between the absorber plate and one-layer cover has the range of 11 to 38 mm for some cities of the country. In addition, the sensitivity analysis of the top loss showed that the order of variables from maximum to minimum is wind speed, the distance between the absorber plate and the cover, collector tilt angle, collector length, absorbent plate temperature and ambient temperature.