Analytical and Experimental Investigation of Overall Heat Loss Coefficient for Single Non-Evacuated Tube Solar Thermal Receiver
Abstract
Concentrating Solar Power (CSP) using Linear Fresnel Reflectors (LFR) is a promising technology for harnessing power from the sun. The tubular receiver in LFR has a significant impact on its efficient performance. In the present work, thermal characteristics of four different configurations and dimensions of absorber and surrounded by the concentric glass tube are studied. The experimental investigations are employed to characterise the nonevacuated LFR receivers using the overall heat loss coefficient (HLC). The absorber tube wall temperatures are achieved between 50°C and 215°C which is typically achieved in LFR. Influence of the angular gap ratio (0.26, 0.625, 0.8 and 1.4) on the overall HLC is investigated (Annular gap ratio is the ratio of annular gap between absorber and glass tube and the outer diameter of the absorber tube). The overall HLC increases with increase in the absorber wall temperature. For a given absorber wall temperature, the overall HLC increases with the increase in the annular gap ratio. The overall HLC obtained from an analytical model is reasonably agree with the experimental results. An empirical correlation for overall HLC as a function of annular gap ratio and difference of absorber temperature and ambient temperature is proposed.
Keywords
Overall heat loss coefficient, Single tube non-evacuated receiver, Linear Fresnel Reflector, Concentrating Solar Power (CSP), Annular gap ratio