Performance and heat transfer evaluation of convex lens solar water heater with serrated, triangular cut and perforated twist inserts

Abstract

This paper studies the performance and heat transfer analysis of Solar water heating systems incorporated by Convex lenses also with two types of twists CSPT(combined Serrated Perforated Twists) and CTPT(combined Triangular cut Perforated Twists) with twist ratios 3 and 6. Convex lenses are preferred to utilize the diffusible radiation and it focuses the solar rays in single point on the absorber plate. It helps the riser tube to get higher solar radiation at the instant. Nearly 45 lenses fixed over the glass and focusing radiations to 9 rows of riser tubes. Generally, twists give a swirling effect to the working fluid and it enables the water to catch up high heat from the riser tubes. In this case, CSPT and CTPT are introduced to examine the heat transfer characteristics. The experiments are carried out for plain and CTPT, CSPT collectors. Reynolds number and the Nusselt numbers are lying between 190 - 1266 and 4.104-16.7331. The friction factor is in the range of 0.035 to 0.1155. The implementation of convex lenses with the insertion of CSPT and CTPT helped to earn better heat transfer. CTPT with minimum twist ratio 3 has provided 1.9 times higher efficiency as compared to CSPT twist inserts. It enhances the overall efficiency by up to 9% than the conventional one.