Heat transfer and friction factor correlations for an impinging air jets solar thermal collector with arc ribs on an absorber plate

Abstract

The thermal enhancement characteristics of a solar thermal collector (STC) roughened with single arc protrusion ribs are investigated. Out of various techniques used for enhancing the performance of STC, jet impingement and artificial roughness (AR) have a dominant role in heat transfer augmentation. The impinging air jets STC is roughened with single arc protrusion ribs of different parametric values. The combined impact of artificial roughness and jet impingement on the thermo-hydraulic performance of STC is experimentally investigated. Reynolds number is varied from 4000 to 18,000 during experimentation. The AR parameters; relative height ratio of the rib is varied from 0.8 to 1.7, relative pitch ratio of the rib is varied from 9 to12, angle of arc protrusion rib from 40° to 80°, streamwise variation to dhy ratio (hydraulic diameter) is from 0.39 to 0.56 and spanwise variation to dhy ratio from 0.82 to 0.99 during experimentation. The parametric values of artificial roughness for the optimum thermo-hydraulic performance of 1.5, are found out to be relative height ratio of rib = 1.1, relative pitch ratio of rib = 10, angle of arc protrusion rib = 60°, streamwise variation to dhy ratio = 0.43 and Span wise variation to dhy ratio = 0.86. Artificial neural network modeling of Nurs – Nusselt number and ff – friction factor is also performed which accurately predicts these factors easily.