Development of new correlations for heat transfer and pressure loss due to internal conical ring obstacles in an impinging jet solar air heater passage

This paper experimentally studies the solar air heater rectangular passages with different types of inside conical ring obstacles for heat transfer enhancement. The experiments were conducted in a turbulent flow regime with Reynolds number ranging from 5,000 to 23,000 under uniform wall heat flux. The optimum values of parameters for obstacle roughened surface arrangement have been obtained and discussed. The optimum value of heat transfer is observed at relative inside conical ring height (H-R/D-H) of 0.110, ratio of inlet flow diameter to inner print diameter of ring (D-IR/D-BR) of 1.7, ratio of ring diameter to ring height (D-O/H-R) of 2.33, relative X-axis pitch (X-S/D-O) of 5.28 and relative Y-axis pitch (Y-S/D-O) of 3.42. The statistical correlations of Nusselt number and friction factor are also developed from the experimental results of inside conical ring obstacles in round jets impingement solar air rectangular passage.