Response surface-based optimization of thermal characteristics for frustum roughened solar air heater: An experimental and numerical study

Abstract

Artificial roughness on the absorber plate of the solar air heater increases its thermal characteristics, thermohydraulic performance, and overall performance of the solar air heater. The roughness and flow parameters selected for artificial roughness play a vital role. Along with selection of geometry, range of roughness parameter at optimum values creates keen interest in research field. The present investigation is in line with the previous work of the authors in which an experimental and numerical simulation was carried out to explore the thermal characteristics of a frustum roughness solar air heater. Roughness configuration such as the relative height of the roughness (e/Dh), the relative diametral ratio(d1/d2), and the roughness to the diameter of the base diameter (e/d1) was calculated to optimize the thermal characteristic. To optimize thermal characteristics (Nusselt number and friction factor) a response surface optimization (RSM) was applied. The suggested design of the experiment (DOE) was performed experimentally and numerically. Data collected from experiment and simulation are used to develop mathematical model using analysis of variance (ANOVA) approach. Nusselt number achieves its maximum optimum value of 256.78 at e/Dh = 0.043, d1/d2 = 2.33, e/d1 = 0.98 and Re = 12500. Friction factor achieves its minimum optimum value of 0.009 at e/Dh = 0.014, d1/d2 = 2.06, e/d1 = 1.44 and Re = 12158.