Novel design of natural double-pass solar air heater for higher thermal performance using vortex generator

Abstract. The present study discusses the effects of apping exible vortex generators on two-dimensional turbulent free convection air ow in a double-pass solar air heater. To this end, two thin elastic winglets used as vortex generators were attached to two absorber walls near the inlet section at an attack angle of 650C. This novel concept was elaborated through transient numerical simulation of the ow eld based on the nite element method and uid-solid interaction. In addition, an extensive comparison of four different congurations was made in this study. The absorber and outlet temperatures as well as the ow rate and velocity eld were carefully calculated, numerical results of which conrmed the considerable enhancement of thermal performance compared to that of conventional parallel double pass heater. The improvement rate was up to 54% in the case of deltaTg = Tgout Tin from 13 to 20C while reducing the ow rate by 33.6%. The present numerical results were validated based on the experimental and numerical data reported in the literature.