공기식 태양열 집열기 내 사분원 저항체 설치 조건에 따른 대류 열전달 및 압력강하 특성 분석

Abstract

Air-based solar collectors are renewable systems that produce heated air using solar thermal energy. However, the thermal efficiency of these systems must be increased because of the low thermal conductivity of air. In this study, the heat transfer and pressure drop characteristics of a developed air-based solar collector with quarter-circle-shaped obstacles on the upper and lower surfaces of an air channel were investigated. Computational fluid dynamics (CFD) was used to analyze the effects of the obstacle installation conditions on the heat transfer and pressure drop. The quarter-circle-shaped obstacle produced a 2.53-fold increase in heat transfer; however, the friction factor also increased 41.38 times. Therefore, the performance factor, which considers heat transfer enhancement and pressure drop, was also evaluated. The performance factor was highest at a Reynolds number of 3000 with installation conditions of e/H = 0.10 and P/e = 40, yielding a value of 1.16. Furthermore, empirical correlations for the Nusselt number and friction factor were developed based on the Reynolds number and obstacle installation conditions. The average absolute percentage errors between the CFD results and the from the correlations were 2.98% and 7.5%, respectively, indicating high agreement between the values.