태양열 공기식 집열기 내 저항체 설치 위치 및 형상에 따른 열전달 및 압력강하 특성에 대한 CFD 해석

Abstract

A solar air heater is a system that converts solar energy into useful thermal energy. However, numerous studies have been conducted to improve its thermal efficiency because of air’s low thermal conductivity. In this study, the thermal performance of a solar air heater was investigated with a computational fluid dynamics analysis; nine configurations varied the installation positions and shapes of obstacles. As a result, the heat transfer performance improved by 1.044 to 1.707 times compared to that of the solar air heater without obstacles. However, the friction factor increased by 1.52 to 9.26 times due to the presence of obstacles. The performance factor was evaluated to account for both the heat transfer enhancement and pressure drop. The highest performance factor was achieved when the quarter-circle-shaped obstacles—with the arc facing the air outlet side—were installed only on the top surface. Additionally, the greatest heat transfer enhancement was observed when obstacles were installed on both the top and bottom surfaces, which also provided a higher performance factor compared with a solar air heater with obstacles only on the bottom surface. Therefore, installing obstacles only on the top surface is preferable for optimizing the performance factor, whereas installing obstacles on both the top and bottom surfaces is more effective for maximizing heat transfer enhancement.