접시형 태양열 집광시스템용 흡수기의 열손실 해석

초록

In order to collect and utilize solar energy at high temperature, a solar energy collecting system that mainly consists of a parabolic dish concentrator and a cavity receiver has been used. Since the entire collected solar energy cannot be transformed into the thermal energy at the cavity receiver due to heat losses, it is important to understand heat transfer mechanism from the receiver to the environment. In the present study, the solar energy collecting system that is installed in Korea Institute of Energy Research are considered, and three modes of heat transfer from the cavity receiver are analyzed and its thermal performance is estimated. The analytical method for predicting conductive heat loss from a cavity receiver is relatively straightforward. On the other hand, the convective and radiative heat losses are rather complicated to be analyzed. The complex geometry of the cavity makes it difficult to use existing analytical models for predicting convective heat loss. For this study, the Stine and McDonald Model, which has shown fairly good prediction for the other application, is used to estimate convective heat loss. Because a cavity receiver is working at high temperature, radiative heat loss becomes significant so that its order of magnitude is similar to that of convective heat loss. Two kinds of techniques for the radiation analysis are used. The Net Radiation Method that is based on the radiation heat balance on the surface is used to calculate the radiation heat transfer rate from the inside surface of the cavity receiver to the environment. And, the Monte-Carlo Method that is the statistical approach is adopted to predict the radiation heat transfer rate from the reflector to the receiver. Based on the heat loss analysis, the performance of the cavity receiver for the KIER solar energy collecting system can be estimated, and the optimal configuration will be obtained.