槽式太阳能集热器集热性能分析

PERFORMANCE ANALYSIS OF PARABOLIC TROUGH SOLAR COLLECTOR

本文运用蒙特卡罗光线追踪法(MCRT)模拟了抛物槽式系统聚光特性,并与计算流体与传热有限容积方法(FVM)结合,进一步研究了吸热管内耦合传热过程。聚光特性分析中考察了光不平行夹角、几何聚光比和边界角对太阳热流密度分布的影响;耦合传热模拟中考虑了液体油热物性随温度的变化以及吸收管外管壁辐射换热。模拟计算表明:模拟计算结果与文献数据对比符合较好,验证了计算方法与模拟程序的正确性。光不平行夹角主要对热流密度圆周方向分布产生影响,使其分布平缓,对热流密度轴向分布影响不大;随着几何聚光比的增大,太阳热流衰减区的角度跨度增大;随着边界角的增大,热流密度圆周分布曲线向圆周角90°方向平移,同时热流密度极大值降低。在太阳直射强度大致相同情况下,入口流速与入口温度对接收管表面对流换热与最大温差影响很大;同时变物性对流体对流换热影响也较大。

In this paper, the heat flux distribution on the outer surface of a the absorber tube of a parabolic solar collector receiver is simulated by Monte Carlo Ray-Trace Method （MCRT）. Nonlinear heat flux distribution is considered as complex boundary condition used in FVM to simulate the coupled heat transfer problem. To investigate the concentrating characteristics, the finite size of sun is considered, and the effects of geometry concentration ratios and rim angles on sun radiation heat flux distributions are also analyzed. Temperature-dependent properties of the oil and thermal radiation between the absorber tube and the outer glass cover are also taken into account. Numerical results show that the predicted results agree well with the data in reference, which proves that the models and methods are feasible. The finite size of sun has significant influence on the heat flux distribution on circle direction, but little influence on the distribution on axial direction. With increasing geometric concentration ratios, the angle span of reducing area becomes larger. With increasing rim angle, the heat flux distribution curve moves towards the direction of circle angle 90° and the maximum value of heat flux density reduces. The convection and maximum temperature difference on the wall of the receiver inner tube are largely influenced by the inlet velocity, inlet temperature and the temperaturedependent properties of the oil, with almost the same direct normal irradiance.