太阳能吸热器内超临界二氧化碳对流换热特性数值研究

Numerical simulation of convection heat transfer characteristics of supercritical carbon dioxide in a concentrating solar power receiver

为分析聚光太阳能热发电中吸热器内超临界二氧化碳(S-CO2)在高温非均匀壁面热流密度分布下的对流换热特性,采用ANSYS Fluent软件建立了管排式吸热器的三维数值模型,对其中S-CO2对流换热特性进行数值仿真,并考虑了吸热器与外界环境的辐射和对流换热,分析了吸热管半周均匀受热、半周周向均匀轴向高斯受热和半周周向余弦轴向高斯受热3种非均匀壁面热流密度分布的影响。仿真结果表明:外界环境的辐射和对流换热对吸热器壁面温度影响较大,相较于未考虑外界环境的辐射和对流换热,考虑辐射和对流换热的壁面最高温度下降6.84%;3种壁面热流密度分布中半周周向余弦轴向高斯受热的吸热器出口温度和壁面最高温度均最高,其壁面最高温度比半周均匀受热高353.4 K;非均匀壁面热流密度分布虽然对吸热器内流体流量分配不均匀性的改善不明显,但可明显削弱流量分配不均造成的各吸热管流体温度偏差的影响。

To analyze the convection heat transfer characteristics of supercritical carbon dioxide(S-CO2)in concentrating solar power receiver at high temperature and with non-uniform wall heat flux distribution,a threedimensional numerical model is established using ANSYS Fluent software for a multi-tube absorber.The radiation and convection heat transfer between the absorber and environment are both considered.The influences of three wall heat flux distributions on the convection heat transfer and flow characteristics of S-CO2 are analyzed.The numerical results show that,radiation and convection heat transfer between the absorber and the environment have significant effects on wall temperature of the absorber.Compared with none radiation and convection heat transfer between the absorber and environment,the maximum wall temperature reduces by 6.84%.Among three wall heat flux distributions,the outlet temperature and maximum wall temperature of the absorber are both the highest for the half non-uniform heated wall with circumferential cosine and axial Gauss.Moreover,its maximum wall temperature is 353.4 K higher than that of the half uniform heated wall.Although the non-uniform heat flux distribution on the wall has insignificant effect on the flow distribution uniformity in the absorber,it can reduce the influence on the fluid temperature deviation in each tube caused by uneven flow distribution.