低熔点熔盐圆管内强迫对流换热

摘要

Molten salt as one of the most promising heat transfer and heat storage media in the concentrating solar power (CSP) system has such advantages as high and wide liquid temperature, good heat transfer performance, low operation pressure and good thermal stability. An experimental study on turbulent convective heat transfer with low-melting point molten salt in a circular tube was conducted by using a self-made parabolic trough solar collecting and heat transfer system with molten salt. The total heat transfer coefficients from water to salt in a concentric tube heat exchanger at different flow rates were obtained. The change of Nusselt number of low-melting point molten salt with Reynolds number was calculated with the least-square method and the experimental correlation were obtained. Comparison was also made between experimental data and well-known convective heat transfer correlations, with the maximum deviations between the present data and curves predicted by Dittus-Boelter, Colburn, Seider-Tate, and Gnielinski equations of+23%,+13%−10%and−20%respectively.%熔融盐具有使用温度高、热稳定性和传热性能好等优点，被认为是太阳能热发电系统中最有前途的传热、蓄热介质之一。通过搭建槽式太阳能熔盐集热传热实验台，进行了低熔点熔盐管内受迫对流换热实验，获得了不同熔盐流速下套管式熔盐-水传热单元的总传热系数；通过最小二乘法获得了低熔点熔盐管内充分发展紊流段对流换热 Nusselt 数随 Reynolds 数的变化曲线和实验关联式，并与经典关联式进行了对比，结果表明，实验数据和Dittus-Boelter方程、Colburn方程、Seider-Tate方程以及Gnielinski方程最大偏差分别为+23%、+13%、−10%和−20%，实验数据和经典公式符合较好。