太阳能槽式集热系统动态传热特性

DYNAMIC HEAT TRANSFER CHARACTERISTICS OF PARABOLIC SOLAR TROUGH COLLECTORS

采用数值模拟方法研究了太阳能槽式集热系统的动态传热特性。建立了管内流体的一维传热模型,并进行了检验,计算结果与实验结果符合较好。采用该模型,该文首先分析了恒定辐射强度下,集热特性受入口温度、环境温度、流体质量流量以及风速的影响规律。然后,研究了辐射强度变化情况下的出口参数动态变化特性。得出:集热管出口温度的变化由于热惯性的影响滞后于辐射强度的变化,对于短期的辐射强度波动,出口温度变化较小,系统可不考虑加入额外的能量。对于全天辐射强度变化,集热管出口温度受辐射影响较大,尽管可忽略短时辐射强度波动的影响,但为维持系统正常运行,蓄热或额外的燃料供应是必须的。

The dynamic heat transfer characteristics of the fluids in an evacuated tube operated in a parabolic solar trough was studied with numerical simulation. One-dimensional model of the fluids was established with verification. The calculation results are agreeable with the experimental results. Based on this model, outlet parameters influenced by inlet temperature, ambient temperature, wind speed and mass flow rate were analyzed under constant solar radiation. Then dynamic characteristics of outlet parameters under a change of solar radiation were analyzed. It indicates that in the evacuated tube, the change of outlet temperature is slower than the change of solar radiation due to the influence of thermal inertia. As regards to a short-time fluctuation of solar radiation, there is a little change for the outlet temperature, and no extra energy is needed. However, for the change of solar radiation in a whole day, the outlet temperature is greatly affected by the fluctuation of solar radiation. Although the influence under a short-time fluctuation can be neglected, in order to maintain the normal operation of the system, extra fuels or thermal storage should be required.