碟式系统半球形接收器热力计算模型的研究

Investigations on the Thermal Calculation Model of Semisphere Cavity Receiver of Dish Solar System

现今针对碟式太阳能集热系统中半球形接收器的研究仅集中在对流换热损失方面,所建立模型的输入量不符合工程实际且实现过程较复杂,没有半球形接收器集热系统的室外试验研究,因此利用TRACEPRO软件获得光学模型后结合传热学原理提出一新的理论模型,该模型的精度可满足工程要求,且运算速度较快,之后以导热油为传热介质利用碟式聚光系统做了户外试验验证理论模型。利用理论模型对影响集热效率的几个因素进行研究,得出以下结论:降低进口温度时应注意使流量高于最低点以避免出现层流,降低流量时类似;辐射强度过高会使集热效率下降,故集热系统的聚焦比不宜过大;流量较高时对效率影响很小,且使收集热量的品位降低,当辐射低而温度高时降低流量反而会使效率和出口温度均升高。

The investigations on the semisphere cavity receiver of dish solar system are focused on its convection heat loss, the input of the model is unrealistic and the realization process is too complex, there is no outdoor experiment about this. So the optical analysis is obtained by TRACEPRO, a new model is presented combined with heat transfer theory, The accuracy of the model with high operating rate can meet the requirements Of engineering. Outdoor experiments with dish solar collector are done to prove the new model. The heat transfer fluid is oil. Finally the investigations on some factors which have influence on the efficiency are done by the model, the conclusion are follows： the flow rate should be keeped higher than the minimum to avoid the laminar flow when decrease inlet temperature, it is similar when decrease the flow rate. The efficiency will decrease when the radiation intensity is too high, so the concentration ratio of solar thermal system should not be too high. The influence on efficiency is very small when flow rate is high, and exergy of the oil decrease with the increase of flow rate, the efficiency and outlet temperature both increase with the decrease of flow rate when radiation is low and temperature is high.