Investigation of non-uniform heating effect on parabolic trough solar absorber

The rapid increase in energy demand and increased global warming have both pushed China to change its current electrical power structure. Solar thermal power generation is an important utilisation of solar energy which can mitigate energy shortages and environment pollution. The parabolic trough collector, which is one kind of concentration solar power technology, has been applied more widely than other solar thermal power technologies such as solar power towers, solar dish systems and linear Fresnel reflectors. The parabolic trough solar collector is the key component of the solar thermal power station. For problems of parabolic trough collector with non-uniform distribution of solar irradiation, computational fluid dynamics was used to simulate the distribution of temperature and velocity of the absorber tube and the effect of inlet parameters of the tube. The solar elevation angle on the heat transfer coefficient and the friction factor were also studied. The results show that the non-uniform distribution of the solar irradiation made the non-uniform distribution of temperature in the crossing section of the absorber tube. Every step of temperature increase in 10K made the heat transfer coefficient increase 4.7% and the friction factor decrease 2.63%. Every step of velocity increase in 0.5m/s made the heat transfer coefficient increase 18% and the friction factor decrease 3.5%. The solar elevation angle had little influence on fluid flow when the working fluid had a high viscosity, and the buoyancy effect could be ignored. In actual operation, the inlet parameters of the tube should be chosen by considering other parameters in order to get the optimal operation efficiency of system.