The Study On Sphere Flow Reveiver For Solar Power Tower Generation

In the tower solar thermal power generation system,the receiver is the device that converts the solar radiation energy into heat energy,and it is the core of the solar thermal system.The outlet temperature and thermal efficiency of the receiver directly affect the solar energy-electricity conversion efficiency of the thermal power generation system.Among the existing receivers,the outlet temperature of the particle receiver is the highest.However,when the micro-particles are running in the receiver,they often encounter many problems,such as easy to be taken out by the outside wind,easy to reunite,easy to be contaminated on the surface of the receiver,and the single cycle effect of the particles is not satisfied.Based on the existing problems of solid particle receivers,a new type of sphere flow receiver using large diameter solid sphere as endothermic medium is proposed,and a spherical thermal model is established.The feasibility of the sphere as an endothermic working fluid is verified by the heat absorption experiment of the sphere,and the thermal model of the sphere is verified by the experimental data.In the analysis of the heat absorption process by using the model,the following conclusions are drawn:1.Increasing the radiation energy flux density on the surface of the receiver can significantly improve the heat efficiency of the receiver.When the average incident energy flux density is increased from 200 kW/m~2to 400 kW/m~2and 600 kW/m~2respectively,the thermal efficiency of the sphere is increased from 77.4%to 86.9%and 89.8%in the process of heating the sphere from 25?to 800?.2.The air velocity has a great influence on the thermal efficiency of the receiver.When the wind speed increases from 0 m/s to 2,5 and 8 m/s,the thermal efficiency of the sphere decreases from 86.9%to 81.2%,77.1%and 73.8%in the process of heating the sphere from25?to 800?.Therefore,adding an air window in front of the receiver to reduce the air velocity of the forward blowing receiver can increase the thermal efficiency of the receiver by more than 5 percent point,or even more than 10 percent point.3.Ambient temperature has a little effect on the endothermic process of spheres.4.Reducing the surface emissivity of the sphere can effectively improve the thermal efficiency of the sphere in the process of heat absorption.When the surface of the sphere is coated with coatings with emissivity of 0.5,0.7 and 0.9,the thermal efficiencies of the sphere heating from 25?to 800?are 89.0%,86.4%and 83.4%respectively.In this paper,On-sun test of multi-spheres heat absorber is also carried out on the central collector of solar thermal power plant.In the experiment,the final temperature of the spheres rise to 800 C,which shows that the sphere flow receiver has certain feasibility in Yanqing tower solar thermal power plant.However.The heat efficiency of the receiver is low due to the low energy flux density at the lighting entrance of the central collector tower.These theoretical and experimental studies provide important references for the design and optimization of spherical receivers.