This article presents an experimental investigation of the heat transfer characteristics as well as energy and exergy performance for a pressurized volumetric solar receiver under variable mass flow rate conditions. During a two-hour period of continuous operation in the morning, the solar irradiance is relatively stable and maintained at approximately 600W/m2, which is beneficial for analyzing the energy and exergy performance of the solar receiver. Experimental results show that the mass flow rate fluctuation has insignificant effect on the solar receiver outlet temperature, whereas the mass flow rate plays an important role in the solar receiver power, energy efficiency and exergy efficiency. The efficiency of the solar receiver is normally above 55% with the highest efficiency of 87%, and under steady state operating conditions the efficiency is maintained at approximately 60%. A very low value of the heat loss factor (0.014 kW/K) could be achieved during the current steady state operating conditions. The highest exergy efficiency is approximately 36%. In addition, as the temperature difference increases, the impact of the exergy factor increases. The highest exergy factor is 0.41 during the entire test.
Conclusions
This paper performed an experimental study to investigate the thermal performance of a pressurized volumetric solar receiver under real solar radiation conditions. In order to design a high efficiency solar receiver, some important parameters such as different porous material, the size of the quartz window, the shape of the cavity, should be selected carefully. In the current work, a parabolic dish with solar tracker system is well designed and the obtained results are analyzed using energy and exergy analyze method. Experimental results reveal that the solar irradiance is almost stable and maintained at around 600 W/m2 from 10:00 am to 12:00 pm. It takes about half an hour to raise the solar receiver outlet temperature from 42℃ to 430℃. After 10:30 am, the outlet temperature increases very slowly with the time. The mass flow rate fluctuation has little effect on the solar receiver outlet temperature. However, the mass flow rate has great influence on the solar receiver power, energy efficiency and exergy efficiency. The efficiency of the solar receiver can be above 55%. The peak value of the efficiency is 87%, and finally, the efficiency is maintained at around 60%. During the steady state, the heat loss becomes lower and UL achieves the minimum value of 0.014 kW/K. The highest exergy efficiency is approximately 36%, whereas the highest energy efficiency is around 87%. As the temperature difference increases, the impact of the exergy factor increases. The highest exergy factor is 0.41 during the entire test.
The results have been published on Applied Thermal Engineering 104 (2016) 212–221.
