Behnia and Reizes have studied combined radiation and natural convection in a rectangular cavity filled with a non-participating fluid. The model was refined by including the aperture area and was later validated with experimental data. Clausing presented an analytical model for estimating the convective heat loss of a large open cubical cavity receiver. Meanwhile, the existence of the aperture causes unavoidable energy losses, including radiative heat loss and convective heat loss, so most studies on the thermal performance of solar cavity receivers focus on thermal efficiency and thermal loss. There is usually an aperture on the front surface of the cavity receiver, through which sunlight concentrated by a heliostat field projects onto the surface inside the cavity. One possible configuration usually used in tower type solar power system is the cavity receiver because of its large surface area and low thermal loss compared to an external receiver. The performance of a solar receiver is in direct relation to the efficiency of the whole power generation system. The solar receiver is a key component, which transforms light into heat in a tower type solar power system.

The equipment cost of tower type systems mainly consists of the costs for the heliostat field and the receiver, and the cost of the receiver accounts for 20% of the total equipment cost. The equipment cost of tower type solar power system is much lower than that of dish type and slightly higher than that of trough type, and the equipment cost will be further reduced in larger scale power generation. Wang reported that the tower type solar power technology has better commercial prospects than those of trough type and dish type solar power technologies in respect of large-scale power generation. The utilization of solar energy for power generation is usually realized by adopting three primary technologies. Solar energy is a kind of non-polluting renewable energy and can be obtained for free, so it has been used more and more extensively.

The purpose of the present study was to determine an appropriate mass flow rate for the receiver of the experimental platform to ensure its efficient operation.Īs problems of energy shortage and environment pollution become more and more serious, clean and renewable energy has been of particular concern and studied all over the World. The curve of thermal efficiency versus mass flow rate was obtained to show that the thermal efficiency increases with increasing mass flow rate within a certain range, and the increase is more remarkable at low mass flow rates. The water/steam cavity receiver of the experimental platform was studied numerically. This model couples three aspects of heat transfer: the radiative heat transfer inside the receiver, the flow boiling heat transfer inside the absorber tubes and the convection heat transfer around the receiver. In order to study the relationship between thermal efficiency and mass flow rate, a computational model for evaluating the thermal performance of a cavity receiver was built and verified. The main reason for the low thermal efficiency was attributed to the low steam mass flow rate, which causes a high proportional heat loss. The results showed that the receiver performed at relatively low thermal efficiencies.

A couple of start-up curves under different working pressures were finally obtained. During start-up the temperature rise rate and the mass flow rate are considered as control variables. The electrical heating mode was chosen to simulate the non-uniform distribution of heat flux on the surface of absorber tubes inside the cavity. The experimental platform was utilized to investigate the start-up performance and operation characteristics of the receiver. An experimental platform was designed and built for testing the thermal performance of a water/steam cavity receiver.

Low mass star order