Abstract:
The numerical study and optimization of combined laminar natural convection and surface radiation heat
transfer in solar cavity receiver with plate fins is presented in this paper. Minimizing heat loss in cavity
receivers is seen as an effective way to enhance the thermal performance and the use of plate fins has
been proposed as a low cost means to minimize heat loss. Firstly, the influence of operating temperature,
emissivity of the surface, orientation and the geometric parameters on the total heat loss from the receiver
was investigated. It was observed that convective heat loss is largely affected by the angle of inclination
of the receiver, the presence of fins and the number of fins in the receiver. As for the radiation heat
loss it was observed that it is mainly influenced by the properties of the cavity receiver surface. The radiation
heat loss was found to be constant at all the angles of the receiver. Significant reduction in natural
convection heat loss from the cavity receiver was accomplished by using the plate fins whereas radiation
heat loss was marginally reduced by about 5%. Secondly, the optimization was conducted to obtain the
optimal fin geometry and lastly, the overall thermal efficiency of the receiver was presented at different
operating temperatures. The overall cavity efficiency marginally increased by approximately 2% with the
insertion of fin plates although the convective heat loss was suppressed by about 20%. This is due to the
fact that radiation heat loss dominates at high operating temperatures compared to convective heat loss.
