Three-dimensional analysis and numerical optimization of combined natural convection and radiation heat loss in solar cavity receiver with plate fins insert

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.

Experimental investigations on thermal performance characteristics of a solar cavity receiver

“…As reported earlier by Ngo et al [8], radiation heat loss remains unaffected by change in inclination angle of a receiver. Therefore, according to them, receiver inclination influences the heat transfer (energy loss) by means of combined conduction and convection.…”

“…As discussed earlier, the loss of energy by conduction mode through the insulation is obtained using Eq. (8). During experimentation, it exhibited a rising trend with the surface temperature of cavity.…”

“…The provision of plate fins significantly reduces the convective heat losses by about 20% from the cavity receiver as well as it reduces the radiative energy losses by about 5% [8]. Radiation energy loss from a cavity receiver is seen to be unchanged for various receiver inclination angles (0°, 90°, and 180°).…”

“…At sideways position, a receiver is dominated by the convective zone which diminishes for down-facing receiver due to stagnant fluid zone inside cavity. The provision of fins improves the receiver collection efficiency by about 2% [8]. Similarly, providing fins inside the conical receiver without glazing exhibited collection efficiency improvement of about 10% as compared to conical receiver with no fins [13].…”

Parametric analysis of small scale cavity receiver with optimum shape for solar powered closed Brayton cycle applications

“…The outlet condition regards the pressure is kept to be at atmospheric pressure and at the relevant suitable conditions with no wind influence was neglected by means of natural convection only will be the convective heat losses [39]. Moreover, the model of the receiver was maintained vertically, 90 o only, as this alignment attains the lowest amount of convective heat losses [25] and [40]. For calculating the radiation losses each model needs the relevant value of view-factor [41] so this was also calculated before computing the radiation heat losses.…”