Numerical Investigations on Minimization of Convective Heat Losses From Hemispherical Cavity Receiver Using Air Curtain

In the present work, numerical investigations are carried out to study the effect of placing an air curtain at the aperture of the hemispherical cavity receiver of solar parabolic dish collector system to reduce convective heat losses. The effect of parameters like jet angle, jet velocity, cavity inclination, and surface temperature on convective heat loss is considered. The effect of jet angle and velocity plays an important role in controlling the heat losses from the receiver. At jet angle of −20 deg, air impinges inside the receiver surface thus diluting hot air inside the receiver. However, for jet angle of 0 deg and 20 deg, jet controls air escaping out of the receiver. There lies optimum jet velocity which can sustain hot air from leaving receiver. This study shows that using an air curtain for the hemispherical cavity receiver minimizes the convective heat losses up to 45% at optimum jet conditions. The convective heat loss is minimum (192 W) for the jet velocity of 2.5 m/s and jet angle of 20 deg which implies that the best containment effect from the air curtain can be obtained at this condition. Further, an artificial neural network model is formulated to predict the heat losses from the receiver for a range of functional parameters based on numerical simulations.