Axially Oriented Structured Porous Layers for Heat Transfer Enhancement in a Solar Receiver Tube

Abstract

The present work reports a numerical investigation of heat transfer and pressure drop characteristics in a solar receiver tube with different shaped porous media for laminar and low Reynolds number turbulent flow regimes. Numerical simulations have been performed with finite volume-based code ANSYS (v-2017) for different shapes of porous layers axially oriented in the tube. The plain-shaped porous medium fitted up to 50% of the tube shows better performance than other-shaped porous layers. Simulations have also been performed for axially oriented structured porous media with different sizes. Axially oriented structured porous medium develops a lateral flow disturbance enhancing the intermixing of the liquid and porous medium at their interface. Structured porous medium with a 3-crest configuration shows the best heat transfer performance among all the shapes of porous media. It offers a maximum of 148% heat transfer enhancement compared to a half-filled plain porous layer, whereas it reports a maximum of 564% enhancement compared to the flow without a porous layer. The lateral flow tendency or the swirling effect helps better heat transfer performance in the axially oriented structured porous media. Performance evaluation criterion (PEC) in all types of porous media is more in the transitional flow regime than in the laminar and turbulent flow regimes. For the same operating conditions, the maximum value of the PEC in the present work is 120% higher than the maximum value of PEC for other-shaped porous media reported in the literature. Correlations for Nusselt number have been developed for both laminar and turbulent flow regimes for three crests shaped porous medium.