Heat and fluid flow enhancement of the structure of a solar air heater with optimized distance between rib and groove

Abstract

A popular and common method to enhance the heat transfer in a flow passage is to artificially roughen the surfaces with ribs, grooves or combination of ribs and grooves (rib-grooved surface). The artificial roughness is often used in heat exchanger systems, such as solar air heaters, nuclear reactors, electronic cooling devices and gas turbine blades .Among the artificially roughen the surfaces, rib-grooved surfaces are one of the popular techniques that are extensively used in plate heat exchanger manufacturing. In fact, the ribs, grooves and their combination increase the fluid flow turbulence near the wall by breaking the laminar sub layer and create local wall turbulence due to flow separation and reattachment, which disrupt the thermal boundary layer and reduce the thermal resistance and greatly enhance the heat transfer. In this paper, heat transfer enhancement of optimized rib-grooved surfaces in channels is multi objectively optimized applying the NSGA II algorithm. The distance between rib and groove was set from 0 to 3w. The optimized distance between rib and groove was d=2.2w which computed by considering maximum heat transfer and minimum friction factor, simultaneously. The effects of Reynolds number of 5000 to 30000 are so investigated. when the velocity of flow increases the nusselt number and pressure drop increase .When the distance between rib and groove increases the nusselt number increased while the friction factor decreases in optimization with NSGAІІ algorithm point=2.2w is the most optimized than other points for Reynolds from 5000 to 30000.