A REVIEW OF CFD INVESTIGATIONS ON HEAT TRANSFER AUGMENTATION OF FORCED CONVECTION SOLAR AIR HEATER THROUGH ENHANCED FLUID TURBULENCE LEVELS

Solar air heaters generally exhibit lower levels of thermal performance due to higher heat losses and poor heat transfer characteristics of air which is the working fluid. Many investigations, both experimental and numerical, have been carried out in the past to overcome these limitations. One of the commonly used techniques for thermal performance enhancement in solar air heaters is to enhance the turbulence levels in the flowing air stream. This paper presents a detailed review of investigations involving numerical studies for thermal performance enhancement of solar air heater by enhancing turbulence levels in the air flow. It is observed that the focus of numerical simulation studies has been on the use of artificial roughness elements, corrugations and vortex generators to achieve higher turbulence levels in the air flow. RNG k-e turbulence model has been commonly used to capture the turbulent flow characteristics. An attempt has also been made to summarize the operating parameters and heat transfer enhancement parameters of various numerical simulation studies done in the past with respect to turbulence enhancement technique.