Cooling Enhancement of Radiators Using Dimples and Delta Winglets Available to Purchase

Cooled exhaust gas recirculation and lower intake manifold temperature (post compressor) are used to meet emission regulations for a turbocharged intercooled diesel engine. This places a significant demand on the cooling load and space constraint on the radiator of the engine. A typical radiator is a cross-flow fin-tube heat exchanger with coolant water flowing inside the tube and ambient air taking out heat from the fin and tube surfaces. The major resistance to heat transfer in this configuration is offered by the air-side heat transfer co-efficient. The current study focuses on enhancing convective cooling rates on air side in a typical radiator which helps in taking additional load of EGR cooling with minimal increase in space and radiator fan power. Published literature clearly indicates that specific geometrical structures such as delta winglets and dimples, when placed in a convective flow path, act as vortex generators. This ability helps in disturbing/disrupting a steady thermal boundary layer, resulting in enhanced convective heat transfer. Detailed CFD simulations have been carried out to study the individual and combined effect of dimples and delta winglets on the heat transfer rates in a typical radiator geometry. Delta winglets on the fins indicated significant heat transfer enhancement but with increased pressure drop. Dimples on the tubes also led to enhanced heat transfer rates, but with a comparatively lesser increase in the pressure drop. A combination of delta winglets on the fins and dimples on the tubes increased the heat transfer rates substantially (+40%) with a minimal increase in pressure drop compared to the baseline case.