Flow structures and heat transfer characteristics in fan flows with and without delta-wing vortex generators

Abstract

Effects of an external delta-wing vortex generator on the flow and heat transfer characteristics in fan flows and uniform flows were experimentally investigated and compared. A heated plate, installed on the bottom wall of a duct, was used as the heat transfer surface. Three-component mean and fluctuating velocity measurements were conducted using a laser Doppler velocimetry to characterize the flow structures and to obtain the near-wall flow parameters, including the axial mean velocity, axial vorticity and turbulent kinetic energy. Temperatures on the heat transfer surface were measured using thermocouples to obtain the Nusselt numbers. Results show that the external delta-wing vortex generator in fan flows has little overall effect on the near-wall averaged axial mean velocity and axial vorticity, but increases the turbulent kinetic energy, in the investigated X/D ranges. The increase in the turbulent kinetic energy by the delta-wing has little effect on heat transfer in the inherently vortical fan flows.Consequently, the delta-wing vortex generator in fan flows has little effect on the heat transfer augmentation.

Heat Transfer and Pressure Drop Characteristics of Fin-Tube Heat Exchangers with Different Types of Vortex Generator Configurations

“…They also indicated that an optimization should be made for the fin with a winglet in order to improve its performance. Chen and Shu (2004) determined the effects of the delta-wing vortex generator on uniform and fan flows as well as on heat transfer. The effect of the delta wing on heat transfer performance is found to be larger for a uniform flow since the fan flow is already vortical without a delta wing.…”

Optimum design parameters of a heat exchanger

“…In similar studies Tahat et al [5], Tahat et al [6], El-sayed et al [7], Chen and Shu [19], Jubran and Al-Salaymeh [20] etc., reported that the total radiative heat-losses from a similar test surface would be about 0.5% of the total electrical heat-input. Also the base plate and fins were of aluminum; their surfaces being highly polished and so of low emissivity.…”

Optimum design-parameters of a heat exchanger having hexagonal fins

“…In similar studies, Tahat et al [4], Tahat et al [5], El-sayed et al [11], Chen and Shu [24], Jubran and Al-Salaymeh [25] reported that the total radiative heat loss from a similar test surface would be about 0.5% of the total electrical input. Also the base plate and fins were of aluminum: their surfaces were highly polished and so of low emissivity.…”