Numerical Simulation To The Convective Heat Transfer In Ducts Enhanced By Field Synergy Principle

Many techniques have been developed to enhance convective heat transfer. However, even for simple single phase flow, there has not been an unified theory to reveal the essence of the enhancement mechanism. In 1998, through analyzing the mechanism of heat transfer in boundary layer, Guo and his co-workers proposed a novel concept for enhancing convective heat transfer that is called the principle of field synergy. The core content of the theory is the correspondence between the thermal performance and the integral of the dot product of the velocity and the temperature gradient. In the current thesis, numerical simulations have been conducted to study the convection in 2-D and 3-D channels designed by the field synergy principle. The studied object is restricted in the periodically fully developed region. For 2-D channel both laminar and turbulence cases have been investigated, while for 3-D channel only laminar case has been computed. The improvement of the synergy degree in the ducts is fulfilled through the deployment of the flow inclining fins. The inclining angle of the fin is from 0°to 23.2°and the dimensionless height of the channel is from 1.167 to 2.833. The effects of the inclining angle and the channel height on the thermal performance have been verified by numerical simulation for different Reynolds numbers. The flow field and the temperature field have been analyzed. The results show that the Reynolds number, the fin inclined angle, and the dimensionless channel height all influence the enhancement effect drastically. To evaluate the enhancement effect of the studied channel reasonably, the assessing method of the same pump power constraint is adopted. For 3-D channel the impact of the fin material on the thermal performance is also discussed. It is found that the fin of copper is apparently superior to the fin of steel in terms of enhancement. In addition, the correspondence between the thermal performance and the integral of the dot product of the velocity vector and the temperature gradient has also been analyzed to show the correctness of the field synergy principle.