Sheng Hongzhi

Numerical Simulation of Fluid Flow and Heat Transfer in a DC Non-Transferred Arc Plasma Torch Operating Under Laminar and Turbulent Conditions

In this work, a magnetic fluid dynamics (MHD) model is used to simulate the electromagnetic field, heat transfer and fluid flow in a DC non-transferred arc plasma torch under laminar and turbulent conditions. The electric current density, temperature and velocity distributions in the torch are obtained through the coupled iterative calculation about the electromagnetic equations described in a magnetic vector potential format and the modified fluid dynamics equations. The fluid-solid coupled calculation method is applied to guarantee the continuity of the electric current and heat transfer at the interface between the electrodes and fluid. The predicted location of the anodic arc root attachment and the arc voltage of the torch are consistent with corresponding experimental results. Through a specific analysis of the influence of mass flow rates and electric current on the torch outlet parameters, the total thermal efficiency, thermal loss of each part, and the laws of the variation of outlet parameters with the variation of mass flow rates and electric current was obtained. It is found that operation under a laminar condition with a limited area of the anode could increase the total thermal efficiency of the torch.

A Study on Heat Transfer for Immersed Tube in Internally Circulating Fluidized Bed

Heat transfer coefficients for horizontally immersed tubes have been studied in a model of ICFB (Internally Circulating Fluidized Bed). The characteristics in ICFB were found to be significantly different from those in bubbling bed. There is a flowing zone with high velocity in the heat exchange zone. The heat transfer coefficients strongly depend on the fluidized velocity in the flowing zone. The heat exchange process and suitable bed temperature can be controlled according to this feature. Based on the results of the experiments, a formulation for heat transfer has been developed.