Numerical study on coupled multiphase thermal and mass transfer of moving surface impacted by jet array in semi-enclosed space

Abstract

The problems of fluid flow, heat transfer and mass transfer involved in the process of impinging jet belt transportation are very common in engineering applications. However, the array jet forms thermal disturbances on the moving impact surface, which leads to the unclear turbulent flow characteristics and the heat and moisture distribution mechanism on the moving surfaces. In this paper, a multi-phase flow model is established for coupled heat and moisture transfer of the array impacting a moving surface in a semi-enclosed space. Based on considering the multi-phase component transmission, the effects of height-to-diameter ratio (H/d), impinging jet velocity (Vjet), and surface moving speed (Vs) on heat and moisture transfer are investigated. The results show that increasing the jet velocity strengthens the phase change evaporation process on the impact surface. The movement of the impact surface makes asymmetric vortices appear on both sides of the peak Reynolds number and Nusselt number in the vertical direction of the space flow field. At the same time, a horseshoe-shaped vortex is formed on the impact surface. When the moving speed of the impact surface increases, the downstream boundary layer becomes thicker due to the disturbance effect of multiple airflows, increasing the uneven distribution of temperature and moisture on the impact surface. The accuracy of the model is examined by making comparisons with experimental results, where the error remains less than 10 %. The results in this paper provide a theoretical basis for parameter optimization and improvement of the process quality in belt transmission equipment.

Keywords

• Array impinging jet
• Impact moving surface
• Multiphase flow thermal and mass transfer
• Semi-enclosed space