Effect of droplet evaporation on the flow structure and heat and mass transfer in a confined swirling gas-droplet flow downstream of a tube sudden expansion

Resumo

The effect of flow swirl parameter and thermophysical properties of the droplet of water, ethanol, and acetone on the structure of turbulent flow and heat transfer in a gas-droplet flow was studied numerically. To describe the dynamics and heat and mass transfer of the two-phase flow, the Eulerian approach was used. The growth of the volume fraction of small particles on the tube axis is typical of a swirling flow because of their accumulation in the zone of reverse flows due to the turbophoresis force. It is shown that the addition of droplets leads to a signifi-cant increase in heat transfer (more than 2.5 times) at mass concentration of droplets M_L1 = 0.1 in comparison with a single-phase swirling flow. Intensification of heat transfer with the use of ethanol droplets is higher than that for water droplets (approximately 10–20 %) and acetone (up to 65 %). When using the droplets of ethanol and acetone, the region of two-phase flow existence reduces, and the degree of suppression of carrier phase turbulence decreases. This is due to a more rapid evaporation of droplets of volatile liquids.