The effect of droplets thermophysical properties on turbulent heat transfer in a swirling separated mist flow

The numerical investigation of the effect of the swirl number and the thermophysical properties of water, ethanol, and acetone droplets on the particle scattering, turbulence modification and heat transfer in a droplet-laden flow is carried out. The set of 3D steady-state Reynolds-averaged Navier-Stokes (RANS) equations for the two-phase flow is utilized. The dispersed phase is modeled by the Eulerian approach. The flow swirling significantly shortens the length of the recirculation zone (up to two times in comparison with non-swirling flow at swirl number S = 0.5) for all types of the studied liquids. The highest value of heat transfer rate is obtained for the ethanol droplets (up to 10%), and the lowest one is obtained for the acetone droplets (up to 50%), both in comparison with water droplets. The swirling of the turbulent mist flow causes heat transfer enhancement (more than 1.5 times in comparison with the non-swirling droplet-laden flow). In the swirling flow, the value of the volume fraction of the dispersed phase has a maximum in the axial region of the pipe, and further in the direction of the wall its value is very small. The effect of heat transfer enhancement weakens with increasing Reynolds number of the flow. A region without droplets appears in the wall zone of the swirling two-phase flow, and the region is largest for acetone droplets.