Direct contact heat transfer enhancement between two stratified immiscible fluids by artificial interface oscillations

摘要

Direct contact heat transfer between stratified immiscible fluids is commonly encountered in solar salt industry, desalination, petrochemical engineering, etc. Usually, the mutual mixing and penetration between stratified flows are weak, and hence the heat and mass transfer rates are quite limited and act as an obstacle in their wider applications. Considering the fact there is always clear surface (interface) between immiscible fluids, this study proposes to stimulate interface oscillations artificially to reinforce the mixing between fluids and thus enhance the transfer processes. The artificial oscillations employed in this paper are sinusoidal wave and their amplitude, period and wave length on the direct contact heat transfer between stratified airstream and water surface are investigated respectively. Heat transfer was found to be enhanced to a great extent by artificial oscillations, ranging from one to three times higher than that without oscillations. With the amplitude, period and wave length covered in this study ranging from 1 mm to 4 mm, 0.1 s to 2 s, and 40 mm to 100 mm, respectively, the heat transfer enhancement effect was found to increase with increase of oscillation amplitude and decrease of wave length, and this effect became more distinct at higher airstream velocity. However, the change of oscillation periods covered in this study shows minor difference on the heat transfer enhancement. Without using special solid inserts or alternation to the heat exchanger structure, artificial oscillation of phasic interface can be a simple and efficient technique to enhance transfer process between stratified flows. (C) 2019 Elsevier Ltd. All rights reserved.