Investigation of the heat transfer and flow characteristics in wavy fins of compact heat exchanger in a sand-dust environment

摘要

The thermal-hydraulic characteristics of aluminum wavy fins of compact heat exchangers in a sand-dust environment are currently unclear. Therefore, in this paper, the effects of particle concentration and size on the heat transfer and pressure loss characteristics of wavy fins, which are analyzed experimentally and numerically, are discussed. In addition, correlation functions of the Colburn and friction factors built using a multiple nonlinear regression based on orthogonal numerical simulation results are presented. It is found that the two-way coupling between the air and the particles can improve the synergy of the velocity and temperature gradient fields. In addition, this coupling can restrain the air turbulent kinetic energy in the near-wall flow zone. Note that the combination of these two effects increases the average Colburn factor. Moreover, as the particle concentration increases in the range of 5-95 g/m~3, both Colburn and friction factors increase almost linearly. On the contrary, these factors decrease roughly exponentially as the particle size changes from 10 to 25 μm. It is worth noting that the Colburn and friction factors change with different rates under different Reynolds numbers so that smaller Reynolds numbers result in higher changing rates of both factors. Furthermore, the thermal-hydraulic performance (heat transfer versus pressure difference) of wavy fins decreases slightly in a sand-dust environment when compared with the conventional environment, but it is insignificant on the whole.