Study of refrigerated mechanism of evaporative of air-water annular two-phase flow in a small vertical tube

Cooling system is a very important part of Polymer Electrolyte Membrane Fuel Cells (PEMFC), in which the flow channel is limited to very narrowness that lead to the heat transfer and flow regulations are different than normal regulations. Based on the study results of heat exchange in two phase annular flow the experimental and theoretical research of gas-saturated water two phase flow in a vertical fine tube (d=2.3 mm) have been introduced in this paper. The semi-theoretical heat transfer correlations were presented for predicting the evaporating heat transfer of two-phase air-saturated water in a small vertical tube. The experimental data agreed reasonably well with the numerical simulations at the same air mass flux. The average heat transfer coefficients of the annular air-saturated water two-phase flow can be increased, and the enhanced heat transfer mechanism is the evaporation of the very thin liquid film attached to the wall. The experiments were performed under the following conditions d=2.3 mm L=394 mm 14° C0<70° C 13 kg/(m².S)a<33 kg/(m².S) 30 kg/(m².S)1,0 <123 kg/(m².s) 45 W\n\n\t\t