Self-oscillatory regime of boiling of a highly subcooled liquid in a flow-passage annular duct

Resumo

The results of an experimental and theoretical investigation of highly subcooled ethanol in an annular flow-passage duct under the conditions of pulsed heat generation in the wall cooled by liquid flow are presented. The formation of a vapor film on the heater wall and long-lasting pressure oscillations of high amplitude in the duct (the self-oscillatory regime) have been observed in experiments. A mathematical model of the ethanol boiling up has been developed to take into account the evaporation of the overheated liquid near the heater wall and the vapor condensa-tion in the flow of a subcooled liquid. The proposed model describes both the decaying oscillations of the vapor layer and the development of the self-oscillatory regime, which predicts well the amplitude and frequency of nonlinear oscil-lations. Numerical computations have shown that the self-oscillatory regime is realized due to evaporation of a periodically renewed microlayer on the heater wall. Computational results agree well with experimental data.