Supercritical heat transfer has been extensively investigated.However,the understanding of this phenomenon and its mechanism is still insufficient.In this study,the supercritical carbon dioxide pool heat transfer is investigated.In the experiment,platinum wire with a length of 22 mm and a diameter of 70 μm was used as a heating and temperature-measuring element.The pressure range of the pressure vessel is 8-10 MPa,and the heat flux range of the heating wire is 0-1800 kW/m2,which is significantly higher than the parameter range in the literature.A variable laminar flow model was used for the numerical simulation of the fluid-structure interaction,and multiscale grid technology was utilized near the heating wire.The numerical simulation results are consistent with the experimental results.Notably,the change of the heat transfer coefficient h with the heat flux qw has a sigmoid curve,and the h-qw curve can be divided into three regions.Before the quasicritical temperature,the Rayleigh number Ra and h increase with increasing qw.When the platinum wire temperature exceeded the quasicritical temperature,h continued to increase until it reached the maximum value because of the enhanced reflux effect of the supercritical fluid.Subsequently,as the thermal resistance of the gas-like film in the near-wall region increased,h decreased with the increase of qw until it reached a minimum value.After exceeding the minimum point of h,because the thermal conductivity of supercritical fluid increased with the increase of temperature at high temperatures,h exhibited an increasing trend with the increase of qw.In this paper,the relation curve between the heat transfer coefficient and the heat flux in the entire parameter range is obtained,and a relatively complete understanding of supercritical cell heat transfer is obtained.
关键词
超临界CO2/池式换热/自然对流/数值模拟
Key words
supercritical CO2/pool type heat transfer/natural convection/numerical simulation
万方数据