超临界碳氢燃料流动换热的仿真研究

建立了适用于温度、压力大范围变化的超临界碳氢燃料换热特性研究的一维模型,试验验证了模型的可靠性,基于该模型分析了质量流率、换热状态转换和压力等因素对超临界碳氢燃料的换热特性的影响。结果表明:4.0 MPa的低压力工况下,在超临界碳氢燃料的拟临界温度附近存在传热强化现象,而7.0 MPa的高压力工况下,该传热强化现象消失;不论质量流率的大小,4.0 MPa工况下的传热系数始终高于7.0 MPa工况下的传热系数,压力的高低在超临界碳氢燃料的汽相换热区对传热性能的影响更为显著;40kg/(m2.s)的低质量流率条件下,由液相换热区向汽相换热区的换热状态转换将导致转换区附近的传热恶化,而增大质量流率则可避免该问题的发生。

Simulation Study of the Flow and Heat Exchange of a Supercritical Hydrocarbon Fuel

Established was a one-dimensional model for studying the supercritical hydrocarbon fuel heat exchange characteristics when the temperature and pressure are changing in a wide range.The reliabilility of the model in question has been verified by the test.Moreover,the influence of such factors as the mass flow rate,heat exchange state conversion and pressure etc.on the heat exchange characteristics of the supercritical hydrocarbon fuel was also analyzed based on the model.It has been found that at a low pressure of 4.0 MPa,an intensified heat transfer phenomena of the supercritical hydrocarbon fuel exists at places nearing the pseudo-critical temperature while at a high preesure of 7.0 MPa,the above-mentioned intensified heat transfer disappears.No matter what the mass flow rate is,the heat transfer coefficient at 4.0 MPa is invariably higher than that at 7.0 MPa.Furtheremore,the magnitude of the pressure has an even conspicuously influence on the heat exchange performance in the steam-phase heat exchange zone of the supercritical hydrocarbon fuel.At a low mass flow rate of 40 kg/(m2·s),the conversion of the heat exchange state from the liquid-pase heat exchange zone to the steam-phase heat exchange zone will lead to a heat transfer deterioration around the heat exchange zones,however,to increase the mass flow rate can avoid the problem.