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超临界类沸腾传热已有初步研究,对类气-类液界面的定义仍不统一。采用层流模型对超临界CO2池式传热特性进行了流固耦合数值模拟研究,d=70μm的铂丝为加热件,热流密度qw范围为0~2000 kW/m2,压力P范围为8~10 MPa,加热丝附近采用多尺度网格进行建模,模拟值与实验数据吻合较好。通过与亚临界传热类比通过计算导热占比Qcon/Qt沿r方向变化规律,将超临界划分为三个区,当T<TL时为类液区(liquid-like,LL),TL<T<TM时为类液向类气转变的过度区(two-phase-like,TPL),T>TM为类气区(vapor-like,VL),与用超临界类沸腾干度x分区规律相同;根据通过计算导热占比确定的类气膜内平均导热λave和导热热阻RG随热流密度qw变化曲线可很好的解释类蒸发区换热系数h随qw的变化规律。本文提出了确定超临界池式传热类气-类液界面的新方法,较好的解释了类蒸发区传热机理,为后续超临界类沸腾池式传热的发展提供了理论基础。The heat transfer of supercritical pseudo-boiling has been preliminarily studied, but the definition of gas-liquid interface is still not uniform. The fluid-structure coupling numerical simulation of heat transfer characteristics in supercritical CO2 pool was carried out using laminar flow model, Platinum wire is the heating element, d=70 μm, the qw range is 0~2000 kW/m2, the P range is 8~10 MPa, multi-scale mesh is used to model the heating wire, simulated values agree well with the experimental data. The results show that the natural convection zone is characterized by an increase in h with qw due to an increase in the circumferential average Rayleigh number Raave of the heating filament with qw. The temperatures of the four characteristic working conditions in the evaporation-like zone of the class show a decreasing trend along the r direction. Analogy with subcritical heat transfer, by calculating the thermal conductivity ratio Qcon/Qt, the supercritical is divided into three regions, T<TL is liquid-like region (LL), TL<T<TM is two-phase-like region (TPL), T>TM is vapor-like region (VL), the rule is the same as that of x partition with supercritical pseudo-boiling dryness; According to the curves of average thermal conductivity λave and thermal resistance RG with heat flux qw determined by calculating thermal conductivity ratio, the variation law of heat transfer coefficient h with qw in evaporation-like region can be well explained, as qw increases, the thermal conductivity thermal resistance RG increases, and the heat from the heating filament is difficult to be transferred to the fluid outside the vapor-like membrane, leading to a decrease in the heat transfer coefficient h when qA<qw<qC, and a significant increase in λave when qw>qC, and the recovery of heat transfer when h rises again.In this paper, a new method for determining the gas-liquid interface of supercritical pool heat transfer is proposed, which explains the heat transfer mechanism of evaporation-like zone well, and provides a theoretical basis for the development of supercritical pool heat transfer in the future.
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Keywords:
- supercritical /
- pool heat transfer /
- fluid-structure coupling /
- numerical simulation
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