超临界CO_(2)池式传热流固耦合传热特性数值模拟

Numerical simulation of fluid-structure coupled heat transfer characteristics of supercritical CO_(2) pool heat transfer

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CO_(2)池式传热特性进行流固耦合数值模拟研究,d=70μm的铂丝为加热件,热流密度q_w范围为0-2000 kW/m^(2),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Q_(con)/Q_(t)沿r方向变化规律,将超临界划分为3个区,当TT_(M)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λ_(ave)和导热热阻R_(G)随热流密度q_(w)变化曲线可很好地解释类蒸发区换热系数h随q_(w)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,较好地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 unified.The fluid-structure coupling numerical simulation of heat transfer characteristics in supercritical CO_(2) pool is carried out by using laminar flow model.Platinum wire is the heating element,with diameter d=70μm.The heat flux density qw is in a range of 0-2000 kW/m^(2),and the pressure P is in a range of 8-10 MPa.Multi-scale mesh is used to model the heating wire,and simulation values accord well with the experimental data.The results show that due to the increase of the circumferential average Rayleigh number Raave of the heating filament with qw,the characteristic of the natural convection zone is that h increases with qw.The temperatures of the four characteristic working conditions in the evaporation-like zone show a downward trend along the r direction.Through analogy with subcritical heat transfer and by calculating the thermal conductivity ratio Qcon/Qt,the supercritical is divided into three regions,T<T_(L) is liquid-like region(L_(L)),T_(L)<T<T_(M) is two-phase-like region(TPL),T>T_(M) is vapor-like region(V_(L)).The rule is the same as that of x partition according to supercritical pseudo-boiling dryness.According to the curves of average thermal conductivity λ_(ave) and thermal resistance RG versus 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 transfer to the fluid outside the vapor-like membrane,leading the heat transfer coefficient h to decrease when q_(A)<qw<q_(C),and a significant increase in λ_(ave) when qw>q_(C),and the recovery of heat transfer when h rises again.In this paper,a new method of determining the gas-liquid interface of supercritical pool heat transfer is proposed.This method can effectively explain the heat transfer mechanism in the evaporation-like zone,and provide a theoretical basis for developing supercritical pool heat transfer in the future.