Forced Convection Phase-Change Heat Transfer with StreamwiseCurvature and Two-Phase Approach Flow

这个项目主要是一个实验性的研究， 对流沸腾传热从小区域到大区域 通道流 结果的应用在于设计 必须冷却小的高热通量区域的设备： 平版印刷术和医学用X射线源、微波 速调管、激光器、微电子和光学器件、气体 涡轮机、聚变反应堆仪表和第一壁， 高速飞机前缘表面淬火 材料加工 理论或科学价值在于 在以下情况下沸腾行为的描述： 热边界层和气泡边界层 厚度相对于沟道尺寸较小。 影响 需要记录的是：加热长度，体积速度， 过冷度，压力，流体类型，流向曲率 加热壁和接近的流动的空隙率 加热表面 该计划首先完成一个正在进行的 壁面凹曲率对过冷度影响的研究 流动沸腾特性 在这项研究中，所有的空隙 被限制在非常靠近加热表面的地方。 下一 阶段和研究的主要部分是一个流动的地方， 接近加热区域的是蒸气的两相混合物 和液体处于热力学平衡。 本研究 来流空泡率和两相流效应 本文将研究直通道内的流动状态 并且在凹弯曲的通道内。 具有凹曲率， 空隙被快速地从加热的壁中传送走， 在弯曲流中建立的横流压力梯度。 目前正在研究这种影响， 其中接近流是过冷液体。 的 继续项目将具有更强的效益 当入口流为两相混合物时， 因为在直线和直线之间， 流动和弯曲流动，在点的热通量 偏离核态沸腾（DNB）。 一旦特征化， 描述，这可以在设计中加以利用， 上述工程系统的冷却方案。

This project is predominantly an experimental study of forced convection boiling heat transfer from small regions to a channel flow. Application of the results lie in the design of equipment where small, high-heat-flux regions must be cooled: x-ray sources for lithography and medicine, microwave klystrons, lasers, microelectronic and optical devices, gas turbines, fusion reactor instrumentation and first walls, high-speed aircraft leading surfaces and quenching in materials processing. Theoretical or scientific value lies in the description of the boiling behavior in situations where the thermal boundary layer and bubble boundary layer thicknesses are small relative to the channel size. Effects to be documented are: heating length, bulk velocity, subcooling, pressure, fluid type, streamwise curvature of the heated wall and the void fraction of the flow approaching the heated surface. The program begins by completing an ongoing study on the effect of wall concave curvature on subcooled flow boiling characteristics. In this study, all the voids are constrained to very near the heated surface. The next phase and the main portion of the study is one where the flow approaching the heated region is a two-phase mixture of vapor and liquid in thermodynamic equilibrium. In this study, the effect of approach flow void fraction and two-phase flow regime will be investigated in flow within straight channels and within concave-curved channels. With concave curvature, voids are rapidly transported away from the heated wall by the cross-stream pressure gradient established in the curved flow. This effect is presently being investigated for a situation where the approaching flow is a subcooled liquid. The continuation project will characterize the stronger benefit that will be seen when the entry flow is a two-phase mixture in that there will be a substantial increase, between straight flow and curved flow, of the heat flux at the point of departure from nucleate boiling (DNB). Once characterized and described, this can be capitalized upon in the design of cooling schemes for the above engineering systems.