Boiling and Condensation in Microchannels

随着目前的趋势是设备的小型化和微尺度工艺的发展，出现了对微尺度传热设备的需求。例如，在微电子处理器中，热传递正在成为与提高性能有关的限制因素。相变对流传热比单相冷却系统提供了显著的性能改进。然而，在微尺度通道中，控制相变和流量分配的机制与宏观尺度下的不同。该项目包括一项实验研究，以解决与微通道中的相变相关的一些问题，以及沸腾/冷凝理论的数值模拟，以帮助设计实验和开发基于微通道中两相流的热交换过程的设计程序。（例如用于热通量和温度测量的微传感器，流体二极管）将能够表征沸腾和冷凝过程中的局部参数，并对沸腾过程进行主动控制。先进的数值技术将补充实验研究，使结果能够应用于其他系统。这种使用创新的微传感器和控制系统的实验，使用先进的微制造设施开发，与数值建模的结合，为这种微尺度传热系统的设计程序的发展提供了一个独特的机会。

With the present trend towards miniaturisation of devices and development of microscale processes, there has arisen the need for microscale heat transfer equipment. For instance, in microelectronic processors, heat transfer is becoming the limiting factor in relation to increasing performance. Convective heat transfer with phase change offers significant performance improvements over single phase cooling systems. However, in microscale channels the mechanisms controlling the phase change and flow distribution differ from those at the macroscale. This project comprises an experimental study to solve some of the problems associated with phase change in microchannels and also the numerical modelling of boiling/condensation theory to both aid in design of experiments and develop design procedures for heat exchange processes based on two phase flow in microchannels.Development of novel experimental techniques (eg microsensor for heat flux and temperature measurement, fluid diode) will enable characterisation of local parameters in both boiling and condensation and active control of the boiling process.State-of-the-art numerical techniques will supplement the experimental investigation, enabling results to be applied to other systems. This combination of experimentation using innovative microsensors and control systems, developed using advanced microfabrication facilities, with numerical modelling offers a unique opportunity for the development of design procedures for such microscale heat transfer systems.