Numerical and experimental studies of heat transfer in steady and unsteady laminar or turbulent natural and mixed convective flows

将在涉及对流换热的五个领域进行研究。许多电子和电气元件使用自然对流进行空气冷却，并且涉及在基本的自然对流传热研究中未处理的几何形状。在第一部分中，将推导出在这种情况下可用来预测传热速率的功方程。将进行数值和实验研究。在第一个研究领域所考虑的实际应用中，有时元件上存在低速流动。在这种情况下，强迫空气速度往往是如此之低，以至于传热是由混合的自然对流和强迫对流进行的。这种流动将在第二个研究领域加以考虑。将再次进行数值和实验工作。这项工作的主要目的是确定混合对流存在的条件。对于与建筑物内气流相似的自然湍流和混合湍流对流情况下使用一系列湍流模型所获得的数值结果，尚未进行系统的研究，并且已有实验结果。这样的研究将在第三个研究领域进行，主要目的是得出在特定流动情况下使用哪种湍流模型的建议。大多数关于盲窗系统传热的研究都假设盲窗系统房间一侧的自然对流是层流的。然而，湍流和非定常流可以在这样的流动中发展。因此，本研究的第四部分将对盲窗系统中紊流和非定常流的发展进行基础实验和数值研究。气体在微型通道系统中的流动，其中通道遵循波浪路径将在第五部分的工作中考虑。这种微型通道系统在许多实际情况下都有应用，在这些系统中的流动在雷诺数低于湍流发展的雷诺数时可能变得不稳定。研究的目的是确定通道几何形状如何影响非定常流发展的条件。

Research in five areas involving convective heat transfer will be undertaken. A number of electronic and electrical components are air-cooled using natural convection and involve geometric shapes that have not been dealt with in basic natural convective heat transfer studies. In the first part of the present work equations that can be used to predict the heat transfer rate in such situations will be developed. Both numerical and experimental studies will be undertaken. In the practical applications considered in the first area of research there is sometimes a low velocity flow over the components. The forced air velocity in such situations is often so low that the heat transfer is by mixed natural and forced convection. Such flows will be considered in the second area of research. Both numerical and experimental work will again be undertaken. The main aims of this work will be to define the conditions under which mixed convection exists. No systematic studies of numerical results obtained using a range of turbulence models for situations involving natural and mixed turbulent convective flows which are similar to air flows in buildings and for which experimental results exist have been undertaken. Such a study will be undertaken in the third study area, the main purpose being to derive recommendations as to which turbulence model to use in a particular flow situation. Most studies of heat transfer across window-blind systems assume that the natural convective flow over the room side of such systems is laminar. Turbulence and unsteady flow can, however, develop in such flows. Therefore in the fourth part of the research basic experimental and numerical studies of the development of turbulent and unsteady flow in window-blind systems will be undertaken. Gas flows in mini-channel systems in which the channel follows a wavy path will be considered in fifth part of the work. Such mini-channel systems are used in a number of practical situations and the flow in these systems can become unsteady at Reynolds numbers that are lower that that at which turbulent flow develops. The purpose of the study is to determine how the channel geometry affects the conditions under which unsteady flow develops.