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

将在五个涉及对流换热的领域进行研究。许多电子和电气部件是使用自然对流进行风冷的，并且涉及基本的自然对流换热研究中没有涉及的几何形状。在本工作的第一部分中，将建立可用于预测这种情况下的传热率的方程。将进行数值和实验研究。在第一个研究领域考虑的实际应用中，有时在部件上存在低速流动。在这种情况下，强迫风速往往很低，以至于换热是自然对流和强迫对流的混合。这种流动将在第二个研究领域考虑。数值和实验工作将再次展开。这项工作的主要目的将是确定混合对流存在的条件。对于涉及类似于建筑物内空气流动的自然和混合湍流对流的情况，没有对使用一系列湍流模型获得的数值结果进行系统研究，并对其进行了实验结果。这项研究将在第三个研究区进行，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。大多数关于百叶窗系统换热的研究都假定这种系统房间侧的自然对流是层流的。然而，湍流和非定常流可能会在这种流动中发展。因此，在第四部分的研究中，将对窗帘系统中湍流和非定常流动的发展进行基本的实验和数值研究。在本工作的第五部分中，将考虑微型通道系统中的气体流动，在该系统中，通道遵循波状路径。这种微型流道系统被用于许多实际情况，当雷诺数低于湍流发展时的雷诺数时，这些系统中的流动可能变得不稳定。这项研究的目的是确定渠道几何形状如何影响非恒定流的发展条件。

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.