Natural convection in an air layer enclosed between two vertical plates with different temperatures

Abstract The temperature field in an air layer enclosed between two isothermal vertical plates with different temperatures has been investigated with the help of a Zehnder-Mach interferometer. Local heat transfer coefficients were derived from the temperature gradients in the air normal to the plate surfaces. Below a certain Grashof number and above a certain value of the height to thickness ratio. heat is transferred from the hot to the cold boundary by conduction in the central part of the layer. Convection contributes only in the corner regions. For large Grashof numbers and below a certain limit of the height to thickness ratio, boundary layers exist along the surfaces of the enclosure, whereas in the central core the temperature is uniform in horizontal planes. The temperature increases, however, in vertical direction. Fluctuations in the flow and wave motions were observed in some of the experiments. Relations for local and average heat transfer are presented.