Modelling of natural convection theory for gases neglecting effect of gravity

Till date, studies involving natural convection over a heated surface have considered the gas to be an ideal gas. According to conventional theory, since density is varying above the hot surface, so the buoyant forces are acting in the presence of gravity. However, the theory of ideal gases, namely the kinetic theory of gases, presumes that the gravity has an extremely negligible effect on gases. Thus, the effect of gravity should not be considered to derive expressions for the coefficient of heat transfer due to natural convection. In this work, air surrounding a heated plate has been assumed to be an ideal gas and the effect of gravity has not been considered. By using the basic equations of fluid and heat transfer, fundamental equations for convection over a horizontal plate (heated surface facing upwards) and vertical plate, have been derived. After non-dimensionalization, five equations to calculate the convective heat transfer coefficient over different range of physical constants are found. Thus, t...