A parabolic dish/cavity receiver configuration is one of the solar thermal systems used for light-heat
conversion at high temperature. Such systems are subject to continuous changes in ambient conditions
such as wind, solar insolation, and ambient temperature. These environmental variations, as well as
changes in receiver inclination angle, affect the overall receiver performance leading to energy loss.
Natural convection contributes a significant fraction of the energy loss and hence a thorough understanding
of its characteristics is essential to effectively minimize it in order to improve the system
efficiency. A three-dimensional numerical investigation was conducted on a modified cavity receiver to
quantify the convective components of the total heat loss and to determine the effects of the operating
temperature, receiver inclination angle, and aperture size on the heat loss. The effects of the variation of
air properties were accounted for by using polynomial relationships for density, specific heat capacity at
constant pressure, dynamic viscosity, and thermal conductivity in the simulation. The calculated natural
convection heat loss showed a nonlinear dependence on the inclination angle and aperture size.
Visualization results such as temperature contours were also presented to gain an insight into the
effects of natural convection.