An experimental study of heat transfer in an open-ended vertical eccentric annulus with insulated and constant heat flux boundaries

In this work free convection in an open-ended vertical eccentric annulus with different eccentric ratios has been experimentally studied with several heat fluxes. For this investigation an outer pipe heated electrically and insulated carefully from the environment, and an inner pipe completely filled with the ceramic wool to maintain the inner boundary insulated were used. The length and the radius ratio of the pipes used in the experiment were 1660 mm and 0.24, respectively. The wall temperature of the outer pipe was measured at different points by thermocouples for the eccentric ratios 0.21, 0.5, 0.7 and 1. The analysis of experimental results indicates that the heat transfer coefficient increases as the eccentric ratio increases up to 0.5. For ratios 0.5-0.7 the heat transfer coefficient remains approximately constant, and beyond that it starts decreasing and reaches a minimum at the eccentric ratio 1.