In the present work, natural convection heat transfer is studied experimentally in a concentric annulus with constant heat flux and stationary outer pipe and rotating and insulated inner pipe. The experimental setup used consisted of an annulus with radius ratio of R_0/R_i=0.253 and length of 2.2m. Heat fluxes of 58, 96.5, 145 and 193W/m2 were applied to the heater in the present study and surface temperature of the outer pipe is measured at 39 points along its length. Average Nusselt number was plotted versus Taylor number. It is observed that Nusselt number slightly decreases up to Taylor number of 4.5E+5.
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