Convective heat transfer in the thermally developing region in a circular channel of the first wall and limiter/divertor plates of a fusion reactor has been analyzed numerically. The surface heat flux on a coolant channel in these plasma facing components varies circumferentially. The flow is assumed non-MHD fully-developed laminar and turbulent in a circular tube. The nonuniformity of surface heat flux greatly affect the Nusselt number and thermal entry length. For the cosine distribution of surface heat flux, the steady-state Nusselt number can be reduced at the point of maximum heat flux by as much as 38%, 62% and 37% for fully-developed laminar Poiseuille, laminar slug and turbulent flows, respectively. Thermal entry length can be increased by up to 2.4 times for laminar flow and 3.5 times for turbulent flow due to the nonuniformity of surface heat flux. If this reduction of Nusselt number due to the nonuniformity of surface heat flux is disregarded, the film temperature drop in the coolant channels of plasma facing components of a fusion reactor will be underestimated by 37% to 62%. This will result in an underestimation of the maximum structure temperature. The increase in entry length is not likely to affect the thermal-hydraulic design of a conventional divertor plate.
