Investigation of Natural Convection Heat Transfer in a Unique Scaled-Down Dual-Channel Facility

Multiphase Reactors Engineering and Applications Laboratory (mReal) has designed and constructed a scaled-down dual-channel facility to investigate plenum-to-plenum natural circulation heat transfer through two channels for coolant flow that would be encountered during a loss of flow accident in the prismatic modular reactor (PMR). Heat transfer characterization of the current facility has been investigated under different upper plenum and cooled channel outer surface temperatures using sophisticated flush mounted heat transfer sensors. Results show a reduction in the values of local heat-transfer coefficient and Nusselt number along the heated channel with increasing outer surface temperatures. One significant observation was the heat transfer reversal close to heated channel exit, where the heat flows from gas to the channel wall. This flow reversal is attributed to recirculation at the heated channel exit to the upper plenum. The average heat transfer results, when compared with previous literature, showed a similar qualitative trend