The effect of magnetic field alignment on heat transfer in liquid metal blanket channels

Several liquid-metal blanket design concepts employ rectangular ducts. If the duct walls can be accurately aligned with the magnetic field, substantial improvement in heat transfer may result due to the favorable characteristics of MHD (magnetohydrodynamic) side layers. A detailed analysis of the velocity and temperature profiles has been carried out under fully developed flow conditions for reactor-relevant Hartmann numbers in the range of 5000 and a wall conductance ration of 0.01. The results show that substantial changes in the wall temperatures can result from changes of only a few degrees in the magnetic field angle. An assessment of the possible sources of misalignment in an operating power-reactor blanket suggests that it will be very difficult to maintain sufficiently good alignment to fully exploit side layers as a means to enhance heat transfer