Investigation of heat transfer during the flow of a mixture of gases with a small Prandtl number in a rod assembly with separating grids

The experimental results on heat transfer during the gas coolant flow in a space formed by a dense packing of seven heated tubes are presented. Eight separating inserts with longitudinal displacers were used to fix the tubes and ensure a uniform gas flow field in the internal and external channels of the tube bundle. Gas mixtures with a large difference in the Prandtl number were used as the working fluid: air (Pr = 0.7) and helium-xenon mixture (Pr = 0.23). The experiments were carried out in the range of Reynolds numbers of 2218–12900.