Unsteady-state heat and mass transfer in complex-shaped channels

Abstract Consideration is given to the problem of unsteady-state heat transfer and working fluid mixing in channels formed by densely packed bundles of oval-shaped coiled tubes with a longitudinally streaming flow and in a plane channel with one-sided heat input. Unsteady-state temperature fields are predicted and experimental results are given for heat and mass transfer processes in bundles of coiled tubes. New laws governing the course of these processes are revealed. It is found that in unsteady-state processes heat transfer coefficients of turbulent diffusion are significantly different from their quasi-stationary counterparts. This difference is determined by the rates of change of boundary conditions—wall temperature and cooling gas flow rate. The explanation for the laws derived is given, as well as recommendations for calculating unsteadystate processes of heat transfer and mixing in channels and determining the limits of applicability of quasistationary values for the coefficients of heat transfer and mixing.