On the Estimates of Convective Heat Transfer Intensification

The results of thermal engineering experiments on a water–water tubular heat exchanger of the tube-in-tube type with heat transfer intensified by periodic confuser–diffuser elements arranged along the channel length at a step equal to the doubled inner diameter of the inner tube are compared with the results of experiments on a similar smooth-tube heat exchanger and the results of calculations by the criterial models of B.S. Petukhov, S.S. Kutateladze, W. Nusselt, and M.A. Mikheev. The comparison showed that the ratio of heat transfers in the tube channels of the intensified and smooth-tube heat exchangers, being a function of the Reynolds and Prandtl numbers, depends on the latter to a much higher extent. As a consequence, at least for water as a medium where the Prandtl number depends on temperature, the intensification of heat transfer is determined not only by the profiling parameters, but also by the parameters of the heat transfer process itself. In addition, the comparison demonstrated that the replacement of experimental data on smooth-tube heat exchangers by the results of calculation by the criterial models worsens the accuracy of estimates and leads to an increase in deviations with an increase in the Reynolds number Re.