Abstract: | The Eckert number phenomenon was investigated theoretically by Geropp in 1969 and describes a reversal in heat transfer from
a moving wall at an Eckert number Ec ≈ 1. In this report the Eckert number phenomenon is confirmed experimentally for the
first time. For that purpose the heat transfer from a heated, vertically rotating cylinder in a crossflow was investigated.
In order to perform the experiments in a range where the predicted phenomenon occurs, extreme rotational speeds were necessary.
A heating concept had to be developed which allowed an input of heating power independent of the speed and which therefore
had to be contact-free. The results show, among other things, that the temperature difference between the wall and the surrounding
fluid has a significant effect on the predicted reversal of heat transfer at the wall. Moreover, maximum heat transfer occurs
at an Eckert number Ec ≈ 0.3, which is of great importance for the cooling of hot surfaces in a gas-flow. |