Project work Tobias Burgholz, Markus Schraven

 

Enhancement of a test facility for heat transfer measurements of free convection flows with Kármán vortex streets

Copyright: EBC The new test facility.

This study deals with test facilities allowing for measurements of the heat transfer in free convection flows with Kármán vortex streets. As a first step, an existing test facility with two steel panel radiators as heat sources is closely examined for weak points and disadvantages, considering both its functional design and reliability as well as the results obtained in previous experiments. From this analysis a set of requirements is derived, leading to a concept for a new test facility using synthetic capillary tube mats instead of panel radiators. The constructional process of the new test facility is described in detail.

With the newly built test facility, a number of experiments are carried out, investigating two-dimensional flows and the impact of differently shaped and sized vortex promoters on the heat transfer. In a second set of experiments, the effect of different installation heights of a 19 mm cylinder is examined. To visualize the structure of the flows and show the existence of Kármán vortex streets with an obstruction body installed, visualizations with fog are conducted.

First results show a better functionality of the test facility and a lower scattering of the heat emission enhancement which, however, is considerably lower than predicted by simulations. Flow visualization shows severe irregularities of the Kármán vortices, thus calling the boundary conditions used in simulations into question.