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Thursday, 13. December 2018
 

Experimental studies of mass and heat transport due to condensation in gap wind tunnels

In many physical processes the condensation and evaporation of water on surfaces is strongly coupled with heat and mass transfer of humidity in air flows. Some examples of such processes are film cooling, cooling of microelectronic devices, heat exchanger, indoor climatisation and perspiration in control of the human body temperature. Since condensation can e.g. cause defects on electronic equipment or leads to corrosion of cooling devices, the processes of condensation received considerable attention in the last decades.
Concerning condensation in ambient air flows, we focus on the topology of droplet and water film formation in convective duct flows by the influence of gravity. Furthermore, we are studying the mutual interaction between the duct flow on the one hand and the mass and topology of condensation on the surface on the other hand. For this purpose, we developed further an optical and non-invasively measurement method which allows for measuring condensation on surfaces with a very high accuracy. To study the mutual interaction between the flow and the condensed water at the surface, as well as the developing of condensed droplets in the flow and boundary layer, we use several measurement techniques e.g. Particle Image Velocimetry (PIV), Laser Doppler Anemometry (LDA) and Phase Doppler Anemometry (PDA). 

Left: An experimental setup for studying the interaction of condensation water and the flow in the boundary layer. The measurement has been performed in a rectangular duct cooled from below by means of LDA and PDA. Right: Statistic distribution of the diameters of condensed water droplets in the boundary layer.
Measured of water droplets on a surface. Left: Height distribution of a large droplet with a maximum height of about 3 mm. Right: The topology of condensed water droplets heights in a flow channel cooled from below.

Contact:

Christian Brückner
German Aerospace Center (DLR)
Institute of Aerodynamics and Flow Technology, Department Ground Vehicles
Phone: +49 551 709-2333

 
German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, SCART
Bunsenstraße 10, 37075 Göttingen, Germany