Fedorova N, Macher P, Jovicic V, Zbogar-Rasic A, Delgado A (2019)
Publication Type: Conference contribution
Publication year: 2019
Pages Range: 43.1-43.7
Conference Proceedings Title: Proceedings der 27. GALA-Fachtagung "Experimentelle Strömungsmechanik"
Event location: Erlangen
ISBN: 978-3-9816764-6-4
The condensation heat transfer takes place in numerous industrial processes. The presented work was motivated by the possibility to increase the energy efficiency of industrial processes through the condensation of water vapour from flue gases (FG). It is especially relevant for such industries, like baking, textile, pulp and paper, drying, etc., where the FG at the end of the process is rich in water vapour (up to 90%vol). This FG is generally composed of non-condensable gas (mostly dry air) and condensable gas (mostly water vapour). Its thermal energy (sensible and latent) can be recovered, thus increasing the overall process efficiency. The heat transfer efficiency plays an important role in the condensation process and is strongly influenced by the condensation type. The dropwise condensation exhibits the increased heat transfer coefficient by up to one order of magnitude, comparing to the filmwise condensation. Therefore, the research interest lies in the investigation of methods, prioritizing the dropwise condensation on solid surfaces. One of the decisive mechanisms for the in-creased heat transfer coefficient and condensation rate is the cyclical sequence of droplet formation, growth and drainage. Among others, these are initiated by the surface properties and gravitational force. In order to investigate the influence of gravity on the surface condensation behaviour, the experimental investigation was done for a variable tilt angle of 0, 30, 60 and 75° relative to the horizontal, using two different sample materials (Aluminium and PTFE-Teflon® discs 60 x 3 mm). The reaction chamber was filled with ambient air and kept at 50°C. Simultaneously, the sample was cooled with air and the water vapour was gradually injected inside the chamber. The condensation on the sample was recorded by the HD camera with 180mm macro lens. The pressure and temperature profiles along the reactor were continuously recorded. The condensation process ran two times faster for the inclination angle of 75° compared to 0° in case of the Al-sample. Since the tilt angle induces the natural convection inside the reaction chamber, the vertical temperature gradient decreased with increasing the inclination angle from 0 to 75° (by 40% for the Al-sample; by 20% for the PTFE-sample). Experimental data indicate that gravity reduces the critical droplet size for drainage (from around 4 to 2mm for both samples) and facilitates coalescence effects. This results in an accelerated cycle of nucleation, droplet growth and drainage.
APA:
Fedorova, N., Macher, P., Jovicic, V., Zbogar-Rasic, A., & Delgado, A. (2019). Experimental investigation of the gravity influence on the condensation behaviour on Al and PTFE-samples. In A. Delgado, B. Gatternig, M. Münsch, B. Ruck, A. Leder (Eds.), Proceedings der 27. GALA-Fachtagung "Experimentelle Strömungsmechanik" (pp. 43.1-43.7). Erlangen.
MLA:
Fedorova, Nataliia, et al. "Experimental investigation of the gravity influence on the condensation behaviour on Al and PTFE-samples." Proceedings of the 27. GALA-Fachtagung "Experimentelle Strömungsmechanik", Erlangen Ed. A. Delgado, B. Gatternig, M. Münsch, B. Ruck, A. Leder, 2019. 43.1-43.7.
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