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Analysis of flow patterns emerging during evaporation in parallel microchannels

Hardt, Steffen and Schilder, B. and Tiemann, D. and Kolb, G. and Hessel, V. and Stephan, Peter :
Analysis of flow patterns emerging during evaporation in parallel microchannels.
[Online-Edition: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2006.06.015]
In: International Journal of Heat and Mass Transfer, 50 (1-2) pp. 226-239. ISSN 00179310
[Article] , (2007)

Official URL: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2006.06.015

Abstract

The evaporation processes of 2-propanol and water in cyclo olefin polymer (COP) and silicon microchannels of square cross-section are studied with a high-speed camera. The COP channels with a cross-section of 50 \textgreekmm × 50 \textgreekmm are rather smooth, whereas the 30 \textgreekmm × 30 \textgreekmm silicon channels have comparatively rough surfaces. For the COP channels, two different evaporation modes are identified, both with oscillating liquid--vapor menisci. One of these modes is characterized by an extremely rapid evaporation and a corresponding discontinuous shift of the meniscus. In the silicon channels four different evaporation modes are observed. Oscillatory motion of the liquid fronts also dominates here, and depending on the total mass flow and the wall temperature the oscillations in different channels are synchronized or desynchronized. Besides the flow patterns also the velocity trajectories of the evaporating liquid fronts are analyzed in detail and show a rather good reproducibility over different channels and different cycles. Compared to most other studies reported in this field, bubble nucleation is found to be of secondary importance for the evaporation processes.

Item Type: Article
Erschienen: 2007
Creators: Hardt, Steffen and Schilder, B. and Tiemann, D. and Kolb, G. and Hessel, V. and Stephan, Peter
Title: Analysis of flow patterns emerging during evaporation in parallel microchannels
Language: English
Abstract:

The evaporation processes of 2-propanol and water in cyclo olefin polymer (COP) and silicon microchannels of square cross-section are studied with a high-speed camera. The COP channels with a cross-section of 50 \textgreekmm × 50 \textgreekmm are rather smooth, whereas the 30 \textgreekmm × 30 \textgreekmm silicon channels have comparatively rough surfaces. For the COP channels, two different evaporation modes are identified, both with oscillating liquid--vapor menisci. One of these modes is characterized by an extremely rapid evaporation and a corresponding discontinuous shift of the meniscus. In the silicon channels four different evaporation modes are observed. Oscillatory motion of the liquid fronts also dominates here, and depending on the total mass flow and the wall temperature the oscillations in different channels are synchronized or desynchronized. Besides the flow patterns also the velocity trajectories of the evaporating liquid fronts are analyzed in detail and show a rather good reproducibility over different channels and different cycles. Compared to most other studies reported in this field, bubble nucleation is found to be of secondary importance for the evaporation processes.

Journal or Publication Title: International Journal of Heat and Mass Transfer
Volume: 50
Number: 1-2
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Institute for Technical Thermodynamics (TTD)
Zentrale Einrichtungen
16 Department of Mechanical Engineering > Institute for Nano- and Microfluidics (NMF)
Date Deposited: 09 Apr 2011 10:32
Official URL: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2006.06.015
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