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High Resolution Measurement of Wall Temperature Distribution During Forced Convective Boiling in a Single Minichannel

Schweizer, N. and Freystein, M. and Stephan, Peter (2010):
High Resolution Measurement of Wall Temperature Distribution During Forced Convective Boiling in a Single Minichannel.
In: ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, [Online-Edition: http://dx.doi.org/10.1115/FEDSM-ICNMM2010-30273],
[Conference or Workshop Item]

Abstract

Cooling systems incorporating convective boiling in mini- and microchannels achieve very high thermal performance. Although many investigations related to the subject have already been conducted, the basic phenomena of the heat transfer mechanisms are not yet fully understood. The development of empirical correlations based only on flow pattern maps does not lead to a deeper knowledge of the mechanisms. In this study a comprehensive measurement technique that was successfully adapted in pool boiling experiments 8,9 was used for the investigation of forced convective boiling of FC-72 in a single rectangular minichannel. This technique allows the measurement of the local temperature with very high spatial and temporal resolution. High speed video recording was used to observe the flow inside the minichannel. The inlet Reynolds number was kept constant for the first measurements to Re = 200 corresponding to a hydraulic diameter of the minichannel of 800 \textgreek{m}m. The Bond number for the proposed setup is about Bo $\approx$ 1.2. Several flow pattern regimes such as bubbly flow, slug flow and partially dryout were observed for heat fluxes up to 25 kW / m2 . From an energy balance at each pixel element of the thermographic recordings the local transient heat flux could be calculated and compared to the flow pattern video recordings. The results of the first experiments already give an indication about the heat transfer mechanisms at different flow regimes.

Item Type: Conference or Workshop Item
Erschienen: 2010
Creators: Schweizer, N. and Freystein, M. and Stephan, Peter
Title: High Resolution Measurement of Wall Temperature Distribution During Forced Convective Boiling in a Single Minichannel
Language: German
Abstract:

Cooling systems incorporating convective boiling in mini- and microchannels achieve very high thermal performance. Although many investigations related to the subject have already been conducted, the basic phenomena of the heat transfer mechanisms are not yet fully understood. The development of empirical correlations based only on flow pattern maps does not lead to a deeper knowledge of the mechanisms. In this study a comprehensive measurement technique that was successfully adapted in pool boiling experiments 8,9 was used for the investigation of forced convective boiling of FC-72 in a single rectangular minichannel. This technique allows the measurement of the local temperature with very high spatial and temporal resolution. High speed video recording was used to observe the flow inside the minichannel. The inlet Reynolds number was kept constant for the first measurements to Re = 200 corresponding to a hydraulic diameter of the minichannel of 800 \textgreek{m}m. The Bond number for the proposed setup is about Bo $\approx$ 1.2. Several flow pattern regimes such as bubbly flow, slug flow and partially dryout were observed for heat fluxes up to 25 kW / m2 . From an energy balance at each pixel element of the thermographic recordings the local transient heat flux could be calculated and compared to the flow pattern video recordings. The results of the first experiments already give an indication about the heat transfer mechanisms at different flow regimes.

Divisions: 16 Department of Mechanical Engineering > Institute for Technical Thermodynamics (TTD)
Exzellenzinitiative > Clusters of Excellence > Center of Smart Interfaces (CSI)
16 Department of Mechanical Engineering
Zentrale Einrichtungen
Exzellenzinitiative
Exzellenzinitiative > Clusters of Excellence
Event Title: ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting
Date Deposited: 17 Mar 2015 14:58
Official URL: http://dx.doi.org/10.1115/FEDSM-ICNMM2010-30273
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