Change search
ReferencesLink to record
Permanent link

Direct link
Experimental investigation of single-phase convective heat transfer in circular microchannels
KTH, Superseded Departments, Energy Technology.
KTH, Superseded Departments, Energy Technology.ORCID iD: 0000-0002-9902-2087
2004 (English)In: Experimental Thermal and Fluid Science, ISSN 0894-1777, Vol. 28, no 2-3, 105-110 p.Article in journal (Refereed) Published
Abstract [en]

In this study, the heat transfer characteristics of single-phase forced convection of R134a through single circular micro-channels with 1.7, 1.2, and 0.8 mm. as inner diameters were investigated experimentally. The results were compared both to correlations for the heat transfer in macroscale channels and to correlations suggested for microscale geometries. The results show good agreement between the classical correlations and the experimentally measured data in the turbulent region. Contrary, none of the suggested correlations for microchannels, agreed with the test data. In the laminar regime, the heat transfer coefficients were almost identical for all three diameters.

Place, publisher, year, edition, pages
2004. Vol. 28, no 2-3, 105-110 p.
Keyword [en]
Convection; Microchannel; Single phase heat transfer; Channel flow; Laminar flow; Turbulence; Microscale geometries; Heat transfer; convection; experimental study; heat transfer; laminar flow; microchannel; single-phase flow; turbulence
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-6863DOI: 10.1016/S0894-1777(03)00028-1ISI: 000187974600005ScopusID: 2-s2.0-0348172185OAI: diva2:11693
QC 20100812. 4th International Conference on Compact Heat Exchangers and Enhancement Technology for the Process Industries. GRENOBLE, FRANCE. 2002Available from: 2007-03-09 Created: 2007-03-09 Last updated: 2011-10-24Bibliographically approved
In thesis
1. Experimental Heat Transfer, pressure drop, and Flow Visualization of R-134a in Vertical Mini/Micro Tubes
Open this publication in new window or tab >>Experimental Heat Transfer, pressure drop, and Flow Visualization of R-134a in Vertical Mini/Micro Tubes
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

For the application of minichannel heat exchangers, it is necessary to have accurate design tools for predicting heat transfer and pressure drop. Until recently, this type of heat exchangers was not well studied, and in the scientific literature there were large discrepancies between results reported by different investigators. The present thesis aims to add to the knowledge of the fundamentals of single- and two-phase flow heat transfer and pressure drop in narrow channels, thereby aiding in the development of this new, interesting technology with the possibility of decreasing the size of electronics through better cooling, and of increasing the energy efficiency of thermal processes and thermodynamic cycles through enhanced heat transfer.

A comprehensive experimental single-phase flow and saturated flow boiling heat transfer and pressure drop study has been carried out on vertical stainless steel tubes with inner diameters of 1.700, 1.224 and 0.826 mm, using R-134a as the test fluid. The heat transfer and pressure drop results were compared both to conventional correlations developed for larger diameter channels and to correlations developed specifically for microscale geometries.

Contrary to many previous investigations, this study has shown that the test data agree well with single-phase heat transfer and friction factor correlations known to be accurate for larger channels, thus expanding their ranges to cover mini/microchannel geometries. The main part of the study concerns saturated flow boiling heat transfer and pressure drop. Tests with the same stainless steel tubes showed that the heat transfer is strongly dependent on heat flux, but only weakly dependent on mass flux and vapor fraction (up to the location of dryout). This behavior is usually taken to indicate a dominant influence of nucleate boiling, and indicates that the boiling mechanism is strongly related to that in nucleate boiling. The test data for boiling heat transfer was compared to several correlations from the literature, both for macro- and mini-channels. A new correlation for saturated flow boiling heat transfer of refrigerant R-134a correlation was obtained based on the present experimental data. This correlation predicts the presented data with a mean absolute deviation of 8%. The frictional pressure drop results were compared to both macro- and mini channel correlations available from the literature. The correlation suggested by Qu and Mudawar (2003) gave the best prediction to the frictional two-phase pressure drop within the studied ranges.

A unique visualization study of saturated flow boiling characteristics in a vertical 1.332 mm inner diameter quartz tube, coated with a transparent heater has also been conducted. The complete evaporation process in a heated circular mini-channel has been studied visually in detail using high speed CCD camera. The study revealed the developments of the flow patterns and the behavior from bubble nucleation to the dry out of the liquid film. The bubble departure frequency, diameter, growth rate, and velocity were determined by analyzing the images. Finally, a flow pattern map for boiling flow in microchannels has been developed based on the test data.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. viii, 103 p.
Trita-REFR, ISSN 1102-0245 ; 2007:59
Minichannel, microchannel, heat transfer, pressure drop, single-phase, two-phase, flow boiling, flow visualization, dry out, bubble behavior, flow pattern.
National Category
Energy Engineering
urn:nbn:se:kth:diva-4299 (URN)978-91-7178-594-7 (ISBN)
Public defence
2007-03-26, F3, Lindstedtsvägen 26, KTH, 10:00
QC 20100812Available from: 2007-03-09 Created: 2007-03-09 Last updated: 2010-08-12Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopusScienceDirect

Search in DiVA

By author/editor
Owhaib, Wahib SuleimanPalm, Björn
By organisation
Energy Technology
In the same journal
Experimental Thermal and Fluid Science
Energy Engineering

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 198 hits
ReferencesLink to record
Permanent link

Direct link