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On the influence of gas mixture composition on gas quenching uniformity and mean
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, Superseded Departments, Mechanics.
(English)Manuscript (Other academic)
Abstract [en]

The use of gas mixtures is widely spread in today's industry. The fields of application go from cooling within refrigerators to the deep freezing of meat balls. One particular application is within the industry of gas heat treating of metal pieces. Such heat treatment involves the cooling of metal pieces, called quenching. The present work investigates the dependence of the performance of a given gas mixture on the geometry of the metal pieces to quench. The heat transfer coefficient and the convection Nusselt number across a short cylinder (D = 150 mm, L = 300 mm) in axial flow for mixtures of hydrogen and nitrogen were computed for six Reynolds numbers in the range 2.0 10(4) to 2.0 10(5). The Nusselt number decreased continually with increasing hydrogen content. Since the existing correlations did not adequately represent the calculated data, modified correlations were developed to describe the influence of transport properties and flow pararmeters on the convective heat transfer over the front and lateral surfaces of the cylinder These correlations are valid for the range of Reynolds numbers 2.0 104 to 2.0 105 and in the range of Prandtl numbers 0.4 to 0.73. A relation giving the heat transfer uniformity as a function of the Reynolds number and Prandtl number of the gas mixture flowing around the cylinder in axial flow has been developed. This correlation is valid within the same range of Reynolds and Prandtl numbers previously given.

Keyword [en]
thermal-conductivity, viscosity, helium
National Category
Computational Mathematics
Identifiers
URN: urn:nbn:se:kth:diva-5204OAI: oai:DiVA.org:kth-5204DiVA: diva2:8020
Note
QC 20101019Available from: 2005-05-31 Created: 2005-05-31 Last updated: 2010-10-19Bibliographically approved
In thesis
1. CFD in the design of gas quenching furnace
Open this publication in new window or tab >>CFD in the design of gas quenching furnace
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis focuses on the numerical and theoretical studies of gas quenching in industrial furnaces. Gas quenching is the rapid cooling of metal pieces, aiming at forcing a phase transformation of the metal structure to improve its mechanical properties. The numerical methodology has been evaluated with respect to the desired accuracy and different aspects of the flow with importance for achieving an optimized process have been investigated. Initially, attention was paid to the flow and heat transfer fields both in an empty furnace and in a furnace loaded with different charges with the objective to study the influence of the charge configuration on the flow and heat transfer uniformity. This study led to the identification of several possible improvements, which are currently being implemented by the industrial partners of this project. As earlier studies had shown the importance of flow uniformity on the quality of the heat treatment, the subsequent work focused substantially on the flow uniformity upstream of the quenching zone resulting in design recommendations for the particular type of furnace under consideration. The dependence of the performance of the coolant medium on its composition was investigated theoretically and an analysis of most important parameters was carried out. Improved knowledge of the effect of gas mixture composition on heat transfer was added to the body of knowledge already available.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xii, 47 p.
Series
Trita-MEK, ISSN 0348-467X ; 2005:12
Keyword
Numerical analysis, Gas quenching, modeling, CFD, gas mixtures, uniformity., Numerisk analys
National Category
Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-239 (URN)
Public defence
2005-06-16, D2, D, Lindstedsvägen 5, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101019Available from: 2005-05-31 Created: 2005-05-31 Last updated: 2010-10-19Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
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  • Other style
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  • Other locale
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Output format
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