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Advanced Course in Heat Exchangers: Theory and Practice. ICHMT Symposium.
1981, Dubrovnik, Croatia

DOI: 10.1615/ICHMT.1981.AdvCourseHeatExch


ISBN Print: 978-0-07062-806-9

Heat Transfer and Critical Heat Flux at Flow Boiling of Nitrogen and Argon within a Horizontal Tube

pages 233-250
DOI: 10.1615/ICHMT.1981.AdvCourseHeatExch.180
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RÉSUMÉ

Local heat transfer and critical heat flux during flow boiling of nitrogen and argon have been studied experimentally in a smooth horizontal copper tube with 14 mm i.d. The main parameters such as heat flux q, mass velocity m, flow quality x and reduced pressure pr have been varied in a wide range.
The influence of the main parameters on the heat transfer coefficients will be discussed. Using recommended equations, the calculated values do not agree satisfactory with experimental data. Therefore a modified correlation is proposed. The measurements show, that the critical heat flux qcrit depends considerably on the pressure and on the flow quality, while the influence of the mass velocity can be neglected in the observed range. Knowing this, a new correlation for the critical heat flux has been developed. The agreement between predicted and measured values is good.
During the measurements with argon a new phenomenon has been noticed. While the adjusted parameters remained constant, the temperature difference between wall and fluid increased slowly up to the burn out. This transient change of the heat transfer coefficient lasted up to 20 h and was probably caused by very small amounts of dissolved CO2.

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