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Heat Transfer Research
IF: 0.404 5-Year IF: 0.8 SJR: 0.264 SNIP: 0.504 CiteScore™: 0.88

ISSN Print: 1064-2285
ISSN Online: 2162-6561

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Heat Transfer Research

DOI: 10.1615/HeatTransRes.v44.i7.10
pages 589-602

EXPERIMENTAL INVESTIGATION OF OPPOSING MIXED CONVECTION HEAT TRANSFER IN A VERTICAL FLAT CHANNEL IN THE TRANSITION REGION. 1. ANALYSIS OF LOCAL HEAT TRANSFER

Robertas Poskas
Lithuanian Energy institute; Kaunas Univerity of Technology, Kaunas, Lithuania
Arunas Sirvydas
Lithuanian Energy Institute, Branduolinës inþinerijos problemø laboratorija, Breslaujos str. 3, LT-44403 Kaunas
Jokubas Kolesnikovas
Lithuanian Energy Institute, Branduolinës inzinerijos problemø laboratorija, Breslaujos str. 3, LT-44403 Kaunas, Lithuania
Raimondas Kilda
Lithuanian Energy Institute, Branduolinës inzinerijos problemø laboratorija, Breslaujos str. 3, LT-44403 Kaunas, Lithuania

ABSTRACT

In this paper, the results of experimental investigation into the local opposing mixed convection heat transfer in a vertical flat channel in the transition region are presented. Variation of the local heat transfer rate at different air pressures (0.1−0.4 MPa), i.e., in the case of different buoyancy effects, was analyzed. The analysis of the results revealed a significant increase in the heat transfer rate on increase in the buoyancy effect at a certain value of x/de. This is related to the change in the flow regime, i.e., formation or disappearance of vortices. Moreover, it was determined that in the case of vortical flow, the heat transfer rate is significantly higher than in the case of turbulent flow, and the transition to turbulent flow occurs at higher Re numbers. Therefore, the results obtained change the concept of the transition from laminar to turbulent flow under a significant buoyancy effect.