Evaluation of flow patterns and elongated bubble characteristics during the flow boiling of halocarbon refrigerants in a micro-scale channel
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
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Data(s) |
18/10/2012
18/10/2012
2010
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Resumo |
In the present study, quasi-diabatic two-phase flow pattern visualizations and measurements of elongated bubble velocity, frequency and length were performed. The tests were run for R134a and R245fa evaporating in a stainless steel tube with diameter of 2.32 mm, mass velocities ranging from 50 to 600 kg/m(2) s and saturation temperatures of 22 degrees C, 31 degrees C and 41 degrees C. The tube was heated by applying a direct DC current to its surface. Images from a high-speed video-camera (8000 frames/s) obtained through a transparent tube just downstream the heated sections were used to identify the following flow patterns: bubbly, elongated bubbles, churn and annular flows. The visualized flow patterns were compared against the predictions provided by Barnea et al. (1983) [1], Felcar et al. (2007) [10], Revellin and Thome (2007) [3] and Ong and Thome (2009) [11]. From this comparison, it was found that the methods proposed by Felcar et al. (2007) [10] and Ong and Thome (2009) [1] predicted relatively well the present database. Additionally, elongated bubble velocities, frequencies and lengths were determined based on the analysis of high-speed videos. Results suggested that the elongated bubble velocity depends on mass velocity, vapor quality and saturation temperature. The bubble velocity increases with increasing mass velocity and vapor quality and decreases with increasing saturation temperature. Additionally, bubble velocity was correlated as linear functions of the two-phase superficial velocity. (C) 2010 Elsevier Inc. All rights reserved. FAPESP (The State of Sao Paulo Research Foundation, Brazil)[05/60031-0] FAPESP (The State of Sao Paulo Research Foundation, Brazil)[06/52089-1] FAPESP (The State of Sao Paulo Research Foundation, Brazil)[07/53950-5] |
Identificador |
EXPERIMENTAL THERMAL AND FLUID SCIENCE, v.34, n.6, p.766-775, 2010 0894-1777 http://producao.usp.br/handle/BDPI/17778 10.1016/j.expthermflusci.2010.01.006 |
Idioma(s) |
eng |
Publicador |
ELSEVIER SCIENCE INC |
Relação |
Experimental Thermal and Fluid Science |
Direitos |
restrictedAccess Copyright ELSEVIER SCIENCE INC |
Palavras-Chave | #Flow boiling #Elongated bubbles #Micro-channel #Flow patterns #2 PHASE FLOW #HEAT-TRANSFER #MICROCHANNELS #VELOCITY #R-134A #WATER #Thermodynamics #Engineering, Mechanical #Physics, Fluids & Plasmas |
Tipo |
article original article publishedVersion |