Evaluation of flow patterns and elongated bubble characteristics during the flow boiling of halocarbon refrigerants in a micro-scale channel

Autor(es)

Alves Arcanjo, Alexandre ^[1] ; Bigonha Tibirica, Cristiano ^[1] ; Ribatski, Gherhardt ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Escola Engn Sao Carlos, Dept Mech Engn, Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: EXPERIMENTAL THERMAL AND FLUID SCIENCE; v. 34, n. 6, p. 766-775, SEP 2010.
• Citações Web of Science: 21

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. (AU)

• Processo FAPESP: 05/60031-0 - Estudo teórico-experimental da ebulição convectiva de refrigerantes halogenados no interior de micro-canais
• Beneficiário: Gherhardt Ribatski
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores
• Processo FAPESP: 07/53950-5 - Estudo teórico-experimental da transferência de calor e do fluxo crítico durante a ebulição convectiva no interior de microcanais
• Beneficiário: Cristiano Bigonha Tibirica
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 06/52089-1 - Estudo teorico experimental da ebulicao convectiva de refrigerantes halogenados no interior de micro canais.
• Beneficiário: Gherhardt Ribatski
• Modalidade de apoio: Bolsas no Brasil - Jovens Pesquisadores