Saturated flow boiling heat transfer and critical heat flux in small horizontal flattened tubes

Autor(es)

Tibirica, Cristiano Bigonha ^[1] ; Ribatski, Gherhardt ^[1] ; Thome, John Richard ^[2]

Afiliação do(s) autor(es)

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

^[2] Ecole Polytech Fed Lausanne, Lab Heat & Mass Transfer LTCM, CH-1015 Lausanne - Switzerland

• Tipo de documento: Artigo Científico
• Fonte: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER; v. 55, n. 25-26, p. 7873-7883, DEC 2012.
• Citações Web of Science: 27

Resumo

This paper presents experimental results for flow boiling heat transfer coefficient and critical heat flux (CHF) in small flattened tubes. The tested flattened tubes have the same equivalent internal diameter of 2.2 mm, but different aspect height/width ratios (H/W) of 1/4, 1/2, 2 and 4. The experimental data were compared against results for circular tubes using R134a and R245fa as working fluids at a nominal saturation temperature of 31 degrees C. For mass velocities higher than 200 kg/m(2)s, the flattened and circular tubes presented similar heat transfer coefficients. Such a behavior is related to the fact that stratification effects are negligible under conditions of higher mass velocities. Heat transfer correlations from the literature, usually developed using only circular-channel experimental data, predicted the flattened tube results for mass velocities higher than 200 kg/m(2)s with mean absolute error lower than 20% using the equivalent diameter to account for the geometry effect. Similarly, the critical heat flux results were found to be independent of the tube aspect ratio when the same equivalent length was kept. Equivalent length is a new parameter which takes into account the channel heat transfer area. The CHF correlations for round tubes predicted the flattened tube data relatively well when using the equivalent diameter and length. Furthermore, a new proposed CHF correlation predicted the present flattened tube data with a mean absolute error of 5%. (C) 2012 Elsevier Ltd. 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