| Full text | |
| Author(s): |
Total Authors: 3
|
| Affiliation: | [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
Total Affiliations: 2
|
| Document type: | Journal article |
| Source: | INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER; v. 55, n. 25-26, p. 7873-7883, DEC 2012. |
| Web of Science Citations: | 27 |
| Abstract | |
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) | |
| FAPESP's process: | 05/60031-0 - Estudo teórico-experimental da ebulição convectiva de refrigerantes halogenados no interior de micro-canais |
| Grantee: | Gherhardt Ribatski |
| Support Opportunities: | Research Grants - Young Investigators Grants |
| FAPESP's process: | 07/53950-5 - A theoretical and experimental study on flow boiling heat transfer and critical heat flux in microchannels |
| Grantee: | Cristiano Bigonha Tibirica |
| Support Opportunities: | Scholarships in Brazil - Doctorate |
| FAPESP's process: | 06/52089-1 - Estudo teorico experimental da ebulicao convectiva de refrigerantes halogenados no interior de micro canais. |
| Grantee: | Gherhardt Ribatski |
| Support Opportunities: | Scholarships in Brazil - Young Researchers |