Flow boiling heat transfer of R134a, R236fa and R245fa in a horizontal 1.030 mm circular channel
- Laboratory of Heat and Mass Transfer (LTCM), Ecole Polytechnique Federale de Lausanne (EPFL), ME G0 520 ME Station 9, Lausanne CH 1015 (Switzerland)
This research focuses on acquiring accurate flow boiling heat transfer data and flow pattern visualization for three refrigerants, R134a, R236fa and R245fa in a 1.030 mm channel. We investigate trends in the data, and their possible mechanisms, for mass fluxes from 200 to 1600 kg/m{sup 2}s, heat fluxes from 2.3 kW/m{sup 2} to 250 kW/m{sup 2} at T{sub sat} = 31 C and {delta}T{sub sub} from 2 to 9 K. The local saturated flow boiling heat transfer coefficients display a heat flux and a mass flux dependency but no residual subcooling influence. The changes in heat transfer trends correspond well with flow regime transitions. These were segregated into the isolated bubble (IB) regime, the coalescing bubble (CB) regime, and the annular (A) regime for the three fluids. The importance of nucleate boiling and forced convection in these small channels is still relatively unclear and requires further research. (author)
- OSTI ID:
- 21169006
- Journal Information:
- Experimental Thermal and Fluid Science, Vol. 33, Issue 4; Other Information: Elsevier Ltd. All rights reserved; ISSN 0894-1777
- Country of Publication:
- United States
- Language:
- English
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