Comparison of Critical Heat Flux for R-134a Flow Boiling in a Horizontal Straight Tube and a Helically-Coiled Tube


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Experimental studies on critical heat flux (CHF) have been conducted in a uniformly heated horizontal straight tube and helically-coiled tube respectively with R-134a as the working fluid. The helically-coiled tube has the same heated length and inner diameter with the straight tube and experiments were performed under the following conditions: pressure from 0.4 to 2.5 MPa, mass flux values from 80 to 1500 kg m-2 s-1, inlet quality from -0.23 to 0.28 and critical quality from 0.65 to 0.86. The CHF data of the helically-coiled tube have been compared with that of the straight tube. The results show that the helically-coiled tube gets significant improvement in the CHF values vs. the straight tube under the same conditions and the degree of improvement depends on the mass flux, system pressure, inlet quality and critical quality.



Advanced Materials Research (Volumes 588-589)

Edited by:

Lawrence Lim




L. Z. Tan et al., "Comparison of Critical Heat Flux for R-134a Flow Boiling in a Horizontal Straight Tube and a Helically-Coiled Tube", Advanced Materials Research, Vols. 588-589, pp. 1813-1816, 2012

Online since:

November 2012




[1] M.M. Shah, Improved general correlation for critical heat flux during upflow in uniformly heated vertical tubes, Int. J. Heat Fluid Flow 8 (1987) 325-335.


[2] H.C. Kim, W.P. Bark, S.H. Chang, Critical heat flux of water in vertical round tubes at low pressure and low flow conditions, Nucl. Eng. Des. 199 (2000) 49-73.

[3] H.C. Kim, S.H. Chang, CHF characteristics of R-134a flowing upward in uniformly heated vertical tube, Int. J. Heat Mass Transfer, 2005, 48 (11): 2242-2249.


[4] R. Sindhuja, A.R. Balakrishnan, S.S. Murthy, Critical heat flux of R-407c in upflow boiling in a vertical pipe, Appl. Therm. Eng. 28 (2008) 1058-1065.


[5] M.K. Jensen, A.E. Bergles, Critical heat flux in helical coils with a circumferential heat flux tilt toward the outside surface, Int. J. Heat Mass Transfer 25 (1982) 1383-1395.


[6] S. Jayanti, G. Berthoud, High-quality dryout in helical coils, Nucl. Eng. Des. 122 (1990) 105-118.


[7] W.M. Ma, M.Y. Zhang, X.J. Chen, High-quality critical heat flux in horizontally coiled tubes, J. Thermal Sci. 4 (1995) 205-211.