This paper reports a study of heat transfer in the post-critical heat flux (post-CHF) regime under forced convective upflow conditions in a uniformly heated vertical tube of 12.7 mm internal diameter and 3 m length. Experiments were conducted with non-azeotropic ternary refrigerant mixture R-407C for reduced pressures ranging from 0.37 to 0.75, mass flux values from 1200 to 2000 kg/m2 s and heat flux from 50 to 80 kW/m2. Data shows a considerable effect of system pressure on the post-CHF heat transfer coefficient for specified mass and heat fluxes. The post-CHF heat transfer coefficients for R-407C are compared with three existing correlations which are found to over predict the current data. A modified correlation to represent the experimental data for R-407C is presented. © 2009 Elsevier Ltd. All rights reserved.

R. Sindhuja

Arcot R. Balakrishnan

Boiling heat transfer

Critical heat flux

Current data

Experimental data

INTERNAL DIAMETERS

Mass flux

REDUCED PRESSURE

REFRIGERANT MIXTURES

SYSTEM PRESSURE

VERTICAL PIPES

VERTICAL TUBE

Heat exchangers

Heat transfer coefficients

pipe

Pressure effects

Table lookup

Heat flux

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Applied Thermal Engineering

The differences between the modern version of the phase rule and the one originally proposed by Gibbs are pointed out. The local analysis implied in Gibbs's approach to the phase rule is carried forward to its logical conclusion using the implicit function theorem. The results of the analysis are used to resolve the apparent contradictions in the interpretation of the phase rule, using the Gibbs-Duhem equations, for a system exhibiting an azeotrope. Specifically, the pitfalls in treating the differentials in the Gibbs-Duhem equations as variations are demonstrated. The critical role played by the rank of a submatrix in the coefficient matrix of the Gibbs-Duhem equations is highlighted. A hierarchy in the application of the phase rule is pointed out and the need for a unified framework for interpreting the phase rule is indicated. © 2012 Elsevier Ltd.

International Communications in Heat and Mass Transfer

Phase rule and the azeotrope - A critique and a new interpretation

The critical heat flux (CHF) in forced convective upflow has been investigated in a uniformly heated vertical tube of 12.7 mm internal diameter and 3 m length for different reduced pressures ranging from 0.32 to 0.98, with non-azeotropic ternary refrigerant mixture R-407C as the working fluid. The onset of CHF was determined by the sudden rise in the wall temperature of the electrically heated tube. Experiments were performed over a wide range of parameters: mass flux values from 200 to 2000 kg/m2 s, pressure from 15 to 45.6 bar and heat flux from 5 to 80 kW/m2. The results show considerably lower critical heat flux at higher pressures as in the case of pure fluids. Finally, a comparison of the experimental data with the available pure fluid correlations has been performed. © 2007 Elsevier Ltd. All rights reserved.

Critical heat flux of R-407C in upflow boiling in a vertical pipe

International Journal of Heat and Mass Transfer

Prediction of dryout and post-dryout heat transfer at high pressures using a one-dimensional three-fluid model

Nuclear Engineering and Design

A look-up table for fully developed film-boiling heat transfer

International Journal of Multiphase Flow

Calculation of dryout and post-dryout heat transfer for tube geometry

Journal of Nuclear Science and Technology

8th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics NURETH-8

Post-CHF heat transfer during two-phase upflow boiling of R-407C in a vertical pipe

Journal	Applied Thermal Engineering
ISSN	13594311
Open Access	No