A new heat transfer correlation for supercritical fluids

Abstract

A new method of heat transfer prediction in supercritical fluids is presented. Emphasis is put on the simplicity of the correlation structure and its explicit coupling with physical phenomena. Assessment of qualitative behaviour of heat transfer is conducted based on existing test data and experience gathered from open literature. Based on phenomenological analysis and test data evaluation, a single dimensionless number, the acceleration number, is introduced to correct the deviation of heat transfer from its conventional behaviour, which is predicted by the Dittus-Boelter equation. The new correlation structure excludes direct dependence of heat transfer coefficient on wall surface temperature and eliminates possible numerical convergence. The uncertainty analysis of test data provides information about the sources and the levels of uncertainties of various parameters and is highly required for the selection of both the dimensionless parameters implemented into the heat transfer correlation and the test data for the development and validation of new correlations. Comparison of various heat transfer correlations with the selected test data shows that the new correlation agrees better with the test data than other correlations selected from the open literature.

Key words： super critical fluids; heat transfer; circular tubes; prediction method

Acknowledgements

The authors would like to thank the National Basic Research Program of China (No. 2007CB209804) for providing the financial support for this study.

Notation

CP	specific heat/(J•kg-1•K-1)
D	diameter/m
e	error of various parameters
F	correction factor
G	mass flux/(kg•m-2•s-1)
Gr	Grashof number
h	enthalpy/(J•kg-1)
Nu	Nusselt number
p	pressure/MPa
pc	critical pressure/MPa
Pr	Prandtl number
q	heat flux/(W•m-2)
Re	Reynolds number
T	temperature/°C
Tc	critical temperature/°C
y	coordination in radial direction/m
z	coordination in axial direction/m
a	heat transfer coefficient/(W•m-2•K-1)
a0	reference heat transfer coefficient/(W•m-2•K-1)
b	thermal expansion coefficient/K-1
l	Thermal conductivity/(W•m-1•K-1)
m	Dynamic viscosity/(kg•m-1•s-1)
pa	acceleration number
pb	buoyancy number
pc	ratio of specific heat
r	density/( kg•m-3)
subscripts
B	bulk
C	calculated
m	measured
W	wall
pc	pseudo-critical

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