Cooling of supercritical CH4/N2 mixture is the most important heat transfer process during coalbed methane (CBM) liquefaction. In this paper, numerical studies of the turbulent convective heat transfer of supercritical CH4/N2 flowing inside a vertical circular tube have been conducted with Lam–Bremhorst low Reynolds turbulence model. The present numerical investigations focus on the effects of the nitrogen content, heat flux, and flow orientation. Results indicate that as nitrogen content increases, the maximum heat transfer coefficient gradually decreases and corresponds to lower temperature. Heat transfer coefficient is slightly affected by heat flux in the liquid-like region and increases with increasing heat flux in the gas-like region. Buoyancy effect gradually increases with decreasing bulk temperature, and reaches its maximum at the pseudo-critical point, and then drops as bulk temperature further decreases. It is significant in the liquid-like region and negligible in the gas-like region. At the same time, buoyancy effect enhances heat transfer in the upward flow and impairs it in the downward flow.

References

References
1.
Lin
,
W. S.
,
Gao
,
T.
,
Gu
,
A. Z.
, and
Gu
,
M.
, 2010, “
CBM Nitrogen Expansion Liquefaction Processes Using Residue Pressure of Nitrogen From Adsorption Separation
,”
ASME J. Energy Resour. Technol.
,
132
(
3
),
032501
.
2.
Duffey
,
R. B.
, and
Pioro
,
I. L.
, 2005, “
Experimental Heat Transfer of Supercritical Carbon Dioxide Flowing Inside Channels (Survey)
,”
Nucl. Eng. Des.
,
235
, pp.
913
924
.
3.
Yoon
,
S. H.
,
Kim
,
J. H.
,
Hwang
,
Y. W.
,
Kim
,
M. S.
,
Min
,
K.
, and
Kim
,
Y.
, 2003, “
Heat Transfer and Pressure Drop Characteristics During the In-Tube Cooling Process of Carbon Dioxide in the Supercritical Region
,”
Int. J. Refrig.
,
26
, pp.
857
864
.
4.
Dang
,
C.
, and
Hihara
,
E.
, 2004, “
In-Tube Cooling Heat Transfer of Supercritical Carbon Dioxide: Part 1 and Part 2
,”
Int. J. Refrig.
,
27
, pp.
737
760
.
5.
Liao
,
S. M.
, and
Zhao
,
T. S.
, 2002, “
Measurement of Heat Transfer Coefficients From Supercritical Carbon Dioxide Flowing in Horizontal Mini/Micro Channels
,”
ASME J. Heat Transfer
,
124
, pp.
413
420
.
6.
Pitla
,
S. S.
,
Groll
,
E. A.
, and
Ramadhyani
,
S. R.
, 2001, “
Convective Heat Transfer In-Tube Flow of Turbulent Supercritical Carbon Dioxide: Part 1 and Part 2
,”
HVAC&R Res.
,
7
, pp.
345
382
.
7.
Son
,
C. H.
, and
Park
,
S. J.
, 2006, “
An Experimental Study on Heat Transfer and Pressure Drop Characteristics of Carbon Dioxide During Gas Cooling Process in a Horizontal Tube
,”
Int. J. Refrig.
,
29
, pp.
539
546
.
8.
Du
,
Z.
,
Lin
,
W.
, and
Gu
,
A.
, 2010, “
Numerical Investigation of Cooling Heat Transfer to Supercritical CO2 in a Horizontal Circular Tube
,”
J. Supercrit. Fluids
,
55
, pp.
116
121
.
9.
Varmazyar
,
M.
, and
Bazargan
,
M.
, 2011, “
Modeling of Free Convection Heat Transfer to a Supercritical Fluid in a Square Enclosure by the Lattice Boltzmann Method
,”
ASME J. Heat Transfer
,
133
,
025501
.
10.
Rousselet
,
Y.
,
Warrier
,
G. R.
, and
Dhir
,
V. K.
, 2011, “
An Experimental Study of Heat Transfer From Small Horizontal Cylinders at Near-Critical Pressures
,”
ASME/JSME 8th Thermal Engineering Joint Conference
, AJTEC2011-44493.
11.
Lam
,
C. K. G.
, and
Bremhorst
,
K.
, 1981, “
A Modified Form of the k-ɛ Model for Predicting Wall Turbulence
,”
J. Fluids Eng.
,
103
, pp.
450
460
.
12.
NIST, 2002,
Standard Reference Database 23, Version 7.0
, “NIST Reference Fluid Thermodynamic and Transport Properties—REFPROP.”
13.
Bruch
,
A.
,
Bontemps
,
A.
, and
Colasson
,
S.
, 2009, “
Experimental Investigation of Heat Transfer of Supercritical Carbon Dioxide Flowing in a Cooled Vertical Tube
,”
Int. J. Heat Mass Transfer
,
52
, pp.
2589
2598
.
14.
Jackson
,
J. D.
,
Cotton
,
M. A.
, and
Axcell
,
B. P.
, 1989, “
Studies of Mixed Convection in Vertical Tubes
,”
Int. J. Heat Fluid Flow
,
10
, pp.
2
15
.
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