Research Papers: Natural and Mixed Convection

Optimum Operating Conditions for Subcritical/Supercritical Fluid-Based Natural Circulation Loops

[+] Author and Article Information
Ajay Kumar Yadav

Assistant Professor
Department of Mechanical Engineering,
National Institute of Technology,
Karnataka, Surathkal,
Mangalore 575025, Karnataka, India
e-mail: ajaykyadav@nitk.edu.in

Souvik Bhattacharyya

Department of Mechanical Engineering,
Indian Institute of Technology Kharagpur,
Kharagpur 721302, India
e-mail: souvik.iit@gmail.com

M. Ram Gopal

Department of Mechanical Engineering,
Indian Institute of Technology Kharagpur,
Kharagpur 721302, India
e-mail: ramg@mech.iitkgp.ernet.in

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received August 2, 2014; final manuscript received September 18, 2015; published online June 14, 2016. Assoc. Editor: Ali Khounsary.

J. Heat Transfer 138(11), 112501 (Jun 14, 2016) (9 pages) Paper No: HT-14-1510; doi: 10.1115/1.4031921 History: Received August 02, 2014; Revised September 18, 2015

Natural circulation loop (NCL) is simple and reliable due to the absence of moving components and is preferred in applications where safety is of foremost concern, such as nuclear power plants and high-pressure thermal power plants. In the present study, optimum operating conditions based on the maximum heat transfer rate in NCLs have been obtained for subcritical as well as supercritical fluids. In recent years, there is a growing interest in the use of carbon dioxide (CO2) as loop fluid in NCLs for a variety of heat transfer applications due to its excellent thermophysical environmentally benign properties. In the present study, three-dimensional (3D) computational fluid dynamics (CFD) analysis of a CO2-based NCL with isothermal source and sink has been carried out. Results show that the heat transfer rate is much higher in the case of supercritical phase (if operated near pseudocritical region) than the subcritical phase. In the subcritical option, higher heat transfer rate is obtained in the case of liquid operated near saturation condition. Correlations for optimum operating condition are obtained for a supercritical CO2-based NCL in terms of reduced temperature and reduced pressure so that they can be employed for a wide variety of fluids operating in supercritical region. Correlations are also validated with different loop fluids. These results are expected to help design superior optimal NCLs for critical applications.

Copyright © 2016 by ASME
Your Session has timed out. Please sign back in to continue.


Wang, K. , Magnus, E. , Yunho, H. , and Radermacher, R. , 2010, “ Review of Secondary Loop Refrigeration System,” Int. J. Refrig., 33(2), pp. 212–234. [CrossRef]
Kumar, K. K. , and Ram Gopal, M. , 2009, “ Carbon Dioxide as Secondary Fluid in Natural Circulation Loops,” Proc. Inst. Mech. Eng., Part E, 223(3), pp. 189–194. [CrossRef]
Yadav, A. K. , Bhattacharyya, S. , and Ram Gopal, M. , 2014, “ On the Suitability of Carbon Dioxide in Forced Circulation Type Secondary Loops,” Int. J. Low Carbon Technol., 9(1), pp. 85–90. [CrossRef]
Kreitlow, D. B. , and Reistad, G. M. , 1978, “ Thermosyphon Models for Downhole Heat Exchanger Application in Shallow Geothermal Systems,” ASME J. Heat Transfer, 100(4), pp. 713–719. [CrossRef]
Torrance, K. E. , 1979, “ Open-Loop Thermosyphons With Geological Application,” ASME J. Heat Transfer, 100(4), pp. 677–683. [CrossRef]
Rieberer, R. , 2005, “ Naturally Circulation Probes and Collectors for Ground-Coupled Heat Pumps,” Int. J. Refrig., 28(8), pp. 1308–1315. [CrossRef]
Zhang, X. R. , and Yamaguchi, H. , 2007, “ An Experimental Study on Evacuated Tube Solar Collector Using Supercritical CO2,” Appl. Therm. Eng., 28(10), pp. 1225–1233. [CrossRef]
Zimmermann, A. J. P. , and Melo, C. , 2014, “ Analysis of a R744 Two Phase Loop Thermosyphon Applied to the Cold End of a Stirling Cooler,” Appl. Therm. Eng., 73(1), pp. 549–558. [CrossRef]
Rieberer, R. , Karl, M. , and Hermann, H. , 2004, “ CO2 Two-Phase Thermosyphon as a Heat Source System for Heat Pumps,” 6th IIR-Gustav Lorentzen Natural Working Fluids Conference, Glasgow, UK, Aug. 29–Sept. 1 pp. 1–8.
Ochsner, K. , 2008, “ Carbon Dioxide Heat Pipe in Conjunction With a Ground Source Heat Pump (GSHP),” Appl. Therm. Eng., 28(16), pp. 2077–2082. [CrossRef]
Sarkar, M. K. S. , Tilak, A. K. , and Basu, D. N. , 2014, “ A State-of-the-Art Review of Recent Advances in Supercritical Natural Circulation Loops for Nuclear Applications,” Ann. Nucl. Energy, 73, pp. 250–263. [CrossRef]
Yadav, A. K. , Ram Gopal, M. , and Bhattacharyya, S. , 2012, “ CO2 Based Natural Circulation Loops: New Correlations for Friction and Heat Transfer,” Int. J. Heat Mass Transfer, 55(17–18), pp. 4621–4630. [CrossRef]
Sabersky, R. H. , and Hauptmann, E. G. , 1967, “ Forced Convection Heat Transfer to Carbon Dioxide Near the Critical Point,” Int. J. Heat Mass Transfer, 10(11), pp. 1499–1508. [CrossRef]
Yamagata, K. , Nishmawa, K. , Hasegawa, T. S. , Fuji, T. , and Yoshida, M. S. , 1972, “ Forced Convective Heat Transfer to Supercritical Water Flowing in Tubes,” Int. J. Heat Mass Transfer, 15(12), pp. 2575–2593. [CrossRef]
He, S. , Kim, W. S. , and Jackson, J. D. , 2008, “ A Computational Study of Convective Heat Transfer to Carbon Dioxide at a Pressure Just Above the Critical Value,” Appl. Therm. Eng., 28(13), pp. 1662–1675. [CrossRef]
Hua, Y. X. , Wang, Y. Z. , and Meng, H. , 2010, “ A Numerical Study of Supercritical Forced Convective Heat Transfer of n-Heptane Inside a Horizontal Miniature Tube,” J. Supercrit. Fluids, 52(1), pp. 36–46. [CrossRef]
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(1), pp. 116–121. [CrossRef]
Yadav, A. K. , Ram Gopal, M. , and Bhattacharyya, S. , 2012, “ CFD Analysis of a CO2 Based Natural Circulation Loop With End Heat Exchangers,” Appl. Therm. Eng., 36, pp. 288–295. [CrossRef]
Yoshikawa, S. , Smith, R. L., Jr. , Inomata, H. , Matsumura, Y. , and Arai, K. , 2005, “ Performance of a Natural Convection Circulation System for Supercritical Fluids,” J. Supercrit. Fluids, 36(1), pp. 70–80. [CrossRef]
Seetharam, T. R. , and Sharma, G. K. , 1979, “ Free Convective Heat Transfer to Fluids in the Near-Critical Region From Vertical Surfaces With Uniform Heat Flux,” Int. J. Heat Mass Transfer, 22(1), pp. 13–20. [CrossRef]
Liao, S. M. , and Zhao, T. S. , 2002, “ Measurements of Heat Transfer Coefficients From Supercritical Carbon Dioxide Flowing in Horizontal Mini/Micro Channels,” ASME J. Heat Transfer, 124(3), pp. 413–420. [CrossRef]
Yamamoto, S. , Furusawa, T. , and Matsuzawa, T. , 2011, “ Numerical Simulation of Supercritical Carbon Dioxide Flows Across Critical Point,” Int. J. Heat Mass Transfer, 54(4), pp. 774–782. [CrossRef]
Yang, J. , Oka, Y. , Ishiwatari, Y. , Liu, J. , and Yoo, J. , 2007, “ Numerical Investigation of Heat Transfer in Upward Flow of Supercritical Water in Circular Tubes and Tight Fuel Rod Bundles,” Nucl. Eng. Des., 237(4), pp. 420–430. [CrossRef]
Lisboa, P. F. , Fernandes, J. , Simoes, P. C. , Mota, J. P. B. , and Saatdjian, E. , 2010, “ Computational-Fluid-Dynamics Study of a Kenics Static Mixer as a Heat Exchanger for Supercritical Carbon Dioxide,” J. Supercrit. Fluids, 55(1), pp. 107–115. [CrossRef]
Vijayan, P. K. , and Austregesilo, H. , 1994, “ Scaling Laws for Single-Phase Natural Circulation Loops,” Nucl. Eng. Des., 152(1–3), pp. 331–347. [CrossRef]
Launder, B. E. , and Spalding, D. B. , 1974, “ The Numerical Computation of Turbulent Flows,” Comput. Methods Appl. Mech. Eng., 3(2), pp. 269–289. [CrossRef]
Yadav, A. K. , Ram Gopal, M. , and Bhattacharyya, S. , 2014, “ Transient Analysis of Subcritical/Supercritical Carbon Dioxide Based Natural Circulation Loops With End Heat Exchangers: Numerical Studies,” Int. J. Heat Mass Transfer, 59, pp. 24–33. [CrossRef]
Kumar, K. K. , and Ram Gopal, M. , 2009, “ Steady-State Analysis of CO2 Based Natural Circulation Loops With End Heat Exchangers,” Appl. Therm. Eng., 29(10), pp. 1893–1903. [CrossRef]
Zhang, X. , Chen, L. , and Yamaguchi, H. , 2010, “ Natural Convective Flow and Heat Transfer of Supercritical CO2 in a Rectangular Circulation Loop,” Int. J. Heat Mass Transfer, 53(19–20), pp. 4112–4122. [CrossRef]
NIST, 2013, Standard Reference Database-refprop, Version 9.1, National Institute of Standards and Technology, Gaithersburg, MD.
Vijayan, P. K. , 2002, “ Experimental Observations on the General Trends of the Steady State and Stability Behaviour of Single-Phase Natural Circulation Loops,” Nucl. Eng. Des., 215(1–2), pp. 139–152. [CrossRef]


Grahic Jump Location
Fig. 1

Schematic of the NCL employed in the model

Grahic Jump Location
Fig. 2

Meshing of a cross section (fluid part only)

Grahic Jump Location
Fig. 3

Variation in heat transfer rate with ΔT for (a) subcritical CO2, (b) supercritical CO2 at 313 K, (c) supercritical CO2 at 323 K, and (d) supercritical CO2 at 333 K

Grahic Jump Location
Fig. 4

Variation of thermophysical properties with pressure

Grahic Jump Location
Fig. 5

Variation of specific heat of CO2 with pressure for different temperatures

Grahic Jump Location
Fig. 6

Variation of optimum pressure of CO2 with temperature

Grahic Jump Location
Fig. 7

Variation of Rayleigh number with pressure for different operating temperatures

Grahic Jump Location
Fig. 8

Variation of modified Rayleigh number with pressure for various operating temperatures

Grahic Jump Location
Fig. 9

(a) Comparison of developed correlations in terms of heat transfer rate and (b) variation of heat transfer rate near the obtained pressure employing correlation based on Rayleigh number

Grahic Jump Location
Fig. 10

Validation of obtained result with experimental data for turbulent flow



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In