Effect of Loop Diameter, Height and Insulation on a High Temperature CO2 Based Natural Circulation Loop
Natural circulation loops (NCLs) are buoyancy driven flow systems without any moving components. NCLs have vast applications in geothermal, solar and nuclear power industry where reliability and safety are of foremost concern. Due to certain favorable thermophysical properties, especially near supercritical regions, carbon dioxide can be considered as an ideal loop fluid in many applications. In the present work, a high temperature NCL that uses supercritical carbon dioxide as loop fluid is analysed. The effects of relevant design and operating variables on loop performance are studied. The system operating under steady state is modelled taking into account the axial conduction through loop fluid and loop wall, and heat transfer with surroundings. The heat source is considered to be a heater with controlled heat flux and heat sink is modelled as an end heat exchanger with water as the external cold fluid. The governing equations for mass, momentum and energy conservation are normalized and are solved numerically using finite volume method. Results are obtained for a loop pressure of 90 bar with the power input varying from 0.5 kW to 6.0 kW. The numerical results are validated against the experimental results reported in the literature in terms of the modified Grashof number (Grm) and Reynolds number (Re). Based on the results, buoyancy and friction dominated regions are identified for a given loop. Parametric analysis has been done to show the effect of loop diameter, loop height, ambient temperature and insulation. The results show that for the high temperature loop, heat loss to surroundings affects the loop performance significantly. Hence this conjugate heat transfer between the loop and surroundings has to be considered in the analysis of high temperature NCLs.
[1] A.K. Yadav, MRamgopal, S. Bhattacharyya, CFD analysis of CO2based natural circulation loop with end heat exchangers, Appl. Therm. Eng., 36 (2012a) 288-295
[2] B.T. Swapnalee, P.K. Vijayan, M. Sharma, D.S. Pilkhwal, Steady state flow and static instability of supercritical natural circulation loops, Nucl.Eng. and Des., 245 (2012) 99–112.
[3] D.B. Kreitlow, G.M. Reistad, Themosyphon models for downhole heat exchanger application in shallow geothermal systems, J. Heat Transfer 100 (1978) 713–719.
[4] D.E. Kim, M.H. Kim, J.E. Cha, S.O. Kim. Numerical investigation on thermal–hydraulic performance of new printed circuit heat exchanger model, Nucl. Eng. Des. 238 (2008) 3269–3276.
[5] D.N. Basu, S. Bhattacharyya, P.K. Das, Effect of geometric parameters on steady-state performance of single-phase NCL with heat loss to ambient, Int. J. Therm. Sci. 47 (2008) 1359–1373.
[6] D.N. Basu, S. Bhattacharyya, P.K. Das, Effect of heat loss to ambient on steady-state behaviour of a single-phase natural circulation loop, Int. J. Therm. Sci. 24 (2007) 1432–1444.
[7] F.C.V.N. Fourie, C.E. Schwarz, J.H. Knoetze, Phase equilibria of alcohols in supercritical fluids Part I. The effect of the position of the hydroxyl group for linear C8 alcohols in supercritical carbon dioxide, J. Supercrit. Fluids 47 (2008) 161–167.
[8] F.W. Dittus, L.M.K. Boelter, Heat transfer in automobile radiators of tubular type, University of California Publications in Engineering, 2 (1930) 443–461.
[9] H. Yamaguchi, X.R. Zhang, K. Fujima, Basic study on new cryogenic refrigeration using CO2 solid–gas two phase flow, Int. J. Refrig. 31 (2008) 404–410.
[10] K.E. Torrance, Open–loop thermosyphons with geological application, J. Heat Transfer 100 (1979) 677–683.
[11] K. Kiran Kumar, M. Ram Gopal, Carbon dioxide as secondary fluid in natural circulation loops, Proc. IMechE, Part E: J. Process Mech. Engg. 223 (2009a) 189-194.
[12] K. Kiran Kumar, M. Ram Gopal, Steady-state analysis of CO2 based natural circulation loops with end heat exchangers, Appl. Therm. Eng. 29 (2009b) 1893–1903
[13] K. Ochsner, Carbon dioxide heat pipe in conjunction with a ground source heat pump (GSHP), Appl. Therm. Eng. 28 (2008) 2077–2082.
[14] K. Wang, E. Magnus, H. Yunho, R. Radermacher, Review of secondary loop refrigeration system, Int.J.of Refrigeration, 33 (2010) 212–234.
[15] L. Chen, X.-R. Zhang, H. Yamaguchi, Z.-S. (Simon) Liu, Effect of heat transfer on the instabilities and transitions of supercritical CO2 flow in a natural circulation loop, Int. J. Heat Mass Transf. 53 (2010) 4101–4111.
[16] M.H. Kim, J. Pettersen, C.W. Bullard, Fundamental process and system design issues in CO2 vapor compression systems, Progress in Energy and Combustion Science, 30 (2004) 119–174.
[17] M. Ishii, I. Kataoka, Scaling laws for thermal-hydraulic system under single phase and two-phase natural circulation, Nucl. Eng. and Des., 81 (1984) 411-425.
[18] M. Misale, P. Garibaldi, J.C. Passos, G.D. Bitencourt, Experiments in a single phase natural circulation mini-loop, Experimental Thermal and Fluid Science, 31 (2007) 1111–1120.
[19] P. Bondioli, C. Mariani, E. Mossa, A. Fedelli, A. Muller, Lampante olive oil refining with supercritical carbon dioxide, J. Am. Oil Chem. Soc. 69 (1992) 477–480.
[20] P.K. Vijayan, H. Austregesilo, Scaling laws for single-phase natural circulation loops, Nucl. Eng. and Des., 152 (1994)331–347.
[21] P.K. Vijayan, Experimental observations on the general trends of the steady state and stability behaviour of single phase natural circulation loops, Nucl. Eng. and Des., 215 (2002) 139–152.
[22] S.K. Mousavian, M.Misale, F. D’Auria, M.A. Salehi, Transient and stability analysis in single phase natural circulation, Annals of Nuclear Energy, 31 (2004) 1177-1198.
[23] S.W. Churchill, H.H.S. Chu, Correlating equations for laminar and turbulent free convection from vertical plate, Int. J. Heat Mass Transfer 18 (11) (1975) 1323–1329.
[24] Dostal, P. Hejzlar, M.J. Driscoll, The supercritical carbon dioxide power cycle: comparison to other advanced power cycles, Nucl. Technol. 154 (2006) 283–301.
[25] Gnielinsky, New equation for heat and mass transfer in turbulent pipe and channel flow, Int. Chemical Engineering, 16 (1976) 359-368.
[26] X. Zhang, L. Chen, H. Yamaguchi, Natural convective flow and heat transfer of supercritical CO2 in a rectangular circulation loop, Int. J. Heat and Mass Transfer 53 (2010) 4112–4122.
[27] Y. Zvirin, A review of natural circulation loops in pressurizes water reactors and other systems, Nucl. Eng. And Des., 67 (1981) 203–225.
[28] B.T. Nijaguna, Thermal Sciences/Engineering Data Book, Allied Publishers Limited, New Delhi, 1992, pp. K-13.
[1] A.K. Yadav, MRamgopal, S. Bhattacharyya, CFD analysis of CO2based natural circulation loop with end heat exchangers, Appl. Therm. Eng., 36 (2012a) 288-295
[2] B.T. Swapnalee, P.K. Vijayan, M. Sharma, D.S. Pilkhwal, Steady state flow and static instability of supercritical natural circulation loops, Nucl.Eng. and Des., 245 (2012) 99–112.
[3] D.B. Kreitlow, G.M. Reistad, Themosyphon models for downhole heat exchanger application in shallow geothermal systems, J. Heat Transfer 100 (1978) 713–719.
[4] D.E. Kim, M.H. Kim, J.E. Cha, S.O. Kim. Numerical investigation on thermal–hydraulic performance of new printed circuit heat exchanger model, Nucl. Eng. Des. 238 (2008) 3269–3276.
[5] D.N. Basu, S. Bhattacharyya, P.K. Das, Effect of geometric parameters on steady-state performance of single-phase NCL with heat loss to ambient, Int. J. Therm. Sci. 47 (2008) 1359–1373.
[6] D.N. Basu, S. Bhattacharyya, P.K. Das, Effect of heat loss to ambient on steady-state behaviour of a single-phase natural circulation loop, Int. J. Therm. Sci. 24 (2007) 1432–1444.
[7] F.C.V.N. Fourie, C.E. Schwarz, J.H. Knoetze, Phase equilibria of alcohols in supercritical fluids Part I. The effect of the position of the hydroxyl group for linear C8 alcohols in supercritical carbon dioxide, J. Supercrit. Fluids 47 (2008) 161–167.
[8] F.W. Dittus, L.M.K. Boelter, Heat transfer in automobile radiators of tubular type, University of California Publications in Engineering, 2 (1930) 443–461.
[9] H. Yamaguchi, X.R. Zhang, K. Fujima, Basic study on new cryogenic refrigeration using CO2 solid–gas two phase flow, Int. J. Refrig. 31 (2008) 404–410.
[10] K.E. Torrance, Open–loop thermosyphons with geological application, J. Heat Transfer 100 (1979) 677–683.
[11] K. Kiran Kumar, M. Ram Gopal, Carbon dioxide as secondary fluid in natural circulation loops, Proc. IMechE, Part E: J. Process Mech. Engg. 223 (2009a) 189-194.
[12] K. Kiran Kumar, M. Ram Gopal, Steady-state analysis of CO2 based natural circulation loops with end heat exchangers, Appl. Therm. Eng. 29 (2009b) 1893–1903
[13] K. Ochsner, Carbon dioxide heat pipe in conjunction with a ground source heat pump (GSHP), Appl. Therm. Eng. 28 (2008) 2077–2082.
[14] K. Wang, E. Magnus, H. Yunho, R. Radermacher, Review of secondary loop refrigeration system, Int.J.of Refrigeration, 33 (2010) 212–234.
[15] L. Chen, X.-R. Zhang, H. Yamaguchi, Z.-S. (Simon) Liu, Effect of heat transfer on the instabilities and transitions of supercritical CO2 flow in a natural circulation loop, Int. J. Heat Mass Transf. 53 (2010) 4101–4111.
[16] M.H. Kim, J. Pettersen, C.W. Bullard, Fundamental process and system design issues in CO2 vapor compression systems, Progress in Energy and Combustion Science, 30 (2004) 119–174.
[17] M. Ishii, I. Kataoka, Scaling laws for thermal-hydraulic system under single phase and two-phase natural circulation, Nucl. Eng. and Des., 81 (1984) 411-425.
[18] M. Misale, P. Garibaldi, J.C. Passos, G.D. Bitencourt, Experiments in a single phase natural circulation mini-loop, Experimental Thermal and Fluid Science, 31 (2007) 1111–1120.
[19] P. Bondioli, C. Mariani, E. Mossa, A. Fedelli, A. Muller, Lampante olive oil refining with supercritical carbon dioxide, J. Am. Oil Chem. Soc. 69 (1992) 477–480.
[20] P.K. Vijayan, H. Austregesilo, Scaling laws for single-phase natural circulation loops, Nucl. Eng. and Des., 152 (1994)331–347.
[21] P.K. Vijayan, Experimental observations on the general trends of the steady state and stability behaviour of single phase natural circulation loops, Nucl. Eng. and Des., 215 (2002) 139–152.
[22] S.K. Mousavian, M.Misale, F. D’Auria, M.A. Salehi, Transient and stability analysis in single phase natural circulation, Annals of Nuclear Energy, 31 (2004) 1177-1198.
[23] S.W. Churchill, H.H.S. Chu, Correlating equations for laminar and turbulent free convection from vertical plate, Int. J. Heat Mass Transfer 18 (11) (1975) 1323–1329.
[24] Dostal, P. Hejzlar, M.J. Driscoll, The supercritical carbon dioxide power cycle: comparison to other advanced power cycles, Nucl. Technol. 154 (2006) 283–301.
[25] Gnielinsky, New equation for heat and mass transfer in turbulent pipe and channel flow, Int. Chemical Engineering, 16 (1976) 359-368.
[26] X. Zhang, L. Chen, H. Yamaguchi, Natural convective flow and heat transfer of supercritical CO2 in a rectangular circulation loop, Int. J. Heat and Mass Transfer 53 (2010) 4112–4122.
[27] Y. Zvirin, A review of natural circulation loops in pressurizes water reactors and other systems, Nucl. Eng. And Des., 67 (1981) 203–225.
[28] B.T. Nijaguna, Thermal Sciences/Engineering Data Book, Allied Publishers Limited, New Delhi, 1992, pp. K-13.
@article{"International Journal of Mechanical, Industrial and Aerospace Sciences:73583", author = "S. Sadhu and M. Ramgopal and S. Bhattacharyya", title = "Effect of Loop Diameter, Height and Insulation on a High Temperature CO2 Based Natural Circulation Loop", abstract = "Natural circulation loops (NCLs) are buoyancy driven flow systems without any moving components. NCLs have vast applications in geothermal, solar and nuclear power industry where reliability and safety are of foremost concern. Due to certain favorable thermophysical properties, especially near supercritical regions, carbon dioxide can be considered as an ideal loop fluid in many applications. In the present work, a high temperature NCL that uses supercritical carbon dioxide as loop fluid is analysed. The effects of relevant design and operating variables on loop performance are studied. The system operating under steady state is modelled taking into account the axial conduction through loop fluid and loop wall, and heat transfer with surroundings. The heat source is considered to be a heater with controlled heat flux and heat sink is modelled as an end heat exchanger with water as the external cold fluid. The governing equations for mass, momentum and energy conservation are normalized and are solved numerically using finite volume method. Results are obtained for a loop pressure of 90 bar with the power input varying from 0.5 kW to 6.0 kW. The numerical results are validated against the experimental results reported in the literature in terms of the modified Grashof number (Grm) and Reynolds number (Re). Based on the results, buoyancy and friction dominated regions are identified for a given loop. Parametric analysis has been done to show the effect of loop diameter, loop height, ambient temperature and insulation. The results show that for the high temperature loop, heat loss to surroundings affects the loop performance significantly. Hence this conjugate heat transfer between the loop and surroundings has to be considered in the analysis of high temperature NCLs.", keywords = "Conjugate heat transfer, heat loss, natural circulation loop, supercritical carbon dioxide.", volume = "10", number = "8", pages = "1476-9", }
