Heat Transfer Analysis in Cooling System of Hydropower’s Generator
ABSTRACT
Cooling process of power plant generator is handled via air-cooled radiators in which the cooling water is supplied from lake with its water temperature varies from season to season. In this study, the effect of temperature fluctuations of cooling water entering the cooling system has been examined via analysis of energy (NTU method) and exergy. The exergy analysis has been done by definition of efficiency coefficient for exergy of cooling media (water) and heating media (air). Besides, the effect of changing the cooling water temperature and flow rate entering the radiators on the cooling system performance has been studied. The results revealed the generator cooling system performance level held sufficient till the temperature of inlet water was kept under 293 k (20°C). On one hand, when the temperature of cooling water at the inlet rises to 12°C, the rate of heat exchange at radiators falls up to 34.3%. On the other hand, by water temperature passing the 12°C limit, the efficiency of cooling media exergy falls to 78% leading to efficiency rise in radiators’ heating media exergy level to 61%. According to the results of this study, changing flow rate of cooling media up to 40% gives rise to the efficiency coefficient of radiators’ cooling media exergy level to about 18.7%. While it does not affect the efficiency level of energy at radiators, the flow rate rise of cooling media may not be considered as a way to give rise to efficiency level of radiators.
Cooling process of power plant generator is handled via air-cooled radiators in which the cooling water is supplied from lake with its water temperature varies from season to season. In this study, the effect of temperature fluctuations of cooling water entering the cooling system has been examined via analysis of energy (NTU method) and exergy. The exergy analysis has been done by definition of efficiency coefficient for exergy of cooling media (water) and heating media (air). Besides, the effect of changing the cooling water temperature and flow rate entering the radiators on the cooling system performance has been studied. The results revealed the generator cooling system performance level held sufficient till the temperature of inlet water was kept under 293 k (20°C). On one hand, when the temperature of cooling water at the inlet rises to 12°C, the rate of heat exchange at radiators falls up to 34.3%. On the other hand, by water temperature passing the 12°C limit, the efficiency of cooling media exergy falls to 78% leading to efficiency rise in radiators’ heating media exergy level to 61%. According to the results of this study, changing flow rate of cooling media up to 40% gives rise to the efficiency coefficient of radiators’ cooling media exergy level to about 18.7%. While it does not affect the efficiency level of energy at radiators, the flow rate rise of cooling media may not be considered as a way to give rise to efficiency level of radiators.
Cite this paper
Doost, A. and Majlessi, R. (2015) Heat Transfer Analysis in Cooling System of Hydropower’s Generator. Open Journal of Applied Sciences, 5, 98-107. doi: 10.4236/ojapps.2015.53010.
Doost, A. and Majlessi, R. (2015) Heat Transfer Analysis in Cooling System of Hydropower’s Generator. Open Journal of Applied Sciences, 5, 98-107. doi: 10.4236/ojapps.2015.53010.
References
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http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.08.006 [3] Wu, S.-Y., Yuan, X.-F. Li, Y.-R. and Xiao, L. (2007) Exergy Transfer Effectiveness on Heat Exchanger for Finite Pressure Drop. Energy, 32, 2110-2120.
http://dx.doi.org/10.1016/j.energy.2007.04.010 [4] Ujiie, R., Arlitt, R. and Etoh, H. (2006) Application of Computational Fluid Dynamics (CFD) on Ventilation-Cooling Optimization of Electrical Machines. Review Energy Technologies Generation, Transmission and Distribution of Electric and Thermal Energy, Contents 4, 17-22. [5] Shlemmer, E., Schoenauer, J., Farnleitner, E. and Mueller, F. (2004) Transient Electromagnetic and Coolant Flow Investigation of Synchronous Generators Using Numerical Approaches. Proceedings of International Conference on Electrical Machines, ICEM, Cracow, 5-8 September 2004. [6] Hribernik, A. and Fike, M. (2011) Investigating the Malfunction of a Hydro-Generator’s Cooling System. 15th International Research/Expert Conference Trends in the Development of Machinery and Associated Technology, Bosnia and Herzegovina, 12-18 September 2011. [7] Siemens Company (1971) Operation and Maintenance Instructions, R-34. AC Generator and Appurtenances, Khuzestan Water and Power Authority DEZ Project. [8] Madadi, H. and Najmin, A. (2009) Survey on Thermal Stratification of Dez Dam Reservoir Using the Model CE-QUAL. 2nd Conference Exhibition of Environment Engineering, Tehran. [9] Production and Exploitation Company of Dez Dam Power Plant, Exploition and Resistance Unit (2012) Thermal Stratification Information of Dez Lake. [10] Incropera, F.P. and De Wite, D.P. (2002) An Introduction to Heat Transfer. 4th Edition, Johan Wily& Sons, Hoboken. [11] Hamid, A. (2011) Heat Exchangers (Principles, Design, Function). University of Tehran Press, Tehran , 656 p. [12] Holman, J.P. (2008) Heat Transfer. 9th Edition, John Wiley, Hoboken.
[1] Dinser, I., Rosen, M.A. (2007) Exergy: Energy, Environment and Sustainable Development. Elsevier, Oxford. [2] Haseli, Y., Dincer, I. and Naterer, G.F. (2008) Optimum Temperatures in a Shell and Tube Condenser with Respect to Exergy. International Journal of Heat and Mass Transfer, 51, 2462-2470.
http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.08.006 [3] Wu, S.-Y., Yuan, X.-F. Li, Y.-R. and Xiao, L. (2007) Exergy Transfer Effectiveness on Heat Exchanger for Finite Pressure Drop. Energy, 32, 2110-2120.
http://dx.doi.org/10.1016/j.energy.2007.04.010 [4] Ujiie, R., Arlitt, R. and Etoh, H. (2006) Application of Computational Fluid Dynamics (CFD) on Ventilation-Cooling Optimization of Electrical Machines. Review Energy Technologies Generation, Transmission and Distribution of Electric and Thermal Energy, Contents 4, 17-22. [5] Shlemmer, E., Schoenauer, J., Farnleitner, E. and Mueller, F. (2004) Transient Electromagnetic and Coolant Flow Investigation of Synchronous Generators Using Numerical Approaches. Proceedings of International Conference on Electrical Machines, ICEM, Cracow, 5-8 September 2004. [6] Hribernik, A. and Fike, M. (2011) Investigating the Malfunction of a Hydro-Generator’s Cooling System. 15th International Research/Expert Conference Trends in the Development of Machinery and Associated Technology, Bosnia and Herzegovina, 12-18 September 2011. [7] Siemens Company (1971) Operation and Maintenance Instructions, R-34. AC Generator and Appurtenances, Khuzestan Water and Power Authority DEZ Project. [8] Madadi, H. and Najmin, A. (2009) Survey on Thermal Stratification of Dez Dam Reservoir Using the Model CE-QUAL. 2nd Conference Exhibition of Environment Engineering, Tehran. [9] Production and Exploitation Company of Dez Dam Power Plant, Exploition and Resistance Unit (2012) Thermal Stratification Information of Dez Lake. [10] Incropera, F.P. and De Wite, D.P. (2002) An Introduction to Heat Transfer. 4th Edition, Johan Wily& Sons, Hoboken. [11] Hamid, A. (2011) Heat Exchangers (Principles, Design, Function). University of Tehran Press, Tehran , 656 p. [12] Holman, J.P. (2008) Heat Transfer. 9th Edition, John Wiley, Hoboken.