現有2 MW級風力渦輪機在台灣熱帶天候運轉有過熱問題，因此本研究使用FLUENT軟體模擬此類風機的機艙與發電機熱流場，並採用可行之散熱改善方法以降低機艙與發電機的溫度分布，目的為建立出風機散熱改善之參考依據。本文參考實際風機建立簡化之幾何外型，建模包含鼻錐、發電機環狀區域、機艙、冷卻風管等幾何結構，其餘較小的次組件則加以省略。
本文先分析風機機艙（含發電機）熱流場分布，並與實際運轉溫度做比較，由此模擬驗證得知高溫集中於發電機環狀區域，其中最大溫度產生於發電機熱源。受到現有冷卻風管的氣流影響，發電機上部環狀及鼻錐流體區域流動較明顯，其餘區域流動則較為緩慢，此流動分布不均導致機艙（含發電機）溫度無法有效冷卻。
依據數值模擬解，本研究建議三種改善冷卻散熱方法。第一種是提升現有冷卻風管入口流速；第二種是在發電機下部環狀區域另外加裝一個送風導管，第三種則是在現有冷卻風管延伸一個分支管進入發電機下部環狀區域。模擬分析分別比較溫度、速度、壓力分布和各區域流場型態來評估三種散熱方法。第一種方案提升入口冷卻流速可降低發電機上部環狀區域溫度和提昇此區域流速，並且導致整體壓力上升，其餘區域溫度降幅有限。第二種方法單獨加裝冷卻導管，導致發電機上部環狀區域溫度增加，並引入冷卻氣流進入發電機下部區域，有效提升此區域流動分布。 第三種方法將冷卻風管延伸分支管，若提升入口流速至12 m/s，整體風機內溫度分布能有效降低，並且提升機艙與發電機的流動，這種方式效果最佳，建議優先考慮安裝。

Current 2 MW wind turbine encounters an overheat problem in Taiwan’s tropic weather, thus this paper simulates the thermo-fluid field inside nacelle and generator of such wind turbine with FLUENT software and adopts feasible cooling solutions to reduce temperature inside nacelle and generator. The simplified geometry use in simulation is base on a realistic wind turbine, including nose, generator, nacelle and cooling pipe, others smaller sub-components are neglected.
The temperature of nacelle including generator is analyzed first and compared with realistic operating temperature of wind turbine. Based on this validation of simulation, the high temperature area is identified on the region of annular generator with maximum temperature located in the heat source inside the generator. Due to the influence of air flow from existing cooling pipe, large flow motion inside the annular upper region of generator and nose region is predicted, while in the rest region the flow is relatively slow, such uneven flow distribution leads to ineffective cooling for nacelle including generator.
Based on simulation results, three improving cooling options are suggested. First option is to increase inlet velocity of cooling pipe. Second approach is to install another cooling pipe into the annular bottom region of generator. Third option is to extend a branch pipe from the existing cooling pipe into annular bottom region of generator. The result is compare contour of temperature, velocity, pressure, and flow field in wind turbine. Increasing cooling velocity can reduce the temperature and enhance flow of annular upper region of generator, which increase the pressure too, but the temperature drop in other flow region is limited. Installing cooling duct alone can lead to temperature increased in annular upper region of generator, but it can effectively improve flow in annular bottom region of generator. Extended branch pipe from cooling pipe and enhanced velocity to 12 m/s can reduce temperature and increased flow motion inside nacelle and generator. This option is most effective in cooling and should be adopted.

Andrew, D. M., Gary, R. B., Thomas, M., Peter, A. D., inventors; General Electric Company, assignee; (2010) Multiple pass axial cooled generator, U. S. patent No. 0289349, Nov. 18.
ANSYS, (2009) ANSYS FLUENT theory guide, ANSYS, Inc.
Barletta, A., Rossi di Schio, E., Zanchini, E., (2003) Combined forced and free flow in a vertical rectangular duct with prescribed wall heat flux, Inter. J. Heat and Fluid Flow, 24:874-887.
Bharat, S. B., inventors; General Electric Company, assignee; (2010) System for heating and cooling wind turbine components. U. S. patent No. 0061853, Mar. 11.
Bharat, S. B., Gary, R. B., Aniruddha, D. G., Patrick, L. J., Charles, G. B. JR., Emil, D. J., Jivtesh, G., inventors; Bedford, Grant Richard London Patent Operation GE International Inc., Representative; (2007) Wind turbine generators having wind assisted cooling systems and cooling methods, EP 1837519, Sep. 26.
Dehghan, A. A., Behnia, M., (1996) Numerical investigation of natural convection in a vertical slot with two heat source, Inter. J. Heat and Fluid Flow, 17:472-482.
Global Wind Energy Council http://www.gwec.net/
James, K., Pyung, H., (2011) Optimizing heat sink geometry for electric vehicle BLDC motor using CFD, Proc. the 2011 Mechanical Engineering Conference on Sustainable Research and Innovation, Kenya, May 5-6.
Khaled, A., Christian, M., Peter, J. E., (2011) 2D and 3D numerical simulation of the wind-rotor/nacelle interaction in an atmospheric boundary layer, J. Wind Eng. Ind. Aerodyn., 99:833-844.
Kim, S. E., Choudhury, D., Patel, B., (1995) A near-wall treatment using wall function Sensitized to pressure gradient, ASME FED, 217, Separated and Complex Flows.
Krishnamoorthi, S., Anand, B., Ravi, K., Srikanth, N., Grevsen, J. K., Jesper, N., Tietze, P. T., inventors; Hoffmann, D. A., Agent; (2010) Wind turbine nacelle with cooler top, WO 085963, 2010 Aug. 5.
Launder, B. E., Spalding, D. B., (1972) Lectures in Mathematical Models of Turbulence, Academic Press.
NORDEX, (2006) NORDEX technical description N90/2500, NORDEX Energy Gmbh, Germany, Sep. 20.
NORDEX, (2009) NORDEX technical description N100/2500, NORDEX Energy Gmbh, Germany, June 22.
Palyvos, J. A., (2008) A survey of wind convection coefficient correlations for building envelope energy systems’ modeling, Applied Thermal Eng. 28:801-808.
Parker Hannifin Precision cooling systems, (2011) Cooling high performance wind turbine systems with two phase evaporative cooling, Parker Hannifin Corporation.
Pasteuning, J. W., Versteegh, C. J. A., inventors; Zonneveld, H. J., agents; (2010) Wind turbine comprising a cooling circuit, W O patent No. 069954, June 24.
Radhakrishnan, T. V., Verma, A. K., Balaji, C., Venkateshan, S. P., (2007) An experimental and numerical investigation of mixed convection from a heat generating element in a ventilated cavity, Experimental Thermal and Fluid Science, 32:502-520.
Raji, A., Hasnaoui, M., Bahlaoui, A., (2008) Numerical study of natural convection dominated heat transfer in a ventilated cavity: Case of forced flow playing simultaneous assisting and opposing roles, Inter. J. Heat and Fluid Flow, 29:1174-1181.
Saeidi, S. M., Khodadadi, J. M., (2006) Forced convection in a square cavity with inlet and outlet ports, Inter. J. Heat Mass Transfer, 49:1896-1906.
Saury, D., Rouger, N., Djanna, F., Penot, F., (2011) Natural convection in an air-filled cavity: Experimental results at large Rayleigh numbers, Inter. Communications Heat Mass Transfer, 38:679-687.
Shih, T. H., Liou, W. W., Shabbir, A., Yang, Z., Zhu, J., (1995) A new k-ε eddy-viscosity model for high Reynolds number turbulent flows-model development and validation, Computer Fluids, 24(3):227-238.
Smaili, A., Masson, C., Taleb, S. R., Lamarche, L., (2006) Numerical study of thermal behavior of a wind turbine nacelle operating in a Nordic climate, Numerical Heat Transfer, Part B, 50:121-141.
STX Wind power B. V. http://www.stxwind.com/nl/products/43-stx72
Sugavanam, R., Ortega, A., Choi, C. Y., (1995) A numerical investigation of conjugate heat transfer from a flush heat source on a conductive board in a laminar channel flow, Inter. J. Heat Mass Transfer, 38(16) :2969-2984.
Trias, F. X., Gorobets, A., Soria, M., Oliva, A., (2010) Direct numerical simulation of a differertially heated cavity of aspect ratio 4 with Rayleigh numbers up to 1011 - Part I: Numerical methods and time-averaged flow, Inter. J. Heat Mass Transfer, 53:665-673.
VDL KLIMA http://www.vdlklima.com/
Versteegh, C. J. A., (2004) Design of the Zephyros Z72 wind turbine with emphasis on the direct drive PM generator, Nordic Workshop on Power and Industrial, NTNU Trondheim Norway, June 14-16.
Vestas http://v112.vestas.com/
Yakhot, V., Orszag, S. A., (1986) Renormalization group analysis of turbulence: I. basic theory, J. Scientific Computing, 1(1):1-51.