纳米流体冲击射流的流动与换热特性研究
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摘要
冲击射流冷却技术因能在局部产生极高的换热系数被认为是解决未来局部高热流密度冷却问题的首选技术之一。但目前应用于射流技术中的传统换热工质的热导率都较低,无法满足高热流密度电子器件冷却的需要,因此提高工质热导率成为强化冲击射流换热的关键。提高液体导热系数的一种有效方式是在液体中添加纳米级的金属、非金属或聚合物固体粒子,即纳米流体。本文尝试将纳米流体技术引入冲击射流强化传热技术,提高射流工质自身的传热性能,以期进一步强化冲击射流冷却系统的传热效率,为提高冲击射流冷却效果提供一种新的手段。主要工作包括以下几个方面：
首先,制备纳米流体并进行悬浮稳定性实验。本文采用两步法,将纳米粒子与基液直接混合,进行一定时间的超声震荡和强烈的机械搅拌,得到不同体积份额的Cu-水纳米流体。悬浮稳定性实验结果表明,此方法制备得到的纳米流体具有较好的稳定性。
其次,研究纳米流体冲击射流的流动和换热特性。建立了测试纳米流体冲击射流冷却性能的实验系统,测试了不同体积份额的Cu-水纳米流体作为换热工质时的换热效果,分析了出口Re数、射流冲击高度、射流冲击角、纳米流体粒子体积份额、粒子粒径以及纳米流体温度对系统换热性能的影响。实验结果表明,纳米粒子的加入增大了基液的冲击射流换热系数,增强了射流换热系统的换热性能。另外,实验结果也表明,由于纳米粒子的小尺寸效应,纳米流体的流动阻力并没有增加,也不会像毫米或微米级粒子易产生磨损、堵塞等不良结果。
再次,综合考虑影响纳米流体冲击射流换热的多种因素,如粒子的微对流和微扩散、流体的流动状态、冲击射流结构参数等,提出了计算悬浮有金属纳米粒子的纳米流体冲击射流换热系数的关联式。关联式的计算结果与实验数据相近,表明关联式正确地描述了纳米流体射流换热过程,可以用来计算纳米流体的冲击射流换热系数。
With the high local heat transfer capacity, jet impingement cooling technique is considered as one of the most powerful cooling solutions for high-heat-flux removal. Although many investigations have been carried out in the area of jet impingement heat transfer over years, the applications in high-density electronic components are limited because of the low thermal conductivity of jet working fluids. The improvement of the thermal properties of jet working fluid may become a trick of augmenting heat transfer performances for the impinging jet system. An effective way of improving the thermal conductivity of fluids is to suspend nanometer solid particles in the carrier fluids, namely nanofluids. The purpose of this paper is to introduce the nanofluids into jet impingement cooling system as the working fluid. It is expected to improve jet impingement performance by the way of improving the thermal conductivity of fluids. The main research contents are the following.
Firstly, nanofluids are prepared and the suspension stability is tested. In this paper, Cu-water nanofluids are prepared by classical two-phase method, in which Cu particles are directly joined into distilled water. In order to obtain the stabilized suspension, mixture is consumingly whisked and vibrated in an ultrasonic vibrator. With this method, several sampled nanofluids with different volume fraction have been prepared. The results of suspension stability tests show that the nanofluids prepared by this method have favorable decentralization property.
Secondly, the heat transfer performance and flow features of nanofluids in jet impingement are studied. An experimental system has been build up to investigate the heat transfer coefficient and the pressure drop of nanofluids in a submerged impinging jet. The effects of such factors as Reynolds number, the distance between the jet outlet and the impingement surface, oblique angle, the volume fraction and dimensions of the suspended nanoparticles are discussed in detail. The experimental results show that the suspended nanoparticles remarkably increase the heat transfer coefficient of the base fluid. In addition, the pressure drop experiments indicate that nanofluids with smack particle volume fraction will not cause significant augmentation in pump power and it is suitable for practical application.
Thirdly, considering both the effects of the suspended nanoparticles and the condition of impinging jet, a new type of the heat transfer correlation for nanofluids in a confined and submerged impinging jet has been proposed The good coincidence between the experimental data and the calculated values show that the correlation correctly describes the energy transport and can be used to predict the impinging jet heat transfer coefficient with nanofluids.
首先,制备纳米流体并进行悬浮稳定性实验。本文采用两步法,将纳米粒子与基液直接混合,进行一定时间的超声震荡和强烈的机械搅拌,得到不同体积份额的Cu-水纳米流体。悬浮稳定性实验结果表明,此方法制备得到的纳米流体具有较好的稳定性。
其次,研究纳米流体冲击射流的流动和换热特性。建立了测试纳米流体冲击射流冷却性能的实验系统,测试了不同体积份额的Cu-水纳米流体作为换热工质时的换热效果,分析了出口Re数、射流冲击高度、射流冲击角、纳米流体粒子体积份额、粒子粒径以及纳米流体温度对系统换热性能的影响。实验结果表明,纳米粒子的加入增大了基液的冲击射流换热系数,增强了射流换热系统的换热性能。另外,实验结果也表明,由于纳米粒子的小尺寸效应,纳米流体的流动阻力并没有增加,也不会像毫米或微米级粒子易产生磨损、堵塞等不良结果。
再次,综合考虑影响纳米流体冲击射流换热的多种因素,如粒子的微对流和微扩散、流体的流动状态、冲击射流结构参数等,提出了计算悬浮有金属纳米粒子的纳米流体冲击射流换热系数的关联式。关联式的计算结果与实验数据相近,表明关联式正确地描述了纳米流体射流换热过程,可以用来计算纳米流体的冲击射流换热系数。
With the high local heat transfer capacity, jet impingement cooling technique is considered as one of the most powerful cooling solutions for high-heat-flux removal. Although many investigations have been carried out in the area of jet impingement heat transfer over years, the applications in high-density electronic components are limited because of the low thermal conductivity of jet working fluids. The improvement of the thermal properties of jet working fluid may become a trick of augmenting heat transfer performances for the impinging jet system. An effective way of improving the thermal conductivity of fluids is to suspend nanometer solid particles in the carrier fluids, namely nanofluids. The purpose of this paper is to introduce the nanofluids into jet impingement cooling system as the working fluid. It is expected to improve jet impingement performance by the way of improving the thermal conductivity of fluids. The main research contents are the following.
Firstly, nanofluids are prepared and the suspension stability is tested. In this paper, Cu-water nanofluids are prepared by classical two-phase method, in which Cu particles are directly joined into distilled water. In order to obtain the stabilized suspension, mixture is consumingly whisked and vibrated in an ultrasonic vibrator. With this method, several sampled nanofluids with different volume fraction have been prepared. The results of suspension stability tests show that the nanofluids prepared by this method have favorable decentralization property.
Secondly, the heat transfer performance and flow features of nanofluids in jet impingement are studied. An experimental system has been build up to investigate the heat transfer coefficient and the pressure drop of nanofluids in a submerged impinging jet. The effects of such factors as Reynolds number, the distance between the jet outlet and the impingement surface, oblique angle, the volume fraction and dimensions of the suspended nanoparticles are discussed in detail. The experimental results show that the suspended nanoparticles remarkably increase the heat transfer coefficient of the base fluid. In addition, the pressure drop experiments indicate that nanofluids with smack particle volume fraction will not cause significant augmentation in pump power and it is suitable for practical application.
Thirdly, considering both the effects of the suspended nanoparticles and the condition of impinging jet, a new type of the heat transfer correlation for nanofluids in a confined and submerged impinging jet has been proposed The good coincidence between the experimental data and the calculated values show that the correlation correctly describes the energy transport and can be used to predict the impinging jet heat transfer coefficient with nanofluids.
引文
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[3]Liu K V, Choi S U S, Kasza K E. Measurements of Pressure Drop and Heat Transfer in Turbulent Pipe Flows of Particulate Slurries. Argonne National Laboratory Report, ANL-88-15,1988
[4]Ahuja A S. Augmentation of Heat Transfer in Laminar Flow of Polystyrene Suspensions. J of Applied Physies,1975,46:3408-3425
[5]Choi S U S. Enhancing Thermal Conductivity of Fluids with Nanoparticles,in:Siginer D A, Wang H P, eds., Developments and Applications of Non-Newtonian Flows, New York:ASME, FED-Vol.231/MD-Vol.66,1995,99-103
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[7]Sparrow E M, Wong T C. Impingement Transfer Coefficients Due to Initially Laminar Slot Jets. International Journal of Heat and Mass Transfer,1975,18:597-605
[8]Viskanta R. Heat Transfer to Impinging isothermal Gas and Flame Jets. Experimental Thermal and Fluid Science,1980,6:111-134
[9]Webb B W, Ma C F. In:Hartnett J P. Advances in Heat Transfer, NewYork:Academic Press,1995,26:105-217
[10]Hoogendoorn C J. The effect of turbulence on heat transfer at a stagnation point, Int. J. Heat Mass Transfer,1977,20:1333-1338
[11]Lytle D, Webb B W. Air jet impingement heat transfer at low nozzle-plate spacing. Int.J.Heat Mass Transfer 1994,37 (12):1687-1697
[12]Ma C F, Zheng Q. Local convective heat transfer from a vertical flat surface to oblique submerged impinging jets of large Prandtl number liquid. Experimental Thermal and Fluid Science,1997,1-10
[13]Popiel C O, Boguslawakj L. Mass or heat transfer in impinging single round jets emitted by a bell-shaped nozzle and shape-ended orifice. Proceedings of the 8th internation Heat Transfer Conferenee,1986,1187-1192
[14]Stevens J, Pan Y, Webb B W. Effect of nozzle configuration on transport in the stagation zone of axisymmetric, impinging free-surface liquid jets-I, Turbulent flow structure. J. Heat Transfer,1992,114:874-879
[15]谢华清,陈立飞.纳米流体对流换热系数增大机理.物理学报,2009,58(4)：2513-2517
[16]Chin Y L, Suresh V G. Prandtl-number effects and generalized correlation for confined and submerged jet impingement. Int. J. Heat Mass Transfer,2001,44:3471-3480
[17]Agabour L, Lienhard J H. Wall roughness effects on stagnation-point heat transfer beneath an impinging liquid jet, Journal of heat transfer,1994,116
[18]王宝官,郑际睿.多排圆孔射流的冲击冷却实验研究.工程热物理学报,1982,3(3)：3
[19]吴建国,池桂兴.喷流换热的最佳结构参数.冶金能源,1982,1：47.50
[20]Masuda H, Ebata A, Teramae K, Hishinuma N. Alternation of Thermal Conduetivity and Viscosity of Liquid by Dispersing Ultla-fine Partieles (Dispersion of γ-Al2O3, SiO2 and TiO2 Ultra-Fine Particles). Netsu Bussei (Japan),1993,4:227-233
[21]Eastman J A, Choi S U S, Li S, Thompson L J, Lee S. Enhanced Thermal Conductivity Through the Development of Nanofluids. in:Komarneni S, Parker J C, Wollenberger HJ, eds, Nanophase and Nanocomposite Materials, Pittsburgh:MRS,1997,3-11
[22]Lee S, Choi S U S, Li S, Eastman J A. Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles. J. of Heat Transfer,1999,121:280-289
[23]Maxwell J C. Electricity and Magnetism, Part Ⅱ,3nd Edition, London:Clarendon press, 1904
[24]Keblinski P, PhillPot S R, Choi S U S, Easnnan J A. Mechanisms of Heat Flow in Suspensions of Nano-Sized Particles(nanofluids). Int J Heat Mass Transfer,2002,45(4): 855-863
[25]Pak B C, Cho Y I. Hydrodynamic and Heat Transfer Study of Dispersed Fluids with Submicron Metallic Oxide Partieles. Experimental Heat Transfer,1998,11(2):151-170
[26]Heris S Z, Esfahany M N, Etemad S G Experimental investigation of convective heat transfer of Al2O3/water nanofluid in circular tube. International Journal of Heat and Fluid Flow,2007,28:203-210.
[27]李强.纳米流体强化传热机理研究[硕士论文].南京：南京理工大学,2004
[28]戴闻亭,李俊明,王补宣,等.细圆管内氧化铜颗粒悬浮液流动与对流换热的实验研究.工业加热,2002,5：1-4
[29]王补宣,李宏,彭晓峰.吸附作用在纳米颗粒悬浮液换热强化中的试验与机理研究.工程热物理学报,2003,24(4)：664-666
[30]Wang B X, Zhou L P, Peng X F. A Fractal model for Predieting the Effective Thermal Conduetivity of Liquid with Suspension of Nanopartieles. Int J Heat Mass Transfer,2003, 46:2665-2672
[31]周乐平,王补宣.颗粒尺寸与表面吸附对低浓度非金属纳米颗粒悬浮液有效导热系数的影响.自然科学进展,2003,13(4)：426-429
[32]Cong T N, Nicolas G, Guillaume P, etc. An experimental study of a confined and submerged impinging jet heat transfer using Al2O3-water nanofluid. International Journal of Thermal Sciences,2009,48:401-411
[33]戴剑侠.微电子芯片冷却的实验研究和数值模拟[硕士论文].镇江：江苏大学,2007
[34]严畅.带出流及横流通道内斜冲击换热研究[硕士论文].西安：西北工业大学,2007
[35]Wang X, et al. Thermal Conductivity of Nanoparticle-Fluid Mixture. J. Thermophys. Heat Transfer.1999,13:474-479
[36]李强,宣益民.纳米流体强化导热系数机理初步分析.热能动力工程,2002,17(102)：568-571
[37]Xuan Y M, Li Q, Hu W F. Aggregation Structure and Thermal Conductivity of Nanofluids, AICHE J,2003,49(4):1038-1043
[38]吴轩,宣益民.基于晶格-Boltzmann方法的纳米流体流动和传热模型.工程热物理学报,2003,23(2)：206-208
[39]Yu W, Choi S U S. The Role of Interfacial Layers in the Enhanced Thermal Conductivity of Nanofluids:A Renovated Maxwell Model. Journal of Nanoparticle Research,2003, 5:167-171
[40]Xue L, Keblinski P, Phillpot S R, et.al. Effect of liquid layering at the liquid-solid interface on thermal transport, Heat Mass Transfer,2004,47:77-84
[41]李晓贺,丰平,贺跃辉,等.纳米粉末在水中分散性的探讨.纳米科技,2007(1)：17-21
[42]Li Q, Xuan Y M. Experimental Investigation on Transport Properties of Nanofluids.In: Wang B X. Heat Transfer Science and Technology 2000. Beijing:High Education Press, 2000,757-762
[43]Xuan Y M, Li Q. Investigation on Convective Heat Transfer and Flow Features of Nanofluids. Journal of Heat Transfer,2003,125:151-155
[44]李相银,王海林,王志兴,等.大学物理实验.北京：高等教育出版社,2004,21.23
[45]钱吉裕,平丽浩,徐德好,等.冲击角对射流强化换热影响的数值研究.工程热物理学报,2007,28：65-68.
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[47]Ma C F. Liquid jet impingement heat transfer with or without boiling. The 10th National Heat Transfer Conference of Italy, Genoa, Italy:Academic Press,1992
[48]Roy G, Nguyen C T, Lajoie P R. Numerical investigation of laminar flow heat transfer in a radial flow cooling system with use of nanofluids. Super Lattices Microstructure,2004, 35:497-511
[49]周力行.湍流气粒两相流动和燃烧的理论与数值模拟.北京：科学出版社,1994,153-200
[2]Maxwell J C. A Treatise on electricity and magnetism,2nd Edition London:Clarendon press,1881
[3]Liu K V, Choi S U S, Kasza K E. Measurements of Pressure Drop and Heat Transfer in Turbulent Pipe Flows of Particulate Slurries. Argonne National Laboratory Report, ANL-88-15,1988
[4]Ahuja A S. Augmentation of Heat Transfer in Laminar Flow of Polystyrene Suspensions. J of Applied Physies,1975,46:3408-3425
[5]Choi S U S. Enhancing Thermal Conductivity of Fluids with Nanoparticles,in:Siginer D A, Wang H P, eds., Developments and Applications of Non-Newtonian Flows, New York:ASME, FED-Vol.231/MD-Vol.66,1995,99-103
[6]Bradbury L J S. The Structure of a Self-Preserving Turbulent Plane Jet. Journal of Fluid Mechanics,1965,23:31-64
[7]Sparrow E M, Wong T C. Impingement Transfer Coefficients Due to Initially Laminar Slot Jets. International Journal of Heat and Mass Transfer,1975,18:597-605
[8]Viskanta R. Heat Transfer to Impinging isothermal Gas and Flame Jets. Experimental Thermal and Fluid Science,1980,6:111-134
[9]Webb B W, Ma C F. In:Hartnett J P. Advances in Heat Transfer, NewYork:Academic Press,1995,26:105-217
[10]Hoogendoorn C J. The effect of turbulence on heat transfer at a stagnation point, Int. J. Heat Mass Transfer,1977,20:1333-1338
[11]Lytle D, Webb B W. Air jet impingement heat transfer at low nozzle-plate spacing. Int.J.Heat Mass Transfer 1994,37 (12):1687-1697
[12]Ma C F, Zheng Q. Local convective heat transfer from a vertical flat surface to oblique submerged impinging jets of large Prandtl number liquid. Experimental Thermal and Fluid Science,1997,1-10
[13]Popiel C O, Boguslawakj L. Mass or heat transfer in impinging single round jets emitted by a bell-shaped nozzle and shape-ended orifice. Proceedings of the 8th internation Heat Transfer Conferenee,1986,1187-1192
[14]Stevens J, Pan Y, Webb B W. Effect of nozzle configuration on transport in the stagation zone of axisymmetric, impinging free-surface liquid jets-I, Turbulent flow structure. J. Heat Transfer,1992,114:874-879
[15]谢华清,陈立飞.纳米流体对流换热系数增大机理.物理学报,2009,58(4)：2513-2517
[16]Chin Y L, Suresh V G. Prandtl-number effects and generalized correlation for confined and submerged jet impingement. Int. J. Heat Mass Transfer,2001,44:3471-3480
[17]Agabour L, Lienhard J H. Wall roughness effects on stagnation-point heat transfer beneath an impinging liquid jet, Journal of heat transfer,1994,116
[18]王宝官,郑际睿.多排圆孔射流的冲击冷却实验研究.工程热物理学报,1982,3(3)：3
[19]吴建国,池桂兴.喷流换热的最佳结构参数.冶金能源,1982,1：47.50
[20]Masuda H, Ebata A, Teramae K, Hishinuma N. Alternation of Thermal Conduetivity and Viscosity of Liquid by Dispersing Ultla-fine Partieles (Dispersion of γ-Al2O3, SiO2 and TiO2 Ultra-Fine Particles). Netsu Bussei (Japan),1993,4:227-233
[21]Eastman J A, Choi S U S, Li S, Thompson L J, Lee S. Enhanced Thermal Conductivity Through the Development of Nanofluids. in:Komarneni S, Parker J C, Wollenberger HJ, eds, Nanophase and Nanocomposite Materials, Pittsburgh:MRS,1997,3-11
[22]Lee S, Choi S U S, Li S, Eastman J A. Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles. J. of Heat Transfer,1999,121:280-289
[23]Maxwell J C. Electricity and Magnetism, Part Ⅱ,3nd Edition, London:Clarendon press, 1904
[24]Keblinski P, PhillPot S R, Choi S U S, Easnnan J A. Mechanisms of Heat Flow in Suspensions of Nano-Sized Particles(nanofluids). Int J Heat Mass Transfer,2002,45(4): 855-863
[25]Pak B C, Cho Y I. Hydrodynamic and Heat Transfer Study of Dispersed Fluids with Submicron Metallic Oxide Partieles. Experimental Heat Transfer,1998,11(2):151-170
[26]Heris S Z, Esfahany M N, Etemad S G Experimental investigation of convective heat transfer of Al2O3/water nanofluid in circular tube. International Journal of Heat and Fluid Flow,2007,28:203-210.
[27]李强.纳米流体强化传热机理研究[硕士论文].南京：南京理工大学,2004
[28]戴闻亭,李俊明,王补宣,等.细圆管内氧化铜颗粒悬浮液流动与对流换热的实验研究.工业加热,2002,5：1-4
[29]王补宣,李宏,彭晓峰.吸附作用在纳米颗粒悬浮液换热强化中的试验与机理研究.工程热物理学报,2003,24(4)：664-666
[30]Wang B X, Zhou L P, Peng X F. A Fractal model for Predieting the Effective Thermal Conduetivity of Liquid with Suspension of Nanopartieles. Int J Heat Mass Transfer,2003, 46:2665-2672
[31]周乐平,王补宣.颗粒尺寸与表面吸附对低浓度非金属纳米颗粒悬浮液有效导热系数的影响.自然科学进展,2003,13(4)：426-429
[32]Cong T N, Nicolas G, Guillaume P, etc. An experimental study of a confined and submerged impinging jet heat transfer using Al2O3-water nanofluid. International Journal of Thermal Sciences,2009,48:401-411
[33]戴剑侠.微电子芯片冷却的实验研究和数值模拟[硕士论文].镇江：江苏大学,2007
[34]严畅.带出流及横流通道内斜冲击换热研究[硕士论文].西安：西北工业大学,2007
[35]Wang X, et al. Thermal Conductivity of Nanoparticle-Fluid Mixture. J. Thermophys. Heat Transfer.1999,13:474-479
[36]李强,宣益民.纳米流体强化导热系数机理初步分析.热能动力工程,2002,17(102)：568-571
[37]Xuan Y M, Li Q, Hu W F. Aggregation Structure and Thermal Conductivity of Nanofluids, AICHE J,2003,49(4):1038-1043
[38]吴轩,宣益民.基于晶格-Boltzmann方法的纳米流体流动和传热模型.工程热物理学报,2003,23(2)：206-208
[39]Yu W, Choi S U S. The Role of Interfacial Layers in the Enhanced Thermal Conductivity of Nanofluids:A Renovated Maxwell Model. Journal of Nanoparticle Research,2003, 5:167-171
[40]Xue L, Keblinski P, Phillpot S R, et.al. Effect of liquid layering at the liquid-solid interface on thermal transport, Heat Mass Transfer,2004,47:77-84
[41]李晓贺,丰平,贺跃辉,等.纳米粉末在水中分散性的探讨.纳米科技,2007(1)：17-21
[42]Li Q, Xuan Y M. Experimental Investigation on Transport Properties of Nanofluids.In: Wang B X. Heat Transfer Science and Technology 2000. Beijing:High Education Press, 2000,757-762
[43]Xuan Y M, Li Q. Investigation on Convective Heat Transfer and Flow Features of Nanofluids. Journal of Heat Transfer,2003,125:151-155
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