转速对三分仓回转式空气预热器热力性能的影响
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摘要
基于有限差分法,将三分仓回转式空气预热器沿旋转方向周向展开,在蓄热元件单元和流体之间划分网格,通过建立每一有限单元内流体和蓄热单元间热平衡方程,利用改良的高斯塞德尔迭代方法计算得到蓄热元件的流体温度场分布。以某600 MW机组三分仓回转式空气预热器为例,详细分析了转速变化时,流体和金属温度场分布、ABS(硫酸氢铵)沉积区域等的变化趋势和规律。研究结果显示:(1)蓄热元件温度随转动角度分布的非线性特征,随转速降低而增加,可以用非稳定换热影响因子Π表征,各个分仓的Π值不同;(2)不同转速下,蓄热元件温度分布曲线,在加热和冷却周期内,各存在一个相对稳定的平衡位置;(3)三分仓空气预热器出口一次风、二次风平均温度随转速的变化趋势,与转子旋向和各空气分仓角度有关。
Based on finite difference method,the tri-sector rotary regenerative air-preheater was spread along the rotor's circular side and mesh between the matrix elements and the fluids was generated.Then the matrix and fluid temperature fields were obtained according to the energy balance equation and using an improved Gauss-Sidel arithmetic.For a600 MW unit tri-sector rotary regenerative air-preheater,a detailed analysis was carried out for the temperature field distributions of the fluid and metal and ammonium bisulfate( ABS) deposition area with different the rotational speeds.The results showed that,1) The nonlinear characteristics of matrix temperature distribution along with the rotation angle increases while the rotational speed decreases,which can be described by the unsteady heat transfer correction factor Π,and for each sector the value of factor Π is different.2) There exist relatively stable balance positions during both heating and cooling periods,which are the intersection points of matrix temperature profile curves with different rotational speeds.3) The effect on average outlet temperatures of primary and secondary air channels from rotor rotational speed depends on the rotor rotation direction and the sector angle division.
Based on finite difference method,the tri-sector rotary regenerative air-preheater was spread along the rotor's circular side and mesh between the matrix elements and the fluids was generated.Then the matrix and fluid temperature fields were obtained according to the energy balance equation and using an improved Gauss-Sidel arithmetic.For a600 MW unit tri-sector rotary regenerative air-preheater,a detailed analysis was carried out for the temperature field distributions of the fluid and metal and ammonium bisulfate( ABS) deposition area with different the rotational speeds.The results showed that,1) The nonlinear characteristics of matrix temperature distribution along with the rotation angle increases while the rotational speed decreases,which can be described by the unsteady heat transfer correction factor Π,and for each sector the value of factor Π is different.2) There exist relatively stable balance positions during both heating and cooling periods,which are the intersection points of matrix temperature profile curves with different rotational speeds.3) The effect on average outlet temperatures of primary and secondary air channels from rotor rotational speed depends on the rotor rotation direction and the sector angle division.
引文
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[7]Sandira Eljan.Influence of rotational speed upon heat transfer in a rotary regenerative heat exchanger[C].12th International Research/Expert Conference“Trends in the Development of Machinery and Associated Technology”TMT 2008,Istanbul,Turkey,2008.
[8]张启.回转式空气预热器温度场数值计算及漏风研究[D].上海:上海交通大学,2009.ZHANG Qi.Numerical calculation of air preheater and study on air leakage[D].Shanghai:Shanghai Jiaotong University,2009.
[2]T.Skiepko.Effect of parameter values on gas and matrix temperature fields in rotary heat exchangers[J].International Journal of Heat and Mass Transfer,1989,32(8):1443–1472.
[3]Chung-Hsiung Li.A numerical finite difference method for performance evaluation of periodic-flow heat exchanger[J].Journal of Heat Transfer,1983,105(3):611-617.
[4]汪军,徐治皋.回转式空气预热器变速优化运行探讨[J].锅炉技术,1998,06:16-19+25.WANG Jun,XU Zhi-gao.A Study on optimal operation of regenerative air preheater at variable rotative velocity[J].Boiler Technology,1998,06:16-19+25.
[5]冷伟,陈曦,于翔,等.回转式空气预热器非稳定换热的分析[J].动力工程,2006,26(3):412-416.LENG Wei,CHENG Xi,YU Xiang,et al.Analysis of unsteady heat exchange of rotary air preheaters[J].Journal of Power Engineering,2006,26(3):412-416.
[6]O.Buyukalaca,T.Yilmaz.Influence of rotational speed of effectiveness of rotary-type heat exchanger[J].Heat and Mass Transfer,2002,38(4-5):441-447.
[7]Sandira Eljan.Influence of rotational speed upon heat transfer in a rotary regenerative heat exchanger[C].12th International Research/Expert Conference“Trends in the Development of Machinery and Associated Technology”TMT 2008,Istanbul,Turkey,2008.
[8]张启.回转式空气预热器温度场数值计算及漏风研究[D].上海:上海交通大学,2009.ZHANG Qi.Numerical calculation of air preheater and study on air leakage[D].Shanghai:Shanghai Jiaotong University,2009.