大型燃煤锅炉内辐射熵产及辐射?试验研究
|
摘要
为了研究燃煤炉膛内辐射传热效率,达到节约能源,降低污染物排放的目的,提出一种大型炉膛内辐射熵产及辐射火用的试验测量方法,并应用于一台200 MW发电机组的670 t/h燃煤锅炉上。通过在锅炉上安装CCD相机获取炉内辐射图像,基于辐射反问题求解方法重建炉膛底部、燃烧器区域及炉膛出口3个截面的炉内温度分布及辐射特性,进而获得炉内煤粉燃烧介质和水冷壁的辐射熵产、辐射熵产数及辐射火用,并分析了炉内温度分布的均匀性及壁面辐射热流对燃煤锅炉内辐射熵产和辐射火用的影响。结果表明,随着燃煤锅炉内温度分布均方差增大,煤粉燃烧介质吸收、发射及散射过程的不可逆性增大,辐射传热效率越低,燃烧介质产生的辐射熵产从419 W/K增至629 W/K,辐射熵产数从0.048增至0.067;随着水冷壁面热流增大,水冷壁面辐射传热过程的不可逆性增大,辐射传热效率降低,水冷壁产生的辐射熵产从1.566 k W/K增至4.575 kW/K,辐射熵产数从0.258增大至0.346;在燃煤锅炉的燃烧器区域,由于燃烧温度相对最高,其辐射换热过程相对最剧烈,有用功相对最多,因而辐射火用相对最大;而对于温度相对最低的炉膛出口区域,其辐射换热过程相对最弱,有用功相对最少,因而辐射火用相对最小。由此可见,对于实际炉膛而言,提高炉膛内温度场的均匀性,尤其是提高炉膛燃烧器区域内温度场的均匀性,对于提高燃煤炉膛辐射传热效率具有重要的意义。
In order to study the efficiency of radiative heat transfer in the coal-fired furnace,and achieve the aim of saving energy and reducing pollutant emissions,this paper presented an experimental measurement method for radiation entropy generation and radiation exergy in large-scale furnaces.The method was applied in a 670 t/h coal-fired boiler of a 200 MW generator unit.The radiative images in the furnace were captured by CCD cameras installed on the boiler.The temperature distributions and radiative properties in three sections of the furnace were reconstructed by the solution of inverse radiation problem.And then,experimental results of radiative entropy generation,dimensionless radiative entropy generation,and radiative exergy of pulverized coal combustion medium and water cooling wall in the furnace were obtained.The effects of standard deviation of temperature distribution in furnace and radiative heat flux of wall on radiative entropy generation and radiative exergy were analyzed.The results show that with the increase of standard deviation of temperature distribution in coal-fired boilers,the irreversibility of absorption,emission and scattering process of pulverized coal combustion medium increase gradually,and the radiation heat transfer efficiency decreases gradually,and generated by combustion medium,the radiative entropy generation increases from 419 W/K to 629 W/K and the dimensionless radiative entropy generation increases from 0.048 to 0.067.With the increase of heat flow on water-cooled wall,the irreversibility of radiation heat transfer process on water-cooled wall increases gradually,and the radiative heat transfer efficiency decreases gradually,so the radiative entropy generation generated by the water cooling wall increases from1. 566 k W/K to 4. 575 k W/K and the dimensionless radiative entropy generation increases from 0.258 to 0.346.In the burner area of the furnace,due to the relatively highest combustion temperature,the radiation heat exchange process is the most intense,leading to the most available work,so the radiative exergy is the largest.In the furnace exit area where the temperature is relatively lowest,the radiation heat transfer process is relatively weakest,and the available work is relatively least,so the radiation exergy is relatively minimal.It can be seen that for the practical furnace,improving the uniformity of the temperature field in the furnace,especially increasing the uniformity of the temperature field in the furnace burner region,is of great significance for improving the radiation heat transfer efficiency of the coal-fired furnace.
In order to study the efficiency of radiative heat transfer in the coal-fired furnace,and achieve the aim of saving energy and reducing pollutant emissions,this paper presented an experimental measurement method for radiation entropy generation and radiation exergy in large-scale furnaces.The method was applied in a 670 t/h coal-fired boiler of a 200 MW generator unit.The radiative images in the furnace were captured by CCD cameras installed on the boiler.The temperature distributions and radiative properties in three sections of the furnace were reconstructed by the solution of inverse radiation problem.And then,experimental results of radiative entropy generation,dimensionless radiative entropy generation,and radiative exergy of pulverized coal combustion medium and water cooling wall in the furnace were obtained.The effects of standard deviation of temperature distribution in furnace and radiative heat flux of wall on radiative entropy generation and radiative exergy were analyzed.The results show that with the increase of standard deviation of temperature distribution in coal-fired boilers,the irreversibility of absorption,emission and scattering process of pulverized coal combustion medium increase gradually,and the radiation heat transfer efficiency decreases gradually,and generated by combustion medium,the radiative entropy generation increases from 419 W/K to 629 W/K and the dimensionless radiative entropy generation increases from 0.048 to 0.067.With the increase of heat flow on water-cooled wall,the irreversibility of radiation heat transfer process on water-cooled wall increases gradually,and the radiative heat transfer efficiency decreases gradually,so the radiative entropy generation generated by the water cooling wall increases from1. 566 k W/K to 4. 575 k W/K and the dimensionless radiative entropy generation increases from 0.258 to 0.346.In the burner area of the furnace,due to the relatively highest combustion temperature,the radiation heat exchange process is the most intense,leading to the most available work,so the radiative exergy is the largest.In the furnace exit area where the temperature is relatively lowest,the radiation heat transfer process is relatively weakest,and the available work is relatively least,so the radiation exergy is relatively minimal.It can be seen that for the practical furnace,improving the uniformity of the temperature field in the furnace,especially increasing the uniformity of the temperature field in the furnace burner region,is of great significance for improving the radiation heat transfer efficiency of the coal-fired furnace.
引文
[1]韩巍,金红光,林汝谋.化石燃料化学能释放的新认识[J].自然科学进展,2005,15(1):84-89.
[2] CALDAS M,SEMIAO V. Entropy generation through radiative transfer in participating media:Analysis and numerical computation[J].Journal of Quantitative Spectroscopy&Radiative Transfer,2005,96(3):423-437.
[3] LIU L H,CHU S X.On the entropy generation formula of radiation heat transfer processes[J].Journal of Heat Transfer:Transactions of the ASME,2006,128(5):504-506.
[4] ZHANG Z N,LI Z C,LOU C.Numerical analysis of radiative entropy generation in a parallel plate system with non-uniform temperature distribution participation medium[J]. Journal of Quantitative Spectroscopy&Radiative Transfer,2019,225:319-326.
[5] CANDAU Y.On the exergy of radiation[J].Solar Energy,2003,75(3):241-247.
[6] LIU L H,CHU S X.Radiative exergy transfer equation thermophys[J].Journal of Heat Transfer:Transactions of the ASME,2009,83:819-822.
[7]楚双霞,刘林华.甲烷-空气扩散燃烧过程熵产分析[J].中国电机工程学报,2008,28(29):34-40.CHU Shuangxia,LIU Linhua. Analysis of entropy generation during methane-air diffusion combustion processes[J].Proceedings of the CSEE,2008,28(29):34-40.
[8] MAKHANLALL D,MUNDA J L,JIANG P.Radiation energy devaluation in diffusion combusting flows of natural gas[J]. Energy,2013,61:657-663.
[9] RAJABI V,AMANI E. A computational study of swirl number effects on entropy generation in gas turbine combustors[J]. Heat Transfer Engineering,2019,40(3/4):346-361.
[10] SCIACOVELLI A,VERDA V,SCIUBBA E. Entropy generation analysis as a design tool-A review[J]. Renewable and Sustainable Energy Reviews,2015,43:1167-1181.
[11]程雪涛,梁新刚.熵产最小化理论在传热和热功转换优化中的应用探讨[J].物理学报,2016,65(18):234-240.CHENG Xuetao,LIANG Xingang.Discussion on the application of entropy generation minimization to the optimizations of heat transfer and heat-work conversion[J].Acta Phys.Sin.,2016,65(18):234-240.
[12]娄春,周怀春,姜志伟,等.炉膛内断面温度场与辐射参数同时重建实验研究[J].中国电机工程学报,2006,26(14):98-103.LOU Chun,ZHOU Huaichun,JIANG Zhiwei,et al. Experimental investigation on simultaneous reconstruction of cross-section temperature distribution and radiation properties in a boiler furnace[J].Proceedings of the CSEE,2006,26(14):98-103.
[13]娄春,周怀春,朱国良,等.煤粉炉内颗粒辐射特性的检测与分析[J].工程热物理学报,2007,28(S2):217-220.LOU Chun,ZHOU Huaichun,ZHU Guoliang,et al. Analysis and measurement of radiative properties of particulate medium in a large-scale coal-fired boiler of power plant[J].Journal of Engineering Thermophysics,2007,28(S2):217-220.
[14]娄春.煤粉炉内三维温度场及颗粒辐射特性重建[D].武汉:华中科技大学,2007:136-140.
[15]楚双霞.非相干辐射传递过程的热力学分析[D].哈尔滨:哈尔滨工业大学,2009:57-67.
[2] CALDAS M,SEMIAO V. Entropy generation through radiative transfer in participating media:Analysis and numerical computation[J].Journal of Quantitative Spectroscopy&Radiative Transfer,2005,96(3):423-437.
[3] LIU L H,CHU S X.On the entropy generation formula of radiation heat transfer processes[J].Journal of Heat Transfer:Transactions of the ASME,2006,128(5):504-506.
[4] ZHANG Z N,LI Z C,LOU C.Numerical analysis of radiative entropy generation in a parallel plate system with non-uniform temperature distribution participation medium[J]. Journal of Quantitative Spectroscopy&Radiative Transfer,2019,225:319-326.
[5] CANDAU Y.On the exergy of radiation[J].Solar Energy,2003,75(3):241-247.
[6] LIU L H,CHU S X.Radiative exergy transfer equation thermophys[J].Journal of Heat Transfer:Transactions of the ASME,2009,83:819-822.
[7]楚双霞,刘林华.甲烷-空气扩散燃烧过程熵产分析[J].中国电机工程学报,2008,28(29):34-40.CHU Shuangxia,LIU Linhua. Analysis of entropy generation during methane-air diffusion combustion processes[J].Proceedings of the CSEE,2008,28(29):34-40.
[8] MAKHANLALL D,MUNDA J L,JIANG P.Radiation energy devaluation in diffusion combusting flows of natural gas[J]. Energy,2013,61:657-663.
[9] RAJABI V,AMANI E. A computational study of swirl number effects on entropy generation in gas turbine combustors[J]. Heat Transfer Engineering,2019,40(3/4):346-361.
[10] SCIACOVELLI A,VERDA V,SCIUBBA E. Entropy generation analysis as a design tool-A review[J]. Renewable and Sustainable Energy Reviews,2015,43:1167-1181.
[11]程雪涛,梁新刚.熵产最小化理论在传热和热功转换优化中的应用探讨[J].物理学报,2016,65(18):234-240.CHENG Xuetao,LIANG Xingang.Discussion on the application of entropy generation minimization to the optimizations of heat transfer and heat-work conversion[J].Acta Phys.Sin.,2016,65(18):234-240.
[12]娄春,周怀春,姜志伟,等.炉膛内断面温度场与辐射参数同时重建实验研究[J].中国电机工程学报,2006,26(14):98-103.LOU Chun,ZHOU Huaichun,JIANG Zhiwei,et al. Experimental investigation on simultaneous reconstruction of cross-section temperature distribution and radiation properties in a boiler furnace[J].Proceedings of the CSEE,2006,26(14):98-103.
[13]娄春,周怀春,朱国良,等.煤粉炉内颗粒辐射特性的检测与分析[J].工程热物理学报,2007,28(S2):217-220.LOU Chun,ZHOU Huaichun,ZHU Guoliang,et al. Analysis and measurement of radiative properties of particulate medium in a large-scale coal-fired boiler of power plant[J].Journal of Engineering Thermophysics,2007,28(S2):217-220.
[14]娄春.煤粉炉内三维温度场及颗粒辐射特性重建[D].武汉:华中科技大学,2007:136-140.
[15]楚双霞.非相干辐射传递过程的热力学分析[D].哈尔滨:哈尔滨工业大学,2009:57-67.