Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

doi:10.1016/S1004-9541(13)60526-1

Chinese Journal of Chemical Engineering ›› 2013, Vol. 21 ›› Issue (6): 654-662.DOI: 10.1016/S1004-9541(13)60526-1

Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

张小斌, 张伟, 张学军

Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China

收稿日期:2012-05-24 修回日期:2012-12-19 出版日期:2013-06-28 发布日期:2013-07-03
通讯作者: ZHANG Xuejun
基金资助:
Supported by the National Natural Science Foundation of China (51276157) and the Natural Science Foundation of Zhejiang Province (LY12E060026).

Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

ZHANG Xiaobin, ZHANG Wei, ZHANG Xuejun

Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China

Received:2012-05-24 Revised:2012-12-19 Online:2013-06-28 Published:2013-07-03
Contact: ZHANG Xuejun
Supported by:
Supported by the National Natural Science Foundation of China (51276157) and the Natural Science Foundation of Zhejiang Province (LY12E060026).

摘要/Abstract

摘要： This paper analyzes the entropy generation rate of simple pure droplet combustion in a temperature-elevated air convective environment based on the solutions of flow, and heat and mass transfer between the two phases. The flow-field calculations are carried out by solving the respective conservation equations for each phase, accounting for the droplet deformation with the axisymmetric model. The effects of the temperature, velocity and oxygen fraction of the free stream air on the total entropy generation rate in the process of the droplet combustion are investigated. Special attention is given to analyze the quantitative effects of droplet deformation. The results reveal that the entropy generation rate due to chemical reaction occupies a large fraction of the total entropy generated, as a result of the large areas covered by the flame. Although, the magnitude of the entropy generation rate per volume due to heat transfer and combined mass and heat transfer has a magnitude of one order greater than that due to chemical reaction, they cover a very limited area, leading to a small fraction of the total entropy generated. The entropy generation rate due to mass transfer is negligible. High temperature and high velocity of the free stream are advantageous to increase the exergy efficiency in the range of small Reynolds number (<1) from the viewpoint of the second-law analysis over the droplet lifetime. The effect of droplet deformation on the total entropy generation is the modest.

关键词: entropy generation, exergy analysis, droplet combustion, numerical simulation

Abstract: This paper analyzes the entropy generation rate of simple pure droplet combustion in a temperature-elevated air convective environment based on the solutions of flow, and heat and mass transfer between the two phases. The flow-field calculations are carried out by solving the respective conservation equations for each phase, accounting for the droplet deformation with the axisymmetric model. The effects of the temperature, velocity and oxygen fraction of the free stream air on the total entropy generation rate in the process of the droplet combustion are investigated. Special attention is given to analyze the quantitative effects of droplet deformation. The results reveal that the entropy generation rate due to chemical reaction occupies a large fraction of the total entropy generated, as a result of the large areas covered by the flame. Although, the magnitude of the entropy generation rate per volume due to heat transfer and combined mass and heat transfer has a magnitude of one order greater than that due to chemical reaction, they cover a very limited area, leading to a small fraction of the total entropy generated. The entropy generation rate due to mass transfer is negligible. High temperature and high velocity of the free stream are advantageous to increase the exergy efficiency in the range of small Reynolds number (<1) from the viewpoint of the second-law analysis over the droplet lifetime. The effect of droplet deformation on the total entropy generation is the modest.

Key words: entropy generation, exergy analysis, droplet combustion, numerical simulation

张小斌, 张伟, 张学军. Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number[J]. Chinese Journal of Chemical Engineering, 2013, 21(6): 654-662.

ZHANG Xiaobin, ZHANG Wei, ZHANG Xuejun . Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number[J]. Chin.J.Chem.Eng., 2013, 21(6): 654-662.

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Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

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