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Research Papers

Comparison of Convective and Radiative Heating Modes on the Thermophysical Changes of a Cerium Nitrate Droplet

[+] Author and Article Information
Binita Pathak

Department of Mechanical Engineering,
Indian Institute of Science, Bangalore,
Bangalore 560012, India

Saptarshi Basu

Department of Mechanical Engineering,
Indian Institute of Science, Bangalore,
Bangalore 560012, India
e-mail: sbasu@mecheng.iisc.ernet.in

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received April 29, 2014; final manuscript received January 12, 2015; published online November 11, 2015. Assoc. Editor: Chakravarthy Balaji.

J. Thermal Sci. Eng. Appl 8(1), 011009 (Nov 11, 2015) (11 pages) Paper No: TSEA-14-1093; doi: 10.1115/1.4030729 History: Received April 29, 2014

In this paper, we try to establish the equivalence or similarity in the thermal and physiochemical changes in precursor droplets (cerium nitrate) in convective and radiative fields. The radiative field is created through careful heating of the droplet using a monochromatic light source (CO2 laser). The equivalence is also established for different modes of convection like droplet injected into a high-speed flow and droplet experiencing a convective flow due to acoustic streaming (levitated) only. The thermophysical changes are studied in an aqueous cerium nitrate droplet, and the dissociation of cerium nitrate to ceria is modeled using modified Kramers' reaction rate formulation. It is observed that vaporization, species accumulation, and chemical characteristics obtained in a convectively heated droplet are retained in a radiatively heated droplet by careful adjustment of the laser intensity. The timescales and ceria yield match reasonably well for both the cases. It is also noted that similar conclusions are drawn in both levitated droplet and a nonlevitated droplet.

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Figures

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Fig. 1

Schematic of the cases studied: convective and radiative heating modes in (a) levitated droplet and (b) nonlevitated droplet (here, C is convective mode of heating and R is the radiative heating mode)

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Fig. 2

Flow field developed within (a) a levitated droplet and (b) droplet in a convective external flow field

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Fig. 3

Variation of (a) temperature at the surface and (b) size of levitated droplet under convective and radiative heating conditions

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Fig. 4

Variation of (a) reaction rate with the reaction time (tR) and (b) the concentration of cerium nitrate and mass of ceria formed at the surface of levitated droplet under convective and radiative heating conditions

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Fig. 5

Distribution of cerium nitrate concentration within the levitated droplet heated (a) in a convective flow field of Tstr = 525 K and Ustr = 1.6 m/s and (b) with radiation of power I = 0.275 MW/m2, Tstr = 300 K, and Ustr = 1.6 m/s, prior to initiation of the reaction

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Fig. 6

Distribution of temperature within the levitated droplet when heated (a) in a convective flow field of Tstr = 525 K and Ustr = 1.6 m/s and (b) with radiation of power I = 0.275 MW/m2, Tstr = 300 K, and Ustr = 1.6 m/s

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Fig. 7

Distribution of relative concentration of ceria with respect to cerium nitrate (mCeO2/(mCeO2+mCe(NO3)3)) within the levitated droplet at the final time-step of the process when heated (a) in a convective flow field of Tstr = 525 K and Ustr = 1.6 m/s and (b) with radiation of power I = 0.275 MW/m2, Tstr = 300 K, and Ustr = 1.6 m/s. (c) Precipitate formation in cerium nitrate precursor droplet. (Reproduced with permission from Saha et al. [8]. © 2009 Elsevier B.V.)

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Fig. 8

Distribution of cerium nitrate concentration within the droplet with Hill's spherical type internal flow field and heated (a) in a convective flow field of Tstr = 525 K and Ustr = 1.6 m/s and (b) with radiation of power I = 0.265 MW/m2, Tstr = 300 K, and Ustr = 1.6 m/s, prior to initiation of the reaction

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Fig. 9

Variation of (a) temperature and (b) concentration of species (cerium nitrate and ceria) at the surface of droplet with Hill's spherical type internal flow field under convective and radiative heating conditions

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Fig. 10

Variation of (a) reaction rate with the reaction time (tR) and (b) the concentration of cerium nitrate and mass of ceria formed at the surface of nonlevitated droplet (Hill's spherical type internal flow field) under convective and radiative heating conditions

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Fig. 11

Distribution of relative concentration of ceria with respect to cerium nitrate (mCeO2/(mCeO2+mCe(NO3)3)) within the nonlevitated droplet at the final time-step of the process when heated (a) in a convective flow field of Tstr = 525 K and Ustr = 1.6 m/s and (b) with radiation of power I = 0.265 MW/m2, Tstr = 300 K, and Ustr = 1.6 m/s

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Fig. 12

The chronology of different processes in droplet lifetime cited. (Reproduced with permission from Pathak et al. [16]. © 2013 Elsevier Ltd.)

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