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

Author(s):  
Binita Pathak ◽  
Saptarshi Basu

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.

Author(s):  
Abhishek Saha ◽  
Erick Tijerino ◽  
Ranganathan Kumar ◽  
Saptarshi Basu

An experimental setup using radiative heating has been used to understand the thermophysical phenomena and chemical transformations inside acoustically levitated cerium nitrate precursor droplets. IR imaging in conjunction with high speed imaging shows presence of four distinct phases of heating. The droplet initially undergoes pure vaporization followed by surface precipitation. This results in a gelatinous phase due to precipitation of cerium nitrate which eventually goes though chemical transformation and forms a porous precipitate. Transmission Electron Microscopy (TEM) of the final precipitate revealed the presence of trapped gases in the form of bubbles. TEM also showed the presence of nano-ceria crystalline structures at 70°C. The current study also looks into the effect of different heating power on the process. At higher power each phase is sustained for smaller duration and higher maximum temperature. At all laser power, TEM showed the formation of nanoceria. In addition, the porosity of the final precipitate increased with power.


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pp. 113-116
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Masaaki KAWAHASHI ◽  
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E. Yu. Koroteeva ◽  
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E. A. Karnozova ◽  
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...  

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pp. 377-384 ◽  
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SYDNEY H. REITER ◽  
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