2013
37
2
2
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ESTIMATION OF THE BREAKUP LENGTH FOR THE
ANNULAR AND THE ROUND LIQUID JET USING
LINEAR INSTABILITY ANALYSIS
2
2
A linear instability analysis of an inviscid annular liquid sheet emanating from anatomizer subjected to inner and outer swirling air streams and a nonswirl round liquid jet has beencarried out. The dimensionless dispersion equation that governs the instability was derived andwas solved by Numerical method to investigate the effects of the liquidgas swirl orientation onthe maximum growth rate and its corresponding unstable wave number that produces the finestdroplets. To understand the effect of air swirl orientation with respect to liquid swirl direction, fourpossible combinations with both swirling air streams with respect to the liquid swirl direction havebeen considered. Results show that at low liquid swirl Weber number a combination of coinnerair stream and counterouter air stream has the largest most unstable wave number and shortestbreakup length. The combination of inner and the outer air stream corotating with the liquid hasthe highest growth rate. Also, the results for round liquid jet and planar liquid sheet show that thelinear theory accurately predicts the variation in breakup length with jet velocity.
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Annular sheet
round jet
atomization
linear analysis
instability
swirl
EXPERIMENTAL, NUMERICAL ANALYSIS AND OPTIMIZATION OF
ELLIPTICAL ANNULAR FINS UNDER FREE CONVECTION
2
2
This paper presents the total heat transfer rate by Elliptical Annular Fin (EAF) andCircular Annular Fin (CAF) by experimental setup, validated CFD analysis and optimization ofEAF using Genetic Algorithm (GA). The experimental result of EAF shows that, the surfacetemperature of EAF goes on decreasing gradually along with the projected surface area in thedirection of the major axis. The STE decreases with the Biot number (Bi) and Shape factor (SF).The rate of reduction of STE with increasing Bi is higher for Bi < 0.013. The experimental resultsare validated with CFD result. The deviation is within acceptable range for surface temperature,STE and fin effectiveness are 58%. The GA developed is validated with the experimental result. Itis observed that, the fin effectiveness is higher when the minor axis touches the circumference ofthe CT, and for smaller values of SF and smaller values of the radius of the CT. This optimizationmethod is universal and may be used for optimization of EAF under specified volume.
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233
239
Axis ratio
biot number
elliptical annular fin
fin effectiveness
heat transfer coefficient