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Eﬀects of variable viscosity on natural convection ﬂow of an optically thick gray gas past a horizontal surface in the presence of internal heat generation

Kannan T., Malleswaran A., Moorthy M. B. K.

Transactions of the Institute of Fluid-Flow Machinery

2018

nr 139

3--22

A numerical investigation to discuss the eﬀects of radiation and variable viscosity on heat and mass transfer characteristics of natural convection over a horizontal surface embedded in a saturated porous medium in the presence of internal heat generation is carried out in this study. The working ﬂuid for the investigation is optically thick gray gas. The Dufour and Soret eﬀects are also taken into account. Similarity transformations are employed to obtain nonlinear ordinary diﬀerential equations from the governing equations of the present problem. The numerical results for the transformed governing equations are computed by using commercial boundary value problem solver for ordinary diﬀerential equations. The eﬀects are discussed by varying the parameters such as radiation, Dufour and Soret numbers, buoyancy ratio, Prandtl number, Schmidt number, and variable viscosity. Presence of internal heat generation enhances the velocity proﬁle and signiﬁcantly decreases the concentration boundary layer thickness. On increasing ﬂuid radiation, the temperature of the ﬂuid is higher than that of the surface and the concentration boundary layer thickness decreases away from the surface.

Analysis of Solid Contamination in Ball Bearing Through Acoustic Emission Signals

Sheriff K. A. I., Hariharan V., Kannan T.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 3

1871--1874

Acoustic emission is one of the effective techniques used for the condition monitoring of rolling element bearings. Contamination is one of the major reasons for bearing early failure due to presence of solid particle in lubricant grease. In most cases, outer race is stationary and the inner race is attached to the rotating assembly. The lubrication is very essential for the bearing to perform under various demanding conditions. The main aim of this project is to analyze the effect of contamination of lubricant by solid particles on the dynamic behavior of rolling bearing. Green sand at three concentration levels 5%, 15%, 25% and different particle sizes 75 μm, 106 μm and 150μm is used to contaminate the lubricant. Experimental tests have been performed for different load and speed condition in good and contaminated ball bearings lubricated with grease. The trends in the amount of AE waves affected by the contamination of the grease were determined. Acoustic emission signals were analyzed in terms of RMS, kurtosis, and peak-peak.