 | Ahuja, K.L. |
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 | Transient Temperature in a Growing Solid
Author : Ahuja, K.L.
Source : Defence Science Journal ; Vol:18(4) ; 1968 ; pp 231-238
Subject : 548 Crystallography;54 Chemistry
Keywords : Law of Cooling;Quadratic Temperature Profile;Heat Balance Integral method
Abstract : Using two parameter quadratic temperature profile in conjunction with the heat balance integral method, approximate solutions for the freezing of a semi infinite slab and inward freezing of a circular cylinder are investigated, with the assumption that the freezing takes place at the surface of the solidifying medium according to Newton's law of cooling. Comparison with the existing solutions on the former problem shows good agreement. |
| | Solidification of a Liquid Sphere with a given Heat Flux at the Surface
Author : Lal, Jangi;Ahuja, K.L.
Source : Defence Science Journal ; Vol:18(3) ; 1968 ; pp 141-146
Subject : 536 Thermodynamics
Keywords : Inward Freezing;Parameter Temperature Profile
Abstract : The method of the heat balance integral is used to investigate of a problem involving the inward freezing of a liquid sphere. The solidification is effected under the assumption of constant heat flux from the surface. Solutions are presented by considering a two parameter temperature profile and the position of the front is expressed in the form of a series in time parameter. Finally the results are graphically exhibited. |
| | Melting of Thin Cylindrical Tubes
Author : Ahuja, K.L.;Kumar, I.J.
Source : Defence Science Journal ; Vol:16(4) ; 1966 ; pp 203-216
Subject : 531 Mechanics
Keywords : Temperature distribution;Heat balance integral;Constant heat flux
Abstract : It has been shown that the use of a polynomial profile for the temperature distribution in the case of thin cylindrical tubes is justified in the Goodman's technique of heat balance integral. The above technique has been used to obtain an approximate solution to the problem of melting (solidification) in a tube which is subjected to a constant heat flux at the inner surface while its outer surface is kept insulated. The temperature history and the melting rate are studied for the time during which the melting proceeds. Lighthill's technique for rendering approximate solution uniformly valid has been used and the first three terms of the series solution have been expressed in terms of an intrinsically small parameter. |
| | Radiative Transfer Effects on the Thermal Instability of a Fluid Spherical Shell
Author : Bahl, S.K.;Ahuja, K.L.
Source : Defence Science Journal ; Vol:16(4) ; 1966 ; pp 223-230
Subject : 536 Thermodynamics
Keywords : Emits thermal radiation;Fluid absorbs
Abstract : The thermal instability of an incompressible fluid spherical shell heated within when the fluid absorbs and emits thermal radiation is considered. Two asymptotic cases of the radiative transfer equation (i) when the fluid is optically thin and (ii) when it is optically thick have been examined. It is observed that radiative transfer for the transparent medium has a stabilising effect on the fluid motion, whereas for opaque medium the fluid behaves like the nonradiative case. |
| | On the change of phase when both the phases have different thermal properties
Author : Ahuja, K.L.
Source : Defence Science Journal ; Vol:13(4) ; 1963 ; pp 277-282
Subject : 532.542 Fluid Dynamics
Keywords : Supercooled fluid
Abstract : The growth of a plane boundary advancing in the supercooled fluid is discussed. The assumption of difference in densities results in a connective motion of the fluid and the mass solidified per unit area per unit time will occupy, on solidification, a different volume from that originally occupied by the fluid. The effect of finite conductivity of the solid on the growth has been studied by taking the Prandtl number different from unity. It is shown that equivalence of interface temperature and surface temperature of the solid leads to the results discussed by Chambre (1). |
| | Heat Flow in a Moving Solid Cylinder
Author : Ahuja, K.L.
Source : Defence Science Journal ; Vol:15(2) ; 1965 ; pp 75-78
Subject : 536 Thermodynamics
Keywords : Velocity ;Hankel;Laplace
Abstract : A transient state problem of heat transfer in a solid cylinder moving with a uniform speed in the direction of its length is considered mathematically. The cylinder is taken to be of infinite length and is maintained initially at a constant temperature Theta. The method of Laplace and the finite Hankel transform has been to obtain the solution. Numerical results for the solution in the positive region are exhibited graphically for two different values of the velocity. |
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