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Laminar Natural Convection In A Discretely Heated Cavity: I—Assessment Of Three-Dimensional Effects, Theodore J. Heindel, S. Ramadhyani, F. P. Incropera Nov 1995

Laminar Natural Convection In A Discretely Heated Cavity: I—Assessment Of Three-Dimensional Effects, Theodore J. Heindel, S. Ramadhyani, F. P. Incropera

Theodore J. Heindel

Two and three-dimensional calculations have been performed for laminar natural convection induced by a 3 × 3 array of discrete heat sources flush-mounted to one vertical wall of a rectangular cavity whose opposite wall was isothermally cooled. Edge effects predicted by the three-dimensional model yielded local and average Nusselt numbers that exceeded those obtained from the two-dimensional model, as well as average surface temperatures that were smaller than the two-dimensional predictions. For heater aspect ratios Ahtr ≲ 3, average Nusselt numbers increased with decreasing Ahtr . However, for Ahtr ≳ 3, the two and three-dimensional predictions were within 5 percent of each other and ...


Laminar Natural Convection In A Discretely Heated Cavity: Ii—Comparisons Of Experimental And Theoretical Results, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani Nov 1995

Laminar Natural Convection In A Discretely Heated Cavity: Ii—Comparisons Of Experimental And Theoretical Results, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani

Theodore J. Heindel

Three-dimensional numerical predictions and experimental data have been obtained for natural convection from a 3 × 3 array of discrete heat sources flush-mounted on one vertical wall of a rectangular cavity and cooled by the opposing wall. Predictions performed in a companion paper (Heindel et al., 1995a) revealed that three-dimensional edge effects are significant and that, with increasing Rayleigh number, flow and heat transfer become more uniform across each heater face. The three-dimensional predictions are in excellent agreement with the data of this study, whereas a two-dimensional model of the experimental geometry underpredicts average heat transfer by as much as 20 ...


Modeling Multiple Reactive Scalar Mixing With The Generalized Iem Model, Kuochen Tsai, Rodney O. Fox Nov 1995

Modeling Multiple Reactive Scalar Mixing With The Generalized Iem Model, Kuochen Tsai, Rodney O. Fox

Rodney O. Fox

An outstanding feature of the amplitude mapping closure is its ability to relax an arbitrary initial probability density function (PDF) to a Gaussian PDF asymptotically. Due to the difficulties in computing either the analytical or numerical solution, the mapping closure has never been applied to multiple scalars with finite reaction rates. In this work, the generalized IEM (GIEM) model is combined with the mapping closure to model the molecular mixing terms in the PDF balance equation. The GIEM model assumes a linear relationship between the rates of change of the reactive scalars and an inert scalar (shadow scalar) during the ...


Study Of The Wear Behaviour Of Al-4.5% Cu-3.4% Fe In Situ Composite: Effect Of Thermal And Mechanical Processing Aug 1995

Study Of The Wear Behaviour Of Al-4.5% Cu-3.4% Fe In Situ Composite: Effect Of Thermal And Mechanical Processing

A.S. Md Abdul Haseeb

Wear behaviour of as-cast and heat-treated spheroidal graphite (SG) cast iron has been studied under dry sliding conditions using a pin-on-disc type apparatus. Wear tests were carried out at a linear sliding speed of 0.88 m s -1, under a constant load of 1.5 kg. All tests were performed in ambient air at room temperature. Extent of wear damage and wear mechanisms were investigated by means of weight loss measurement, optical microscopy, microhardness measurement and X-ray diffractometry on wear debris. The wear rate measured after 9500 m of sliding is found to be about three times higher in ...


The Spectral Relaxation Model Of The Scalar Dissipation Rate In Homogeneous Turbulence, Rodney O. Fox May 1995

The Spectral Relaxation Model Of The Scalar Dissipation Rate In Homogeneous Turbulence, Rodney O. Fox

Rodney O. Fox

A model for the effect of scalar spectral relaxation on the scalar dissipation rate of an inert, passive scalar (Sc>1) in fully developed homogeneous turbulence is presented. In the model, wave-number space is divided into a finite number [the total number depending on the turbulence Reynolds number Re, and the Schmidt number (SC)] of intermediate stages whose time constants are determined from the velocity spectrum. The model accounts for the evolution of the scalar spectrum from an arbitrary initial shape to its fully developed form and its effect on the scalar dissipation rate for finite Re, and Sc>1 ...