The numerical simulations of reactive turbulent flows and heat transfer in an industrial slab reheat furnace in which the combustion air is highly preheated have been carried out. The influence of the ratio of the air and fuel injection velocities on the NOx production rate in the furnace has also been studied numerically. A moment closure method with the assumed β probability density function (PDF) for mixture fraction was used in the present work to model the turbulent non-premixed combustion process in the furnace. The combustion model was based on the assumption of instantaneous full chemical equilibrium. The turbulence was modeled by the standard k-ε model with a wall function. The numerical simulations have provided complete information on the flow, heat, and mass transfer in the furnace. The results also indicate that a low NOx emission and high heating efficiency can be achieved in the slab reheat furnace by using low NOx regenerative burners. It is found that the air/fuel injection velocity ratio has a strong influence on the NOx production rate in the furnace.

A quasi-three-dimensional numerical model is proposed to predict the performance of large power plant condensers. The proposed model is applied to a 350 MW power plant condenser under two different loading and operational conditions to demonstrate its predictive capability. The predictions are compared with the experimental data. The comparison is favorable. The equations governing the conservation of mass, momentum, and air mass fraction are solved in primitive variable form using a semi-implicit consistent control-volume formulation in which a segregated pressure correction linked algorithm is employed. The modeling of the condenser geometry, including the tube bundle and baffle plates, is carried out based on a porous media concept using applicable flow, heat, and mass transfer resistances.

The flow field through tubes with multiple axisymmetric constrictions in tubes was studied numerically. Two practical problem cases were considered and the numerical scheme was developed for both. In the first case there are one, two, three and four constrictions in the tube. The effects of the number of constrictions on wall shear stress, pressure drop, streamline, vorticity and velocity distributions as the flow passes through the tube were studied and the development of the periodicity characteristics was investigated. In the second case there were multiple constrictions in the tube equidistant from each other. For this case the governing equations were reformulated for a module at a sufficient distance downstream from the inlet where the entrance region effects could be ignored and flow field is assumed to repeat itself. The flow field solutions were obtained in this region. The governing equations were formulated in curvilinear co‐ordinates and a finite volume discretization procedure was used to solve the problem. The computations were carried out over a range of Reynolds numbers between 50 to 250 for constrictions with 75 percent area reduction. The method is validated by comparing some of the solutions with experimental results.

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The pulsatile¯ow in a pipe with a moving boundary has been studied for a viscous, incompressiblē uid by solving the Navier-Stokes equations numerically. The governing equations were formulated in boundary ®tted curvilinear coordinates and a ®nite volume discretization procedure was used to solve the problem. This analysis is based on the assumption that the¯ow has a simple periodic pulsation and the shape of the wall changes according to the frequency of pulsation. The presence of the moving boundary causes unsteadiness in the¯ow behaviour as the vibrating wall has a nonlinear interaction with the¯ow. A detailed analysis of the¯ow ®eld is presented here for a range of frequencies (5 a 10) where a is the reduced frequency parameter and a Reynolds number of 100.