Numerical Simulation of 2-Dlaminar Flow, Heat Generation and Forced Convection from Rectangular Blocks in a Narrow Channel PDF Download

Author: İbrahim Özkol
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Languages : en
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Book Description
In this study, a directional-implicit Computational Fluid Dynamics (CFD)finite difference code is developed so as to simulate the direct and indirect heat removal through conduction and convection processes from the rectangular blocks attached to the lower surface of a narrow- channel geometry. Two dimensional, unsteady, incompressible, laminar form of the Navier -Stokes (N-S) equations are considered. L sing the stream function-vorticity approach, they are discretized via finite difference technique, under the assumption of the Taylor series expansions. The discretized equations than reduced to a three-banded form of a matrix equality ready to be used conjugate solution formulation. In the same manner, two dimensional unsteady' energy· equation discretized with the source term included into three-banded matrix form. Tw-o field equations are solved numerically for various channel-rectangular block geometries so as to study the steady--state heat transfer characteristics inside channel with possible heat generation inside the blocks. It is shown that the numerical model is capable of simulating the main features of the flow- field. Detailed benchmarks of the present numerical model is attempted so as to validate the devoloped algorithm. The streamvise extension of the recirculation zone behind the rectangular block which is a function of the Reynolds number is very well simulated. Furthermore, it was shown that the heat transfer characteritics of the zone agrees well with the experinıental and theoretical observations in the literature. Prepared algorithm is a highly' stable algorithm but show'ing slow convergence to a steady state value. Conjugate solution property of the present approach enables one to study complex thermal characteristics of fluid-solid and solid-solid interactions. Beside the classical boundary conditions of the thermal field, the problem domain is further complicated by the presence of discrete heat sources in the rectangular blocks in form of the infinite small heat generating sheet. Heat generatedat various transfer positions are convected by the fluid downstream. The near wall flow temperature and the Nusselt number distributions over the surface depict the most features of the complex fluid-solid interaction. The steady state temperature inside the blocks and in the substrate are found to be functions of the flow Reynolds number. Prandtl number, heat source position and substrate bottom surface temperature. Due to the heat generation the flow is heated well above its inlet value. This causes continous heat flow from fluid to the lower plate in the recirculating regions of the rectangular blocks and in the cavities where there are more than one obstacle. The present model can simulate the chip cooling problems for integrated circuit components, i.e, chips, on a horizontal printed curcuit board which is containing heat generatin; rectangular blocks attached to a single layer substrate. Results consistency with other studies, which are reported in literature, is discussed.