A Study of Numerical Modeling of Heat Transfer in Wall-Adjacent Turbulent Flows
نویسنده
چکیده
-In this paper we present some of the most practical problems of convective heat transport to or from a rigid surface, the flow in the vicinity of the body is in turbulent motion. On the hand, at the solid-fluid interface itself, the noslip boundary condition ensures that turbulent velocity fluctuations vanish. But, at the wall, the diffusive transport of heat and momentum in the fluid is precisely expressible by the laws of applicable to laminar flow. Because, the turbulent shear stress, and often the turbulent heat flux, can, by continuity, increase only as the cube of the distance from the wall, there is a thin but very important sublayer immediately adjacent to the solid surface where the transport of heat and momentum is predominantly by molecular diffusion. Further from the wall, again by virtue of the cubic variation, there is a very rapid changeover to the state where turbulent transport dominates, a condition that normally prevails over the remainder of the flow. This thin sublayer and the adjacent transition region extending to the fully turbulent regime collectively we shall term the viscosity affected-sublayer (VSL); is the subject of the present paper. Furthermore, we are concerned with how one can accurately model the flow in this region in a form suitable for use in CFD software. However, the accuracy is not only criterion.
منابع مشابه
Numerical Predictions of Turbulent Mixed Convection Heat Transfer to Supercritical Fluids Using Various Low Reynolds Number k-e Turbulence Models
There are a number of systems in which supercritical cryogenic fluids are used as coolants or propellant fluids. In some modern military aircraft, the fuel is pressurized above its critical point and used as a coolant to remove heat from the aircraft engine. Accurate prediction of heat transfer coefficients to turbulent flows of supercritical fluids is essential in design of such systems. One o...
متن کاملNumerical study of influence of type of nanoparticles and volume fraction on turbulent heat transfer coefficient and pressure loss inter a tube
The conventional liquids have some limitations regarding the thermal properties. The nanoparticles addition is one of the techniques which can modify them. In this research, heat transfer coefficient (h) and pressure loss (Δp) of various nanofluids containing Al2O3, SiO2 and MgO nanoparticles dispersed in water in an annular tube with constant wall temperature were numerically considered. Accor...
متن کاملNumerical simulation of nanofluid flow over diamond-shaped elements in tandem in laminar and turbulent flow
In this paper, the Al2O3-water nanofluid flow in laminar and turbulent flows inside tubes fitted with diamond-shaped turbulators is numerically modeled. The nanofluid flow is modeled by employing a two-phase mixture method and applying the constant heat flux boundary condition at tube walls. In the results, the effects of different parameters such as the geometry of turbulators, volume fraction...
متن کاملNumerical analysis of heat transfer enhancement and flow structure of alternating oval tubes by considering different alternate angles under turbulent flow
In this research, the convective heat transfers of turbulent water fluid flow in alternating oval tubes is studied using computational fluid dynamics. The purpose of the study is to analyze the heat transfer enhancement and secondary internal flows under different alternate angles. Also, comparing the effect of two schemesfor the domain discretization to be used in the soluti...
متن کاملComparison of convective heat transfer of turbulent nanofluid flow through helical and conical coiled tubes
Application of nanofluid and coiled tubes are two passive methods for increasing the heat transfer. In the present study, the turbulent flows of water and nanofluid in coiled tubes heat exchanger were numerically studied. CuO-water nanofluid containing 1 vol% copper oxide nanoparticles was used and single-phase approach was considered for nanofluid flow. The effect of different geometrical para...
متن کاملA New Model for Prediction of Heat Eddy Diffusivity in Pipe Expansion Turbulent Flows
A new model to calculate heat eddy diffusivity in separating and reattaching flows based on modification of constant Prt is proposed. This modification is made using an empirical correlation between maximum Nusselt number and entrance Reynolds number. The model includes both the simplicity of Prt=0.9 assumption and the accuracy of two-equation heat-transfer models. Furthermore, an appropriate l...
متن کامل