Determination of surface convective heat transfer coefficients by CFD
نویسندگان
چکیده
Heat and vapour convective surface coefficients are required in practically all heat and vapour transport calculations. In building envelope research, such coefficients are often assumed constants for a set of conditions. Heat transfer surface coefficients are often determined using empirical correlations based on measurements of different geometry and flows. Vapour transfer surface coefficients have been measured for some specific conditions, but more often, they are determined with the Chilton-Colburn analogy using known heat transfer coefficients. This analogy breaks down when radiation and sources of heat and moisture are included. Experiments have reported differences up to 300%. In this paper, the heat transfer process in the boundary layer is examined using Computational Fluid Dynamics (CFD) for laminar and turbulent air flows. The feasibility and accuracy of using CFD to calculate convective heat transfer coefficients is examined. A grid sensitivity analysis is performed for the CFD solutions, and Richardson Extrapolation is used to determine the grid independent solutions for the convective heat transfer coefficients. The coefficients are validated using empirical, semi-empirical and/or analytical solutions. CFD is found to be an accurate method of predicting heat transfer for the cases studied in this paper. For the laminar forced convection simulations the convective heat transfer coefficients differed from analytical values by ±0.5%. Results for the turbulent forced convection cases had good agreement with universal law-of-the-wall theory and with correlations from literature. Wall functions used to describe boundary layer heat transfer for the turbulent cases are found to be inaccurate for thermally developing regions.
منابع مشابه
Cfd Analysis of Convective Heat Transfer Coefficients on the Exterior Surfaces of a Cubic Building
The forced convective heat transfer at the surfaces of a cubic building in an atmospheric boundary layer is investigated with CFD. Heat transfer in the boundary layer is modelled using low-Reynolds number modelling (LRNM) and standard wall functions (SWFs). SWFs are found to overestimate the convective heat transfer coefficient (CHTC) significantly. Using a customised wall function (CWF) for te...
متن کاملHeat Transfer over a Flat Plate in Laminar Flow Using Computational Fluid Dynamics
The aim of this paper is the theoretical estimations for boundary layer thickness and heat transfer coefficient which is analysed using CFD with certain parametric functions and partial differential equations as well. Along with it the feasibility of the convective heat transfer coefficient for the calculations examined during their rendering certainty with CFD methods. The equations have been ...
متن کاملNumerical Determination and Treatment of Convective Heat Transfer Coefficient in the Coupled Building Energy and Cfd Simulation
The integration of building Energy Simulation (ES) and Computational Fluid Dynamics (CFD) programs eliminates many assumptions employed in the separate applications, resulting in more accurate predictions of building performance. This paper discusses the methods used to determine convective heat transfer on interior surfaces of building envelope, which is the key linkage between ES with CFD pro...
متن کاملNumerical Simulation of Laminar Convective Heat Transfer and Pressure Drop of Water Based-Al2O3 Nanofluid as A Non Newtonian Fluid by Computational Fluid Dynamic (CFD)
The convective heat transfer and pressure drop of water based Al2O3 nanofluid in a horizontal tube subject to constant wall temperature condition is investigated by computational fluid dynamic (CFD) method. The Al2O3 nanofluid at five volume concentration of 0.1, 0.5, 1.0, 1.5 and 2 % are applied as a non Newtonian power law and Newtonian fluid with experimentally measured properties of density...
متن کامل