Diego Angeli^a,*, Arturo Pagano^b, Mauro A. Corticelli^a, Alberto Fichera^b, Giovanni S. Barozzi^a

Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-9, 2011, DOI:10.5098/hmt.v2.2.3003

Abstract A numerical analysis of transitional natural convection from a confined thermal source is presented. The system considered is an air-filled, square-sectioned 2D enclosure containing a horizontal heated cylinder. The resulting flow is investigated with respect to the variation of the Rayleigh number, for three values of the aspect ratio A. The first bifurcation of the low-Ra fixed-point solution is tracked for each A-value. Chaotic flow features are detailed for the case A = 2.5. The supercritical behaviour of the system is investigated using nonlinear analysis tools and phase-space representations, and the effect of the flow More >

Rajesh Kumar Panda, B.V.S.S.S. Prasad^*

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-10, 2011, DOI:10.5098/hmt.v2.1.3008

Abstract Conjugate heat transfer from a flat circular disk is investigated both computationally and experimentally with a constant heat flux imposed on its bottom surface and a shower head of air jets impinging on the top surface. The shower head consists of a central jet surrounded by four neighboring perimeter jets. Measured temperature data at twelve locations within the plate are compared with the conjugate heat transfer result obtained at the same locations computationally by Shear Stress Transport (SST) κ-ω turbulence model. The spacing to orifice diameter ratio (H/d = 1 to 4), the jet Reynolds… More >

Oronzio Manca^*, Sergio Nardini, Daniele Ricci

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-8, 2011, DOI:10.5098/hmt.v2.1.3007

Abstract Convective heat transfer may be enhanced passively by adopting rough surfaces. Ribs break the laminar sub-layer and create local turbulence in the channel, reducing thermal resistance and enhancing the heat transfer. However, higher losses are expected. In this paper a numerical investigation is carried out on air forced convection in a rectangular ribbed channel. A three-dimensional model is developed to study the effect of the angle between the fluid flow direction and the ribbed surface, provided with rectangular turbulators, in the turbulent flow. Simulations s that Nusselt numbers as well as the pressure drops increase More >

Patrick H. Oosthuizen^*

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-8, 2011, DOI:10.5098/hmt.v2.1.3004

Abstract The convective heat transfer to a window below which is mounted a natural convective heater has been numerically studied. The flow has been assumed to be three-dimensional and steady and to involve regions of laminar and turbulent flow. Fluid properties have been assumed constant except for the density change with temperature which leads to the buoyancy forces. The solution has been obtained using a commercial cfd code. Results have been obtained for a Prandtl number of 0.7. The effects of changes in the flow variables on the window Nusselt number and on the flow and More >

Muhammad M. Rahman^*, Phaninder Injeti

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-9, 2011, DOI:10.5098/hmt.v2.1.3003

Abstract This paper presents the effects of protrusions on heat transfer in a microtube and in a two-dimensional microchannel of finite wall thickness. The effects of protrusion shape, size, and number were investigated. Calculations were done for incompressible flow of a Newtonian fluid with developing momentum and thermal boundary layers under uniform and discrete heating conditions. It was found that the local Nusselt number near a protrusion changes significantly with the variations of Reynolds number, height, width, and distance between protrusions, and the distribution of discrete heat sources. The results presented in the paper demonstrate that More >

De-Shin Liu, Kuo-Liang Cheng, Zhen-Wei Zhuang, T. C. Lee

The International Conference on Computational & Experimental Engineering and Sciences, Vol.19, No.2, pp. 41-42, 2011, DOI:10.3970/icces.2011.019.041

Abstract High speed spindle is the key component for high precision machine center. The optimum design of spindle cooling system have to achieve to avoid the high heat produce by the build-in motor that can make great damage to the spindle bearing systems. This paper presents a new solid-fluid coupling computing method for design high speed spindle cooling system. Energy equation has been formed for a control volume within the cooling channel to describe the heat absorbing by the coolant moving in a constant speed. Finite different method is applied to solve temperature rising in the More >

Chein-Shan Liu

The International Conference on Computational & Experimental Engineering and Sciences, Vol.16, No.2, pp. 53-54, 2011, DOI:10.3970/icces.2011.016.053

Abstract We consider an inverse problem for identifying a time-space-dependent heat transfer coefficient h(x,t) in a two-dimensional heat conduction equation, with the aid of an extra measurement of temperature at the top side of a rectangular plate. Finite differences are used to discretize the governing equation and boundary conditions of Neumann type, and then the Fictitious Time Integration Method (FTIM) is used to solve a large scale linear system of unknown variables. The numerical results show that the FTIM is effective and robust against noise. More >

M.M. Kaminski

CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.2, pp. 113-140, 2011, DOI:10.3970/cmes.2011.080.113

Abstract The main aim of this work is to demonstrate a solution to the transient problems for the statistically homogeneous media with random physical parameters. This is done with the use of the stochastic perturbation technique based on the general order Taylor series expansions and the additionally modified implementation of the Finite Element Method. Now, both the Direct Differentiation Method as well as the Response Function Method are employed to form and solve up to the nth order state equations. Computational implementation of both approaches is illustrated using two examples - by determination of the probabilistic More >

Xiao Zhao¹, Haitian Yang^1,2, Qiang Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.2, pp. 139-160, 2011, DOI:10.3970/cmes.2011.074.139

Abstract A piecewised adaptive algorithm in the time domain is presented to solve the transient convection-diffusion heat transfer problem. By expanding all variables at a time interval, an initial and boundary value problem is decoupled into a series of recursive boundary value problems which can be solved by FEM or other well developed numerical schemes to deal with boundary value problems. A steady computing accuracy can be adaptively maintained via the power increase of the expansion, particularly when the step size varies in the whole computing process. Additionally for the nonlinear cases, there is no requirement More >

Jui-Hsun Ni, Cheng-Chi Chang, Yue-Tzu Yang, Cha’o-Kung Chen¹

CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.1, pp. 37-52, 2011, DOI:10.3970/cmes.2011.072.037

Abstract The hybrid method, which combines differential transformation and finite difference approximation techniques, is utilized to solve hyperbolic-type heat conduction (bio-heat) problems in one dimension. To capture the thermal behavior in a living tissue subjected to constant or exponential surface heating with the thermal wave model of bio-heat transfer, the relaxation time and the heat wave, which propagates in a direction perpendicular to the skin surface, are considered. The results show that the hybrid method can be used to solve hyperbolic heat conduction problems accurately. More >