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  • Open Access

    ARTICLE

    ANALYTICAL SOLUTION FOR A CLASS OF FLAT PLATE CONJUGATE CONVECTIVE HEAT TRANSFER PROBLEMS

    Antti Lehtinena, Reijo Karvinenb,∗

    Frontiers in Heat and Mass Transfer, Vol.2, No.4, pp. 1-6, 2011, DOI:10.5098/hmt.v2.4.3004

    Abstract Analytical solutions for three different flat plate conjugate heat transfer cases are presented. The cases are as follows:transient heat transfer of a thin plate with uniform heat generation; the Luikov problem in which one plate surface is kept in a constant temperature and the other one is cooled by forced convection ; and a modified Luikov problem with heat generation on one surface and convection on both surfaces of the plate. All the cases are solved for both laminar and turbulent flows with P r ≥ 1. The solutions in the paper are based on More >

  • Open Access

    ARTICLE

    ON UNCERTAINTY AND LOCAL SENSITIVITY ANALYSIS FOR STEADY-STATE CONJUGATE HEAT TRANSFER PROBLEMS PART 1: EMISSIVITY, FLUID TEMPERATURE, AND CONDUCTANCE

    Christian Rauch*

    Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-8, 2011, DOI:10.5098/hmt.v2.3.3006

    Abstract In recent years, significant effort has been placed into developing automated multi-physics simulation. The exchange of boundary conditions has lead to more realistic as well as more complex simulations with usually slower convergence rate when the coupling is being performed between two different codes. In this paper the equations of local sensitivities for element centered steady-state combined convection, conduction, and thermal radiation problems are being derived. A numerical analysis on the stability of the solution matrix is being conducted. Partial uncertainties and the relative importance of the heat transfer modes are investigated by their uncertainty More >

  • Open Access

    ARTICLE

    BIO-HEAT TRANSFER SIMULATION OF SQUARE AND CIRCULAR ARRAY OF RETINAL LASER IRRADIATION

    Arunn Narasimhan*, Kaushal Kumar Jha

    Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-8, 2011, DOI:10.5098/hmt.v2.3.3005

    Abstract Pan Retinal photocoagulation (PRP), a retinal laser surgical process, is simulated using a three-dimensional bio-heat transfer numerical model. Spots of two different type of array, square array of 3 × 3 spots and a circular array of six spots surrounding a central spot, are sequentially irradiated. Pennes bio-heat transfer model is used as the governing equation. Finite volume method is applied to find the temperature distribution due to laser irradiation inside the human eye. Each spot is heated for 100 ms and subsequently cooled for 100 ms with an initial laser power of 0.2 W. More >

  • Open Access

    ARTICLE

    NUMERICAL INVESTIGATION OF NON-NEWTONIAN FLOW AND HEAT TRANSFER IN TUBES OF HEAT EXCHANGERS WITH RECIPROCATING INSERT DEVICES*

    D. S. Martínez, J. P. Solano, J. Pérez, A. Viedma

    Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-10, 2011, DOI:10.5098/hmt.v2.3.3002

    Abstract Non-Newtonian flow and heat transfer in tubes of heat exchangers with reciprocating insert devices have been numerically investigated. The heat exchanger is mechanically assisted by a reciprocating cylinder, which moves the scraping rods inserted in the tubes. An array of semi-circular elements is mounted on each rod, with a pitch p=5D. These elements fit the internal diameter of the tubes. During the reciprocating motion, they scrape the inner tube wall, avoiding fouling. Additionally, the movement of the inserted device generates macroscopic displacements of the flow, which continuously mix core regions with peripheral flow. A power More >

  • Open Access

    ARTICLE

    FLOW SEPARATION IN FALLING LIQUID FILMS

    Georg F. Dietze, Reinhold Kneer

    Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-14, 2011, DOI:10.5098/hmt.v2.3.3001

    Abstract Despite the use of liquid films in a wide variety of technical applications involving heat and mass transfer (e.g. nuclear reactors, cooling towers and gas turbines), where they often play an important role, the underlying momentum and heat transport processes within these thin liquid layers remain to be fully elucidated. In particular, this applies to the influence that surface waves, developing due to the film’s natural instability, exert on the mentioned processes. In this context, it has been suggested by several experimental and numerical observations that momentum and heat transfer in the capillary wave region… More >

  • Open Access

    ARTICLE

    A CORRELATION FOR NUSSELT NUMBER UNDER TURBULENT MIXED CONVECTION USING TRANSIENT HEAT TRANSFER EXPERIMENTS

    N. Gnanasekaran, C. Balaji*

    Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-6, 2011, DOI:10.5098/hmt.v2.2.3008

    Abstract This paper reports the results of an experimental investigation of transient, turbulent mixed convection in a vertical channel in which one of the walls is heated and the other is adiabatic. The goal is to simultaneously estimate the constants in a Nusselt number correlation whose form is assumed a priori by synergistically marrying the experimental results with repeated numerical calculations that assume guess values of the constants. The convective heat transfer coefficient “h”is replaced by the Nusselt number (Nu) and the constants in the Nusselt number are to be evaluated. From the experimentally obtained temperature More >

  • Open Access

    ARTICLE

    BIFURCATIONS OF NATURAL CONVECTION FLOWS FROM AN ENCLOSED CYLINDRICAL HEAT SOURCE

    Diego Angelia,*, Arturo Paganob, Mauro A. Corticellia, Alberto Ficherab, Giovanni S. Barozzia

    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 >

  • Open Access

    ARTICLE

    CONJUGATE HEAT TRANSFER FROM A FLAT PLATE WITH SHOWER HEAD IMPINGING JETS

    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 >

  • Open Access

    ARTICLE

    NUMERICAL STUDY OF AIR FORCED CONVECTION IN A CHANNEL PROVIDED WITH INCLINED RIBS

    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 >

  • Open Access

    ARTICLE

    A NUMERICAL STUDY OF THE EFFECT OF A BELOW-WINDOW CONVECTIVE HEATER ON THE HEAT TRANSFER RATE FROM A COLD RECESSED WINDOW

    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 >

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