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Axial Heat Conduction

The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform

Bernhard Weigand – 1st expert on this subject based on the ideXlab platform

  • Axial Heat Conduction effects in the thermal entrance region for flows in concentric annular ducts correlations for the local bulk temperature and the nusselt number at the outer wall
    International Journal of Heat and Mass Transfer, 2016
    Co-Authors: M Axtmann, M Heier, W Hilali, Bernhard Weigand

    Abstract:

    Abstract Streamwise Heat Conduction in the flow can affect the Heat transfer in ducts. This is mainly relevant for flows with small Prandtl numbers or in micro-channels. In both situations the Peclet number is small, so Axial Heat Conduction in the fluid cannot be neglected. In literature analytical solutions of this so called extended Graetz problem are well documented. In the present paper correlations are developed for the local bulk-temperature and the local Nusselt number at the outer wall in the thermal entrance region of concentric annular ducts. Correlations are given for laminar and turbulent fully-developed flow and different thermal boundary conditions. The correlations also consider the effect of different ratios of the inner radius to the outer radius of the annular ducts.

  • Heat Transfer in Duct Flows for Small Peclet Numbers (Elliptic Problems)
    Analytical Methods for Heat Transfer and Fluid Flow Problems, 2015
    Co-Authors: Bernhard Weigand

    Abstract:

    This chapter is concerned with the Heat transfer in duct flows for small Peclet number. For these kind of applications Axial Heat Conduction in the flow can no longer been ignored. This leads to an elliptic energy equation. Analytical solutions methods for these problems are discussed extensively in this chapter.

  • Axial Heat Conduction effects in the entrance region of laminar duct flows correlations for the local nusselt number
    International Communications in Heat and Mass Transfer, 2014
    Co-Authors: Bernhard Weigand, M Abdelmoula

    Abstract:

    Abstract Axial Heat Conduction effects within the fluid can be important for duct flows if the Prandtl number is low (liquid metals) or if the hydraulic diameter of the channel is very small (micro-channels). Exact analytical solutions for the extended Graetz problem for such situations are well known and documented in literature. In the present paper suitable correlations are developed for the local Nusselt number in the thermal entrance region in a parallel plate channel and in a pipe. Correlations are given for different thermal boundary conditions and for Axial positions before (x   0) the jump in wall temperature or wall Heat flux.

Satoru Momoki – 2nd expert on this subject based on the ideXlab platform

  • effects of viscous dissipation and fluid Axial Heat Conduction on Heat transfer for non newtonian fluids in ducts with uniform wall temperature part i parallel plates and circular ducts
    International Communications in Heat and Mass Transfer, 2005
    Co-Authors: Odgerel Jambal, Toru Shigechi, Ganbat Davaa, Satoru Momoki

    Abstract:

    Abstract Laminar Heat transfer in parallel plates and circular ducts subject to uniform wall temperature is studied by taking into account both viscous dissipation and fluid Axial Heat Conduction in an infinite region. Developing temperature fields are evaluated numerically by a finite-difference method for various Brinkman numbers (Br) and Peclet numbers (Pe). Nusselt numbers are presented graphically for Pe = 10 and Pe → ∞, and Br = 0, ± 0.5 and ± 1 for non-Newtonian fluids described by the power-law model with the flow index of n = 0.5, 1.0 and 1.5. It is shown that Nusselt number has a single fixed value independent of Br in the thermally developing region and its numerical value is equal to that at the fully developed region for non-zero Br, when the preHeating of incoming fluid due to both viscous dissipation and fluid Axial Heat Conduction is considered.

  • effects of viscous dissipation and fluid Axial Heat Conduction on Heat transfer for non newtonian fluids in ducts with uniform wall temperature part ii annular ducts
    International Communications in Heat and Mass Transfer, 2005
    Co-Authors: Odgerel Jambal, Toru Shigechi, Ganbat Davaa, Satoru Momoki

    Abstract:

    Abstract The present paper, which is an extension of a previous study [O. Jambal, T. Shigechi, D. Ganbat, S. Momoki, Int. Commun. Heat Mass Transf. 32(9) (2005) 1165] on laminar Heat transfer to non-Newtonian fluids in parallel plates and circular ducts, deals with concentric annular ducts subjected to a step change in wall temperature. A finite-difference scheme is applied to determine the velocity and temperature fields. Developing Nusselt numbers are graphically shown for various Brinkman numbers and Peclet numbers and the effects of viscous dissipation, fluid Axial Heat Conduction, non-Newtonian behavior together with the radius ratio effect on Heat transfer are discussed.

  • laminar Heat transfer with viscous dissipation and fluid Axial Heat Conduction for modified power law fluids flowing in parallel plates with one plate moving
    Jsme International Journal Series B-fluids and Thermal Engineering, 2003
    Co-Authors: Toru Shigechi, Satoru Momoki, Ganbat Davaa, Odgerel Jambal

    Abstract:

    Using the fully developed laminar velocity distributions obtained by applying the modified power-law model proposed by Irvine and Karni, the thermal-entrance-region Heat transfer of non-Newtonian fluids flowing in parallel plates with one plate moving is investigated taking into account both viscous dissipation and fluid Axial Heat Conduction for two kinds of thermal boundary conditions, namely, constant temperature and constant Heat flux at the moving wall. The energy equation subject to a constant temperature at upstream infinity, fully developed temperature profile at downstream infinity and the appropriate thermal boundary conditions at the upper and lower walls is numerically solved by the finite difference method as an elliptic type problem. The effects of the moving plate velocity, rheological properties, Brinkman number and Peclet number on the temperature distribution and Nusselt numbers are discussed for both Newtonian and pseudoplastic fluids

Benjamin A Wilhite – 3rd expert on this subject based on the ideXlab platform

  • analysis of solid phase Axial Heat Conduction upon hot spot formation in a one dimensional microreactor
    Chemical Engineering Journal, 2019
    Co-Authors: Sunjeev Venkateswaran, Costas Kravaris, Benjamin A Wilhite

    Abstract:

    Abstract A generalized one-dimensional model of a non-isothermal, monolithic microreactor is developed to investigate the impact of solid-phase Axial Heat Conduction upon hot-spot formation. The model consists of a pair of first-order differential equations describing an exothermic reacting fluid which exchanges Heat with the solid-phase that comprises the monolithic microreactor. Solid-phase Axial Heat Conduction and exchange with an isothermal coolant is described by an additional second-order ordinary differential equation, with boundary conditions accounting for the possibility of conductive Heat losses to adjacent fluid distribution manifolds. Criticality analysis is performed using both the explicit Van Welsenaure and Froment (VWF) criteria and implicit Morbidelli and Varma (MV) criteria. Results indicate that the VWF criteria applied to the limiting case of negligible Axial Heat Conduction provides a reliable, albeit conservative, criteria for hot-spot prevention. Additionally, MV criteria applied to the case of sufficiently high Axial Heat Conduction yields criteria for ensuring hot-spot formation. Analysis using MV criteria indicates that the introduction of mild solid-phase Axial Heat Conduction promotes hot-spot formation so long as Heat losses to manifolds is minimal.

  • parametric study of solid phase Axial Heat Conduction in thermally integrated microchannel networks
    Industrial & Engineering Chemistry Research, 2008
    Co-Authors: Angela M Moreno, Kevin Murphy, Benjamin A Wilhite

    Abstract:

    A parametric study is presented to highlight design challenges of thermally integrated microchannel networks for portable chemistry and/or fuels reforming. One-dimensional modeling analysis of Heat transfer in a two-fluid system is presented for the case of (i) two nonreacting fluids (Heat exchanger), (ii) a single exothermic reacting fluid and a second nonreacting fluid (regenerative combustor), and (iii) one exothermic reacting fluid and a second endothermic reacting fluid (Heat exchanger reactor). In each case, the influence of solid-phase thermal conductivity and thermal packaging upon thermal efficiency, reaction conversion, and steady-state multiplicity is investigated. Results demonstrate the importance of both packaging and solid-phase Axial thermal Conduction upon system performance, with optimal performance obtained using low thermal conductivity substrates. Modeling analysis predicts steady-state multiplicity when employing low thermal conductivity materials, illustrating the need for future de…