Ko, Kang-Hoon (2004-12). Heat transfer enhancement in a channel with porous baffles. Doctoral Dissertation. Thesis uri icon

abstract

  • An experimental and numerical investigation of heat transfer enhancement in a three dimensional channel using wall mounted porous baffles was conducted. The module average heat transfer coefficients were measured in a uniformly heated rectangular channel with staggered positioned porous baffles. A numerical procedure was implemented, in conjunction with a commercially available Navier-Stokes solver, to model the turbulent flow in porous media. The Brinkman-Forchheimer-Extended Darcy model was used for modeling fluid flow through the porous baffles. Conventional, oneequation, and two-equation models were used for heat transfer modeling. The accuracy and characteristics of each model were investigated and discussed. The results were compared with experimental data. Baffles were mounted alternatively on the top and bottom walls. Heat transfer coefficients and pressure loss for periodically fully developed flow and heat transfer were obtained for different pore densities (10, 20, and 40 pores per inch (PPI)) with two different baffle heights ( / h h B D = 1/3 and 2/3), and two baffle thicknesses ( / t h B D = 1/3 and 1/12). The Reynolds number (Re) was varied from 20,000 to 50,000. To compare the effect of foam metal baffles, the data for conventional solid-type baffles was obtained for ( / t h B D =1/3). The maximum uncertainties associated with the module Nusselt number and friction factor were 5.8% and 4.3%, respectively. The experimental procedure was validated by comparing the data for the straight channel without baffles ( / h h B D = 0) with those in the literature. The use of porous baffles resulted in heat transfer enhancement as high as 300% compared to heat transfer in straight channels without baffles. However, the heat transfer enhancement per unit increase in pumping power was less than one for the range of parameters studied in this work. Correlation equations were developed for the heat transfer enhancement ratio and the heat transfer enhancement per unit increase in pumping power in terms of Reynolds number. The conventional theoretical model, the dispersion conductivity model, and the modified two-phase model using the local thermal non-equilibrium theory were considered. The results from each model were compared against the experimental data, and compared to each other to investigate the efficiency of each model. Also, the characteristics of each model were discussed.
  • An experimental and numerical investigation of heat transfer enhancement in a

    three dimensional channel using wall mounted porous baffles was conducted. The

    module average heat transfer coefficients were measured in a uniformly heated

    rectangular channel with staggered positioned porous baffles. A numerical procedure

    was implemented, in conjunction with a commercially available Navier-Stokes solver, to

    model the turbulent flow in porous media. The Brinkman-Forchheimer-Extended Darcy

    model was used for modeling fluid flow through the porous baffles. Conventional, oneequation,

    and two-equation models were used for heat transfer modeling. The accuracy

    and characteristics of each model were investigated and discussed. The results were

    compared with experimental data.

    Baffles were mounted alternatively on the top and bottom walls. Heat transfer

    coefficients and pressure loss for periodically fully developed flow and heat transfer

    were obtained for different pore densities (10, 20, and 40 pores per inch (PPI)) with two

    different baffle heights ( / h h B D = 1/3 and 2/3), and two baffle thicknesses ( / t h B D = 1/3

    and 1/12). The Reynolds number (Re) was varied from 20,000 to 50,000. To compare

    the effect of foam metal baffles, the data for conventional solid-type baffles was

    obtained for ( / t h B D =1/3). The maximum uncertainties associated with the module

    Nusselt number and friction factor were 5.8% and 4.3%, respectively. The experimental

    procedure was validated by comparing the data for the straight channel without baffles

    ( / h h B D = 0) with those in the literature.

    The use of porous baffles resulted in heat transfer enhancement as high as 300%

    compared to heat transfer in straight channels without baffles. However, the heat transfer

    enhancement per unit increase in pumping power was less than one for the range of

    parameters studied in this work. Correlation equations were developed for the heat

    transfer enhancement ratio and the heat transfer enhancement per unit increase in

    pumping power in terms of Reynolds number.

    The conventional theoretical model, the dispersion conductivity model, and the

    modified two-phase model using the local thermal non-equilibrium theory were

    considered. The results from each model were compared against the experimental data,

    and compared to each other to investigate the efficiency of each model. Also, the

    characteristics of each model were discussed.

publication date

  • December 2004