Exergy Optimization in a Steady Moving Bed Heat Exchanger Articles uri icon

publication date

  • January 2009

start page

  • 584

end page

  • 600

volume

  • 1161

international standard serial number (ISSN)

  • 0077-8923

electronic international standard serial number (EISSN)

  • 1749-6632

abstract

  • This work provides an energy and exergy optimization analysis of a moving bed heat exchanger (MBHE). The exchanger is studied as a cross-flow heat exchanger
    where one of the phases is a moving granular medium. The optimal MBHE dimensions
    and the optimal particle diameter are obtained for a range of incoming fluid
    flow rates. The analyses are carried out over operation data of the exchanger
    obtained in two ways: a numerical simulation of the steady-state problem and an
    analytical solution of the simplified equations, neglecting the conduction
    terms. The numerical simulation considers, for the solid, the convection heat
    transfer to the fluid and the diffusion term in both directions, and for the
    fluid only the convection heat transfer to the solid. The results are compared
    with a well-known analytical solution (neglecting conduction effects) for the
    temperature distribution in the exchanger. Next, the analytical solution is used
    to derive an expression for the exergy destruction. The optimal length of the
    MBHE depends mainly on the flow rate and does not depend on particle diameter
    unless they become very small (thus increasing sharply the pressure drop). The
    exergy optimal length is always smaller than the thermal one, although the
    difference is itself small.