On departure from local thermal equilibrium in porous media due to a rapidly changing heat source: the Sparrow number

Effect of Adding a Regenerator to Kornhauser's MIT "Two-Space" (Gas-Spring + Heat Exchanger) Test Rig

“…A thermal non-equilibrium model which assumes that the regenerator porous matrix and gas average temperatures can differ by several degrees at a given axial location and time during the cycle is employed. A survey of the porous-media literature supports the need for thermal non-equilibrium porous-media models for Stirling regenerators 1,22,30,34 . Numerical simulation results of the pressure, temperature, velocity and surface heat transfer variations in the 3-space domain are post processed for thermodynamic loss calculations.…”

“…1-D regenerator models, used in Stirling engine design, use thermal non-equilibrium models and suggest regenerator porous matrix and gas average temperatures can differ by several degrees at a given axial location and time during the cycle 33 . A survey of the porous-media literature supports the need for thermal non-equilibrium porous-media models for thermal storage applications such as Stirling regenerators 1,2,22,23,30 . It is anticipated that a thermal non-equilibrium model such as that presented here, when incorporated in commercial CFD codes, will improve our ability to accurately model Stirling regenerators relative to current thermal-equilibrium porous-media models.…”

Multiscale Modeling of Multiphase Fluid Flow

“…Majority of the simulations have been done using idealized volume average models. Volume-averaged simulations based on one-temperature model [189,220] using the LTE assumption have found the results to be inaccurate, for cases where the difference of thermal conductivity between the foam and PCM is very large or when PCM is under rapid heating or cooling especially for small Sparrow numbers [221]. Subsequently, volume-averaged twotemperature model with local thermal non-equilibrium (LTNE) assumption has been utilized.…”

An Initial Non-Equilibrium Porous-Media Model for CFD Simulation of Stirling Regenerators

“…Minkowycz 13 analyzes departure from local thermal equilibrium in porous media due to a rapidly changing heat source. The analysis is done for a sinusoidally-varying imposed heat-flux at one of the boundaries for the cases of no-flow and steady-flow in the same direction as the imposed heat-flux.…”