Measurement and Correlation of Directional Permeability and Forchheimer's Inertial Coefficient of Micro Porous Structures Used in Pulse Tube Cryocoolers

Abstract

The operation of pulse tube cryocoolers (PTCs) is based on complicated and poorly-understood solid-fluid interactions involving periodic flows of a cryogenic fluid in a flow loop that includes components filled with micro porous structures. CFD simulation is the current trend in modeling of pulse-tube cryocoolers. Such simulations can only be meaningful if correct closure relations are available. The objective of this investigation is to measure and empirically correlate the axial hydrodynamic parameters for two widely used cryocooler regenerator structures. A test section will be designed, constructed and instrumented for the measurements. Porous structures tested will include 325 and 400-Mesh stainless screens, each at two different porosities. Tests will be performed with helium as the working fluid, over a wide range of parameters. The longitudinal permeabilities and Forchheimer s inertial coefficients will then be obtained in an iterative process where agreement between the data and the predictions of detailed CFD simulations for the entire test sections and their vicinity are sought. Empirical correlations representing the longitudinal permeability and Forchheimer s coefficient in terms of relevant dimensionless parameters will then be developed.