Pressure Drop over Regenerators in Oscillating Flow
Modeling the performance of pulse tube coolers and stirling coolers involves estimating the pressure drop over the regenerator. Such pressure drop estimates are generally based on steady flow correlations which do not necessarily apply to oscillating flow. The present paper contains experimental data on the pressure drop over regenerators subjected to an oscillating flow of helium gas at 300K and a charge pressure of 11 atm. Each regenerator tested consists of a thin wall stainless steel tube packed with just one of the following materials: stainless steel screen of mesh-size 250, 300 or 400, or stainless steel felt made of wires 12 µm or 30 µm in diameter. The oscillating flow is established by means of a linear compressor (15 cc) operating between 40 Hz and 70 Hz connected to the inlet of the regenerator. The mass flow is derived from the measured pressure oscillations in a reservoir connected to the regenerator outlet. A differential pressure gauge is applied over the regenerator. Heat exchangers around and in-line with the regenerator stabilize its temperature. The pressure drop and mass flow data are converted into correlations for the friction factor as a function of Reynolds number at given void fraction and frequency. Steady flow measurements have been applied as a reference in order to note the extent to which the oscillations contribute to the pressure drop.
KeywordsPressure Drop Steady Flow Friction Factor Void Fraction Pulse Tube
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