ABSTRACT
Pulse tube refrigerators have no moving parts in the cold region. It brings long-life operation, high reliability, and low vibration at the cold section. A fundamental difficulty in all PTRs is that their working fluid compression and expansion processes are not well-defined, and poorlyunderstood thermal relaxation and phase-lag phenomena dominate their operation. Crucial among these is the phase angle between pressure and mass flow. In this paper, the commercial computational fluid dynamic (CFD) package Fluent is utilized for modeling the ITPTR and OPTR system that includes compressor, a transfer line, regenerator, cold and warm heat exchangers, pulse tube, an inertance tube (ITPTR)/an orifice valve (OPTR) and a reservoir. The simulations represented a fully-coupled system operating in steady periodic mode. The PTR system consists of a dual opposed piston compressor, an aftercooler, a regenerator, a pulse tube, cold and warm heat exchanger, inertance tube/orifice valve and reservoir.
For each system three separate simulations are analyzed. First simulation assumed an adiabatic cold-end heat exchanger (CHX); another assumed a known cooling heat load, and the last assumed a pre-specified CHX temperature. Each simulation started with an assumed uniform system temperature, and continued until steady periodic conditions are achieved. The general results like phase relation between cold end mass flow rate and pressure, temperature distribution along the axial direction, cooling behaviour and refrigeration load is presented and comparison between ITPTR and OPTR has been made.
Results show that the use of the ITPTR configuration offers a better potential for higher performance and efficiency for given geometry.
Keywords: Orifice pulse tube, Inertance pulse tube, dual opposed piston compressor, Regenerator, CFD.
