An Optimization Program for Modeling Pulse Tube Coolers

Abstract

ARCOPTR is a program developed at NASA-Ames Research Center for modeling pulse tube coolers. The ARCOPTR is a 1-D model that treats all the components of an orifice pulse tube cooler or a pulse tube cooler employing an inertance tube. It analyzes the thermodynamic equations for the regenerator and assumes that all mass flows, pressure oscillations and temperature oscillations are small and sinusoidal. The resulting mass flows and pressures are matched at the boundaries with the other components of the cooler: compressor, aftercooler, cold heat exchanger, pulse tube, hot heat exchanger, orifice/inertance tube and reservoir. The results of the calculation are oscillating pressures, mass flows and enthalpy flows in the main components of the cooler. An optimizer has been built into the ARCOPTR that allows optimization of the cooler parameters to attain maximum efficiency. The parameters that can be optimized are the length and the diameter of the regenerator and those of the pulse tube, the wire diameter and the mesh size of the regenerator screen, and the orifice opening or in the case of an inertance tube, its length and diameter. In this study, pulse tube cooler configurations, employing an orifice or an inertance tube, have been optimized using the ARCOPTR. The optimum parameters are plotted as a function of the regenerator diameter. In the optimization the pressure ratio in the pulse tube is maintained at 1.2 by adjusting the compressor stroke.