In order to discuss a pulse-tube refrigerator using thermoacoustic theory, one must know the behavior of oscillating fluid. Already proposed are two methods of estimating fluid behavior: simulation employing the virtual PV method and simulation using
THERMOACOUSTICA based on the thermoacoustic theory. Here, we propose an other method of estimating fluid behavior without using simulation. Since the thermoacoustic theory is one of the linear theories, a pulse-tube refrigerator is represented by an electric circuit, except for parts where the temperature distribution is inhomogeneous. The pulse-tube part, where the temperature is inhomogeneous, is permitted to be represented by an electric circuit, because thermodynamic process of fluid in the part is isentropic in good approximation. Thus, a pulse-tube refrigerator except for the regenerator corresponds to an equivalent circuit. Oscillating pressure and volume velocity correspond to AC voltage and AC current, respectively. Work flow corresponds to electric power transmitted and fluid channel to a transmission line with loss. The kinematic energy of fluid corresponds to the energy of a magnetic field, potential energy due to gas-spring to the energy of an electric field, dissipation of the kinetic energy to dissipation due to series resistance of inductance in the equivalent circuit and dissipation of the potential energy to parallel resistance of capacitance in the circuit. Numerical examples clarify the difference of fluid behavior in the pulse-tube part among the basic pulse-tube, orifice type and double inlet refrigerators. Finally proposed are experimental approaches of estimating circuit parameters and a new method of controlling third generation pulse-tube refrigerators.
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