MODELING OF INERTANCE TUBE BASED ON RLC CIRCUIT ANALOGY Sarkar M., Atrey M. D. Indian Institute of Technology Bombay, Powai, Mumbai - 400076, India. Pulse tube refrigerators (PTRs) are categorized into various types based on the type of phase shifting mechanism involved in it: Basic pulse tube refrigerator (BPTR), Orifice pulse tube refrigerator (OPTR), Double inlet pulse tube refrigerator (DIPTR) and Inertance tube pulse tube refrigerator (ITPTR). ITPTR has thin capillary tube (called as Inertance tube) which acts as phase shifter. This tube provides additional phase shift between pressure and mass flow rate at the warm end when compared with the phase shift provided by simple orifice. Due to this, with proper sizing and dimensioning of phase shifting tube in ITPTR, optimum cooling effect can be achieved. In the present work a simple model to analyze the phase shift characteristics of an Inertance tube has been presented. The basic principle of this model is to establish a simple behavioral character of fluid flow through an Inertance tube, analogous to a RLC circuit. Here every component of a PTR system has been associated with electrical elements & pressure difference and mass flow rates are viewed as potential difference and current. This model is clubbed with Isothermal model for ITPTR, by taking the mass flow rate at the entry of Inertance tube from Isothermal model. The pressure variations obtained are then compared with practical results and they are found to be closer than what obtained from Isothermal model. Key words: Inertance tube, PTR, RLC Circuit, Isothermal Model INTRODUCTION Introduction of an Inertance tube with pulse tube refrigerator (PTR) is one of the most important modifications that have been done for improving the performance of the cryocooler. The phase shift, between pressure and mass flow rate at the warm end in pulse tube section, provided by these thin capillary tubes greatly affects the performance of PTR. Hence deciding the size and length of Inertance tube is very crucial. Many numerical and analytical models have been introduced to analyze the performance characteristics of Stirling type PTR. One of the most important model, is the Isothermal model introduced by Zhu and Chen [1] for Orifice Pulse Tube Refrigerator. In the present work a simple analytical model using RLC circuit analogy has been presented which is clubbed with Isothermal model for Inertance Pulse Tube Refrigerator (ITPTR) to determine the pressure variation in the pulse tube section. The results are compared with that obtained by Isothermal model alone. For the above analysis it is assumed that spatial variation of pressure is negligible and the mass flow rates being closely the same in case of Isothermal model and RLC flow model.