Numerical Analysis of Double Inlet Pulse Tube Refrigerator

Abstract

Pulse Tube cryocooler or Pulse Tube Refrigerator (PTR) is a compact refrigerator which is capable of attaining a cryogenic temperature below 123 K (-150 K). As there are no moving components at low temperature side of PTR, it attracts the attention of various researchers. The advantages are mainly its simplicity, low vibration at cold end side, low cost, long life span and ease of manufacturing. With the tremendous development in the performance of PTR and due to its compactness, PTR has a wide range of applications like infrared sensors, aerospace, night vision equipments, communication, micro-biological sciences, superconductivity, in medical science and SQUID. In this present work, modeling and numerical simulation is carried out for Double Inlet Pulse Tube Refrigerator (DIPTR).There are various types of PTRs on the basis of way of their development stages. DIPTR is the modification of Orifice Pulse Tube Refrigerator (OPTR), by simply adding one more valve in between the hot end side of pulse tube and inlet to the regenerator. This arrangement is very much useful to prevent the flow of large amount of gas into pulse tube through the regenerator as in case of OPTR. Here, a two dimensional (2D) model of DIPTR is created using ANSYS Design Modeler and Computational Fluid Dynamics (CFD) solution approach is chosen for numerical simulation purpose. The detailed study on cool down behavior at cold end of DIPTR, pressure variation at inlet and also heat transfer has been performed using CFD package FLUENT software (ANSYS FLUENT 15.0.0). Four numbers of cases have been chosen in which the pressure User Defined Functions (UDFs) are different and all other parameters remain unchanged. Pressure UDFs are applied at inlet as a boundary condition to define the oscillating motion of piston inside the piston-cylinder arrangement. The four pressure UDFs are of different wave forms such as Sinusoidal, Rectangular, Triangular and Trapezoidal. Pulse tube dimension is taken as 15 mm diameter and 250 mm length. The regenerator and other heat exchangers are specified as porous zones with a porosity of 0.6. The operating frequency for all cases is 2 Hz. After simulation using four pressure UDFs, it has been found that pressure UDF generating triangular pressure wave is more efficient than other pressure UDFs and a temperature of 111 K is obtained using triangular wave form of pressure.