Heat Transfer Study for Estimating Temperature Distribution inside the Sample Environment of a Helium Gas Cryocooler

The superconductive character of a material is mainly dependent on three factors, one of which is temperature. The exceptional feature about superconductors is that once current is setup in them, it can persist in superconducting loops virtually for several years without decay given the adequate conditions of temperature, current density and magnetic field. In this thesis we discuss the thermal characteristics inside the cryocooler utilized in testing High Temperature Superconducting (HTS) materials. The test sample is cooled to temperatures as low as 4.2 K in a space filled with helium gas. Prior experiments were conducted using liquid nitrogen and therefore only tested to 77 K. The opportunity to use helium gas instead of liquid cryogens such as liquid nitrogen and helium, offers a more flexible and safer environment. The cooling in a cryocooler system is mainly driven by conduction and convection heat transfer through the helium gas, therefore it is generally not as good as a cryogenic liquid in removing heat produced during an experiment. To verify that the system can be properly utilized for the planned experiments, it became necessary to estimate the temperature distribution in the cryostat when a typical thermal load such as the test rig hardware is placed in the sample area of the cryocooler. An analysis using finite element model was sought to provide answers regarding the temperature profile. The results demonstrated that the amount of mass and material properties of the test rig elements can affect the temperature distribution. These finding can help in designing test hardware adequate for a given test requirements.