Have you ever wondered how the images taken by the Hubble Space Telescope can reveal galaxies and stars which are many light years away? The Telescope itself is subject to intense cycles of hot and cold as it revolves around the earth, but seldom falters in its performance. The fantastic high resolution images taken by the Hubble telescope have Cryogenic Technology to thank, for keeping their imaging sensors working well.
Cryogenics is the branch of physics that deals with very low temperatures and their effect on matter. It is the science and technology of temperatures below 120 K. Liquid natural gas, liquid propellants of rocket engines, and liquid nitrogen and oxygen for medical applications are examples of applications of Cryogenic Technology.
In the field of space applications, infrared sensors are very important for measuring chemical constituents in the atmosphere, viewing distant galaxies and stars, for identifying and tracking targets within a missile-defense system. The sensors have to be cooled to cryogenic temperatures for operation and efficiency. Cryocoolers are mechanical devices that can achieve cryogenic temperatures. Pulse tube cryocooler technology enables the infrared sensors to be cooled in a reliable, efficient manner for long periods of time upto many years.
Scientists from the Indian Institute of Science have developed an indigenous pulse tube cryocooler which can achieve temperatures of 74 K. It is driven by a light weight, high efficiency moving magnet pressure wave generator. This is cold enough to condense oxyen, argon and even nitrogen.. Their “Stirling type pulse tube cooler and pressure wave generator” uses helium gas as a coolant, and runs with an input power of 59 Watts.
This type of cryocooler is a 'regenerative'cryocooler. The main heat exchanger in this cooler is a regenerator. In a regenerator, incoming hot gas transfers heat to the matrix of the regenerator, which is transferred to the cold gas, flowing in the opposite direction through the same channel. This is similar to how the human body cools itself. When warm blood flows from the muscles to the skin, some of the heat is lost through the skin to the air, and some is lost into the adjacent tissue. Cold blood on the way back from the skin collects some of the heat in the tissue helping cool the new warm blood flowing towards the skin a little better. The tissue is the regenerator.
Now that the working prototype has been built, the team of scientists are confident of increasing the efficiency and cooling power . “By reducing the wall thickness of the regenerator, the parasitic loads can be reduced and the design target can be achieved,” suggests Mr. Kranthi in the manuscript.
About the Authors:
Kranthi Kumar J. is a PhD student at the Center for Cryogenic Technology, IISc. Dr. Jacob S. andDr. Karunanithi R are professors at the Center for Cryogenic Technology, IISc. Dr. Narasimham G. S. V. L. is a Professor at the Department of Mechanical Engineering, Indian Institute of Science. Damu C., Praveen T., Samir M., were project staff at the Center for Cryogenic Technology.
Their manuscript has been published in Physics Procedia: http://www.sciencedirect.com/science/article/pii/S1875389215004356