Analysis and Optimization of Process Parameters of Heat Exchangers and Turbines for Helium Refrigerator/Liquefier

Abstract

A Helium liquefier and refrigerator is very vital component of many superconducting magnets, fusion devices, Tokamaks etc. So it is very important to optimize helium liquefier/refrigerator. This project work involves analysis and optimization of the process parameters (helium flow rate, pressure and temperature) for main components (8 different heat exchangers and 3 different turbo-expanders) of helium plant of refrigeration capacity 1 kW at 4.5 K. This is a part of the indigenous helium plant development work going on at IPR, Bhat, Gandhinagar, Gujrat. Nevertheless, this plant can be operated in mixed mode also as helium refrigerator-cum-liquefier (HRL), although it is optimized for refrigeration load. To optimize process of any helium refrigeration/liquefaction cycle, it is very important to consider one independent variable at a time and under valid assumptions, study and analyze its effect on the process. From the analysis, the optimized value of the concerned and considered process variable is selected. The main components of an HRL that affect process parameters are compressor, heat exchangers ,expansion engines and expansion valves .The present analysis is basically concerned with the parameters of the heat exchangers vis –a-vis expansion engines. In the present analysis mainly total compressor mass flow rate, fraction of total compressor mass flow diverted towards expansion engines (turbo expanders), inlet temperature to various expansion engine and heat exchangers are analyzed and optimized using steady state approach. The present study, analysis and optimization of the important process parameters is done taking logical assumptions and fulfilling important practical constraints that are explained in this report. The work involves:  Study different thermodynamic configurations of HRL.  Study the HRL, existing at IPR.  Study different component working principle and design aspects also.  Study and analyze different practical factors and inefficiencies of main components that can affect the performance of HRL.  Find out different possible methods to analyze the given thermodynamic configuration to find liquefaction and refrigeration capacity. v  Choose the best method from point-4 and make a computer code to analyze and get the HRL performance.  Generate different graphical trends from analysis and optimization for variation of different process parameters of components.  Find the optimum process parameters of main components.