The screw compressor is a rotary positive displacement compressor, capable of compressing gas, vapors, and refrigerants. It is commonly used in various applications, including building and architecture, food, chemical process, pharmaceutical, metallurgical industries, refrigeration, air conditioning, vehicle superchargers and in cryogenic helium compression applications. The main characteristics that make the screw compressor attractive include high rotational speed, compactness, ability to maintain high efficiency over a wide range of operating conditions, long service life, and good reliability.An oil-flooded twin screw compressor is selected for investigation in the present work due to its reliability, large capacity, and capability to handle helium’s high heat of compression. Oil-flooded screw compressors refers to the oil being injected into the compression process and mixed with helium. The benefits of injected oil are cooling the helium, creating sealing between rotors, lubrication, and higher performance. In helium systems, the loss of power within the compression system is roughly two-thirds. With such a high loss in power, it is imperative to understand the need for investigating the design and thermodynamic parameters that impact the overall performance of these machines.Initially, a review of different types of compressors is carried out to determine the best suited compressor for helium compression in this current work. A numerical model was created to simulate the compression process of the screw compressor. The model consists of three segments: rotor curve generation, thermodynamic analysis, and performance prediction. The geometric data are a necessary input for the thermodynamic analysis; however, the thermodynamic analysis segment can be used for any rotor geometry. The thermodynamic analysis outputs the thermodynamic parameters as a function of the male rotation angle of helium and oil. The performance prediction determines characteristics of performance such as the volumetric and isothermal efficiencies. The model was validated using a commercial software, which was developed on the basis of extensive screw compressor data. The model predicted performance with reasonable accuracy varying at extreme case with a maximum of a 13\% difference. Using the numerical model, the oil analysis in this thesis determined that the compressor performance is highly dependent on oil injection parameters. The isothermal efficiency spanned from 49.9\% to 56.5\% when adjusting the mass flow rate and oil injection position of the oil. Experimental results determined that the discharge temperature has the biggest impact on compressor performance.
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