Theoretical Study on the Performance of a Wet Turbine for Helium Refrigerators
In a large helium refrigerator, the power input can be reduced by using the expansion process of a wet turbine in place of a J-T valve (Joule Thomson valve). The cooled helium gas with a temperature between 6 K and 9 K and a pressure of 12 Bar is liquefied between 15 % and 80 % in the wet turbine, depending on the operating condition of the liquefying mode and the refrigerating mode. The turbine efficiency or performance is considered to be largely affected by the growth of the liquid phase in the expansion process of the turbine. In this study, a theoretical method is proposed to calculate the wetness effect of the helium on the turbine performance, and it is shown for a radial inflow wet turbine that the turbine output at 4.5 K is 5 % lower at 20 % of wetness and 20 % lower at 80 % wetness.
KeywordsExpansion Process Work Output Turbine Rotor Slip Ratio Turbine Inlet Temperature
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