Analysis of cooling capacity and optimization of compressor outlet pressure for KW class helium refrigerator/liquefier

Abstract

The main components of a helium liquefier determines the performance for a given compressor flow rate are Turbine, HE and JT valve. Turbine and JT valve produces cooling effect by isentropic and isenthalpic expansion. For each configuration main components can have different operating process parameters leading to different performance of HRL. This project involves the analysis and optimization of compressor outlet pressure for a given configuration. JT valve is at the lowest temperature to get the highest liquefaction which depends on the performance of other components so optimization of process parameter of JT valve is not considered here. One of the different cycle configurations is analyzed and is often used in HRL. This configuration, planned to use for the indigenous helium plant, has 3 turbines and 8 HE which produces liquid helium at 4.5 K. 1st and 2nd turbines operates at warmer temperature compared to 3rd and those are connected in series. Helium stream coming out of the 1st turbine passes to HE which will reduce its temperature before entering the 2nd turbine. Helium flow rate supplied by the compressor system is 210 g/s at 14 bar and 310 k. Effects of compressor flow rate and pressure on the cooling capacity of the plant have been analyzed. A part of this flow rate passes through a 1st and 2nd turbine for isentropic expansion to 1.2 bar and then this low pressure helium stream comes back to compressor suction through different HE to transfer cooling effect to the hot stream coming from the compressor. 3rd turbine will expand to 4 bar and this stream further passes through a HE before entering the JT valve for liquid helium production. This work involves different practical factors and in efficiencies of main components. The analysis result for flow of 140 g/s at 14 bars is further compared with the performance of existing helium plant at IPR which has same compressor flow parameter. The results are also compared with that of the aspen tech software.