Open AccessThermodynamic comparison of small liquid nitrogen generators driven by mixed-refrigerant J-T refrigerators and gas expansion cycles
Author(s) -
Haocheng Wang,
Heng Guo,
G F Chen,
Qinglu Song,
Maoqiong Gong
Publication year - 2020
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/755/1/012021
Subject(s) - refrigerant , isentropic process , exergy , gas compressor , thermodynamics , air separation , liquefaction , bar (unit) , type (biology) , materials science , refrigeration , chemistry , physics , ecology , organic chemistry , biology , oxygen , meteorology
The thermodynamic comparison of small mixed-refrigerant J-T (MRJT) and gas expansion (Kapitza cycle) LN 2 generators are conducted by the exergy method in this paper. Both of two types are employed for low pressure N 2 liquefaction and air separation (< 9.0 bar). Pure N 2 , PSA units or cryogenic air separation columns are used for LN 2 production. The MRJT type is driven by single-stage compressors. It is indicated that the efficiency of MRJT type is higher than Kapitza type. With pure N 2 at 8.0 bar, the figures of merit ( FOM ) of MRJT and Kapitza types are 26.86% and 12.79%, respectively. With mini air separation columns, the FOM of MRJT and Kapitza types are 21.42% and 11.34%, respectively. The large exergy losses in the compressor unit and non-isentropic expansion are the main reasons of the inferior efficiency of the Kapitza type. In addition, the Kapitza type requires larger total compressor displacement than the MRJT type. The MRJT type is recommended to be used in small LN 2 generators.