Effectiveness analysis of pre-cooling methods on hydrogen liquefaction process

Effectiveness analysis of pre-cooling methods on hydrogen liquefaction process

The purpose of this analytic study is to design and examine an efficient hydrogen liquefaction cycle by using a pre-cooler. Theliquefaction cycle is primarily comprised of a pre-cooler and a refrigerator. The fed hydrogen gas is cooled down from ambienttemperature (300 K) to the pre-cooling coolant temperature (either 77 K or 120 K approximately) through the pre-cooler. There aretwo pre-cooling methods: a single pre-coolant pre-cooler and a cascade pre-cooler which uses two levels of pre-coolants. Afterheat exchanging with the pre-cooler, the hydrogen gas is further cooled and finally liquefied through the refrigerator. The workingfluids of the potential pre-cooling cycle are selected as liquid nitrogen and liquefied natural gas. A commercial software AspenHYSYS is utilized to perform the numerical simulation of the proposed liquefaction cycle. Efficiency is compared with respect tothe various conditions of the heat exchanging part of the pre-cooler. The analysis results show that the cascade method is moreefficient, and the heat exchanging part of the pre-coolers should have specific UA ratios to maximize both spatial and energyefficiencies. This paper presents the quantitative performance of the pre-cooler in the hydrogen liquefaction cycle in detail, whichshall be useful for designing an energy-efficient liquefaction system.

The purpose of this analytic study is to design and examine an efficient hydrogen liquefaction cycle by using a pre-cooler. Theliquefaction cycle is primarily comprised of a pre-cooler and a refrigerator. The fed hydrogen gas is cooled down from ambienttemperature (300 K) to the pre-cooling coolant temperature (either 77 K or 120 K approximately) through the pre-cooler. There aretwo pre-cooling methods: a single pre-coolant pre-cooler and a cascade pre-cooler which uses two levels of pre-coolants. Afterheat exchanging with the pre-cooler, the hydrogen gas is further cooled and finally liquefied through the refrigerator. The workingfluids of the potential pre-cooling cycle are selected as liquid nitrogen and liquefied natural gas. A commercial software AspenHYSYS is utilized to perform the numerical simulation of the proposed liquefaction cycle. Efficiency is compared with respect tothe various conditions of the heat exchanging part of the pre-cooler. The analysis results show that the cascade method is moreefficient, and the heat exchanging part of the pre-coolers should have specific UA ratios to maximize both spatial and energyefficiencies. This paper presents the quantitative performance of the pre-cooler in the hydrogen liquefaction cycle in detail, whichshall be useful for designing an energy-efficient liquefaction system.