Abstract
Modern process plants for the liquefaction of natural gas operate at high pressure to improve the overall efficiency of the cryogenic process. Following the condensation of the refrigerated gas the pressurized Liquefied Natural Gas (LNG) is expanded to a lower pressure suitable for storage and transportation. The expansion process generates some vapour and cools the remaining liquid.
The aim of using an expander rather than a Joule-Thomson valve is to increase the amount of liquid and to decrease the amount of vapour at the outlet of the expander. By employing a two-phase expander with draft tube at the exit an increased amount of liquid is produced in a near-isentropic expansion process. The fluid dynamic operation and the thermodynamic performance of two-phase LNG expanders is presented and analyzed.