05.5 Liquefaction

Joule-Thomson Expansion (LearnChemE.com, 7min) describes the Joule-Thomson coefficient - (dT/dP)_H. For non-ideal fluids (including liquids), the temperature usually drops as the pressure drops. From a molecular perspective, it requires energy to rip molecules apart when they are in their attractive wells, and this energy must be taken from the thermal energy of the molecules themselves if the system is adiabatic. This video refers to the PREOS.xls spreadsheet to be used more in Unit II, but you can get the idea of how the Joule-Thomson expansion provides a basis for any liquefaction of any chemical, including the liquefaction that occurs in refrigeration and the one that occurs in a process designed to simply recover liquid product (e.g. liquefied natural gas (LNG), aka. methane).

Comphrehension Questions:

1. Referring to the table for R134a in Appendix E-12, compute the fraction liquid at 252K after throttling from a saturated liquid at 300K.

2. Referring to the table for R134a in Appendix E-12, compute the fraction liquid at 252K after expanding a saturated liquid at 300K through a reversible turbine.