Prediction of final temperature following Joule-Thomson expansion of nitrogen gas

Abstract

This paper shows a theoretical prediction of the final temperature T a which can be obtained using the Joule-Thomson (J-T) effect by expanding nitrogen gas across a throttling valve to 0.101 MPa. An iteration method using the J-T coefficient μ is first used to predict T a. The Benedict-Webb-Rubin (BWR) and Redlich-Kwong (RK) equations are used to determine the specific volume and the derivatives of properties, respectively. Values of T a can be well predicted by a five-step expansion simulation, except for cases where the isenthalpic lines to 0.101 M Pa cross a region around T = 120–160 K and P = 6.0 M Pa. In this region, calculated μ are lower than the experimental data. By equalizing the value of enthalpy after expansion to that before expansion and using the Peng-Robinson (PR) equation to calculate the departure function, the values of T a can also be well predicted by the second method, except for P b > 3.5 M Pa in the cases where T b = 170 and 150 K.