PREDICTION OF FINAL TEMPERATURE FOLLOWING JOULE-THOMSON EXPANSION OF NITROGEN GAS

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