Enthalpy determinations on the helium‐nitrogen system

Abstract

AbstractExperimental isobaric heat capacity and differential latent heat measurements have been made on the helium‐nitrogen system. Compositions studied were nominal 5, 25, 50, and 100% helium in nitrogen over the range 0 to 2,000 lb./sq.in.abs. and −250° to 50°F.These data, combined with the previously reported work on nitrogen and the Joule‐Thomson coefficients of Roebuck, are used to construct the complete pressure‐enthalpy‐composition network over the investigated limits of pressure and temperature.The enthalpies obtained from experimental heat capacity and Joule‐Thomson data are compared with enthalpies computed from PVT data. The changes of phase determined by differential latent heat measurements are compared with literature vapor‐liquid equilibrium data.This information is used to prepare pressure‐enthalpy diagrams for all the mixtures investigated. A three‐dimensional representation of the data on a pressure‐enthalpy‐composition diagram is presented. Constructions are outlined from which heats of mixing and partial molal enthalpies can be obtained.The thermodynamic network developed is believed accurate within 1% and should be of use to those concerned with low‐temperature separation of helium from nitrogen.