Joule‐Thomson effects for mixtures of helium‐nitrogen‐methane and hydrogen‐nitrogen‐methane

Abstract

Experimental isenthalps and correspondingThis paper presents a body of reliable thermodynamic data for two ternary gas mixtures over a practical range of pressures and temperatures. The prediction methods for Joule-Thomson coefficients are then applied using the virial equation and several other empirical equations of state.Several of the standard mixture rules were used for the constants in these equations in an effort to shed light on the question of how to use equations of state in cases where gas mixtures include simple, but dissimilar gas molecules. MATERIALSTwo ternary gas mixtures, each containing one of the socalled quantum gases, were chosen for study. It was felt that these would afford a relatively difficult application for equation of state mixing rules, as well as being of some current practical interest.One mixture ( A ) was an equimolar mixture of helium, nitrogen, and methane, and the other mixture ( B ) was an equimolar mixture of hydrogen, nitrogen, and methane. The two ternary mixtures were obtained as mixtures of chemically pure grade helium, hydrogen, and methane, and a prepurified grade of nitrogen, from Air Products and Chemicals, Inc.Nominal compositions of the gas mixtures were checked by chemical analysis of samples drawn from the experimental system at the end of each run in the program. The composition of mixture A was obtained by a weighted average of four analyses from two industrial analytical laboratories to give 34.1 2 0.2 mole % helium, 33 5 2 0.7 mole % nitrogen, and 32.4 & 0.5 mole % methane. Mixture B was analyzed by the same laboratories from three separate samples to give 32.6 0.3 mole % hydrogen, 33.2 f . 0.7 mole % nitrogen, and 34.2 2 0.5 mole % methane. EXPERIMENTThe experimental procedure, as described by Stockett and Wenzel (25) and by Ahlert and Wenzel (2), consisted of measuring integral Joule-Thomson effects by expanding the gas across an insulated throttling valve. Once equilibrium was established in the circulating gas system observations were recorded at 5-min. intervals over a period of 45 min. The criterion for equilibrium was that the variations in temperature of all the thermocouples in the system was within 0.06 to 0.08"K. over a 15-min. period, The usual variation experienced in t h i s investigation over a 15-min. period was about 0.02"K. Each set of observations included the recording of the inlet and outlet gas temperatures, the two corresponding valve surface temperatures, the flow rate, and the inlet and outlet pressures. Temperatures and pressures were read to 0.002"K. and 0.1 lb/s in., respectively. The usual procedure in developing the isen&lp was to pass through a series of decreasing outlet pressures while maintaining the inlet pressure and temperature constant. The pressure was reduced in steps of 150 to 200 lb./sq.in.abs.Errors in this system were carefully analyzed by Ahlert and Wenzel (2), and this analysis was confirmed both analytically and experimentally here. The cumulative effect of all errors is heavily influenced by pressure gauge pre...

Joule–Thomson Effect on a CCS-Relevant (CO2 + N2) System

“…At present, most of the research studies on the Joule–Thomson effect focus on pure substances such as N 2 , CO 2 , H 2 , Ar, He, CH 4 , C 2 H 2 , etc. − Also, there are also a small number of binary and ternary mixtures’ Joule–Thomson effect reports. − For binary systems, only (CO 2 + CH 4 ) and (CO 2 + Ar) systems that contain the components relevant to CCS have been reported. Due to the difficulty in constructing experimental devices and measuring the Joule–Thomson effect, equations of state, − molecular simulation, − and computer software modeling have been popular with mathematical modeling on the Joule–Thomson effect, in recent years.…”