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This work presents a parametric study on the similitude between hydrogen and helium distribution when released in the air by a source located inside of a naturally ventilated enclosure with two vents. Several configurations were experimentally addressed in order to improve knowledge on dispersion. Parameters were chosen to mimic operating conditions of hydrogen energy systems. Thus, the varying parameters of the study were mainly the source diameter, the releasing flow rate, the volume and the geometry of the enclosure. Two different experimental setups were used in order to vary the enclosure's height between 1 and 2 m. Experimental results obtained with helium and hydrogen were compared at equivalent flow rates, determined with existing similitude laws. It appears, for the plume release case, that helium can suitably be used for predicting hydrogen dispersion in these operating designs. On the other hand e when the flow turns into a jet e non negligible differences between hydrogen and helium dispersion appear. In this case, helium e used as a direct substitute to hydrogen e will over predict concentrations we would get with hydrogen. Therefore, helium concentration read-outs should be converted to obtain correct predictions for hydrogen. However such a converting law is not available yet.

vapor-liquid equilibrium (VLE) data for the (O 2 + C 3 H 8 ) binary system were measured using a "static-analytic" method coupled to a gas chromatograph analysis at temperatures of (110.22, 120.13, 130.58, and 139.95) K. Parameters of a proposed thermodynamic profile were adjusted on the basis of experimental VLE data determined in this work, allowing a complete isothermal phase diagram for this hazardous system to be obtained. The vapor-liquid-liquid equilibrium (VLLE) thermodynamic behavior was predicted by modeling and then confirmed by visual observations. On the basis of this work, solubility values of propane in liquid oxygen can be deduced for both the propane-lean and propane-rich liquid phases at temperatures above the melting temperature of pure propane. The device allowing these data to be measured for such a hazardous mixture is also presented, as are the accuracies of the measurements. Experimental SectionChemicals. Oxygen (CAS no. 7782-44-7) was obtained from Air Liquide with guaranteed mole fraction purity > 0.999995. Propane was provided by Messer with certified mole fraction purity > 0.9995.Apparatus. The method used in the present work was of the "static-analytic" type with a rapid online sampler-injector (ROLSI; Guilbot et al. 7 ) pneumatic microsampling device and online gas chromatographic analyses. 7,8 A 12 cm 3 Hastelloy C276 equilibrium cell was specifically designed and built in order to withstand pressures up to 300 MPa in case of accidental internal ignition of the oxygen-propane mixture. 6 Inside the cell, temperature and pressure were measured with uncertainties † Part of the "Sir John S. Rowlinson Festschrift".