Post-doc: Heat transfer characterization in cryogenic environments

Organisation/Company CNRS Department Institut NEEL Research Field Engineering Chemistry Physics Researcher Profile Recognised Researcher (R2) Application Deadline 2 Feb 2026 - 23:59 (UTC) Country France Type of Contract Temporary Job Status Full-time Hours Per Week 35 Offer Starting Date 1 May 2026 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Is the Job related to staff position within a Research Infrastructure? NoOffer DescriptionLiquid hydrogen is characterized by several important limitations and challenges that restrict its current use. One of them is the cryogenic boiling losses associated with storing, transporting and handling of liquid hydrogen and which can consume up to 40% of its available combustion energy. Molecular hydrogen exists in two allotropic (spin isomers) forms, ortho-hydrogen and para-hydrogen, differentiated by the nuclear spin state of the protons in each hydrogen atom. For a given temperature, the equilibrium ratio of ortho- to para-hydrogen concentrations can be calculated [1]. However, the kinetics of the conversion can take weeks when the temperature is rapidly dropped, and this conversion is exothermic. Therefore, reliable in situ measurement's method of this ortho-para ratio is important for the hydrogen industrial sector.One way to measure these concentrations consists in using the thermal properties of hydrogen, such as the enthalpy difference [2] or the difference of thermal conductivity [3] between ortho and para hydrogen. Transport of heat in a fluid is usually assumed to be determined together by advection and diffusion phenomena. In some specific cases, transport of heat relies upon complex processes at molecular scale that can potentially deviate from conventional transport by heat diffusion. In these conditions, the thermal conductivity is no longer a constant parameter but varies in time and space, leading either to faster or slower heat transport. Fluids close to super-critical conditions like dihydrogen in cryogenic conditions exhibit for instance a super diffusivity of heat with a transport much faster than expected by normal diffusion [4]. A solid understanding of the anomalous transport properties of heat in unconventional conditions [5] opens the way for more robust and faster concentration estimates based on thermal conductivity measurements.[1] L. Barrón-Palos, R. Alarcon, S. Balascuta et. al., Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission, Nuclear Instruments and Methods in Physics Research, 2011, 659, 579-586.[2] J. Essler, C. Haberstroh, Performance of an ortho-para concentration measurement cryostat for hydrogen, AIP Conf. Proc., 2012, 1434 (1), 1865–1872.[3] D. Zhou, G.G. Ihas and N.S. Sullivan, Determination of the Ortho-Para Ratio in Gaseous Hydrogen Mixtures, Journal of Low Temperature Physics, 2004, 134, 401–406.[4] B. Zappoli, D. Bailly, Y. Garrabos et al., Anomalous heat transport by the piston effect in supercritical fluids under zero gravity, Phys. Rev. A, 1990, 41(4), 2264.[5] A. Lemarchand, B. Nowakowski, G. Dumazer, and C. Antoine, Microscopic simulations of supersonic and subsonic exothermic chemical wave fronts and transition to detonation, Journal of Chemical Physics, 2011, 134, 034121.The objective of the ANR PARACHUTE project is to develop a reliable, portable sensor based on indirect measurement of thermal conductivity. The postdoctoral researcher will participate in the design of a cryostat with engineers from the Néel Institute. This cryostat will be used to conduct kinetic studies of ortho-para conversion using a Raman spectrometer, which will serve as a reference tool for monitoring the ortho-para ratio over time. In addition, a sensor based on indirect measurement of thermal conductivity, developed in parallel with the project, will be tested by the postdoctoral researcher for the characterization of ortho-para mixtures.The postdoctoral researcher will also be responsible for developing and using physical models and behavioral models to extract information on ortho and para H2 concentrations under laboratory conditions. Finally, he or she will propose an evaluation of the method's effectiveness and suggestions for improving test conditions.The project is a collaboration between Néel Institute (https://neel.cnrs.fr/) and Laboratory George Friedel (LGF – UMR 5307 – Mines Saint-Etienne https://www.mines-stetienne.fr/lgf/) within the PAR-ACHUTE project, funded by the ANR. The position will be based at Néel Institute in Grenoble, with regular meetings to Mines Saint-Etienne. Coordinators and colleagues: Patricia de Rango and Guillaume Donnier Valentin (CNRS Néel Institute), Riadh Lakhmi, Mathilde Rieu and Guillaume Dumazer (EC-LGF), and Gaetan Becker (Fives CRYO).The candidate will be employed by CNRS at Institut Néel, with a fixed-term post-doctoral contract for a duration of 18 months.The Institut Néel is a CNRS laboratory (related to CNRS Physique) with around 300 permanent staff and 150 PhD students and post-doc. As a fundamental research laboratory in condensed matter physics, the Néel Institute also forges interdisciplinary links with chemistry, engineering and the life sciences. The main areas of research are magnetism and spin electronics, photonics and non-linear optics, quantum, molecular and wide band gap electronics, correlated systems, quantum fluids and superconductivity, as well as materials for energy. The post-doc recruited will join the Matériaux Rayonnements Structure (MRS) team, whose expertise ranges from elaboration methods to structural and functional characterization, supported by theoretical developments. This team has been working for many years on metal hydrides for hydrogen storage, and has several hydrogen test benches at its disposal. Researchers at the Institut Néel benefit from the support of a dozen technology clusters, and in particular the Cryogenics cluster, which focuses on the design, production and development of original cryogenic devices. Mines Saint-Etienne describes itself as a responsible engineering school, driving innovation with a societal impact. With over 200 years of history and the excellence of our staff and students, we are committed to education, research, innovation, transfer to industry and scientific, technical and industrial culture. With 2,500 students, 500 staff and a budget of €50m, we have 3 campuses dedicated to the industry of the future, health and well-being and digital sovereignty and microelectronics, located in 3 major cities: Saint-Etienne, Lyon and Aix-Marseille-Provence. Ranked in the national Top 10 by the magazine l'Etudiant and in the international rankings, Mines Saint-Etienne is a member of the T.I.M.E. network of the world's best technological universities and, through its membership of the Institut Mines-Telecom, a member of the European University EULIST. The SPIN centre (Science of Industrial and Natural Processes), which will be heavily involved in the post-doc, is developing its expertise within Mines Saint-Etienne in the field of Process Engineering applied to dispersed systems: grains, particles, drops, bubbles and porous media. He also has skills in the development of sensors and instrumentation.PhD in Physics of transport processes, Thermodynamics, Condensed-Matter Physics or a closely related discipline.The project's subject includes different disciplines (fluid mechanics, transfers, engineering, automatics) and involves also digital and experimental development. Therefore, strong versatility is expected from the candidate.Excellent written and oral communication skills. #J-18808-Ljbffr