Enhancement of the liquefaction rate in small-scale helium liquefiers working near and above the critical point

Letter.-- et al.Low-temperature research laboratories with typical liquid-helium consumption of the order of tens of liters per day have greatly benefited from the recent development of small-scale liquefiers. In general, these liquefiers are based on Gifford-McMahon or pulse-tube closed-cycle refrigerators with a nominal cooling power ranging from 1 to 1.5 W at 4.2 K. The liquefaction rate for these cryocooler-based liquefiers depends on the pressure at which the helium is liquefied, although the final user conditions of the produced liquid helium are always atmospheric pressure and boiling temperature (e.g., 4.2 K at 100 kPa). Here, we show a systematic study on this effect, in which an enhancement in excess of 70% in liquefaction rate is found experimentally for pressures near and above the critical point of helium (220 kPa). We propose that the underlying mechanism for the liquefaction enhancement is based on the increase in cryocooler cooling power with temperature and the decrease of the helium enthalpy with pressure.Financial support from the Spanish Ministry of Economy and Competitiveness through Project No. IPT-2012-0442-420000, in addition to European Union FEDER funds, is gratefully acknowledged.Peer Reviewe

Système et procédé de liquéfaction de gaz

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly above atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimal liquefaction rates.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, GWR Instruments, Inc.B1 Patente sin examen previ

Sistema y método de licuefacción de gas

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly above atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimal liquefaction rates.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, GWR Instruments, Inc.A3 Informe de búsqueda internaciona

Sistema y método de licuefacción de gas

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly above atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimal liquefaction rates.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, GWR Instruments, Inc.A2 Solicitud de patente sin informe sobre el estado de la técnic

Gas liquef action system and method

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly aboye atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimalliquefaction rates.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, GWR Instrument INCA2 Solicitud de patentes sin informe sobre el estado de la técnic