Joule–Thomson effect

Joule–Thomson effect
Name	Joule–Thomson effect
Discovered	1852
Discoverers	James Prescott Joule; William Thomson, 1st Baron Kelvin
Field	Thermodynamics; Fluid dynamics; Cryogenics

Joule–Thomson effect The Joule–Thomson effect describes the temperature change of a real gas when it undergoes an isenthalpic expansion through a porous plug or throttle, first characterized in experiments by James Prescott Joule and William Thomson, 1st Baron Kelvin. It is a cornerstone of thermodynamics and engineering practice for gas liquefaction, relevant to technologies developed by institutions like Royal Society laboratories, industrial firms such as Air Liquide and Linde plc, and research programs at universities including University of Cambridge, Imperial College London, and Massachusetts Institute of Technology. The effect underpins historical projects from the Haber process era through modern cryogenics applications employed by agencies like NASA and laboratories at CERN.

Introduction

The phenomenon observed by James Prescott Joule and William Thomson, 1st Baron Kelvin in the 19th century involves the cooling or heating of a gas when expanded at constant enthalpy across a restriction; results influenced developments at organizations such as Royal Institution and British Association for the Advancement of Science. Early measurements informed designs by engineers associated with firms like Sulzer and BASF and influenced cryogenic work at institutes such as Cold Spring Harbor Laboratory and facilities run by General Electric. The practical identification of inversion temperatures and throttle behavior fed into projects at Harvard University, University of Oxford, and industrial research at Siemens and Westinghouse Electric Corporation.

Theory and Thermodynamic Basis

Thermodynamic interpretation uses enthalpy as a state function in classical thermodynamics treatments common to curricula at University of Cambridge, Princeton University, and Yale University. The effect arises because real gases deviate from ideal-gas behavior described by equations associated with Sadi Carnot and concepts related to Rudolf Clausius and Ludwig Boltzmann. Analyses employ equations of state developed by John Dalton, Anders Jonas Ångström, and more complex models like the van der Waals equation and Redlich–Kwong equation. Thermodynamic derivations reference properties studied by Josiah Willard Gibbs and formalized in texts by scholars from University of Göttingen and École Normale Supérieure. The sign and magnitude of temperature change depend on intermolecular forces studied in work by Johannes Diderik van der Waals contributors and experimentalists connected to Maxwell-era science at institutions like Trinity College, Cambridge.

Mathematical Description and Coefficients

Mathematically, the Joule–Thomson coefficient μJT = (∂T/∂P)H is derived in frameworks used at Massachusetts Institute of Technology and Caltech and is expressed using partial derivatives central to analyses by Carl Friedrich Gauss and Joseph-Louis Lagrange methods. Derivations employ thermodynamic identities from the work of Rudolf Clausius and Josiah Willard Gibbs and use state functions from equations of state like van der Waals equation, Peng–Robinson equation, and Soave modification. The inversion temperature concept, applied in liquefaction cycles developed by Heinz London-era researchers and industrial pioneers at Linde plc and Air Liquide, marks where μJT changes sign; this concept was integral to low-temperature advances associated with Heike Kamerlingh Onnes at Leiden University and cryogenic studies by Walther Nernst at University of Göttingen.

Experimental Demonstrations and Measurements

Classic experiments by James Prescott Joule and William Thomson, 1st Baron Kelvin used apparatus similar in spirit to setups later refined at National Physical Laboratory and laboratories at École Polytechnique. Measurements require precise thermometry technologies developed by groups at National Institute of Standards and Technology and cryogenic instrumentation advanced at Los Alamos National Laboratory and Argonne National Laboratory. Modern demonstrations use high-pressure facilities and gas-handling systems produced by firms such as Parker Hannifin and research platforms at Lawrence Berkeley National Laboratory. Experimental data have been collected in collaborations between universities like Stanford University and industrial partners including ExxonMobil and Shell plc, informing international standards maintained by organizations such as International Organization for Standardization and American Society of Mechanical Engineers.

Practical Applications and Engineering Use

Engineering exploitation of the effect is central to cryogenic liquefaction processes invented by Carl von Linde and implemented by companies like Linde plc and Air Products and Chemicals, Inc., and underlies refrigeration cycles in technologies marketed by Carrier Global Corporation and Trane Technologies. Processes such as the Linde process and Claude cycle used in natural gas processing and oxygen production are employed at petrochemical complexes run by Royal Dutch Shell and BP plc and in industrial gas facilities operated by Air Liquide. Spaceflight cryogenic systems for agencies like NASA and European Space Agency use Joule–Thomson coolers alongside cryocooler technologies from firms such as Honeywell and Thales Group. Medical applications in magnetic resonance imaging systems at hospitals affiliated with Johns Hopkins University and Mayo Clinic rely on liquid helium produced using Joule–Thomson-based cascades.

Limitations, Exceptions, and Related Phenomena

Limitations arise because ideal gases predicted by Boyle's law and models associated with Jacques Charles show no Joule–Thomson temperature change; exceptions occur near critical points studied by Pierre Curie and André-Marie Ampère-era thermodynamicists. Related phenomena include adiabatic free expansion explored by Émile Clapeyron's successors, throttling losses analyzed in turbomachinery developed by Sir Frank Whittle and Gerhard Neumann, and shock-wave heating encountered in hypersonics researched by Von Kármán-era groups at California Institute of Technology and Princeton University. Advances in theoretical understanding continue in contemporary research programs at Max Planck Society institutes and national laboratories such as Oak Ridge National Laboratory, often in collaboration with corporations like Boeing and General Dynamics.

Category:Thermodynamics