Optimization of the Composition of a Gas Mixture in a Joule-Thomson Cycle

• Published in: HVAC&R research Vol. 10; no. 2; pp. 213 - 230
• Main Authors: Keppler, Florian, Nellis, Gregory, Klein, Sanford A.
• Format: Journal Article
• Language: English
• Published: Atlanta Taylor & Francis Group 01.04.2004; Taylor & Francis Ltd
• ISSN: 1078-9669; 2374-4731; 1938-5587; 2374-474X
• DOI: 10.1080/10789669.2004.10391100

Mixed gas working fluids can be used within Joule-Thomson devices to achieve a greater refrigeration effect than is possible with a pure substance. Lower temperatures and higher cooling powers can be obtained with appropriate mixtures, resulting in lower operating pressures and mass flow rates. This paper describes a computational tool that allows the composition of gas mixtures to be optimized for a particular operating condition. Automated optimization algorithms are described, evaluated, and validated for two- and three-component mixtures consisting of nitrogen and various hydrocarbons. A genetic optimization algorithm was found to be the most robust and reliable technique and was adapted to this application. Subsequently, the optimization space was extended to a larger number of components for a range of load temperatures and operating pressures. The performance of optimized hydrocarbon gas mixtures is compared with that of nonflammable hydrofluorocarbon mixtures for a range of load temperatures and supply pressures.