Speaker
Mr
Thomas M. Kochenburger
(Institute of Technical Thermodynamics and Refrigeration, Karlsruhe Institute of Technology, Germany)
Description
High temperature superconducting devices are currently tested worldwide in many pilot projects for the efficient transportation of electrical energy. Primary cooling down to 65 – 70 K is mostly achieved by either subatmospheric liquid nitrogen, by closed cycle turbo-Brayton plants or by batteries of Stirling cryocoolers. In order to increase the current density in the superconductors, a further reduction of operating temperatures to below 60 K is desirable. This work examines the potential of two-stage mixed refrigerant cascades as an efficient and reliable alternative for cooling in this temperature range.
The envisioned process consists of a low-temperature stage operating between about 55 and 120 K with a refrigerant mixture consisting of neon, nitrogen and oxygen at high pressure (100/45 bars at pressure/suction side, respectively) . The inclusion of oxygen lowers the freezing temperature of the mixture to about 52 K. Precooling to 110 – 120 K is achieved with a high temperature stage consisting of a conventional mixed refrigerant cycle.
The concept was evaluated by simulation of the low temperature stage with Aspen Plus. First results predict an overall efficiency of 7.1 % of Carnot. The influence of the fluid property models on calculated cycle efficiency and optimum composition is discussed.
Primary author
Mr
Thomas M. Kochenburger
(Institute of Technical Thermodynamics and Refrigeration, Karlsruhe Institute of Technology, Germany)
Co-authors
Prof.
Lothar R. Oellrich
(Institute of Technical Thermodynamics and Refrigeration, Karlsruhe Institute of Technology, Germany)
Prof.
Steffen Grohmann
(Institute of Technical Thermodynamics and Refrigeration, Karlsruhe Institute of Technology, Germany)
