Speaker
Mr
Thomas M. Kochenburger
(Karlsruhe Institute of Technology, Institute for Technical Thermodynamics and Refrigeration)
Description
High-temperature superconductors offer new perspectives for efficient transportation of electrical energy in urban and industrial power grids. The size of the components is in many cases limited by the available refrigeration technology. In the operating temperature range of 65 – 70 K, cooling is presently achieved by liquid nitrogen, turbo-Brayton plants or batteries of regenerative cryocoolers. However, none of these options is practicable in applications requiring a few kilowatt of cooling power. Also a reduction of the temperature to below 60 K is desirable in order to increase the current density in the superconductors.
Two-stage mixed-refrigerant Joule-Thomson cascades can present a reliable and highly scalable refrigeration alternative in this temperature range. The first stage of the envisioned process consists of a classical mixed-refrigerant cycle for pre-cooling to 120 K. The second, low-temperature stage operates with a mixture of nitrogen, oxygen and neon at high pressure.
In order to avoid combustible hydrocarbon refrigerants in the pre-cooling stage, this work examines the use of a new mixture with low flammability consisting of nitrogen, argon, R-14, R-23 and R-1234yf. The applicability of different equations of state for the prediction of the thermophysical behavior of the mixture by is discussed.
Author
Mr
Thomas M. Kochenburger
(Karlsruhe Institute of Technology, Institute for Technical Thermodynamics and Refrigeration)
Co-author
Prof.
Steffen Grohmann
(Karlsruhe Institute of Technology, Institute for Technical Thermodynamics and Refrigeration, Institute for Technical Physics)
