Publication
Hermetic, small-scale turbo compressors supported on gas-lubricated bearings and driven by high-speed electric motors represent a promising technology to increase the efficiency of domestic heat pumps and air conditioners. Moreover, thanks to the oil-free system and the high power density compared to positive displacement machines, turbo compressors offer promising perspectives for further applications in transportation. This paper describes the design of a brine-to-water heat pump test bench for small-scale oil-free turbo compressors. The system tests simulate the operating points of the turbo compressor under real heat pump conditions. In addition, the surge and power limits of the compressor are measured, as well as the efficiencies of the frequency converter and the system. The motor test speed ranged from 120'000 to 230'000 rpm. Preliminary experimental tests were performed with evaporating temperatures ranging from -10 degrees C to 15 degrees C. The tests have shown that the simulated operating points can be achieved up to a pressure ratio of 2.75. For higher pressure ratios, the surge line and the maximal electrical power become limiting parameters. Out of this experimental data, potential applications like residential or aerospace air conditioning or floor heating applications are proposed. Furthermore, an outlook for future tests and system modifications is given.