Experimental and numerical analysis of a two-stage turbo compressor system for industrial superheated steam drying

Industrial drying and dehydration processes require intensive use of energy and account for a large proportion of national industrial energy consumption in industrialized countries. Currently, a high share of this energy is based on the use of fossil fuels with limited utilization of waste heat streams. This leads to a great potential for improvement in order to reduce energy consumption and CO2 emissions. For example, heat pump systems can be applied in drying processes to reduce energy consumption and increase the share of renewable energy while replacing the consumption of fossil fuels. A newly developed compressor technology enables the cost-effective use of heat pumps working at supply temperatures of up to 150 °C.

The aim of this master's thesis was the experimental analysis of the turbo compressor technology performance as well as the development of a numerical turbo compressor model and the evaluation of the two-stage turbo compressor performance.To analyse the performance of the turbo compressors technology, experiments were performed at the test facility developed by SINTEF Energy Research. A suitable numerical turbo compressor model was identified and validated for the development of a system model. The achieved results and experiences were used for the evaluation of the two-stage turbo compressor performance.

The experiments demonstrated a stable operation of the two-stage turbo compressor system. The compressor maps have been created which allow an analysis of the performance and operating range of the turbo compressor. The numerical models were able to reproduce the results in a good approximation and allowed the estimation of further operating points. During this elaboration, the system was able to compress superheated steam from atmospheric pressure to above 3.0 bar, where it can be condensed at a saturation temperature of 133.5 °C. The COP of the performed investigation was 5.9, when the achievable condensation energy is compared to the total amount of energy supplied to the system.