Abstract
Multi-vane expanders are positive displacement volumetric machines which are nowadays considered for application in micro-power domestic ORC systems as promising alternative to micro turbines and other volumetric expanders. The multi-vane expander features very simple design, low gas flow capacity, low expansion ratios, an advantageous ratio of the power output to the external dimensions and are insensitive to the negative influence of the gas-liquid mixture expansion. Moreover, the multi-vane expander can be easily hermetically sealed, which is one of the key issues in the ORC system design. A literature review indicates that issues concerning the application of multi-vane expanders in such systems, especially related to operating of multi-vane expander with different low-boiling working fluids, are innovative, not fully scientifically described and have the potential for practical implementation. In this paper the results of numerical investigations on multi-vane expander operating conditions are presented. The analyses were performed on three-dimensional numerical model of the expander in ANSYS CFX software. The numerical model of the expander was validated using the data obtained from the experiment carried out on a lab test-stand. Then a series of computational analysis were performed using expanders' numerical model in order to determine its operating conditions under various flow conditions of different working fluids.
Highlights
Organic Rankine Cycle systems (ORCs) are the Clausius-Rankine (CR) vapour power plants adopting low boiling working fluids
ORC systems provide the opportunity for heat harvesting from renewable and waste sources featuring low (40-250 °C) and medium temperature (250-500 °C) of the carrier and convert this energy into electricity, useful heat and cool
Ongoing research and development works on small- and micro-power ORCs are focused on the selection of working fluid, heat exchangers, pumps and expanders design
Summary
Organic Rankine Cycle systems (ORCs) are the Clausius-Rankine (CR) vapour power plants adopting low boiling working fluids. Ongoing research and development works on small- and micro-power ORCs are focused on the selection of working fluid, heat exchangers, pumps and expanders design. Compared to the other types of volumetric machines and micro turbines, multi-vane machines features a lower gas flow capacity and lower expansion ratios It can be hermetically sealed, which is one of the key issues in the ORC system design. Multi-vane machines are insensitive to the negative influence of the gas-liquid mixture expansion which, in the case of powering ORC systems by heat sources featuring floating thermal characteristics, is a great advantage. The above described features of multi-vane expanders indicate that these machines may be a promising alternative to micro turbines and other volumetric expanders applied in small- and micro-power CHP ORC prototypes designed for domestic generation of electricity and useful heat by prosumers. The results from the experiment were in a good agreement with the numerical predictions so the model was validated for a given range of temperature and pressure parameters
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