NUMERICAL AND EXPERIMENTAL INVESTIGATION ON THE ROTARY VANE EXPANDER OPERATION IN MICRO ORC SYSTEM

asme-orc2015 Tracking Number 78

Volumetric expanders are nowadays used in micro, small and medium power ORC systems. As it was indicated by Bao and Zhao (2013) most often spiral and screw machines are applied. However, it can be seen that the application of rotary vane expanders is also growing (Tchanche et al. (2011)). Rotary vane expanders are particularly interesting because of the many advantages they have. The most important features of such expanders are: very simple construction; high power in relation to the dimensions; the ability to operate in low inlet pressure and wet gas conditions; low weight; lack of clearance volume; lack of steering valves; possibility to construct an oil-free machines; ease of sealing; the ability to operate at low rotational speeds and a low price. As it was described by Gnutek and Kolasiński (2013) power range of the rotary vane expanders is 0.1—7 kW, thus these machines are particularly interesting for micro and domestic ORC systems. Vane expanders used in ORC systems are very similar to these commonly used in pneumatic systems, however, it is necessary to carry out the appropriate adaptation of the machine. This includes special hermetic sealing, lubrication and cooling. As a part of the research works on ORC power systems with vane expanders conducted by the authors on Wrocław University of Technology a research test-stand (comprehensively described by Gnutek and Kolasiński (2013)) was designed and realized. This micro power, R123 based, ORC prototype enables experimental analysis of the vane expander operation under different conditions. In this article authors present the results of numerical simulation of vane expander operation in ORC prototype and compared them with the results of experiment. 3D model of the expander was built and analyzed in ANSYS CFX based on the geometrical data obtained by complete disassembly of the machine. The numerical analysis included the same, as in the case of the experiment, expander operating conditions, i.e. pressure, temperature and R123 flow rate at the inlet and outlet of the expander.