Thanks to their positive features, i.e., simple design with a small number of moving parts, easy manufacturing, and low production and purchase costs, multi-vane expanders are promising for application in micro-power organic Rankine cycle systems. These expanders are simple in design, small in dimensions, inexpensive, and feature low gas flow capacity and expansion ratio. The processes of heat exchange inside the working chambers of the multi-vane machine have a significant impact on its operation and efficiency. Therefore, they are undoubtedly important from a scientific and practical point of view. The literature review shows that to date the processes of heat exchange taking place in multivane machines have not been analyzed in detail, therefore there is a lack of experimental and modelling results related to these processes. Although some analytical models related to these phenomena were formulated, there is a lack of comprehensive model analysis. The heat transfer process in a multi-vane machine is also significantly affected by the phenomenon of the boundary layer scraping by a vane. The result shows that this condition leads to disturbances in the fluid velocity profile in the gap between the vane and the cylinder. In this paper, the discussion of heat transfer models and results of experimental research and modelling on the heat transfer in multi-vane expander are reported. Experimental results show that the heat transfer direction changes during the machine operation. Modelling was focused on determining the heat transfer coefficients in the expander under various flow conditions. The comparison of the modelling results suggests that applicability of models available in the literature and applied for modelling the heat transfer in other machines and devices with rotating vanes (e.g., scraped surface heat exchangers) is limited in the case of estimating the heat transfer processes in multi-vane machines.     «

Thanks to their positive features, i.e., simple design with a small number of moving parts, easy manufacturing, and low production and purchase costs, multi-vane expanders are promising for application in micro-power organic Rankine cycle systems. These expanders are simple in design, small in dimensions, inexpensive, and feature low gas flow capacity and expansion ratio. The processes of heat exchange inside the working chambers of the multi-vane machine have a significant impact on its operati...     »