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Uusitalo, Antti
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Uusitalo
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Antti
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Antti Uusitalo
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Numerical Analysis of Aerodynamics and Performance of a Radial-Inflow Micro-ORC TurbineArdaneh, Fatemeh; Zocca, Marta; Uusitalo, Antti; Turunen-Saaresti, TeemuOrganic Rankine Cycle (ORC) has proven to be an effective way to recover waste heat. The performance of ORC systems is profoundly affected by turbine selection, which is one of the most critical components. In this study, a numerical aerodynamic analysis of a micro-ORC turbine is carried out as an effort towards the formulation of a reduced order model (ROM) of the turbine for the dynamic simulation of the complete ORC system. The studied turbine is the radial-inflow turbine of the waste heat recovery micro-ORC test rig at the Laboratory of Fluid Dynamics, LUT University. The performance of the turbine, which features a highly supersonic flow at the stator outlet, is evaluated through steady-state CFD simulations of the complete turbine geometry using linear siloxane MDM (Octamethyltrisiloxane C8H24O2Si3) as working fluid. Results are discussed and compared with experimental data. Turbine efficiency is studied numerically at varying rotational speeds (25000-31000 rpm). A significant fluctuation in the flow angle at the stator is observed at low rotational speeds, while it decreases at higher speeds. At increasing rotational speed, the analysis shows a corresponding increase in the discharged flow rate, and the turbine efficiency up to 0.2061 kg/s and 79.3, respectively. Moreover, the flow features through the turbine nozzle ring and rotor blades are examined and discussed for selected operating conditions- Analytical estimation of the presence of non-condensable gases in the condensate tank of an Organic Rankine CycleDhanasegaran, Radheesh; Uusitalo, Antti; Honkatukia, Juha; Turunen-Saaresti, TeemuThe presence of non-condensable gases (NCGs) can have a negative impact on the ORC performance due to the reduced expansion ratio over the expander. The presence of NCGs can reduce the turbine expansion ratio significantly, especially in such systems in where siloxanes or high molecular weight hydrocarbons are used, requiring condensing pressures well below the atmospheric pressure. The ORC facility that uses siloxane MDM as the working fluid at LUT University has been considered in the present study. Experimental and simulation data of the facility from the previously published studies suggest that defining the working fluid state in the condenser and condensate tank suffers from significant uncertainty due to the existence of NCGs. Therefore, an attempt has been made to analytically estimate the quantities of NCGs present in the condensate tank of the ORC system using 1-D calculations based on ideal gas assumptions. It was assumed, that air is the NCG that is present inside the condensate tank for simplifications. Since the compressibility factor of MDM vapor is close to 1 at such low condensing temperatures, its behavior is close to ideal gas and hence, the assumption of ideal conditions seems viable. Data from three different experimental measurements with varying temperatures have been tested using the proposed analytical method and the corresponding quantities of the MDMair mixture during the system operation have been estimated. The results showed that the presence of the NCG was dominant, especially in the case of measurement data with lower temperatures, and was reduced for higher condensate tank temperatures.
