Exergy analysis of the revolving vane expander

• Main Author: Wong, Kin Keong
• Other Authors: Ooi Kim Tiow
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Mechanical engineering::Motors, engines and turbines
• Online Access: http://hdl.handle.net/10356/60490
• Institution: Nanyang Technological University

This report presents an exergy analysis of the Revolving Vane (RV) expander. Exergy, also known as availability, is the maximum amount of useful work that can be derived from a substance in bringing it to an equilibrium state with the environment. The application of exergy analysis is beneficial to the study of the RV expander as it incorporates the first and second law of thermodynamics, which makes the analysis of efficiency more comprehensive. The objectives of the report are to evaluate the sources of irreversibilities or exergy destruction within the expander during operation and to identify the optimum working conditions of the expander. The sources of exergy destruction are identified as throttling of fluid, heat transfer between fluid and expander solid mass, mixing of inflow fluid with bulk fluid in control volumes, and friction between moving components. The working principles of the RV expander are formulated using mathematical modelling and the operation of the expander is simulated using a computer code in Matlab programming language. The working fluid selected is air. The model accounts for the geometrical configuration, valve flow, thermodynamic properties of the working fluid, and leakages within the expander. The exergy analysis model is then applied to identify and quantify the various sources of exergy destruction. The second-law efficiency of the expander under the benchmark operating conditions is 30.0%. A parametric study is conducted to evaluate the optimum working conditions of the RV expander. The parameters which are varied are suction reservoir pressure, rotational speed, and rotational inertia of the cylinder. At each parametric study, one of the parameters is varied while keeping the others constant. By comparing the second-law efficiencies of each parametric study, the result shows that the expander is desirable to operate at high suction reservoir pressure, low rotational speed and low inertia of cylinder.