1,721,121 research outputs found
Energy Performance and Fluid Leakage in Rotary Volumetric Machines at Off-Design Operating Conditions
No full textThe main purpose of the present paper is to establish a thermodynamic model to examine the energy advantages of rotary machines when used as volumetric expanders. The screw expander is a particular volumetric machine which can exploit energy in working fluids of high temperature and pressure to produce mechanical power without high fluid velocities. In this research, to describe the real expansion process of the screw expander, a part-load numerical model is investigated also considering all the energy losses which affect thermodynamic performance at off-design working conditions (including fluid leakage losses). An energetic assessment of the part-load behavior is then performed to predict best working conditions of the screw expander
THERMODYNAMIC ANALYSIS OF SCREW EXPANDERS AT PART-LOAD WORKING CONDITIONS: ENERGY LOSSES, FLUID LEAKAGE AND OVERALL EFFICIENCY
No full textThis research provides fundamental principles to study the thermodynamic performance of the screw expander at part-load working conditions. Screw expanders are rotary-type volumetric machines which can convert thermal to mechanical energy with a satisfactory efficiency even for low-grade heat sources and when expanding fluid in two-phase conditions, unlike standard dynamic expanders which are unable to handle with liquid droplets. However, since screw expanders operate at off-design condition in most situations, calculating expander efficiency under fluctuating working conditions appears to be a crucial issue. Hence, in this study, a part-load thermodynamic model on the real expansion process of the screw expander is investigated considering all the energy losses affecting actual working conditions, also including variable fluid leakage losses. Therefore, in relation to the part-load behavior of this volumetric power machine, the optimum working conditions together with the resultant best global efficiencies are defined and shown. Lastly, the predicted energy performance is compared with experimental data, so obtaining a good agreement between the calculated and measured overall efficiency of screw expanders
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