TRANSIENT MODELING OF FLOWS THROUGH SUCTION PORT AND VALVE LEAVES OF HERMETIC RECIPROCATING COMPRESSORS

摘要

The thermodynamic performance of hermetic reciprocating compressors is strongly effected by the design of the suction and discharge port and valve leaves. The experimental indicator or the so called pV diagrams are frequently used to identify the losses caused by the vibration of the valve leaves. In addition to such experimental techniques, extensive research efforts have been spent on the simulation of the thermodynamic cycle of compressors coupled with valve vibrations. However, such simulation models require the so-called flow coefficients both for the ports and the valve leaf openings where these coefficients can be obtained either experimentally or numerically. In this study, the results of the steady state computational fluid dynamics (CFD) analysis conducted for a typical suction port and valve leaf at different lifts and pressure drops are presented. The mass flow rates obtained for different lifts are correlated according to the series orifice model which is widely used in the literature. In the second part of the study, a dynamic pressure difference is applied through the port and the valve leaf and the momentary mass flow rate is calculated via both CFD and the series orifice model employing the flow coefficients derived from the steady state analysis. Both the transient and the cycle integrated characther of the mass flow rates obtained by the two methods are compared to each other and the effects of adapting such a method to the simulation programs are discussed.