Time Resolved Mass Flow Measurement for a Reciprocating Compressor

The instantaneous mass flow was measured during the intake and discharge processes of a reciprocating gas compressor (1)*. The purpose of these measurements was to identify the mechanism which caused a loss of adiabatic and volumetric efficiency that could not be accounted for by valve flow losses. The measurements were made wi ·th square-edged orifices and fast response differential pressure transducers. The time integral of the flow checked within 2 percent of the average flow measured by calorimet.ric means. The instantaneous mass flow rates and the P-V data were used to integrate the unsteady First Law of thermodynamics for an open system in order to obtain instantaneous mixed mean gas temperature and instantaneous heat flux into the gas. The results show that poor compressor performance was caused by the entropy generation associated with the cyclic heat transfer between the compressor wall and the gas, the magnitude of which was on the order of compressor power. A phase lag was also found between the heat flux and the temperature difference based on the bulk gas temperature, indicating that conventional heat transfer correlations based on this 6T will be indadequate.