Thermodynamic analysis of a CNG refueling station considering the reciprocating compressor

Abstract

The reciprocating compressor is the heart of a CNG refueling station with dominating influence on refueling process. The main operating cost of a CNG refueling station arises from the compressor input work. The reciprocating compressor have not been subjected to previous studies which investigated the CNG refueling stations. The main objective of the present work is to apply a thermodynamic analysis for modeling a CNG refueling station, including on-board NGV cylinder, reservoir tanks, connecting pipes and especially reciprocating compressor. Unlike most previous researches, pressure variation of the reservoir tanks during the filling process have been considered which necessary for compressor modeling. The results of the present work have been validated against the previous experimental data and theoretical studies. The additional experimental data, measured by the present authors, is also used to analyze and identify the compressor performance in unsteady conditions. The simulation result of mass flow rate is a good agreement with the experimental values. The results show that variations in the compressor discharge pressure have no effect on the first and intermediate compressor pressure. It has also no effect on the compressor delivery mass flow rate. The energy consumption by the compressor for a cycle (including discharge and charge zones) is found to be 61.86 kWh. The average specific energy consumption to fill a vehicle is found to be 0.250 kWh/kg.