A thermodynamic analysis of refueling a Natural Gas Vehicle cylinder from a cascade reservoir using chilled natural gas

Fill ratios obtained using the chilled gas were greater than refueling at ambient, however it was expected that using chilled gas fill ratios would be greater than 80%, this was not observed. The highest fill ratio obtained was 70.13%. Further analysis on the performance of the reservoir temperatures selected showed that the lower reservoir temperatures mitigated the effects of the Heat of Compression during refueling far better than refueling from ambient. This manifested in reduced in-cylinder temperature rise during refueling and higher fill ratios at completion of fill. Therefore, it was concluded that the Reservoir Temperature (Tres) has the greatest effect on the refueling process and lower Reservoir Temperatures are key to obtaining fill ratios >80%. Further study is definitely required into this novel method of obtaining a quality fill with CNG.