Thermal Management For Efficient Fast Refill Of Compressed Natural Gas

As an alternative fuel, compressed natural gas (CNG) plays an important role fueling transportation. Like driving other types of vehicles, drivers of CNG-powered vehicles prefer to refill on-board CNG tanks in a short time, which is referred to as fast refill. Accompanied by a fast pressure increase in the cylinder, temperature will also rise significantly due to re-compression work with limited time for the heat to dissipate. This phenomenon ends with a common problem referred to as under-refill, which means less mass filled than the standards. This article presents a summary of the research works to solve this problem and improve fill efficiency by thermal management. Twodimensional axisymmetric CFD (computational fluid dynamics) simulations of unsteady, compressible, turbulent flow in fast refill process are conducted. Three different types of thermal management concepts are discussed, including active cooling, pre-chilling and real-time chilling. The results show that thermal management is a promising way to mitigate the under-refill problem with a maximum of 7% increase of fill efficiency achieved by active cooling. These provide guidelines for future research on improving fill efficiency through cooling strategies in which real-time chilling should be firstly focused on.