Experimental investigation on a novel pressure-driven heating system with Ranque–Hilsch vortex tube and ejector for pipeline natural gas pressure regulating process

Highlights: • A novel PNG pressure regulating cycle is proposed to improve energy utilization performance. • An ejector and a vortex tube are adopted to realize the continuously absorbing heat from ambient air. • Experimental results are presented to verify its feasibility and advantages. -- Abstract: In this work, a novel pressure-driven heating system with a Ranque–Hilsch vortex tube and ejector to recover pressure losses and absorb energy from the ambient environment to heat pipeline natural gas (PNG) is proposed to take the place of the conventional heating system with a boiler. A vortex tube to produce the high-temperature and low-temperature streams simultaneously with its energy separation effect and an ejector to drive the internal subcycle within the system to heat the low-temperature stream by the ambient air are installed. They regulate the PNG pressure and absorb heat from the ambient air while maintaining simplicity and reliability. To study the performance of this new system, an analogical experimental rig was established with pressurised air as the working fluid. The experimental results verified the heating capacity of the system, in which a significant temperature rise greater than 9 K was obtained with a small pressure drop of approximately 1.0 MPa. Compared with a sole throttling valve, an energy-saving ratio of no less than 0.35 was achieved.