Numerical Simulation of Natural Gas Pipeline in Dense and Hybrid Phases

Transmission of natural gas via pipelines is predominantly employed due to its cost-effectiveness compared to other methods. Transportation of natural gas through pipelines faces several challenges, such as high energy consumption, significant pressure drops, and two-phase flow problems. In this study, the transmission of natural gas in dense, hybrid (regions of dense phase and near-dense phase), and vapor phases was investigated to address some of these limitations. Additionally, mathematical models of quadratic forms for the pressure drop in the dense phase and hybrid modes, in terms of the diameter, mass flow, and length of the pipeline, were proposed. According to the models, the pipeline diameter had a more significant effect on the pressure drop than the flow rate and pipeline length. Moreover, the results showed that the energy consumption of the heat exchanger for the hybrid mode was 35% less than the dense phase. On average, the densities in dense phase and hybrid modes were 2.5 times higher than the two-phase flow. The pressure drop and velocity in the dense phase and hybrid modes were 2.2 times less than the two-phase conditions. In the dense phase and hybrid modes, the capacity of the pipeline for natural gas transmission increased by 52% compared with two-phase gas transmission.