Employing enhanced geometries in water bath heating system of natural gas pressure drop stations: Comparative study

Abstract

In pressure drop stations (PDSs), the natural gas (NG) is heated before its pressure is reduced. It is commonly performed in a water bath heating system equipped with a serpentine-shaped pipe-line and a fire tube. A part of NG is burned in the fire tube, and the produced heat is transferred to water as heat transfer media. Then, the NG following through the pipe-line achieves the heat, and its temperature goes up. In this study, three enhanced geometries, namely twisted-insert (TI), twisted-tube (TT), and corrugated-tube (CT), are proposed to enhance thermal performance of the pipe-line and reduce fuel consumption of the heating system. Firstly, the obtained results are validated with data collected from a real PDS with the capacity of 1000 m3/h. It is found that the mean deviation between the current results and the real data is less than 1%. Then, the enhanced models are examined at three different levels of the specific design factor, i.e. ratio of 360° twist-pitch (or wave-length) to straight-section. It is found that replacing an enhanced model with the reference model can noticeably affect both thermal and hydraulic characteristics of the pipe-line. For given operating conditions, the use of the TI, TT, and CT models can enhance the NG temperature by about 6, 2, and 3 K compared to the reference model. At the same time, the pressure drop of the NG increases about 10, 7, and 12 times higher than the reference model. As a rule of thumb, the TI, TT, and CT models can reduce the length of the pipe-line by about 50%, 25%, and 37.5%, respectively.