A hydrodynamic model for predicting the flow of natural gas and condensate in transmission pipelines has been developed. This steady state model was used to study the temperature profile along a transmission pipeline. The model is based on formulating the problem in terms of mass, momentum, and energy balance equations. Thermodynamic properties are determined using flash and thermo-physical properties calculators based on a Volume Translated Peng-Robenson EOS (VTPREOS).

This new model will provide gas transmission engineers with a versatile tool for modeling multiphase flow in pipelines. It will also provide approximations to the parameters of most importance to them specifically, the impact of temperature and terrain effects on liquid dropout. Liquid formation is a major concern for transmission companies due to the significant decrease in gas flow capacity, inaccuracy in metering, and potential damage to instrumentation and equipment. This model simply tells the field engineer where and how much liquid will form. This information is valuable for locating and sizing liquid collection tanks, and in the design of a cost effective pigging schedule.

The results of the systematic numerical studies showed that the temperature of the gas decreased from the inlet condition to that of the surrounding temperature within 3 miles of the inlet. In addition a temperature rise of up to 5 degrees Fahrenheit was observed when an undulating terrain was simulated (in downhill flow).

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