Main aspects of liquefied natural gas process line thermal and hydraulic calculations

Abstract

The rapid growth of liquefied natural gas consumption makes the issues of its transportation more urgent. At present, liquefied natural gas pipeline transportation is carried out only by means of short length process lines. This paper discusses the main features of cryogenic liquids pipeline transportation that obstruct its spread. The proposed model allows to carry out thermal and hydraulic calculations of an underground cryogenic pipeline. The distinctive feature of this model is the fact that it takes into account the changes in basic thermodynamic parameters of cryogenic liquid. The model is based on the Darcy-Weisbach equation and a differential heat transfer equation. In addition, the influence of the Joule-Thomson coefficient inversion on the temperature of the pumping cryogenic liquid was discussed. The comparative analysis of the pipeline construction efficiency made of ultra-high molecular weight polyethylene and AISI 321 steel was conducted. It was found that the use of polymer materials contributes to an increase in the transportation distance. The developed model can be applied for estimation of the transportation parameters change of single-phase fluid flow. The obtained results can be used in initial analysis of the process lines designing and construction.

Research of the possibility of transmission of liquefied natural gas through a pipeline by a non-pressure method

“…Calculation of pressure losses in the section of a two-phase LNG flow using the formulas for a single-phase flow leads to significantly underestimated results [12], [17]. In engineering practice, to calculate two-phase flows, simplified methods are usually used that are not related to the consideration of specific flow regimes: a model with phase slip (Lockhart-Martinelli correlation) and a homogeneous model [14], [20] to [21]. When calculating a two-phase flow according to the model with phase slip, pressure losses in a turbulent flow regime are determined by the equation [14]:…”

“…At low steam contents of the flow and high mass velocities, the homogeneous model has the greatest agreement with the experimental data. The essence of the model is that a two-phase flow is considered as a single-phase flow, in which the specific volume in each section of such a flow is related to the mass vapor content and the specific volume of each of the phases [20] to [21]:…”

“…The equation for calculating friction losses is written in a form similar to the Darcy-Weisbach equation [20] to [21]:…”

“…In view of the complex nature of the dependence of ф on the operating parameters of the two-phase flow, in engineering calculations, ф = 1 is taken. The main assumptions of the homogeneous model consist in the assumption of the equality of the linear velocities of vapor and liquid, the thermodynamic equilibrium of phases, and the applicability of the dependences to the two-phase flow for calculating the friction coefficient of a single-phase flow [20] to [21]. Having analyzed the known mathematical models of two-phase liquid flows, the authors proposed the following method for calculating a two-phase LNG flow.…”

Development of a model of the optimal temperature mode of the main gas pipeline operation

“…The reason for this is the incorrect model. In [10], the authors analyze the change in the Joule-Thomson coefficient for methane with a change in its pressure and temperature. A possible inversion of the change in heat transfer for typical gas pumping conditions is shown.…”