Calculating heat loss of buried gas pipeline with state equations

Heat loss through buried natural gas pipeline is always one of the significant issues and it has been considered in different ways by researchers. Most of the equations used commonly for pressure loss calculations require the use of a single value of temperature. This, of necessity, is some kind of an average temperature. In a numerical (computer) solution one devides the line into a series of constant temperature section; an analytical (manual) solution may treat the entire line as one section. However one does it, the temperature used should be representative of what is anticipated. The value used has a direct impact on the physical property values used. Prediction of the temperature distribution in the flowing system may be as important as the pressure profile. The numerical computation of natural gas pipeline temperature drop will provide the reference data for the design of gas pipeline, crude oil pour points, vapor-liquid phase behavior, water content of gas, the judgement of hydrate formation, the normal production and operation,. So because of that a reliable temperature prediction is an early step in the calculation procedure. The temperature at any point is predictable through use of a first law thermodynamic energy balance. The enthalpy of a gas increases with decreasing pressure; it is almost independent of pressure for a liquid. So, the enthalpy at any point in the line depends both on pressure at that point and the heat energy lost or gained through the pipe wall. In this paper, for the first time, we calculated heat loss once by numerical methods and the other time with state equations such as Van der Waals, Virial, Pitzer… by using Rasht-Qazvin pipeline data, afterwards we compared them with each other and at the end the error percentage of the states formula were estimated. When conducting tests on bare pipes it is very desirable that the room temperature remain constant throughout the work, for the rate of heat loss is dependent upon the absolute temperature as well as upon the temperature difference.

کلیدواژه ها:

Buried pipeline ، Heat loss ، Natural gas ، State equations