International Journal of Mechanical Sciences 49 (2007) 989–1000 The effect of major parameters on simulation results of gas pipelines Farzad Abdolahi a,Ã , Ali Mesbah b , Ramin B. Boozarjomehry c , William Y. Svrcek d a Department of Chemical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran b DelftChemTech, Faculty of Applied Sciences, Delft University of Technology, Delft, The Netherlands c Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran d Department of Chemical Engineering, University of Calgary, Alta., Canada Received 12 May 2006; accepted 10 December 2006 Available online 5 February 2007 Abstract Predictions of the gas temperature and pressure profiles are vital to the design and operation of gas transmission lines. Available analytical methods for the calculation of these profiles are evaluated and a numerical framework for the rigorous calculation has been developed. The predictions from both the analytical and numerical procedure have been compared to field data from the Iranian Gas Trunk-lines (IGAT). These comparisons showed that all the available methods were tuned using data obtained from small to medium diameter pipes extrapolated poorly to large diameter pipelines. In order to improve the predictions for large diameter pipelines, the effect of model parameters such as soil thermal conductivity, pipe relative roughness and velocity profile correction factor has been evaluated. The results show that temperature and pressure profiles at high Reynolds number are sensitive to the Fanning friction factor; however, thermal conductivity and velocity distribution correction factor have almost no effect on the temperature and pressure profiles provided these parameters were set at an average acceptable industry value. Since the pressure profile for large diameter pipes was most sensitive to the Fanning friction factor a parameter optimization method was used to fine-tune the Fanning friction factor as a function of Reynolds number at an average accepted industry relative pipe roughness. r 2007 Elsevier Ltd. All rights reserved. Keywords: Gas transmission pipelines; Numerical method; Optimization; Friction factor 1. Introduction In order to design or operate gas transmission systems, there has been a need for a workable method to relate the transmitted gas volume to the temperature, pressure, pipe length, pipe diameter, pipe roughness, Reynolds number and gas composition. There have been two general solution approaches, the first of these is closed form analytical and involved numerous simplifying assumptions and approx- imations. These analytic closed form equations often lead to poor predictions, mainly due to the simplifying assumptions, which were primarily made for ease of hand calculations. The second approach uses numerical meth- ods, which greatly mitigates the need for many of the simplifying assumptions and/or approximations. In this paper these two approaches are reviewed and a developed rigorous numerical approach is used to evaluate the influence of model parameters such as pipe roughness, soil thermal conductivity and velocity profile correction factor on pipeline pressure and temperature profiles. The developed numerical procedure is validated using field data from the Iranian Gas Trunk-lines (IGAT) by adjusting the pipe roughness and soil thermal conductivity to minimize the differences between the model predictions and the field data. 2. Model development 2.1. Momentum balance A steady-state momentum balance on a differential control volume of pipe leads to 1 r dP dL þ u du ag c dL þ 2fu 2 g c D i þ g g c dZ dL ¼ 0, (1) ARTICLE IN PRESS www.elsevier.com/locate/ijmecsci 0020-7403/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijmecsci.2006.12.001 Ã Corresponding author. Fax: +98 21 66957784. E-mail address: abdolahi@ut.ac.ir (F. Abdolahi).