Determination of Pipe Roughness and Heat Transfer Coefficient in Pipeline Networks Using Multidomain Solution Method

In the development of new pipeline projects, all too often assumptions that are made in the initial stages of the business development opportunity are, for the most part, overly conservative. This inaccuracy is carried out through to the operation of the pipeline system and most assumptions do not change with subsequent expansions in the future until a conscious effort is made to determine and monitor those significant parameters that impact the pipeline’s overall performance. In highly complex systems such as NOVA Gas Transmission Ltd.’s (NGTL’s) pipeline network, with over 21400 Km of pipe segments of different sizes and ages, for an accurate determination of pressure drop while 12 BCF of gas, on average, is flowing through our network, we need a technique to precisely assess the values of friction factor and heat transfer coefficient. These values have a profound impact on the accuracy of the hydraulic simulations. The calculated values of pressure, flow rate, and temperature may be distorted by imprecise values of some parameters, such as friction factor or heat transfer coefficient. Thus, a proper estimation of these parameters is of great importance to the successful numerical flow simulation. Both friction factor and heat transfer coefficient are very difficult to measure; therefore, their values can only be assessed by solving an inverse problem (i.e. parameter identification process). Since the parameter estimation procedure reported in this paper requires multiple solution of inviscid gasdynamics differential equations, describing the gas flow through the pipeline system, a multidomain solution method has been applied to effectively solve the parameter identification problem.