A shortcut to optimize pipe diameters by economic criteria – chemical engineering gas delivery


In recent decades, the impact of energy costs on the transport of fluids has led to a significant reduction in fluid velocity and an increase in the diameter of the pipeline. In this article, an improved shortcut methodology is presented for estimating the optimal diameter of pipelines. Besides the laminar flow regime, the algorithm can be applied, for the first time, to the complete turbulent flow region. Several examples are presented that demonstrate the simplicity of the method and illustrate the impact of changes in economic parameters on the optimal diameter of pipelines. electricity 2pm mp3 Moreover, a sensitivity analysis was done to show that the optimization model provides the solution in an acceptable range, especially for the conceptual phase of projects, as well as for basic design.

Engineers that work in the chemical process industries (CPI) in fields such as process engineering, oil-and-gas engineering, heating, ventilation and air conditioning (HVAC), thermal and hydroelectric power and related disciplines, quite often perform calculations for pipeline-system transportation of fluids. Fluids flow through plant equipment including reactors, separators, heat exchangers, boilers, tanks, radiators and other devices that are connected by pipes or channels. power outage houston today In this article, we will consider only continuous steady-state transport of fluids.

Economic criteria is, in most cases, crucial for the design of plants, so the optimum size of the series of units that the plant consists of provides the lowest life-cycle cost of any project. The cost of piping typically represents up to 35% of plant capital cost [ 1]. Fluid pumping cost is also an important part of plant operation cost. According to the U.S. Dept. of Energy (DOE), 16% of a typical facility’s electricity costs are involved with pumping of fluids [ 2]. gas in babies how to get rid of it It is therefore useful to design the piping system as close as possible to the optimal value, in order to minimize the sum of the capital and operating expenses.

Mathematically rigorous methods for selecting pipe diameters are time-consuming because they involve detailed (iterative) procedures to determine the minimum capital and operating costs. Simple equations, like the one proposed in this article, can provide reasonably accurate estimates of optimal pipe diameters in the initial stages of a plant design, which are a good starting point for a more rigorous procedure.

The first pipe economic optimization model was published in 1937 for turbulent flow in hydraulically smooth pipes [ 3] and three years later the model was broadened for laminar flow [ 4]. These models are widely cited in literature and they even became classic university lectures [ 5]. Recently, a new model was published for hydraulically rough pipes [ 6].

Energy loss in the pipeline includes fluid friction loss, but also potential and kinetic energy losses. This model excludes the latter two losses since the pumping height is always a fixed value and fluid density is considered to be constant. This means that the pressure drop can be calculated as the sum of the friction pressure drop (Δ p fr, Pa) and minor pressure losses (Δ p ml, Pa):

Equation (13) provides an implicit calculation procedure, since the pipe diameter has to be known in order to obtain the friction factor or vice versa. electricity bill nye worksheet Solving of Equation (21), (22) or (23) also demands the iterative procedure since ξ is a function of fluid velocity. The easiest way for solving the listed equations is to make the assumption of a fluid velocity or friction factor and then apply an iterative procedure. In case of turbulent flow, no more than three iterations are needed. For laminar flow, no more than five iterations are needed.

Rules of thumb from various literature sources give the results presented in Table 2. gas 47 cents The value calculated by Equation (13) gives the velocity that is significantly lower than the ones from the cited recommendations. The consequential total pipeline cost is about 30% greater than the one calculated by hereby proposed model. This fact is in good agreement with the conclusion from Ref. 10 about the influence of energy cost on pipe diameter in recent decades.

For the next example, consider the flow of bitumen through a carbon-steel pipeline with D = 82.5 mm, with volumetric flowrate of V = 20 m 3 h. At 150°C, the density of bitumen is ρ = 959 kg/m 3 and the viscosity is η = 0.407 Pa·s. What is the optimal pipe diameter and what savings can be obtained after replacing the existing pipeline with the optimal one if the length of pipeline is L = 1,000 m?

For further analysis, we have used the standard steel pipe DN100 (O.D. = 114.3 mm, I.D. = 107.1 mm). gas 87 Using Equations (2) and (10), capital cost is C c = 17,350 $/yr, operational costs are C e = $6,820/yr, so the total cost is C = $24,170/yr. For D = 82.5 mm, the pipeline total cost is C = $31,090/yr. This means that, after replacement, each year the savings will be $6,920, and the investment will be paid off after 4.5 yr.

On the other hand, recommended velocities and pressure drops from the literature are: 0.6–1.0 m/s in Ref. 14, 0.9–1.2 m/s and 450 Pa/m in Ref. 13, 0.2–1 m/s in Ref. 15, 0.9–1.5 m/s in Ref. 16 for viscous oils and pipelines with nominal diameter DN80–DN250. It is obvious that these recommendations are not covering the region of laminar flow, and one can make a serious mistake by following them.

In this case, the mean value of the pipeline diameter is in the range D opt = 316–371 mm, which is a variation of less than±10% of the pipe diameter of D opt = 341 mm obtained in Example 1. Following the data from Table 4, for this example, one can conclude that the variation of pipe diameter is not significant due to the (very strong) exponent 5 + x = 6.5 in Equation (13).

Srbislav Genic´ is full professor of heat transfer operations and equipment, mass transfer operations and equipment and Economic analysis in process engineering at the Dept. of Process Engineering of the Faculty of Mechanical Engineering of the University of Belgrade (Kraljice Marije 16, 11120 Belgrade 35; Phone: +381-11-3302-200; Email: sgenic@mas.bg.ac.rs). His research interests include heat and mass transfer processes and equipment. electricity symbols ks2 He holds B.Sc., M.Sc., and Ph.D. degrees in mechanical engineering from the University of Belgrade. He is a court expert and registered Professional Engineer in Serbia.

Branislav Jac´imovic´ is retired full professor of Heat transfer operations and equipment and Mass transfer operations and equipment at the Dept.of Process Engineering of the Faculty of Mechanical Engineering of the University of Belgrade. He is a registered Professional Engineer in Serbia and holds B.Sc., M.Sc., and Ph.D. degrees in mechanical engineering at University of Belgrade. He has over 35 years experience in the field of separation processes (especially distillation) and heat exchangers design.