Gas Flow In Pipe Research Articles

Numerical prediction of turbulent heat transfer in gas pipe flows subject to combined convection and radiation

An analysis is made of the interactive heat transfer problem involving turbulent forced convection and radiation in the thermal development region of a gas pipe flow. A source of distortion of temperature and heat transfer rates is usually attributed to the presence of thermal radiation in high-temperature gas flows. In particular, this paper is concerned with a situation wherein an absorbing-emitting gas having a fully developed turbulent velocity enters an isothermal pipe with black walls. The turbulent model adopted for the velocity profile involves the solution of one differential equation for the kinetic energy of turbulence. Under the idealization of gray gas, the radiation contribution is modeled by a differential method, the so-called method of moments, that circumvents the partial integrodifferential equation typical of this kind of problem. Accordingly, the new formulation governing the combined heat exchange process accounts for a coupled system consisting of a partial differential equation for temperature and an ordinary differential equation for the irradiation. The former is solved by a hybrid methodology using the method of lines in conjunction with a control volume discretization in the radial direction only. Similarly, the latter is discretized by control volumes too. Solutions of the resulting initial value problem were obtained numerically by a Runge-Kutta-Fehlberg scheme, which deals successively with the associated system of algebraic equations. Remarkably rapid convergence was achieved by adopting a coordinate transformation that clusters grid points near the wall. Results based on 10 lines are presented for the axial distributions of bulk temperature and total Nusselt numbers as a function of the controlling parameters of the combined heat exchange process. The numerical predictions have been compared with the available results, and the agreement was satisfactory for all cases tested.

Leak detection and location in gas pipelines

Describes a new method for detecting and locating leaks in long pipelines, based on an extended Kalman filter for the nonlinear distributed parameter system representing gas flow in pipes. Artificial leak states at predefined positions along the pipeline are included in the filter model, and relationships to estimate the actual leak position are derived. Simulation results are presented to assess the method.< >

A mixing system for gas flow

A mixing system is presented for gas flow in pipes, cooling towers, chimneys and other applications. The system bases on vortices produced with special vortex generators of different shapes and arrangements. A good mixture can be received within an extremely short distance. The pressure drop of the mixing elements is low. The mixing system may be applied to different and complicated flow systems.

Simulation models for gas transmission networks

This paper reviews the methods which have been developed to solve the equations of gas flow in pipes. These methods have been incorporated into computer programs which are used to simulate the behaviour of gas transmission and distribution systems. The equations, representing conservation of mass and a force balance, are subjected to various treatments (namely the methods of finite differences, characteristics, and Galerkin) which must include provision for time-dependent non-linear boundary conditions and machine constraints. For most purposes the equations can be greatly simplified without loss of any important information.

Joule‐Thomson effects on turbulent graetz problem for gas flows in pipes with uniform wall temperature

AbstractThe Joule‐Thomson effect is known to be important in arctic gas pipelines. The Joule‐Thomson effects on forced convective heat transfer in the thermal entrance region of pipes with uniform wall temperature are studied for steady fully developed turbulent gas flows by the Graetz method. Thermal entrance heat transfer results are presented for Prandtl number 0.72, Reynolds number 105 and Brinkman number ± 0.1, ± 1.0 with Joule‐Thomson parameter Jμ ranging from 0 to 1.0 to cover the possible range in practical applications. Bulk temperatures and Nusselt numbers are also presented for fully developed flow with Reynolds numbers from 5 × 103 to 106. For given Prandtl and Reynolds numbers, the asymptotic Nusselt number is found to be dependent on the Joule‐Thomson parameter only and is independent of Brinkman number. The fully developed bulk temperature is a linear function of Brinkman number and a linear relationship exists between the bulk temperature parameter (‐θbf/Br) and the Joule‐Thomson parameter Jμ for given Prandtl and Reynolds numbers.

Hydrate formation during gas flow in pipes

The problem of crystalline hydrate formation during nonisothermal stationary flow of an ideal gas in a circular inclined pipe is studied. A model is proposed for the growth of the hydrate layer on the pipe walls.

Compressibility Effects on Transient Gas Pipe Flow

Abstract Methods of iterative solution for the partial-differential equations governing the transient flow of gases in pipelines are obtained by using the method of characteristics and linear finite-difference techniques. Solutions are developed for (1) a constant gas compressibility factor throughout transient conditions, and (2) a variable gas compressibility factor at constant temperature, dependent upon pressures encountered during transient flow. Theoretical studies are made to compare results using both approaches for pipelines operating at various constant flowing temperatures. Results show greater differences between the two methods at lower values of flowing temperature due to the more rapidly changing compressibility factor as a function of variable pressure. Introduction The partial-differential momentum and mass equations describing transient gas pipe flow have been solved by various numerical methods. Among the techniques frequently employed in recent studies are implicit finite-differences and the method of characteristics. While these studies have been concerned with the numerical techniques and stability criteria required in transient flow solutions, few investigations have examined the effect of a variable gas compressibility factor on transient behavior. The purpose of this study is to develop and apply the numerical equations of transient gas pipe flow based on (1) a constant gas compressibility factor evaluated at the average of inlet and outlet pressures at initial time, and (2) a gas compressibility factor completely dependent upon the gas pressures encountered in the pipeline during steady- and unsteady-state flow. For both approaches, digital computer solutions of the partial-differential equations describing gas pipe flow are made possible by application of the characteristics transformation and linear finite-difference approximations. The theoretical results, based on both constant and variable gas compressibility, are compared graphically for various transient flow conditions with particular emphasis placed upon temperature effects. Numerous limiting assumptions are required in the development of any steady- or unsteady-state flow equations. In this study, the following assumptions are made.

Role of concentration level of the nondiffusing species in turbulent gas phase mass transfer at ordinary mass transfer rates

AbstractNumerical solutions to the diffusion‐convection equations are obtained with a digital computer to establish the role of concentration level of the nondiffusing species in nonequivolume diffusion in fully developed turbulent flow of gases in pipes. Results indicate that under ordinary mass transfer rates for a system at constant Schmidt and Reynolds numbers product of the gas‐phase mass transfer coefficient and the log mean partial pressure of the nondiffusing gas is nearly constant both in the mass transfer entry region and in the fully developed region. These results are compared with the experimental data on vaporization and absorption processes.We show that the effect of the mass transfer section length on the rate of turbulent mass transfer is quite significant. Furthermore, the results of the diffusion—convection analysis are in better agreement with experimental data for sections of finite length than results calculated from the momentum‐mass transfer analogy. The two methods agree in the limit for tubes of infinite length.

On the development of the flow of a viscous heat-conducting gas in a pipe

Approximation equations for gas flows considering viscosity and heat conductivitys and with partial consideration for the non-linear componcnts were developed in order to solve certain problems. The equations can be used in calculations of diffusors, losses in gas pipe flows etc. (R.V.J.)

Comments on formulae for the flow of gases in pipes at low pressures

Comments on formulae for the flow of gases in pipes at low pressures

The Calculation of Compressible Fluid Flow by the Use of a Generalized Entropy Chart

Calculations of the flow of gases in pipes or ducts of varying cross-sections are important in the design of turbines and compressors, nozzles for various applications, exhaust or radiator ducts, thrust augmenting devices, etc. Provided certain simplifying assumptions are made, there is no difficulty in writing down the basic equations, but when the velocities are comparable to that of sound and compressibility effects cannot therefore be neglected, the solution of the transcendental equations present difficulties which hinder a clear discussion of the physical phenomena. Here the problem is solved by the use of a generalized entropy chart, off which results may be directly read. For example, if the conditions in the reservoir from which the gas is assumed to be discharged are known, the complete conditions at any given cross-section may be read off when two parameters at the section considered are specified. The parameters may include the velocity, pressure, density, temperature, local Mach number, local velocity of sound, area of cross-section, mass flow per unit area, momentum per second, etc. The method is not confined to isentropic flows and may be applied to such problems as the flow in straight pipes or convergent and divergent nozzles including losses by either friction or condensation shocks. The co-ordinates of the chart are: dimensionless entropy σ = ( s— s0) J/R and dimensionless enthalpy ι = h/h0 = T/T0 where the meaning of the symbols is given later. All other variables are expressed in terms of these two co-ordinates and tables for several values of the ratio of specific heats are included to facilitate the drawing of such charts. The method does not aim at presenting new facts, but its usefulness lies in the provision of a comprehensive graphical means of calculating one-dimensional flow of compressible fluids. The charts lend themselves to the construction of a mechanical device for simplifying their use, such as a portable scale with sliding curves.

The Flow of Gases in Pipes at Low Pressures

Data are presented on the flow of air at low pressures in copper pipes of radius 0.795 and 1.30 cm; iron pipes of radius 2.64, 5.12, and 10.1 cm; and for hydrogen in a copper pipe of radius 1.30 cm. Data are also given for the resistance to flow of air in 1½- and 3-inch nominal pipe size elbows, for 1½-inch Kinney bellows valves, and for short sections of 1-inch nominal pipe size iron pipe connecting large gas chambers. The data on straight iron and copper pipes, together with the data from the literature on glass capillaries, are correlated by the introduction of a correction factor F in Poiseuille's equation. F is correlated graphically in terms of a dimensionless group representing the ratio of mean free path to pipe radius, with separate curves for iron pipe and for copper and glass pipes or capillaries.