Hydrodynamics of non-isothermal turbulent airflows in ducts of annular section

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Authors:

A.G. Butenko, Cand. Sci. (Tech), Associate Professor, Odessa National Polytechnic University, Senior Lecturer of the Department of Applied Ecology and Fluid Dynamics, Odessa, Ukraine

Abstract:

Purpose. Determination of hydrodynamic features of non-isothermal turbulent flow of air in the pressure channel of the annular section with the boundary conditions of the first kind.

Methodology. The realization of the research objective was carried out by means of numerical simulation in the SOLID WORKS COSMOS FLO software.

Findings. The dependences of changes of the hydraulic coefficient of the friction along the annular channel, heated through the inner wall were obtained as well as graphs of dependences of the local value of Darcy coefficient on the Reynolds number for different values of the degree of uneven distribution of viscosity in the section. The values of the thickness of wall layers, shear stresses and velocity gradients near the channel walls were calculated. The features of hydrodynamic stabilization of non-isothermal turbulent flow in a channel of the annular section were analyzed.

Originality. It has been proved that hydraulic resistance along the flow increases under a turbulent flow of the air stream in the annular flow channel of cross section when heating through inner wall under boundary conditions of the first kind. The explanation for this effect is given by the analysis of the causes and nature of changes along the channel thickness of wall layers, shear stresses and velocity gradients. It has been found that the increase of the degree of uneven distribution of viscosity in this section leads to a decrease of the local values of the coefficient of hydraulic losses. The value of turbulent viscosity has been proposed as a criterion on the basis of analyzing the hydrodynamic stabilization peculiarities of non-isothermal flow.

Practical value. Non-isothermal turbulent flow in the flow channel of the annular section is typical for pipe-in-pipe heat exchangers. The design of these devices involves their hydraulic calculation. Currently, such calculations are carried out ignoring nonuniformity of the temperature field. The revealed regularities allow taking into account the nature of non-isothermal flow, and thereby improve the accuracy of hydraulic calculations.

References:

1. Butenko, A.G. (2005), “The influence of transverse gradient of viscidity on characteristics of circular laminar flow”, Trudy Odesskogo Politekhnicheskogo Universiteta, no. 1(23), pp. 185–188.

 Бутенко А.Г. Влияние поперечного градиента вязкости на характеристики ламинарного потока в трубе кольцевого сечения / А.Г. Бутенко // Труды Одесского политехнического университета: научный и научно-производственный сборник по техническим и естественным наукам. – 2005. – Вып. 1(23). – С. 185–188.

2. Alyamovskiy, A.A., Sobachkin, A.A. and Odintsov, Ye.V. (2005), Solid Works Kompyuternoye modelirovaniye v inzhenernoy praktike [Solid Works. Computer Modeling in Engineering Practice], VHV-Peterburg, St.-Petersburg, Russia.

 SolidWorks. Компьютерное моделирование в инженерной практике / [Алямовский А.А., Собачкин А.А., Одинцов Е.В. и др.] – СПб.: ВХВ-Петербург, 2005. – 800 с.

 

 

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Date 2015-03-27 Filesize 553.02 KB Download 499

 

Tags: non-isothermal flowfluid propertieshydraulic frictionshear stressesvelocity gradientthickness of the boundary layerturbulent viscosity

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