Wyniki wyszukiwania - BazTech

1

Rheodynamics non-viscous medium in long (cylindrical) pipes: using the Ostwald-De Ville model

Brovatets Oleksandr, Chоvniuk Yuiry, Moskvitina Anna

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

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2020

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Vol. 9, No 2

19--22

EN

While heating the soil in greenhouses, ground heat exchangers are used, as well as when accumulating heat in soil massifs for further use of heat by heat pumps, or when accumulating heat from solar collectors in heat accumulators. In such cases, a coolant moves in the heat exchangers, which will not freeze or boil, most often these are solutions polyethylene/ethylene glycol, which belong to nonlinear viscous fluids. In this work, the nonisothermal motion of a nonlinear-viscous fluid (within the framework of the Ostwald - de Ville model) in a flat channel with a given heat flow on the wall is investigated. A characteristic feature of the flow of such media is their high thermal sensitivity due to phase and structural transformations. Therefore, with a change in temperature, there is a sharp change in rheological properties. For a number of materials, for example, for polyethylene glycol (ethylene glycol) mixtures, for glycerol solutions, these changes can occur in a fairly narrow temperature range. The flow in a channel is considered, the length of which is much greater than the length of the hydrodynamic and thermal initial sections. The case is investigated when the temperature changes along the channel. Channels of arbitrary cross-section (and, in particular, rectangular and circular) are considered. The situation is analyzed when the temperature changes along the channel, and this change is rather weak in relation to the temperature change along the channel walls (in the transverse direction, that is, in the plane of symmetry). To describe the state of the system, the so-called state diagram (dependence of the temperature on the axis of symmetry of the channel on the heat flux).

2

CFD analysis of non-Newtonian and non-isothermal lubrication of hydrodynamic conical bearing

Czaban A.

Journal of KONES

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2014

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Vol. 21, No. 4

49--56

EN

In this work is shown the result of CFD simulation of hydrodynamic conical bearing lubrication with consideration of non-isothermal oil flow in a bearing lubrication gap and also with assumption, that oil has non- Newtonian properties. The determination of hydrodynamic pressure distribution in bearing gap was carried out by using the commercial CFD software ANSYS Academic Research for fluid flow phenomenon (Fluent). Calculations were performed for bearings without misalignment, i.e. where the cone generating line of bearing shaft is parallel to the cone generating line of bearing sleeve. The Ostwald-de Waele model for non-Newtonian fluids was adopted in this simulation. The coefficients of Ostwald-de Waele relationship were determined by application of the least squares approximation method and fitting curves described by this model to the experimental data, obtained for some motor oils, presented in previous work. The calculated hydrodynamic pressure distributions were compared with the data obtained for corresponding bearings, but assuming that the flow in the bearing lubrication gap is isothermal. Some other simplifying assumptions are: a steady-state operating conditions of a bearing, incompressible flow of lubricating oil, no slip on bearing surfaces, pressure on the side surfaces of bearing gap is equal to atmospheric pressure. This paper presents results for bearings with different rotational speeds and of different bearing gap heights.

3

Metodologia badań nieizotermicznego przepływu ciekłych układów dyspersyjnych

Dybek B., Hapanowicz J., Witczak S.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 2

31-32

PL

W niniejszej pracy opisano budowę i możliwości pomiarowe instalacji badawczej służącej do eksperymentalnej oceny zjawisk towarzyszących nieizotermicznemu przepływowi układu dwufazowego ciecz - ciecz w poziomych rurach o różnej średnicy. Wskazano na przyjęte sposoby pomiaru określonych parametrów procesowych i interpretacji ich wyników oraz ilościową oceną dokładności pomiaru.

EN

The paper describes measurement possibilities of experimental set-up assigned to the evaluation of phenomena occurring during non-isothermal liquid - liquid two-phase flow in horizontal pipes of different diameters. Methods accepted in measurement of process parameters were indicated. The detailed interpretation of obtained results and the quantitative evaluation of measurement accuracy were discussed.

4

Numerical simulation of the isothermal and nonisothermal flow in a rotating cavity

Zieliński A., Tuliszka-Sznitko E.

Inżynieria Chemiczna i Procesowa

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2006

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T. 27, z. 3/1

951-963

EN

The 3D direct numerical simulation is performed to study the isothermal and nonisothermal flow in the rotating annular cavity of aspect ratio 9. Identification and characterization of mechanisms, related to the laminar-turbulent process in rotating cavities, should improve the prediction methods and lead to new, more effective boundary layer control strategies. Numerical computations are based on a pseudo-spectral Chebyshev-Fourier method for solving the governing equations. The numerical computations allowed us to describe the steady axisymmetric basic state and 3D instability structures which appear in the transitional flow.

PL

Badano trójwymiarowy, niestacjonarny i nieizotermiczny przepływ między dwoma wirującymi dyskami i dwoma cylindrami. Badania prowadzono metodą bezpośrednią spektralnej kolokacji opartej na szeregu Fouriera i szeregu Czebyszewa. Analizowano struktury niestabilnościowe powstające w różnych warunkach brzegowych w obszarze przejścia laminarno-turbulentnego. Stwierdzono występowanie wirów cylindrycznych i pozytywnych wirów spiralnych w konfiguracji wirnik-stojan, a także negatywnych wirów spiralnych w przestrzeni o dyskach wirujących w przeciwnych kierunkach.

5

Hot-wire anemometer with the modulated overheating ratio-an instrument for measuring non-isothermal flows

Kiełbasa J.

Applied Mechanics and Engineering

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1998

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Vol. 3, no 4

695-714

EN

The paper presents the method for simultaneous measurements of flow velocity and the temperature of the medium, using a single wire probe operating in a constant-temperature system wherein the overheating ratio undergoes sine modulations. Theoretical bases for these measurements are presented here together with some examples of velocity and temperature distribution patterns in the temperature and velocity wake formed behind the hot wire used to provide a test environment for the proposed scheme.