Труды сотрудников ИВМ СО РАН

/ I. I. Ryzhkov // International Journal of Heat and Mass Transfer. - 2013. - Vol. 66. - pp. 461-471, DOI 10.1016/j.ijheatmasstransfer.2013.07.044 . - ISSN 0017-9310
Аннотация: A simple and efficient method for solving the extended Graetz problem with specified heat flux in a circular pipe for a multicomponent fluid with Soret and Dufour effects is proposed. With a help of linear transformation of temperature and concentrations, the mass transfer equation and boundary conditions for each component are reduced to the form, which is completely identical to the thermal Graetz problem. The case when only the Soret effect is relevant is studied separately. It is shown that the above-described reduction fails when thermal and solutal Peclet numbers are equal. An alternative method of solution is proposed in this case. Examples of heat and mass transfer in a circular pipe for low Peclet numbers in a model fluid and for high Peclet numbers in the water-alumina nanofluid are considered. The proposed method can be extended to a parallel plate channel as well as annular region between cylindrical pipes with specified heat flux. However, the method cannot be applied to problems, where the temperature is specified on the impermeable pipe wall. В© 2013 Elsevier Ltd. All rights reserved.

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Доп.точки доступа:
Ryzhkov, I.I.; Рыжков, Илья Игоревич

[Text] / I. I. Ryzhkov, A. V. Minakov // Int. J. Heat Mass Transf. - 2014. - Vol. 77. - P956-969, DOI 10.1016/j.ijheatmasstransfer.2014.05.045. - Cited References: 44. - This work is supported the Krasnoyarsk Regional Foundation of Scientific and Technical Activity (Grant No. 02/13) and the Russian President Grant No. MK-6296.2013.8. . - ISSN 0017-9310. - ISSN 1879-2189РУБ Thermodynamics + Engineering, Mechanical + Mechanics

Аннотация: Laminar convective heat transfer of water-alumina nanofluid in a circular tube with uniform heat flux is investigated numerically on the basis of two-component model, which takes into account nanoparticle transport by diffusion and thermophoresis. A new expression for thermophoretic mobility is suggested on the basis of existing experimental results and theoretical concepts. It is shown that thermophoresis leads to a significant reduction of nanoparticle volume fraction in the boundary layer near the wall. The corresponding viscosity reduction causes the velocity increase near the wall and flattening of velocity profile near the tube axis to keep the mass flow rate constant. The decrease of wall shear stress leads to the decrease of the required pressure drop. The calculations for two-component model provide higher values of the local and average heat transfer coefficients in comparison with the one-component model. The difference does not exceed 10% and decreases with increasing the thermal Peclet number. The calculations for one-component model show the independence of local and average Nusselt numbers on the nanoparticle volume fraction. The results for two-component model predict the increase of Nusselt number when the thermophoretic effect becomes stronger. The effectiveness of water-alumina nanofluid is analyzed by plotting the average heat transfer coefficient against the required pumping power. It is shown that the nanofluid shows better performance than the base fluid in the range of low pumping power and, correspondingly, low inlet velocity. (C) 2014 Elsevier Ltd. All rights reserved.

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Держатели документа:
[Ryzhkov, Ilya I.] SB RAS, Inst Computat Modelling, Krasnoyarsk 660036, Russia
[Minakov, Andrey V.] Siberian Fed Univ, Inst Engn Phys & Radio Elect, Krasnoyarsk 660041, Russia
ИВМ СО РАН

Доп.точки доступа:
Ryzhkov, I.I.; Рыжков, Илья Игоревич; Minakov, A.V.; Минаков, Андрей Викторович; Krasnoyarsk Regional Foundation of Scientific and Technical Activity [02/13]; Russian President Grant [MK-6296.2013.8]

[Text] / S. V. Kozlova, I. I. Ryzhkov // Eur. Phys. J. E. - 2014. - Vol. 37, Is. 9. - Ст. 87, DOI 10.1140/epje/i2014-14087-0. - Cited References: 44. - The authors are grateful to Dr. A. V. Minakov for assistance in ANSYS Fluent numerical calculations. This work is supported the Krasnoyarsk Regional Foundation of Scientific and Technical Activity (Grant 02/13). . - ISSN 1292-8941. - ISSN 1292-895XРУБ Chemistry, Physical + Materials Science, Multidisciplinary + Physics, Applied + Polymer Science

Аннотация: In this paper, laminar convective heat transfer of water-alumina nanofluid in a circular tube with uniform heat flux at the tube wall is investigated. The investigation is performed numerically on the basis of two-component model, which takes into account nanoparticle transport by diffusion and thermophoresis. Two thermal regimes at the tube wall, heating and cooling, are considered and the influence of nanoparticle migration on the heat transfer is analyzed comparatively. The intensity of thermophoresis is characterized by a new empirical model for thermophoretic mobility. It is shown that the nanoparticle volume fraction decreases (increases) in the boundary layer near the wall under heating (cooling) due to thermophoresis. The corresponding variations of nanofluid properties and flow characteristics are presented and discussed. The intensity of heat transfer for the model with thermophoresis in comparison to the model without thermophoresis is studied by plotting the dependence of the heat transfer coefficient on the Peclet number. The effectiveness of water-alumina nanofluid is analyzed by plotting the average heat transfer coefficient against the required pumping power. The analysis of the results reveals that the water-alumina nanofluid shows better performance in the heating regime than in the cooling regime due to thermophoretic effect.

WOS

Держатели документа:
[Kozlova, Sofya V.
Ryzhkov, Ilya I.] Inst Computat Modelling SB RAS, Krasnoyarsk 660036, Russia
ИВМ СО РАН

Доп.точки доступа:
Kozlova, S.V.; Ryzhkov, I.I.; Рыжков, Илья Игоревич; Krasnoyarsk Regional Foundation of Scientific and Technical Activity [02/13]