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Geometrical and kinematic analysis of turbulence in jets for energy efficient ventilation

Gumen O., Dovgaliuk V., Mileikovskyi V.

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

2016

nr 1(17)

15--20

We show an approach to estimate turbulence intensity of turbulent jet boundary layer. This approach uses geometric and kinematic analysis of simplified scheme of its macrostructure. It is a continuation of researches performed by professor of Heat Gas Supply and Ventilation Department of Kyiv National University of Construction and Architecture Andrei Tkachuk. The obtained value of maximal turbulence intensity is coincides with known experimental data. This approach allows estimating of turbulence parameters of ventilation currents for energy efficiency optimization of air exchange organization.

Przedstawiono podejście do oceny intensywności przepływu powietrza w turbulentnej warstwie granicznej. Podejście to wykorzystuje geometryczną i kinematyczną analizę uproszczonego schematu jej makrostruktury. Zaprezentowana analiza jest kontynuacją badań przeprowadzonych przez profesora Wydziału Ciepła i Wentylacji Kijowskiego Narodowego Uniwersytetu Budownictwa i Architektury Andrzeja Tkaczuka. Otrzymana wartość maksymalnej intensywności turbulentnego przepływu jest zbieżna ze znanymi już danymi eksperymentalnymi. Podejście to pozwala na oszacowanie parametrów turbulentnego przepływu powietrza w wentylacji w celu optymalizacji pod kątem jej efektywności energetycznej.

Heat transfer of viscoelastic fluid flow due to nonlinear stretching sheet with internal heat source

Nandeppanavar M. M., Siddalingappa M. N., Jyoti H.

International Journal of Applied Mechanics and Engineering

2013

Vol. 18, no. 3

739--760

In the present paper, a viscoelastic boundary layer flow and heat transfer over an exponentially stretching continuous sheet in the presence of a heat source/sink has been examined. Loss of energy due to viscous dissipation of the non-Newtonian fluid has been taken into account in this study. Approximate analytical local similar solutions of the highly non-linear momentum equation are obtained for velocity distribution by transforming the equation into Riccati-type and then solving this sequentially. Accuracy of the zero-order analytical solutions for the stream function and velocity are verified by numerical solutions obtained by employing the Runge-Kutta fourth order method involving shooting. Similarity solutions of the temperature equation for non-isothermal boundary conditions are obtained in the form of confluent hypergeometric functions. The effect of various physical parameters on the local skin-friction coefficient and heat transfer characteristics are discussed in detail. It is seen that the rate of heat transfer from the stretching sheet to the fluid can be controlled by suitably choosing the values of the Prandtl number Pr and local Eckert number E, local viscioelastic parameter k1 and local heat source/ sink parameter β.

Flow and heat transfer at a nonlinearly shrinking porous sheet: the case of asymptotically large powerlaw shrinking rates

Prasad K. V., Vajravelu K., Pop I.

International Journal of Applied Mechanics and Engineering

2013

Vol. 18, no. 3

779--791

The boundary layer flow and heat transfer of a viscous fluid over a nonlinear permeable shrinking sheet in a thermally stratified environment is considered. The sheet is assumed to shrink in its own plane with an arbitrary power-law velocity proportional to the distance from the stagnation point. The governing differential equations are first transformed into ordinary differential equations by introducing a new similarity transformation. This is different from the transform commonly used in the literature in that it permits numerical solutions even for asymptotically large values of the power-law index, m. The coupled non-linear boundary value problem is solved numerically by an implicit finite difference scheme known as the Keller- Box method. Numerical computations are performed for a wide variety of power-law parameters (1 < m < 100,000) so as to capture the effects of the thermally stratified environment on the velocity and temperature fields. The numerical solutions are presented through a number of graphs and tables. Numerical results for the skin-friction coefficient and the Nusselt number are tabulated for various values of the pertinent parameters.