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Nusselt number

About: Nusselt number is a research topic. Over the lifetime, 28564 publications have been published within this topic receiving 636431 citations. The topic is also known as: Nusselt number.


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TL;DR: In this paper, the enhancement of momentum and heat transfer caused by stationary streamwise vortices due to a Coriolis instability in a rotating straight channel is examined, and it is shown that the changes in skin friction and Nusselt number depend on changes in the spanwise averaged mean flow and temperature distributions.
Abstract: The enhancement of momentum and heat transfer caused by stationary streamwise vortices due to a Coriolis instability in a rotating straight channel is examined. It is shown that the changes in skin friction and Nusselt number depend on changes in the spanwise averaged mean flow and temperature distributions. Hot wire anemometry was used to experimentally determine the streamwise velocity and temperature distributions in a cross stream plane 68 channel widths downstream of the inlet. A technique to accurately compensate the velocity readings for the varying temperature in the channel was developed. It is shown that the streamwise vortices give rise to disturbance profiles which are close to those obtained from linear theory for small rotation numbers and that in this region there is no enhancement of either the averaged momentum or heat transfer. However, even for a disturbance amplitude in the streamwise velocity of the order of 20%, the disturbances are close to linear (both the disturbance distribution ...

21 citations

Journal ArticleDOI
TL;DR: In this paper, an analysis for the nonlinear steady boundary layer flow and heat transfer of an incompressible tangent hyperbolic non-Newtonian fluid from horizontal circular cylinder in the presence of thermal and hydrodynamic slip condition is presented.
Abstract: An analysis is presented for the nonlinear steady boundary layer flow and heat transfer of an incompressible tangent hyperbolic non-Newtonian fluid from horizontal circular cylinder in the presence of thermal and hydrodynamic slip condition. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a second-order accurate implicit finite-difference Keller Box technique. The numerical code is validated with previous studies. The influence of a number of emerging non-dimensional parameters, namely Weissenberg number $$(W_{e})$$ , power law index $$(n)$$ , velocity slip parameter $$(\hbox {S}_\mathrm{f})$$ , thermal jump parameter $$(\hbox {S}_\mathrm{T})$$ , Prandtl number (Pr), magnetic parameter $$(M)$$ and dimensionless tangential coordinate $$(\xi )$$ on velocity and temperature evolution in the boundary layer regime are examined in detail. Furthermore, effects of these parameters on surface heat transfer rate and local skin friction are also investigated. Validation with earlier Newtonian studies is presented and excellent correlation achieved. It is observed that velocity, skin friction and heat transfer rate are reduced with increasing Weissenberg number ( $$W_{e}$$ ), whereas, temperature increases slightly. Increasing power law index ( $$n$$ ) increases velocity and heat transfer rate but decreases temperature and skin friction. An increase in $$S_{f}$$ , is observed to enhance velocity and heat transfer rate but decreases temperature and local skin friction. Whereas, increasing $$S_{T}$$ , is found to decrease velocity, temperature, skin friction and Nusselt number. The study is relevant to chemical materials processing applications.

21 citations

Journal ArticleDOI
TL;DR: In this paper, a two-population entropic multi-relaxation lattice Boltzmann model is used to simulate thermal convective turbulence in the Rayleigh-Benard regime.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the authors derived a heat transport model based on the vortex dynamics for two-dimensional elliptic cylinders by considering vorticity is acted by flow, which has shear and swirl.
Abstract: Non-canonical wakes of two-dimensional elliptic cylinders are analysed numerically for their near- and far-wake characteristics. The governing equations are solved using an immersed boundary method based projection scheme. The wakes are then classified into three distinct types according to diverse flow and thermal properties. An unexpected mean temperature evolution along the centreline of the wake is observed for certain wake states. In order to explain this unusual variation, novel heat transport models are constructed based on the vortex dynamics. These models are derived by considering vorticity is acted by flow, which has shear and swirl. Mechanisms of the primary vortex street breakdown and formation of the secondary vortex street are also proposed based on these models. A new phenomenon namely ‘dual near-wall instantaneous recirculation’ is observed, and its appearance is found to be a function of length of the primary von Karman vortex street. The same phenomenon is also found to be responsible for the secondary peak in the Nusselt number variation along the circumference of the cylinder. Despite varied differences between the wake types, it is observed that the transitions occur through a supercritical Hopf bifurcation in all of them, at least in the von Karman region of the wake. Low-frequency unsteadiness observed in the far wakes is examined through a signal decomposition method. Our results show that the secondary low frequency is resulting from the transition region which has a negative instability slope. Finally, onset of the primary vortex street breakdown and its scale in terms of Reynolds number is computed.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the boundary layer flow and heat transfer of an incompressible Jeffrey's viscoelastic fluid from a non-isothermal wedge is analyzed and the surface of the wedge is maintained at a constant temperature.

21 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,501
20222,876
20211,929
20201,776
20191,745
20181,522