A new configuration of bend tubes for compound optimization of heat and fluid flow

Hajmohammadi, M.R.; Eskandari, Hamed; Saffar‐Avval, Majid; Campo, Antônio

doi:10.1016/j.energy.2013.09.046

Cited by 58 publications

(14 citation statements)

References 34 publications

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“…In curved pipes with 180°bends, the excess pressure drop and the excess entropy generation bring forth serious penalties. To overcome these difficulties, a new partially curved pipe consisting of three straight pipe segments connected with two 90°bends was investigated in Hajmohammadi et al 9 It was shown that the new curved pipe is advantageous because the pressure drop and entropy generation are considerably reduced. In Kim et al, 10 it was shown that new characteristic parameters can be used to represent the flow development in helical pipes.…”

Section: Introductionmentioning

confidence: 99%

Steady laminar flow in a 90° bend

Pantokratoras

2016

Advances in Mechanical Engineering

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This research undertook an assessment of the characteristics of laminar flow in a 90°bend. The research utilised the computational fluid dynamics software tool ANSYS Fluent, adopting a finite volume method. The study focused on pressure decreases, velocity profiles, Dean vortices and Dean cells present in the bend. The results indicated that the Dean vortices first appear slightly at the bend, take a clear form at the exit pipe and disappear further downstream. This article contains also an original chart for determining the Darcy-Weisbach friction factor, while the areas of pipe where Dean vortices and Dean cells formed are presented in a bifurcation diagram.

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Section: Introductionmentioning

confidence: 99%

Steady laminar flow in a 90° bend

Pantokratoras

2016

Advances in Mechanical Engineering

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“…In recirculation zones, as done in [24]. In addition to the onset of flow separation, it is also advisable to study the onset of instability in Newtonian and non-Newtonian fluids.…”

Section: Discussionmentioning

confidence: 99%

Laminar flow of non-Newtonian shear-thinning fluids in a T-channel

2015

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Please cite this article as: Khandelwal, V., Dhiman, A., Baranyi, L., Laminar flow of non-Newtonian shear-thinning fluids in a T-channel, Computers & Fluids (2014), doi: http://dx.Abstract Flow characteristics of non-Newtonian power-law fluids in a right-angled horizontal T-channel are studied in the laminar regime. In particular, the two-dimensional numerical computations are performed using Ansys Fluent for the following range of physical parameters: Reynolds number (Re) = 5-200 and power-law index (n) = 0.2-1 (covering shearthinning, n<1 and Newtonian, n=1 fluids). The flow fields have been explained by streamline contours. The engineering parameters such as wake/recirculation length, critical Reynolds number for the onset of flow separation and the variation of viscosity along the lower wall of side branch are calculated for the above range of settings by using constant density and nonNewtonian power-law viscosity model. The results showed that for a particular n, length of recirculation zone increases in the side branch with increasing Re. Also, it increases with decreasing n for the fixed Re. The critical Reynolds number for the onset of flow separation decreases with decreasing n. A simple wake-length correlation is also established at different values of Re and n for the range of parameters.Nomenclature D non-dimensionalizing length scale, m 2 I second invariant of the rate of deformation tensor, s -2 L d side branch length, m L r length of recirculation region, m L 1 total length in mainstream direction, m m power-law consistency index, Pa s n n power-law index N cells total number of cells in the domain P pressure, Pa Re Reynolds number t time, s U velocity along X-axis, m/s V velocity along Y-axis, m/s avg V average velocity of the fluid at inlet, m s -1 W b width of side branch, m W c width of main branch, m X d downstream length of main branch, m X u upstream length of main branch, m X coordinate in side stream direction, m Y coordinate in mainstream direction, m 3 Greek Symbols ρ density of fluid, kg m -3 δ minimum grid spacing, m ∆ maximum grid spacing, m  power-law viscosity, Pa s τ extra stress tensor, Pa  rate of deformation tensor, s -1 IntroductionPipe networks are widely used for transportation of liquids and gases. These networks vary from a few pipes to complex assembly of very large number of pipes. In addition to pipes, the network also consists of components causing boundary layer separation due to change in the momentum of the flow. In this work, we have concentrated our attention on a very common component of a pipe network: the T-channel. The flow of Newtonian fluids in a T-channel is characterised by two separation zones: one in the branched channel, another along the left wall of the main branch at the junction, and a stagnation point near the downstream corner of the junction (Fig. 1). A separation zone can be defined as the region of recirculating fluid with very low velocities; therefore it has a strong sediment deposition potential. Continuous sediment deposition over a period...

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“…By morphing a curved pipe with a 180 bend into a partially curved configuration, M.R. Hajmohammadi et al [17] accomplished a considerable reduction of pressure drop and entropy generation of the customarily used bend tubes. F. Pask et al [18] demonstrated a generalized methodology of systematic approach to industrial oven optimization for better heat performance, pressure loss or energy saving.…”

Section: Introductionmentioning

confidence: 98%