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Withada Jedsadaratanachai - One of the best experts on this subject based on the ideXlab platform.
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3d numerical study on flow structure and heat transfer in a circular tube with v baffles
Chinese Journal of Chemical Engineering, 2015Co-Authors: Withada Jedsadaratanachai, Nuthvipa Jayranaiwachira, Pongjet PromvongeAbstract:Abstract A 3D numerical investigation has been carried out to examine periodic laminar flow and heat transfer characteristics in a circular tube with 45° V-baffles with isothermal wall. The computations are based on the finite volume method (FVM), and the SIMPLE algorithm has been implemented. The fluid flow and heat transfer characteristics are presented for Reynolds numbers ranging from 100 to 2000. To generate main longitudinal vortex flows through the tested section, V-baffles with an attack angle of 45° are mounted in tandem and in-Line Arrangement on the opposite positions of the circular tube. Effects of tube blockage ratio, flow direction on heat transfer and pressure drop in the tube are studied. It is apparent that a pair of longitudinal twisted vortices (P-vortex) created by a V-baffle can induce impingement on a wall of the inter-baffle cavity and lead a drastic increase in heat transfer rate at tube wall. In addition, the larger blockage ratio results in the higher Nusselt number and friction factor values. The computational results show that the optimum thermal enhancement factor is around 3.20 at baffle height of B = 0.20 and B = 0.25 times of the tube diameter for the V-upstream and V-downstream, respectively.
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effects of blockage ratio and pitch ratio on thermal performance in a square channel with 30 double v baffles
Case Studies in Thermal Engineering, 2014Co-Authors: Withada Jedsadaratanachai, Amnart BoonloiAbstract:This article presents flow configurations and heat transfer characteristics in an isothermal square channel with 30° double V-baffles. The influences of blockage ratios (b/H, BR=0.05–0.25) and pitch ratios (L/H, PR=1–2) for Reynold numbers, Re=100–1200 are investigated numerically. The 30° double V-baffles are placed on both two opposite walls of the square channel with in-Line Arrangement and each V-tip pointing downstream. The numerical results are presented in four parts; accuracy validations, flow structures, heat transfer behaviors and performance evaluations. It is found that the use of the double V-baffles performs higher heat transfer rate and pressure loss than the smooth channel with no baffle. The rise of the blockage ratio and reducing the pitch ratio lead to the increase in heat transfer rate and pressure loss. The optimum thermal enhancement factor is found to be about 3.2 at PR=1, BR=0.10 and Re=1200.
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effect of pitch to height ratio on flow visualization heat transfer and thermal performance in a round tube with upstream rwvg
Advances in Mechanical Engineering, 2014Co-Authors: Withada Jedsadaratanachai, Nuthvipa JayranaiwachiraAbstract:Fully developed periodic laminar flow and heat transfer in an isothermal wall tube with 45° upstream rectangular winglet vortex generators (RWVG) with closed end are investigated numerically. The fluid flow and heat transfer characteristics are proposed for Reynolds numbers based on the diameter of the tube, Re = 100 to 2000. The RWVGs with an attack angle of 45° are mounted with in-Line Arrangement on both sides of a plate and the closed tip pointing upstream is inserted in the middle of the tested tube to produce longitudinal vortex flows through the tested section. Effects of different blockage ratios (b/D, BR) and pitch spacing ratios (P/D, PR) on heat transfer, pressure loss, and the thermal enhancement factor (TEF) in the round tube are studied. The results show that the longitudinal vortex flows can induce impinging flows on a tube wall leading to an extreme increase in heat transfer rate over the round tube for all cases. Additionally, the rise in the BR and the reduction of PR result in the incre...
Brian Harbourne - One of the best experts on this subject based on the ideXlab platform.
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real and complex supersolvable Line Arrangements in the projective plane
Journal of Algebraic Combinatorics, 2020Co-Authors: Krishna Hanumanthu, Brian HarbourneAbstract:If we regard a set of s Lines in $${\mathbb P}^2$$ over either the reals or the complex numbers as an algebraic plane curve, then it is an open problem to classify for all s those for which the number $$t_2$$ of points of multiplicity 2 satisfies $$t_2<\lfloor s/2\rfloor $$ . By the Sylvester–Gallai theorem, there are no nontrivial (i.e., not a pencil or a near pencil) real Arrangements with $$t_2=0$$ , but there are complex Arrangements with $$t_2=0$$ and it is an open problem to classify them. In this paper, we initiate a classification of an interesting class of Line Arrangements called the supersovable Line Arrangements and give a partial classification for them over the reals or the complex numbers. In particular, we show that a complex Line Arrangement which is nontrivial cannot have more than 4 modular points and we completely describe those with 3 or 4 modular points.
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real and complex supersolvable Line Arrangements in the projective plane
arXiv: Algebraic Geometry, 2019Co-Authors: Krishna Hanumanthu, Brian HarbourneAbstract:We study supersolvable Line Arrangements in ${\mathbb P}^2$ over the reals and over the complex numbers, as the first step toward a combinatorial classification. Our main results show that a nontrivial (i.e., not a pencil or near pencil) complex Line Arrangement cannot have more than 4 modular points, and if all of the crossing points of a complex Line Arrangement have multiplicity 3 or 4, then the Arrangement must have 0 modular points (i.e., it cannot be supersolvable). This provides at least a little evidence for our conjecture that every nontrivial complex supersolvable Line Arrangement has at least one point of multiplicity 2, which in turn is a step toward the much stronger conjecture of Anzis and Toh\v{a}neanu that every nontrivial complex supersolvable Line Arrangement with $s$ Lines has at least $s/2$ points of multiplicity 2.
Ali Kosar - One of the best experts on this subject based on the ideXlab platform.
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The effect of Arrangement type and pitch ratio on the performance of micro-pin-fin heat sinks
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: Ali Mohammadi, Ali KosarAbstract:This study focuses on comparison of in-Line and staggered Arrangements of circular micro-pin fins (MPF) in a rectangular micro-channel with the dimensions ( l ′ × w ′ × h ′) of 0.5 × 1.5 × 0.1 mm^3. The height ( H ) and diameter ( D ) of the MPFs are both 0.1 mm. Two horizontal ( S _L) and vertical ( S _T) distances of 0.15 and 0.3 mm are considered with each type of Arrangement, which results in four in-Line and four staggered configurations. The simulations are run at five Reynolds numbers ( Re ) between 20 and 150, and a constant heat flux (HF) of 30 W cm^−2 was applied through the bottom surface of the MHS as well as the liquid interacting surfaces of MPFs. The results are analyzed using four evaluative parameters, namely pressure drop, friction factor (FF), Nusselt number ( Nu ) and thermal–hydraulic performance index (TPI). These parameters were significantly affected by the wake length behind MPFs. In cases with a large horizontal pitch ratio ( S _L/ D = 3), the wake length behind all columns (except the last one) could extend more (up to 2D) which in cases with the in-Line Arrangement typically resulted in higher pressure drop and FF (up to 10%) compared to similar cases with S _L/ D = 1.5. In cases with S _T/ D = 3, the larger available cross section among MPFs typically resulted in lower pressure drop (up to 36%) and Nu (up to 8%) compared to similar cases with S _T/ D = 1.5. With the same S _L/ D and S _T/ D , staggered Arrangements generally had higher pressure drop, FF and Nu (up to 56, 39 and 9%, respectively) compared to similar in-Line Arrangements. Finally, the best TPI was attained with staggered Arrangements with S _T/ D = 1.5 with 10% higher TPI compared to the reference case.
Amnart Boonloi - One of the best experts on this subject based on the ideXlab platform.
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effects of blockage ratio and pitch ratio on thermal performance in a square channel with 30 double v baffles
Case Studies in Thermal Engineering, 2014Co-Authors: Withada Jedsadaratanachai, Amnart BoonloiAbstract:This article presents flow configurations and heat transfer characteristics in an isothermal square channel with 30° double V-baffles. The influences of blockage ratios (b/H, BR=0.05–0.25) and pitch ratios (L/H, PR=1–2) for Reynold numbers, Re=100–1200 are investigated numerically. The 30° double V-baffles are placed on both two opposite walls of the square channel with in-Line Arrangement and each V-tip pointing downstream. The numerical results are presented in four parts; accuracy validations, flow structures, heat transfer behaviors and performance evaluations. It is found that the use of the double V-baffles performs higher heat transfer rate and pressure loss than the smooth channel with no baffle. The rise of the blockage ratio and reducing the pitch ratio lead to the increase in heat transfer rate and pressure loss. The optimum thermal enhancement factor is found to be about 3.2 at PR=1, BR=0.10 and Re=1200.
A Sadrul K M Islam - One of the best experts on this subject based on the ideXlab platform.
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three dimensional performance analysis of plain fin tube heat exchangers in transitional regime
Applied Thermal Engineering, 2013Co-Authors: Arafat A. Bhuiyan, Ruhul M Amin, A Sadrul K M IslamAbstract:Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a four-row plain fin-and-tube heat exchanger using the Commercial Computational Fluid Dynamics Code ANSYS CFX 12.0. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 400 to 2000. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-ω) with steady and incompressible fluid flow. Model validation is carried out by comparing the simulated case friction factor (f) and Colburn factor (j) with the experimental data of Wang et al. [1]. Reasonable agreement is found between the simulations and experimental data. In this study the effect of geometrical parameters such as fin pitch, longitudinal pitch and transverse pitch of tube spacing are studied. Results are presented in the form of friction factor (f) and Colburn factor (j). For both laminar and transitional flow conditions heat transfer and friction factor decrease with the increase of longitudinal and transverse pitches of tube spacing whereas they increase with fin pitches for both in-Line and staggered configurations. Efficiency index increases with the increase of longitudinal and transverse pitches of tube spacing but decreases with increase of fin pitches. For a particular Reynolds number, the efficiency index is higher in in-Line Arrangement than the staggered case.