The Experts below are selected from a list of 486 Experts worldwide ranked by ideXlab platform
A Zamzamian - One of the best experts on this subject based on the ideXlab platform.
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effects of geometrical parameters on performance of plate fin heat exchanger vortex generator as core surface and nanofluid as working media
Applied Thermal Engineering, 2014Co-Authors: M Khoshvaghtaliabadi, Faramarz Hormozi, A ZamzamianAbstract:Abstract Forced convective heat transfer with laminar and steady-state flow of copper-base deionized water nanofluid inside the vortex-generator plate-fin channels was studied experimentally and also numerically using CFD method. In the experimental section, a setup with capability to provide a constant wall temperature condition was fabricated. Single-phase (homogeneous) and two different two-phase (mixture and Eulerian) models were accomplished for temperature dependent thermo-physical properties in the numerical section. For the case under consideration, the mixture model gives closer predictions of the convective heat transfer coefficient to the experimental data than the homogeneous and Eulerian models. For nanofluids under consideration, the average relative error of Nusselt number between experimental data and CFD results based on mixture model was about 3.0%. Also, it was illustrated that the homogeneous and Eulerian models underestimated Nusselt number. Influences of two operating Factors (i.e. Reynolds number and nanoparticles concentration) and seven geometrical parameters (i.e. wing height, wing width, channel length, longitudinal wings pitch, transverse wings pitch, wings attach angle, and wings attack angle) were investigated on performance of a plate-fin heat exchanger with vortex-generator channels. Finally, two correlations were developed for Colburn Factor and Fanning Friction Factor variations based on Reynolds number, nanoparticles weight fraction, and geometrical parameters.
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wavy channel and different nanofluids effects on performance of plate fin heat exchangers
Journal of Thermophysics and Heat Transfer, 2014Co-Authors: M Khoshvaghtaliabadi, A Zamzamian, Faramarz HormoziAbstract:In the present research, an experimental study of forced convective flows of different nanofluids through a corrugated wavy channel at a constant wall temperature condition was performed. Effects of different parameters, including nanoparticle concentration (copper nanoparticles in deionized water), types of oxide nanoparticles (SiO2, TiO2, ZnO, Fe2O3, Al2O3, and CuO), and types of base fluid (deionized water–ethylene glycol mixture), for different volumetric flow rates were examined. The convective heat transfer coefficient and pressure drop measurements were carried out. Results indicate that, for all the values of the flow rate, the Nusselt number augments and Fanning Friction Factor reduces as the concentration of the copper nanoparticles decreases. In addition, it is shown that the SiO2-deionized water nanofluid yields the best thermal–hydraulic performance among the studied oxide nanoparticles in deionized water, and the TiO2- and CuO-deionized water nanofluids come in second and third. It is also f...
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experimental analysis of thermal hydraulic performance of copper water nanofluid flow in different plate fin channels
Experimental Thermal and Fluid Science, 2014Co-Authors: M Khoshvaghtaliabadi, Faramarz Hormozi, A ZamzamianAbstract:Abstract An experimental assessment of the copper–water nanofluid flow through different plate-fin channels is the main purpose of this study. Seven plate-fin channels, including plain, perforated, offset strip, louvered, wavy, vortex generator, and pin, were fabricated and tested. The copper–water nanofluids were produced by a one-step method, namely electro-exploded wire technique, with five nanoparticles weight fractions (i.e., 0%, 0.1%, 0.2%, 0.3%, and 0.4%). The required properties of the nanofluids were systematically measured, and empirical correlations were proposed. To obtain accurate results, a highly precise test loop with the ability to produce a constant wall temperature was designed and fabricated. The results depicted that both the convective heat transfer coefficient and the pressure drop values of all the channels enhance with increasing the nanoparticles weight fraction. The appropriate thermal–hydraulic performance and maximum reduction of surface area were found for the vortex generator channel. Finally, correlations were proposed to predict the Nusselt number and Fanning Friction Factor of the base fluid and nanofluids flows in the studied plate-fin channels.
Viedma Robles Antonio - One of the best experts on this subject based on the ideXlab platform.
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Heat transfer enhancement of laminar and transitional Newtonian and non-Newtonian flows in tubes with wire coil inserts.
'Elsevier BV', 2014Co-Authors: Martínez Hernández, David Sebastián, Solano Fernández, Juan Pedro, García Pinar Alberto, Viedma Robles AntonioAbstract:This work presents an experimental study on two different wire coils inserted in a smooth tube using both Newtonian and non-Newtonian fluids to characterize their thermohydraulic behavior in laminar and transitional flow. Dimensionless pitches of the wire coils were chosen as p=D = 1 and 2, whereas dimensionless wire diameter was e=D = 0.09 for both wire coils. Non-Newtonian tests considered different viscosity types with concentration of 1% of CMC (carboxyl-methyl-cellulose) solution in water at several temperatures; a wide range of flow conditions has been covered: Reynolds number from 10 to 1300 and Prandtl number from 150 to 1900. Newtonian test were carried out with propylene glycol as working fluid, covering a similar range of Reynolds number as the previously indicated for non-Newtonian fluids. Isothermal pressure drop tests and heat transfer experiments under uniform heat flux conditions were performed, and results were contrasted with own experimental data for the smooth tube and with well-know analytical solutions. At low Reynolds numbers, both wire coils behave as a smooth tube but accelerate transition to critical Reynolds numbers down to 500. Maximum augmentations of Fanning Friction Factor of 3.5 times and of 4.5 times of Nusselt number have been found with respect to the smooth tube
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Flow Pattern Assessment in Tubes of Reciprocating Scraped Surface Heat Exchangers
'Elsevier BV', 2011Co-Authors: Solano Fernández, Juan Pedro, García Pinar Alberto, Vicente Quiles, Pedro Ginés, Viedma Robles AntonioAbstract:Flow pattern in the tubes of an innovative scraped surface heat exchanger with reciprocating scrapers has been experimentally investigated. The scraper consists of a concentric rod inserted in each tube of the heat exchanger, mounting an array of semicircular plugs that fit the inner tube wall. A hydraulic piston provides the scraper with constant-velocity reciprocating motion. Phase-averaged velocity fields have been obtained with PIV technique for both scraping semi-cycles, with special emphasis on the effect of the scraping velocity (velocity ratio) and Reynolds number. Visualization results have been contrasted with experimental data on Fanning Friction Factor, obtaining a clear relation between flow patterns, pressure drop augmentation and turbulence promotion. CFD simulations for quasi-steady laminar flow provide a further insight into the relation of the flow structures with wall shear stress, and the contribution of pressure forces to global head losses, for each scraping semi-cycle.This research has been partially financed by the DPI2007- 66551-C02 grant of the Spanish Ministery of Science and the company ”HRS Spiratube”. The authors are grateful to SEDIC-SAIT (UPCT) for providing the technical resources for CFD computation
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The effect of velocity ratio on thermal-hydraulic performance of reciprocating scraped surface heat exchangers at low Reynolds number
2009Co-Authors: Solano Fernández, Juan Pedro, García Pinar Alberto, Vicente Quiles, Pedro Ginés, Viedma Robles AntonioAbstract:The thermal-hydraulic performance of a reciprocating scraper inserted in a round tube at low Reynolds number is studied. Pressure drop and heat transfer characteristics have been experimentally determined in static conditions in laminar regime (Reh=30), and results are contrasted with dynamic performance at several velocity ratios (ω=0.1 - 1). Maximum increases of Fanning Friction Factor of the order of 1.2 have been found, together with increases in Nusselt number of the order of 2, using propylene-glycol as working fluid.This research has been partially financed by the DPI2007-66551-C02-01 grant of the ''Dirección General de Investigación del Ministerio de Educación y Ciencia de España'' and the “HRS Spiratube” company
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Experimental study of heat transfer and pressure drop in mechanically-assisted heat exchangers with active scrapers
'Begell House', 2006Co-Authors: Solano Fernández, Juan Pedro, García Pinar Alberto, Vicente Quiles, Pedro Ginés, Viedma Robles AntonioAbstract:A mechanically assisted heat exchanger has been studied. The reciprocating movement of the active insert device, located inside a round tube, generates macroscopic displacements of the flow, increasing heat transfer. At the same time, the inner tube wall scraping avoids fouling. Pressure drop and heat transfer characteristics have been experimentally studied, in order to characterize the thermo-hydraulic behaviour of the dynamic insert device, using propylene-glycol as working fluid. Experimental results for Fanning Friction Factor and Nusselt number as functions of flow and dimensionless geometric parameters have been presented. Friction Factor increases up to two times at higher Reynolds numbers for different scraping frequencies. Nusselt number increases up to four times at low Reynolds numbers, for different scraping frequencies. At high Reynolds number, no influence of the scraping frequency is shown.This research has been partially financed by the DPI2003-07783-C02 grant of the ''Dirección General de Investigación del Ministerio de Educación y Ciencia de España'' and the “HRS Spiratube” company
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Experimental investigation on heat transfer and Frictional characteristics of wire coils inserts in transition flows at different Prandtl number
Elsevier Science, 2005Co-Authors: García Pinar Alberto, Vicente Quiles, Pedro Ginés, Viedma Robles AntonioAbstract:Helical-wire-coils inserted in a round tube have been experimentally studied in other to obtain their thermohydraulic behaviour in laminar, transition and turbulent flows. Using water and propylene glycol mixtures at different concentrations, a wide range of flow conditions was covered: Reynolds Number from 100 to 90 000 and Prandtl number from 2.8 to 200. Six Wire coil insets were tested, with a geometric range of helical pitch 1.17 less than p/e less than 33 and helix angle 30º less than infinity less than 53º. Wire coils were tightly attached to the inner tube surface. Experimental correlations of Fanning Friction Factor and Nusselt number as functions of flow and dimensionaless geometric parameters are proposed. Results show that wire colis increse pressure drop up to 8 times and heat transfer up to 4 times compared to the empty smooth tube. Moreover these insert devices accelerate transition to critical Reynolds numbers down to 700. Transition to turbulent flow occurs softly without unstabilities in flow, due to the swirl flow induced by the wires
C W Bullard - One of the best experts on this subject based on the ideXlab platform.
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air side thermal hydraulic performance of multi louvered fin aluminum heat exchangers
International Journal of Refrigeration-revue Internationale Du Froid, 2002Co-Authors: Man-hoe Kim, C W BullardAbstract:An experimental study on the air-side heat transfer and pressure drop characteristics for multi-louvered fin and flat tube heat exchangers has been performed. For 45 heat exchangers with different louver angles (15–29°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm), a series of tests were conducted for the air-side Reynolds numbers of 100–600, at a constant tube-side water flow rate of 0.32 m3/h. The inlet temperatures of the air and water for heat exchangers were 21 and 45°C, respectively. The air-side thermal performance data were analyzed using effectiveness-NTU method for cross-flow heat exchanger with both fluid unmixed conditions. The heat transfer coefficient and pressure drop data for heat exchangers with different geometrical configurations were reported in terms of Colburn j-Factor and Fanning Friction Factor f, as functions of Reynolds number based on louver pitch. The general correlations for j and f Factors are developed and compared to other correlations. The f correlation indicates that the flow depth is one of the important parameters for the pressure drop.
Man-hoe Kim - One of the best experts on this subject based on the ideXlab platform.
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CFD Analysis on the Air-Side Thermal-Hydraulic Performance of Multi-Louvered Fin Heat Exchangers at Low Reynolds Numbers
MDPI AG, 2017Co-Authors: Arslan Saleem, Man-hoe KimAbstract:The air-side thermal-hydraulic performance of multi-louvered aluminium fin heat exchangers is investigated. A systematic numerical study has been performed to analyze the air-sde thermal hydraulic characteristics over a wide range of Reynolds number i.e., from 30 to 500. Air-side heat transfer coefficient and pressure drop were calculated and validated over the mentioned band of Reynolds numbers. The critical Reynolds number was determined numerically; and also the variation of flow pattern along with the air-side heat transfer coefficient and pressure drop in a multi-louvered heat exchanger associated with R e c r i has been reported. Moreover, a parametric study of the multi-louvered aluminium fin heat exchangers was also performed for 36 heat exchanger configurations with the louver angles (19–31°); fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm); and the geometric configuration exhibiting the highest air-side heat transfer coefficient was reported. The air-side heat transfer coefficient and pressure drop results for different geometrical configurations were presented in terms of Colburn j Factor and Fanning Friction Factor f; as a function of Reynolds number based on louver pitch
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air side thermal hydraulic performance of multi louvered fin aluminum heat exchangers
International Journal of Refrigeration-revue Internationale Du Froid, 2002Co-Authors: Man-hoe Kim, C W BullardAbstract:An experimental study on the air-side heat transfer and pressure drop characteristics for multi-louvered fin and flat tube heat exchangers has been performed. For 45 heat exchangers with different louver angles (15–29°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm), a series of tests were conducted for the air-side Reynolds numbers of 100–600, at a constant tube-side water flow rate of 0.32 m3/h. The inlet temperatures of the air and water for heat exchangers were 21 and 45°C, respectively. The air-side thermal performance data were analyzed using effectiveness-NTU method for cross-flow heat exchanger with both fluid unmixed conditions. The heat transfer coefficient and pressure drop data for heat exchangers with different geometrical configurations were reported in terms of Colburn j-Factor and Fanning Friction Factor f, as functions of Reynolds number based on louver pitch. The general correlations for j and f Factors are developed and compared to other correlations. The f correlation indicates that the flow depth is one of the important parameters for the pressure drop.
Antonio Barletta - One of the best experts on this subject based on the ideXlab platform.
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mixed convection flow in a vertical circular duct with time periodic boundary conditions steady periodic regime
International Journal of Heat and Mass Transfer, 2004Co-Authors: Antonio Barletta, Rossi E Di SchioAbstract:Mixed convection flow in a vertical circular duct subjected to a periodic sinusoidal temperature change at the wall is investigated. The analysis is performed by considering fully-developed parallel flow and steady-periodic regime. The local momentum and energy balance equations, together with the constraint equations which arise from the definition of mean velocity and mean temperature, are written in a dimensionless form and mapped into equations in the complex domain. One obtains two independent boundary value problems, which provide the mean value and the oscillating term of the velocity and temperature distributions. These boundary value problems are solved analytically, and the velocity and temperature distributions are obtained as functions of three parameters: the Prandtl number, Pr, the dimensionless frequency X, the ratio between the Grashof number Gr and the Reynolds number Re. The Fanning Friction Factor and the dimensionless heat flux are evaluated. 2004 Elsevier Ltd. All rights reserved.
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Combined forced and free flow in a vertical annular duct with circumferentially non uniform boundary conditions
place:BIRMINGHAM, 2004Co-Authors: Antonio Barletta, Stefano Lazzari, Enzo ZanchiniAbstract:The combined forced and free flow in a vertical annular duct is studied. The thermal boundary conditions are non\u2013axisymmetric and such that no axial temperature change takes place. Fully\u2013developed and steady\u2013state laminar flow is considered and the Boussinesq approximation is invoked. The effect of viscous dissipation is neglected. The Fourier series expansion method is employed to obtain the analytical expressions of the dimensionless temperature field, of the dimensionless velocity field and of the Fanning Friction Factor. To illustrate the general solution, a sample case is described in detail: an annular duct such that the inner wall is half adiabatic and half with a uniform heat flux, while the outer wall is kept at a uniform temperature
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Mixed convection flow in a vertical circular duct with time-periodic boundary conditions: steady-periodic regime.
'Elsevier BV', 2004Co-Authors: Antonio Barletta, Rossi E Di SchioAbstract:Mixed convection flow in a vertical circular duct subjected to a periodic sinusoidal temperature change at the wall is investigated. The analysis is performed by considering fully-developed parallel flow and steady-periodic regime. The local momentum and energy balance equations, together with the constraint equations which arise from the definition of mean velocity and mean temperature, are written in a dimensionless form and mapped into equations in the complex domain. One obtains two independent boundary value problems, which provide the mean value and the oscillating term of the velocity and temperature distributions. These boundary value problems are solved analytically, and the velocity and temperature distributions are obtained as functions of three parameters: the Prandtl number, Pr, the dimensionless frequency Ω, the ratio between the Grashof number Gr and the Reynolds number Re. The Fanning Friction Factor and the dimensionless heat flux are evaluated
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Fully developed mixed convection with steady\u2013periodic velocity oscillations in a vertical circular duct
place:BIRMINGHAM, 2004Co-Authors: Antonio Barletta, Rossi E Di SchioAbstract:The subject of the analysis is the combined forced and free convection of a Newtonian fluid in a vertical cylindrical duct with circular cross section. Reference is made to the non\u2013stationary steady\u2013periodic regime, determined by sinusoidal oscillations of the wall temperature. The fully developed region is studied, and the velocity field is assumed to be parallel to the axial direction. The investigation is performed with analytical methods. In particular, the momentum and energy local balance equations, together with the boundary conditions and the constraint equations which arise from the definition of mean velocity and mean temperature, are written in a dimensionless form and expressed as real parts of differential complex\u2013valued equations. Two independent boundary value problems are obtained, which provide the mean value and the oscillating term of the velocity and temperature distributions. The velocity and temperature distributions, as well as the Fanning Friction Factor, are obtained as functions of three parameters: the Prandtl number, Pr, the dimensionless frequency \uad, the ratio between the Grashof number Gr and the Reynolds number Re
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combined forced and free flow in a vertical rectangular duct with prescribed wall heat flux
International Journal of Heat and Fluid Flow, 2003Co-Authors: Antonio Barletta, Rossi E Di Schio, Enzo ZanchiniAbstract:Abstract In this paper, combined forced and free convection is studied in a vertical rectangular duct with a prescribed uniform wall heat flux (H2 boundary condition). A different heat flux value for each plane wall is considered; the condition of a uniform wall heat flux throughout the duct results as a special case. The local momentum and energy balance equations are written in a dimensionless form and solved numerically, by means of a Galerkin finite element method. The numerical solution gives the dimensionless velocity and temperature distributions, together with the values of the Fanning Friction Factor, of the Nusselt number, of the momentum flux correction Factor and of the kinetic energy correction Factor. These dimensionless parameters are reported as functions of the aspect ratio and of the ratio between the Grashof number, Gr , and the Reynolds number, Re . The threshold values of Gr / Re for the onset of flow reversal are evaluated.
