The Experts below are selected from a list of 20793 Experts worldwide ranked by ideXlab platform
H Howmik - One of the best experts on this subject based on the ideXlab platform.
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analysis of Heat Transfer and pressure drop characteristics in an offset strip fin Heat exchanger
International Communications in Heat and Mass Transfer, 2009Co-Authors: H Howmik, Kwan-soo LeeAbstract:Abstract A steady-state three-dimensional numerical model was used to study the Heat Transfer and pressure drop characteristics of an offset strip fin Heat exchanger. Water was the Heat Transfer medium, and the Reynolds number Redh ranged from 10 to 3500. Variations in the Fanning friction Factor f and the Colburn Heat Transfer Factor j relative to Redh were observed. General correlations for the f and j Factors were derived, and these could be used to analyze fluid flow and Heat Transfer characteristics of offset strip fins in the laminar, transition, and turbulent regions. Finally, three performance criteria (j/f, j/f1/3, and JF) were adopted, and the best performance criteria for the cases Pr = 7 and Pr = 50 were chosen to be JF and j/f1/3, respectively.
Kwan-soo Lee - One of the best experts on this subject based on the ideXlab platform.
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analysis of Heat Transfer and pressure drop characteristics in an offset strip fin Heat exchanger
International Communications in Heat and Mass Transfer, 2009Co-Authors: H Howmik, Kwan-soo LeeAbstract:Abstract A steady-state three-dimensional numerical model was used to study the Heat Transfer and pressure drop characteristics of an offset strip fin Heat exchanger. Water was the Heat Transfer medium, and the Reynolds number Redh ranged from 10 to 3500. Variations in the Fanning friction Factor f and the Colburn Heat Transfer Factor j relative to Redh were observed. General correlations for the f and j Factors were derived, and these could be used to analyze fluid flow and Heat Transfer characteristics of offset strip fins in the laminar, transition, and turbulent regions. Finally, three performance criteria (j/f, j/f1/3, and JF) were adopted, and the best performance criteria for the cases Pr = 7 and Pr = 50 were chosen to be JF and j/f1/3, respectively.
Amit Dhiman - One of the best experts on this subject based on the ideXlab platform.
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Non-Newtonian power-law fluid’s thermal characteristics across periodic array of circular cylinders
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019Co-Authors: Ram Pravesh, Amit Dhiman, R. P. BhartiAbstract:The thermal characteristics of incompressible non-Newtonian power-law fluids across periodic array of circular cylinders have been examined using the finite volume-based numerical solver ANSYS-FLUENT for the following ranges of physical parameters: Reynolds number; 1 ≤ Re ≤ 40: Prandtl number; 1 ≤ Pr ≤ 100: power-law index; 0.40 ≤ n ≤ 1.8; and fluid volume fractions ranging from 0.70 to 0.99. The thermal features have been described via isotherm patterns, local and average Nusselt numbers and the Colburn Heat Transfer Factor and found to be strongly dependent over the above physical parameters. It was observed that the dense isotherms with the increasing inertial and viscous diffusion suggest an improvement in the rate of Heat Transfer across the periodic cylinders. An increase in local Nusselt number was seen with the increasing values of Re and/or Pr across all the fluid volume fractions. Further, the different behavior of the average Nusselt number was noticed because of the shear-thinning and shear-thickening natures. An enhancement of about 97% was noticed in the shear-thinning region between the extreme fluid volume fractions for the highest value of Pr and the lowest values of Re and n . However, in many cases, the enhancement was noticed to be even more than 100%. An empirical correlation for the average Nusselt number and the Colburn Heat Transfer Factor ( j _ H ) has been developed to give the additional physical insight of the results. Finally, the comparison was made with the available literature which displayed a good agreement with the present results.
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Opposing buoyancy characteristics of Newtonian fluid flow around a confined square cylinder at low and moderate Reynolds numbers
Numerical Heat Transfer Part A: Applications, 2016Co-Authors: Deepak Kumar, Amit DhimanAbstract:ABSTRACTThe influence of opposing-buoyancy mixed convection from a square cylinder in a vertical channel has been studied at Reynolds numbers (Re) = 1–100, Richardson numbers (Ri) = 0 to −1, and blockage ratios (β) = 10–50% for air as a working fluid. The onset of a steady to a time-periodic regime is found for Ri = 0 (at Re = 35, 65, 74, and 62), Ri = −0.5 (at Re = 12, 39, 48, and 54), and Ri = −1 (at Re = 9, 30, 39, and 50) for β = 10%, 25%, 30%, and 50%, respectively. The initiation of flow separation is also determined. Finally, the correlations of Strouhal number, drag coefficient, and the Colburn Heat Transfer Factor were obtained.
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Transition to periodic unsteady and effects of Prandtl and Richardson numbers on the flow across a confined Heated trapezoidal prism
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2015Co-Authors: Malik Parveez, Amit Dhiman, Tanveer RasoolAbstract:The effects of wall confinements ( β ) and of Prandtl numbers ( Pr ) on the laminar flow around a Heated trapezoidal prism are investigated numerically for Pr = 0.71–100 and β = 12.5–50 % at low Reynolds numbers ( Re ). The critical value of the Reynolds number (i.e., the transition from a steady to a time-periodic regime) is calculated and it exists between Re = (36 and 37), (60 and 61) and (91 and 92) for the blockage ratios of 12.5, 25 and 50 %, respectively. The average Nusselt number increases with increasing Re and/or Pr and/or blockage ratio. The variation of local Nusselt number on each surface of the obstacle and the representative isotherm contours are presented to elucidate the role of Pr and blockage ratio on the Heat Transfer from the trapezoidal prism. The maximum Heat Transfer enhancement with respect to a square prism on the basis of equal projected area is found to be approximately 31 and 45 % for the blockage ratios of 12.5 and 25 %, respectively, for Pr = 0.71 and Re = 1. The Colburn Heat Transfer Factor correlations are also obtained for the preceding range of settings. Finally, the influence of Richardson number ( Ri = 0–1) on the flow and Heat Transfer characteristics has been studied for air as working fluid.
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Power-law shear-thinning flow around a Heated square bluff body under aiding buoyancy at low Reynolds numbers
Korean Journal of Chemical Engineering, 2014Co-Authors: Neha Sharma, Amit Dhiman, Surendra KumarAbstract:Power-law shear-thinning fluid flow over a Heated square bluff body is numerically investigated under aiding buoyancy mixed convection at low Reynolds numbers. Semi-explicit finite volume code is developed to solve the governing equations along with the appropriate boundary conditions. Both aiding buoyancy and shear-thinning natures are found to augment the Heat Transfer rate from the surface of the long square bar. In aiding buoyancy, the total drag coefficient is found to be more for the square cylinder than that of the circular cylinder, whereas the average cylinder Nusselt number for the square cylinder is found to be lower than the circular one on equal side/diameter basis. Maximum augmentation in Heat Transfer is found to be approximately 20% with respect to forced convection. Finally, a Heat Transfer correlation is established by using the Colburn Heat Transfer Factor.
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Heat Transfer to power-law dilatant fluids in a channel with a built-in square cylinder
International Journal of Thermal Sciences, 2009Co-Authors: Amit DhimanAbstract:Abstract In this study, Heat Transfer to power-law dilatant fluids from a long square cylinder (Heated) confined in a channel in the steady flow regime is investigated. The effects of Reynolds number, Prandtl number and flow behavior index on the Heat Transfer characteristics of a cylinder is examined for the range of conditions 1 ⩽ Re ⩽ 45 , 1 ⩽ n ⩽ 2.0 and 1 ⩽ Pr ⩽ 100 (the maximum Peclet number being 4000) for a fixed blockage ratio, β = 1 / 8 . The variation of the local Nusselt number on the individual surfaces of the square obstacle for the constant wall temperature (CWT) and uniform Heat flux (UHF) boundary conditions prescribed on the surface of the square obstacle are presented. Likewise, the representative isotherm plots for the two classical thermal boundary conditions are shown. The average Nusselt number and the Heat Transfer Factor ( j h ) have also been calculated. Irrespective of the value of the flow behavior index, the value of the local Nusselt number at each corner of the square cylinder increases with an increase in the Reynolds and/or Prandtl number. The average Nusselt number increases monotonically with an increase in the Reynolds and/or the Prandtl number. Finally, simple Heat Transfer correlations have been provided for the range of conditions covered here.
R P Chhabra - One of the best experts on this subject based on the ideXlab platform.
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forced convection Heat Transfer from an elliptical cylinder to power law fluids
International Journal of Heat and Mass Transfer, 2008Co-Authors: Ram P Bharti, P Sivakumar, R P ChhabraAbstract:Abstract Forced convection Heat Transfer to incompressible power-law fluids from a Heated elliptical cylinder in the steady, laminar cross-flow regime has been studied numerically. In particular, the effects of the power-law index (0.2 ⩽ n ⩽ 1.8), Reynolds number (0.01 ⩽ Re ⩽ 40), Prandtl number (1 ⩽ Pr ⩽ 100) and the aspect ratio of the elliptic cylinder (0.2 ⩽ E ⩽ 5) on the average Nusselt number (Nu) have been studied. The average Nusselt number for an elliptic cylinder shows a dependence on the Reynolds and Prandtl numbers and power-law index, which is qualitatively similar to that for a circular cylinder. Thus, Heat Transfer is facilitated by the shear-thinning tendency of the fluid, while it is generally impeded in shear-thickening fluids. The average Nusselt number values have also been interpreted in terms of the usual Colburn Heat Transfer Factor (j). The functional dependence of the average Nusselt number on the dimensionless parameters (Re, n, Pr, E) has been presented by empirically fitting the numerical results for their easy use in process design calculations.
Ryozo Ooka - One of the best experts on this subject based on the ideXlab platform.
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shape optimization of water to water plate fin Heat exchanger using computational fluid dynamics and genetic algorithm
Applied Thermal Engineering, 2015Co-Authors: Ryozo OokaAbstract:Abstract In the design calculation of a plate-fin Heat exchanger, the convective Heat Transfer coefficients of the plate and fin are often simplified to the same value. Further, in the calculation of the convective Heat Transfer coefficient, the Colburn Heat Transfer Factor and Fanning friction Factor are generally obtained using empirical equations. In this work, to obtain more precise results, the convective Heat Transfer coefficients of the plate and fin are defined as independent parameters. The Colburn Factor and Fanning Factor are obtained according to the results of computational fluid dynamics. The fin height, fin pitch, fin thickness, and fin length are considered as four design parameters. A modified number of entropy production units (Ns) is adopted. Ns due to friction (NsΔP), Ns due to Heat Transfer (NsΔT), and NsTotal are considered as three objective functions. The optimal structural parameters of a water-to-water plate-fin Heat exchanger applied to an air-conditioning system are obtained using genetic algorithm by single objective optimization and multi-objective optimization.