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Showing papers by "Ephraim M Sparrow published in 2017"


Book ChapterDOI
TL;DR: In this paper, several physical situations are examined: fluid flows (1) with secondary swirl, (2) in a pipe bend, (3) in round pipes, (4) in rectangular duct, and finally (5) through perforated plates.
Abstract: In this chapter, several physical situations are examined: fluid flows (1) with secondary swirl, (2) in a pipe bend, (3) in round pipes, (4) in a rectangular duct, and finally (5) through perforated plates. In each of these cases, validation was performed using accurate and complete experimental results available in the published literature to be compared with appropriate numerical simulations. Different quantities are used for validation metric depending on the availability of experimental data, i.e., comparing velocity profiles, local Nusselt numbers, and pressure drop. Several popular turbulence models, κ − ɛ, RNG κ − ɛ, κ − ω, SST κ − ω, and WALE LES were investigated. The first two cases, (1) and (2), utilized available velocity and turbulence profiles at the inlet of the solution domain. From Case (1), the SST κ − ω turbulence model clearly was the preferred choice because of the good agreement with experimental data and the shorter CPU time required as compared to the LES model. The remaining cases (2)–(5) were primarily investigated with the SST κ − ω turbulence model. Overall, the SST κ − ω turbulence model performed very well compared to the available experimental data for all of the cases investigated here.

22 citations


Journal ArticleDOI
TL;DR: In this article, the intrinsic unsteady heat transfer on the surface of a cylinder in crossflow has been investigated in detail by numerical simulation as a function of the freestream turbulence intensity and the Reynolds number.

15 citations


Journal ArticleDOI
TL;DR: In this paper, the perforated plate pressure drop decreased moderately with an increasing angle of attack, an outcome directly relevant to design, and the Reynolds numbers that defined each flow regime were definitively determined.
Abstract: Purpose The purpose of this paper is to provide both directly applicable fluid-flow results and fluid-mechanic fundamentals for flow impinging at an angle of attack on a perforated plate. Design/methodology/approach A physical situation was modeled with high fidelity, and the model was implemented by numerical simulation. The simulations spanned all possible flow regimes including laminar, intermittent (transitional) and turbulent, and the Reynolds numbers that defined each flow regime were definitively determined. The Reynolds numbers ranged from 0.1 to 30,000, the angles of attack included 0, 5, 15 and 22.5° and the host duct dimensions varied appropriately. Findings It was found that the perforated-plate pressure drop decreased moderately with an increasing angle of attack, an outcome directly relevant to design. The pattern of fluid flow caused by the presence of the plate was dominated by a large recirculation zone situated downstream of the plate in a corner between the plate and an adjacent wall. The recirculation zone played the role of a blockage which deflected the flow emerging from the apertures in the plate toward the opposite wall. Originality/value (a) Pressure drop information directly applicable to design, (b) downstream distance from the plate at which the plate-created flow disturbance disappears, (c) account taken of the intermittent flow regime between laminar and turbulent, (d) implementation of a new metric to characterize the strength of turbulence.

7 citations


Journal ArticleDOI
TL;DR: In this article, numerical simulation is used to focus on limited locations in the United States (Phoenix, AZ, Miami, FL, and Minneapolis, MN) for mid-summer and mid-winter climatic conditions.
Abstract: Extensive recent published literature has shown that the use of selectively highly reflecting coatings for solar beam radiation incident on roof surfaces during the summer has increased the solar albedo and decreased the need for electricity consumption to maintain building temperatures. In this paper, other issues relevant to the temperatures, heat fluxes, and human comfort related to solar energy are addressed. In particular, numerical simulation is used to focus on limited locations in the United States (Phoenix, AZ, Miami, FL, and Minneapolis, MN) for mid-summer and mid-winter climatic conditions. At these locations, two different insulation systems relevant to residential housing in the United States are considered. Not only is solar beam radiation taken into account, but also is infrared sky radiation, humidity of the surrounding air, cloud cover, air temperature, and the emissivity of water vapor droplets. The results presented include: (a) diurnal temperature and heat flux variations at the exterior surfaces, (b) temperatures and heat fluxes at internal surfaces, (c) heat flowing from the internal surfaces, (d) an accounting of the heat transferred respectively by conduction, convection, and radiation at the exterior surface, (e) convective heat transfer coefficients at the exterior surface. The results are presented over a 24-h period on both June 21 and December 21. Equal focus was given to summer-season and winter-season performance of the radiatively selective coating. It was found that although the coating was highly advantageous for summer conditions, it significantly increased the power requirements for winter heating.

6 citations


Journal ArticleDOI
TL;DR: In this article, the performance of perforated plates in fluid-flow applications is evaluated by measuring the pressure drop of the working fluid, and the design parameters which affect the pressure loss are Reynolds number (A), porosity (B), non-dimensional thickness of the plate (C) and hole pattern (D).
Abstract: The performance of the perforated plates in fluid-flow applications is evaluated by measuring the pressure drop of the working fluid. The purpose of this investigation is to determine how different parameters affect the capability of the perforated plates and modify the design by using a design of experiment analysis, namely Taguchi method for optimization. The flow characteristics, which were obtained by the Computational Fluid Dynamics (CFD) software package ANSYS-CFX, were used for this analysis. The design parameters which affect the pressure loss are Reynolds number (A), porosity (B), non-dimensional thickness of the plate (C) and hole pattern (D). The level of importance of the design parameters are determined by use of analysis of variance method, ANOVA. According to the analysis, the optimum values are obtained for the case A8B2C2D1 (Re = 15000, porosity = 50.3, t/D = 1, and staggered hole). The most effective design parameter on the results is found as porosity (92%), while the least effective is the hole pattern (0.2%). A special dividend of this work was to demonstrate the capabilities of the Taguchi Method as a powerful means of increasing the effectiveness of numerical simulation.

5 citations




BookDOI
07 Apr 2017
TL;DR: In this article, the authors quantitatively demonstrate the necessity of taking into account all of the characteristic features of the fluid flow that is delivered to the heat exchanger, including swirl, eddies, backflow, cross-sectional nonuniformities and unusually high turbulence, almost all of which are embedded in actual fluid flows delivered to heat exchangers.
Abstract: Heat exchangers usually involve two or more fluids having different temperatures. The performance of heat exchangers depends critically on the nature of the participating fluid flows. Over the years of traditional heat exchanger design, the most accounted feature of the fluid flow has been its magnitude. This is because design procedures for heat exchangers have been closely connected to fan/blower/pump curves in which the magnitude of the delivered flow is linked to the pressure rise. However, those characteristic curves do not take into account swirl, eddies, backflow, cross-sectional nonuniformities, and unusually high turbulence, almost all of which are embedded in actual fluid flows delivered to heat exchangers. The focus of this chapter is to quantitatively demonstrate the necessity of taking into account all of the characteristic features of the fluid flow that is delivered to the heat exchanger. This is accomplished by treating the fan/blower/pump and the heat exchanger as a single interactive system. In such a treatment, it is mandatory that fan rotation is fully considered to ensure that all rotation-based flow characteristics are included. The composite system, consisting of the fluid mover and the heat exchanger, is solved by numerical simulation. The fluid flows produced by this approach are a more true representation of reality.

2 citations


Journal ArticleDOI
TL;DR: It is indicated that a pressure-resistant multi-lumen catheter better preserves cell viability compared to the standard, and is shown to resist hemolysis for all tested and simulated balloon pressures and flowrates up to 10ml/min.

2 citations


Journal ArticleDOI
TL;DR: The results presented in this paper pinpoint the locations and causes of sound generation that can cause audible discomfort for patients.
Abstract: Purpose The study described here aims to set forth an analysis approach for a specific biomedical therapeutic device principally involving fluid mechanics and resulting sound generation. The function of the therapeutic device is to clear mucus from the airways of the lungs. Clearance of the airways is a primary means of relief for cystic fibrosis and is also effective in less profound dysfunctions such as asthma. The complete system consists of a device to periodically pulse air pressure and a vest that girdles the abdomen of the patient and receives and discharges the pulsating airflow. The source of pulsed air can be tuned both with respect to the amplitude and frequency of the pressure pulsations. Design/methodology/approach The key design tools used here are computational fluid dynamics and the theory of turbulence-based sound generation. The fluid flow inside of the device is multidimensional, unsteady and turbulent. Findings Results provided by the fluid mechanic study include the rates of fluid flow between the device and the inflatable vest, the rates of air supplied to and extracted from the device, the fluid velocity magnitudes and directions that result from the geometry of the device and the magnitude of the turbulence generated by the fluid motion and the rotating component of the device. Both the velocity magnitudes and the strength of the turbulence contribute to the quantitative evaluation of the sound generation. Originality/value A comprehensive literature search on this type of therapeutic device to clear mucus from the airways of the lungs revealed no previous analysis of the fluid flow and sound generation inside of the device producing the pulsed airflow. The results presented in this paper pinpoint the locations and causes of sound generation that can cause audible discomfort for patients.

Journal ArticleDOI
TL;DR: The two-pronged approach developed here was shown to be capable of coping with an operating feature called stopflow wherein an officiating physician orders an immediate cessation of fluid flow and the thermal events following stopflow are well described by the numerical simulations.