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Showing papers by "Ephraim M Sparrow published in 2013"


Journal ArticleDOI
TL;DR: A new mass transfer model has been formulated and implemented for predicting the penetration of liquid medication into an arterial wall and found that the drug concentration at a clinically relevant depth in the artery wall varied linearly with the duration of the therapy, increased with increasing values of the driving pressure, and decreased for higher viscosities of the advecting fluid.

39 citations


Journal ArticleDOI
TL;DR: In this paper, a double-pipe configuration of a two-fluid heat exchanger was selected for study and the authors quantified the axial variations of the temperature and heat flux along the wall separating the pipe and annulus flows.
Abstract: This investigation was performed in order to quantify the validity of the assumed constancy of the overall heat transfer coefficient U in heat exchanger design. The prototypical two-fluid heat exchanger, the double-pipe configuration, was selected for study. Heat transfer rates based on the U = constant model were compared with those from highly accurate numerical simulations for 60 different operating conditions. These conditions included: (a) parallel and counter flow, (b) turbulent flow in both the pipe and the annulus, (c) turbulent flow in the pipe and laminar flow in the annulus and the vice versa situation, (d) laminar flow in both the pipe and the annulus, and (e) different heat exchanger lengths. For increased generality, these categories were further broken down into matched and unmatched Reynolds numbers in the individual flow passages. The numerical simulations eschewed the unrealistic uniform-inlet-velocity-profile model by focusing on pressure-driven flows. The largest errors attributable to the U = constant model were encountered for laminar flow in both the pipe and the annulus and for laminar flow in one of these passages and turbulent flow in the other passage. This finding is relevant to microchannel flows and other low-speed flow scenarios. Errors as large as 50% occurred. The least impacted were cases in which the flow is turbulent in both the pipe and the annulus. The general level of the errors due to the U = constant model were on the order of 10% and less for those cases. This outcome is of great practical importance because heat-exchanger flows are more commonly turbulent than laminar. Another significant outcome of this investigation is the quantification of the axial variations of the temperature and heat flux along the wall separating the pipe and annulus flows. It is noteworthy that these distributions do not fit either the uniform wall temperature or uniform heat flux models.

23 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method to accelerate the rate of delivery of therapeutic drugs to human tissues by using a balloon filled with a homogeneous mixture of the drug and the carrier fluid.
Abstract: The focus of this paper is to propose, model, and characterize a means of accelerating the rate of delivery of therapeutic drugs to human tissues. The investigated means is a pressurized, permeable-walled balloon filled with a homogeneous mixture of the drug and the carrier fluid. The fluid mixture, driven by pressure, traverses the thickness of the balloon wall through laser-drilled pores. The number and deployment of the pores can be controlled to a high degree of precision. As a consequence, the wall of the balloon can be regarded as a homogeneous porous medium, and the traversing fluid flow can be analyzed by means of porous media models. When the balloon is in intimate contact with the surface of a tissue bed, the therapeutic fluid flows in series as it passes through the balloon wall and penetrates the tissue. The flow rate can be controlled by proper selection of the balloon permeability, the viscosity of the flowing medium, and the pressure internal to the balloon. The delivered concentration of the drug was predicted by coupling the present balloon-focused theory with a previously developed tissue-bed model that includes both diffusion and advection processes. The tribologic interaction of the pressurized balloon with an artery wall was investigated experimentally to assess the possible formation of aneurysms.

17 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated diffuser-created parasitic pressure losses that occur in response to all possible operating conditions, including the Reynolds number at diffuser inlet, the diffuser opening angle, and the ratio of the exit and inlet diameters of the diffusers.

15 citations


Journal ArticleDOI
TL;DR: In this paper, a case study is presented to clarify the accuracy of a measurement technique commonly used in industry to estimate the temperature of a flowing fluid, which utilizes a temperature measurement on the outside surface of the pipe in which the fluid is flowing.

15 citations



Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that the Coanda effect can be used to affect the trajectory of fine fibers created by the melt-blown process, and the range of standoff distances for which the presence of a plane wall induced the coanda effect was determined.
Abstract: The goal of this investigation is to demonstrate, by means of numerical simulation, that the Coanda effect can be used to affect the trajectory of fine fibers created by the melt-blown process. The Coanda effect serves to modulate the direction of fluid motion, and, in turn, the change in the pattern of fluid flow alters the fiber trajectories. Primary focus is accorded to the use of plane walls to induce the Coanda effect, but some consideration is given to curved Coanda-inducing walls for comparison purposes. The lateral standoff distance between the location of the fiber exit from the die and the Coanda-inducing wall was varied parametrically. The range of standoff distances for which the presence of a plane wall induced the Coanda effect was determined. Another outcome of general significance is that the Coanda effects induced by a curved wall and a plane wall are of comparable magnitude.

12 citations


Journal ArticleDOI
TL;DR: In this paper, the authors identify the existence of various sub-regimes within the laminar-flow regime, including friction-dominated flow, inertial-lossdominated flow and transition between these flows.
Abstract: There are many modalities that may be used to enhance heat transfer performance. One of these modes, the embossing of channel walls with dimples and/or protrusions, is a technique which has the advantage of simplicity of fabrication. The assessment of the quality of a geometry-based heat transfer enhancement technique frequently involves the change in pressure drop that accompanies the geometric modification. This realization provides the motivation for the investigation reported here. The focus of this work is the identification of the existence of various sub-regimes within the laminar-flow regime. The investigation was implemented by numerical simulation supplemented by a three-dimensional model of periodic fully developed flow. The selected channel-height Reynolds number range extended from 200 to 800. Within this range, three sub-regime laminar flows were identified: friction-dominated flow, inertial-loss-dominated flow, and the transition between these flows. Another focus of the results was the pre...

11 citations


Journal ArticleDOI
TL;DR: In this article, a numerical simulation model was used to predict particle separation and concomitant mass transfer by means of a swirl chamber or swirl tube, where the particle-laden flow was ducted through a straight pipe to a three-bladed swirl generator from which the emergent swirling flow entered a settling chamber where the centrifugal forces propelled the particles toward the chamber walls.
Abstract: The goal of this investigation is to formulate, implement, and definitively validate a numerical simulation model to predict particle separation and concomitant mass transfer by means of a swirl chamber or swirl tube. The separation model encompassed three-dimensional turbulent fluid flow abetted with a particle transport model. All components of the model were used in their native form, without tuning or adaptation to accommodate the problem in question. Experiments were performed which were a precise replica of the numerical simulations in order to provide an unequivocal basis for evaluating the efficacy and validity of the simulation model. The experiments involved air flow as the carrier fluid. The particle-laden flow was ducted through a straight pipe to a three-bladed swirl generator from which the emergent swirling flow entered a settling chamber where the centrifugal forces propelled the particles toward the chamber walls. At the downstream end of the chamber, provision was made for the wall-adjac...

3 citations