Additional Pressure Drop Research Articles

Heat transfer characteristics and novel optimization of a supercritical N-decane-Cooling tube under gravity condition

To study the flow and heat transfer characteristics of supercritical n-decane in the actual regenerative cooling tube, the heat transfer characteristics in a horizontal square tube under a single-side heated condition with considering and ignoring gravity were numerically investigated. The k-ωSST turbulence model was used and tested against the experimental data. The heat transfer characteristics on circumferential walls were presented and the radial flow pattern in the main flow zone and the boundary layer zone was analyzed to explore the mechanism of the heat transfer under gravity conditions. It was found that the heat transfer was enhanced at the bottom wall and weakened at the remaining three walls because of the secondary flow caused by gravity effect. Furthermore, the heat transfer would be enhanced when the velocity component of the boundary layer along the normal direction of the wall is toward the wall. Besides, a brand-new structure constructed by ribs section and smooth section was proposed. The additional pressure drop caused by the enhanced heat transfer structure can be reduced by up to 95.4% with the same heat transfer performance compared with the traditional ribs-tube structure which ribs spread all over a tube.

A hydrophobic porous substrate-based vapor venting technique for mitigating flow boiling instabilities in microchannel heat sink

With the onset of nucleation, flow boiling in microchannels is susceptible to undesirable flow instabilities resulting in fluctuating wall temperature and large pressure drops. It is imperative to develop a passive technique to mitigate flow boiling instabilities and enhance the thermo-hydraulic performance of the heat sink without additional pressure drops. The present work explores a hydrophobic porous polydimethylsiloxane (PDMS) substrate-based vapor venting technique to mitigate flow boiling instabilities in microchannels. The hydrophobic porous substrate fitted at the channel exit manifold attracts the vapor plug, assists in vapor venting, and thus facilitates the easy evacuation of the bubbles from the channel. Flow boiling experiments are performed with deionized water in rectangular cross-section microchannels for a heat flux range of 10–260 W/cm2 and the coolant mass flux range of 206–335.49 kg/m2s. Heat transfer and pressure drop characteristics of the proposed configuration are compared with those of the conventional configuration. The proposed design suppresses the wall temperature oscillation and pressure oscillations. It produces a 32 % enhancement in heat transfer coefficient and a 63 % reduction in pressure drop compared to the conventional outlet configuration. The new configuration significantly reduces the bubble ebullition cycle, resulting in an efficient bubble evacuation from the channels. Further, frequent flushing of the vapor slug in the new design reduces the temperature fluctuations and enhances the heat transfer coefficient. The heat transfer augmentation is more pronounced at higher heat flux with more vapor generation rates.

Production performance of the low-permeability reservoirs: Impact of contamination at the wellbore vicinity

Hydrocarbon reservoirs with low porosity and permeability are usually vulnerable to be contaminated owing to the drilling and completion fluids-induced formation damage, which significantly impedes the efficient production of hydrocarbon. However, most current productivity prediction models introduce the concept of skin factor to capture the near-wellbore contamination, which only considers the change of permeability before and after contamination, whereas neglecting the change of threshold pressure gradient (TPG) affected by the permeability reduction. Also, few works have been done to focus on the influences of contamination, TPG, sensitivity of rock porosity to internal stress, and fluid compressibility simultaneously in the actual production process of the low-permeability reservoir. Therefore, to bridge the knowledge gap, this study presents a new comprehensive productivity model encompassing those multiple influencing factors. Firstly, the seepage area is divided into contaminated zone and uncontaminated zone. Thereafter, the proposed model is established based on non-Darcy seepage theory and continuity principle, comprehensively taking account of the effects of different permeability and TPG between contaminated zone and uncontaminated zone, stress sensitivity based on primary stress in porous media, and the fluid compressibility. Subsequently, the newly proposed model is proved to be reliable through the consistency between the simplified model and the existing models in the literatures. Finally, the sensitivity analysis is employed to investigate the effects of key parameters. Main results show that a) the decreased permeability affected by contamination would result in increased TPG, further lowering the well productivity. b) Contamination, TPG and stress sensitivity will cause additional pressure drop and production loss, which will overestimate the production rate by neglecting them. While the fluid compressibility could boost the well productivity, which will underestimate the production rate by ignoring it. c) The order of productivity influencing factors is contamination > TPG > the fluid compressibility > stress sensitivity. d) Contamination and the TPG are significant influencing factors at stage of high bottomhole pressure. Moreover, the influence degree of contamination, the fluid compressibility and stress sensitivity gradually increase, while the influence degree of the TPG greatly decreases with lower pressure.

Application of oscillation flow to horizontal gas–particle two-phase flow

The purpose of this study is to apply the oscillation flow induced by a combination of a circular cylinder and non-uniform soft fins to gas–solid two-phase flows to reduce the transport gas velocity and power consumption in a horizontal pipe. In order to evaluate the oscillation flow, several different sizes of square and circular cylinders are used to combine four pieces of soft fins with non-uniform lengths, which are mounted on the horizontal central plane in front of the particle supply. The test pipe comprises a horizontal acrylic pipe with a length of 5 m and an inside diameter of 80 mm. Spherical polyethylene particles with an average diameter of 2.3 mm and density of 978 kg/m3 were used as the test particles. The average gas velocity was 9–16 m/s, and the solid mass flow rate was 0.11–0.51 kg/s. It is found that the combination of a circular cylinder or square cylinder of L = 10 mm with non-uniform soft fins causes the lowest pressure drop and highest velocity fluctuation in the oscillation flow based on single-phase flow (gas only) measurement. Compared to conventional gas–solid two-phase flows, the reduction in the minimum transport velocity, pressure drop, power consumption, and additional pressure drop were obtained using a combination of a circular cylinder with non-uniform soft fins. This combination provides the highest reduction rates in the minimum conveying velocity and an additional pressure drop by approximately 10.0% and 34.1%, respectively. Based on particle image velocimetry measurements, the time-mean particle velocity and particle fluctuating velocity of a circular cylinder with non-uniform soft fins were higher than those of conventional flows near the bottom part of the pipe, thus easily accelerating and suspending particles near the pipe bottom, even at lower gas velocities.

A Three‐Dimensional Study of Wormhole Formation in a Porous Medium: Wormhole Length Scaling and a Rankine Ovoid Model

AbstractUnderstanding how wormholes develop and how they change the permeability of the porous medium is important for many natural and industrial processes in subsurface solid‐fluid systems. We conduct core flood tests to study the wormhole formation in a porous medium under different flow rates and at different moments before breakthrough. We show that the wormholes created in core flood tests have lengths following a power‐law distribution, with more short ones than long ones. This statistical nature of the wormhole lengths allow one to experimentally study the wormhole competition in 3‐D: Many wormholes develop initially near the inlet, but only a few develop further. Our experimental results also show that the existing wormhole‐matrix models underestimate wormhole lengths because of the neglected additional pressure drop caused by the radial flow near the wormhole tip. We improve upon the existing models by approximating the radial flow near the wormhole tip with a Rankine ovoid model.

Effects of rolling motion on transient flow behaviors of gas-liquid two-phase flow in horizontal pipes

The investigation of transient flow behaviors of gas-liquid two-phase flow under ocean conditions is vital to the application of gas-liquid transport in ocean engineering area. In this paper, the gas-liquid two-phase flow numerical model of rolling horizontal pipe is established based on CFD code combined with user-defined functions (UDF). The three-dimensional rolling flow fields are simulated using the volume of fluid (VOF) model, RNG k−ε turbulence model and additional inertia force method. First, the simulation results are compared with the experimental data, which revealed a reasonable agreement. Then, the variation in transient flow behaviors by horizontal pipe (L = 2.0 m, D = 0.035 m) with varying rolling conditions (θm = 2°-6°, T = 0.5–4.0 s) and flow velocities (jG = 0.1–10.0 m/s, jL = 0.1–0.5 m/s) are investigated. The results showed that the rolling motion caused agglomeration of dispersed bubbles and gas slugs into a continuous gas column, increased the cross-sectional void fraction significantly. The variation of additional inertial force and pressure drop increased with the increase of rolling angle and the decrease of the rolling period. Compared with the rolling angle, the transient flow behaviors are more sensitive to the rolling period. In addition, as the initial gas volume fraction increased, the effects of rolling motion on the transient flow behaviors decreased gradually. These qualitative conclusions may serve as a reference for gas-liquid transport simulations under rolling conditions.

Large-deposit non-linear chemical reactive flows in porous media: Identifiability and observability

This work discusses the use of additional pressure drop measurements in the characterisation of chemical reactive flow in porous media resulting in insoluble solid deposition. Previous studies of this problem have used outlet breakthrough concentration of one species and pressure drop across the sample during the commingled injection of reacting species, to determine model coefficients. In this work, we consider the introduction of additional measurements of pressure drop across subsections of the sample. The recently derived analytical model is compared to laboratory data to demonstrate the validity of both the model and additional measurement data. The effect of measuring different quantities is assessed by considering the identifiability of the model parameters. All parameters exhibit finite confidence intervals, however, datasets neglecting breakthrough concentration result in higher parameter uncertainty. Higher parameter uncertainty is shown to result in uncertainty in deposit profiles and prediction of pressure drop at higher length scales, demonstrating the importance of limiting parameter uncertainty through experimental design.

Effect of tapered headers on pressure drop and flow distribution in a U-type polymeric solar absorber

This study inspects the effect of tapered headers on pressure drop and flow distribution in a U-type polymeric absorber with novel tapered headers and lens-shaped absorber strings using a validated thermo-hydraulic model. The model results are compared with those obtained from the literature to attain credibility in the flow distribution trend for the U-configuration. A good agreement between the developed discrete model and comparison cases is found. Moreover, in order to examine the efficacy of tapered headers in more detail, different scenarios are treated in terms of header configuration by applying cylindrical geometry in one or both inlet/outlet headers. The outcomes exemplify that even a slight cone angle of 1.73° in headers can significantly reduce non-uniformity (φmax< 8%) with negligible influence on the total pressured drop. Yet, further reduction in maldistribution (φmax< 5%) can be achieved in U-type absorbers if the tapered outlet header is combined with a cylindrical inlet header in the range of AR≤ 3.34 and DR≤ 0.24. In this case, a compromise between additional pressure drop and flow distribution degree should be found. The present study offers a systematic approach for conducting thermo-hydraulic analysis in flat-plate solar collectors with complex absorber compositions and geometries.

Turbulent convective heat transfer behavior of supercritical water flowing upward in 2 × 2 rod bundle channels with various spacers

The turbulent flow and heat transfer characteristics of supercritical water, flowing in vertical 2 × 2 rod bundle channel, are numerically investigated to find useful methods to improve the cooling performance in the core of a supercritical water-cooled reactor. The heat transfer behavior as a function of mass flux and inlet temperature is analyzed and discussed. Standard grid and helical wire spacers are added to the channel, and overall heat transfer performance is evaluated and compared. The results indicate that the fuel rods can be cooled more effectively when the fluid temperature is near the pseudocritical point due to the high specific heat capacity at this temperature and pressure, and the local heat transfer coefficient can be improved greatly from the application of grid spacers; however, heat transfer enhancement only happens in limited regions downstream of the grid spacers. By contrast, strong swirl flow can be induced by a helical wire, thus the mixing of coolant is strengthened, and the convective heat transfer is enhanced. However, local hot spots also occur in the region near the wires. Both grid and helical wire spacers will lead to an increase in pressure loss, but the additional pressure drop induced by the helical wire is smaller, hence better comprehensive heat transfer performance is achieved for a wire-wrapped channel. Moreover, heat transfer performance can also be enhanced by reducing the pitch of the spacers. This suggests that applying spacers and optimizing their configurations and structures is helpful to achieving better cooling performance in rod bundle channels.

Effect of surfactants on droplet generation in a microfluidic T-junction: A lattice Boltzmann study

Droplet generation in a T-junction with surfactants is simulated using our recently developed lattice Boltzmann method. The method is first used to explore the effect of surfactant concentration ψb on droplet generation. As ψb increases, droplet generation tends to shift from squeezing to dripping regime and then to jetting regime. In the clean system, the upstream pressure varies almost periodically with time. However, in the surfactant-laden system, the upstream pressure no longer varies periodically but overall increases with time for droplet generation in squeezing and dripping regimes. This is because the addition of surfactants results in an additional pressure drop between the front and rear of the generated droplet. Then, droplet generation in both clean and surfactant-laden systems is compared to explore the surfactant role under different values of the capillary number Ca. In either clean or surfactant-laden system, the pressure upstream of the junction rapidly decreases as Ca increases. In the presence of surfactants, the upstream pressure overall increases with time for droplet generation in squeezing and dripping regimes, but the increased amplitude decreases with Ca. Finally, we establish the phase diagrams describing how the droplet generation regime varies with flow rate ratio and Ca in both clean and surfactant-laden systems. It is found that the addition of surfactants reduces the critical capillary number distinguishing squeezing from dripping and the critical capillary number distinguishing dripping from jetting.

MODEL FOR DETERMINING TOTAL SKIN IN HORIZONTAL WELLS COMPLETED WITH SLOTTED LINERS

The installation of slotted liners in horizontal wells controls formation sand production and prevents damage to installed downhole and surface facilities. Howbeit, while mitigating sand production, slotted liners also create skin problems when formation fines plug the slots, causing flow convergence and turbulence. These problems create additional pressure drop around the wellbore and, thus, reduction in production. A new analytical skin model is developed to account for the total skin slotted liners that incorporates distance between slots. Moreover, the effects of skin on flow rate, slot penetration ratio, slot width, distance between slots, wellbore radius, and slot length were also investigated. Results from this model show good agreement when validated with existing models. With an application illustrated in this paper, this model can be used in the optimization of slotted liner designs.

Proppant Packing Near the Fracture Tip during Tip Screenout: Asymptotic Models for Pressure Buildup Calibrated on Field Data and Verified with Two-Continua Simulations

Summary We analyze pressure slopes during buildup when proppant placement into a fracture results in tip screenout (TSO), as observed in real field data on pumping of fracturing jobs. The phenomenon is described by proppant packing and jamming near the fracture tip, leading to TSO. Transient evolution of the zone of packed proppant near the tip and associated additional pressure drop along the packed bank are evaluated. Under the assumption of constant fracture height, the additional pressure drop during TSO grows as t(1+α), where tα is the law of proppant concentration growth (pressure drop grows quadratically in time, if the proppant concentration on surface at the blender grows linearly in time). The model is calibrated on field data from fracturing jobs in Western Siberia, Russia. These approximate models are verified with the two-continua model of proppant transport used to describe the process of proppant packing and jamming near the fracture tip. We also show how predictions of bottomhole pressure (BHP) growth during TSO obtained using proppant transport models implemented into existing hydraulic fracturing simulators can be significantly improved by a reasonable (based on behavior of dense suspensions at the packing limit) modification to parameters, describing suspension shear viscosity.

Exploring the potential of electrostatic precipitation as an alternative particulate matter filtration system in aircraft cabins.

On most modern airliners, cabin air pressurization, heating, and renewal are mainly achieved using air supplied from the gas turbine engines during flight. This air intake impairs the motors yield and needs to be conditioned, leading to energy overconsumption. Recent advances in thermal management enable aircraft manufacturers to reduce further the intake airflow needed to maintain cabin temperature at high altitude. Nevertheless, for lower air renewal rates, an appropriate air filtration system will be needed to maintain acceptable air quality in the cabin. In this context, Clean Sky 2 Joint Undertaking (CS2JU) project EC2S (Environment Control Secondary System) aims at developing an integrated filtration system to be implemented in existing cabin air management systems (so-called environmental control system-ECS). The EC2S unit will include three filtration units addressing separately volatile organic compounds (VOCs), CO2 , and particulate matter (PM). Circulated air in the ECS is conventionally filtered on pleated HEPA filters that generate substantial pressure drop. Since the EC2S VOCs and CO2 filtration units would generate additional pressure drop in the ECS system, electrostatic precipitation is foreseen as a low flow resistance alternative for PM removal. This paper reports the development and performance assessment of a two-stage electrostatic precipitator (ESP) designed for aircraft recirculated air filtration. The ESP prototype presents high single-pass particle collection rates (i.e., over 90% for airborne particles with an aerodynamic diameter of 0.5μm or larger), low-pressure drop (i.e., 4Pa at nominal flowrate), and a limited ozone generation rate (i.e., below 8mgh-1 ).

Mixing Improvement in a T-Shaped Micro-Junction through Small Rectangular Cavities.

The T-shaped micro-junction is among the most used geometry in microfluidic applications, and many design modifications of the channel walls have been proposed to enhance mixing. In this work, we investigate through numerical simulations the introduction of one pair of small rectangular cavities in the lateral walls of the mixing channel just downstream of the confluence region. The aim is to preserve the simple geometry that has contributed to spread the practical use of the T-shaped micro-junction while suggesting a modification that should, in principle, work jointly with the vortical structures present in the mixing channel, further enhancing their efficiency in mixing without significant additional pressure drops. The performance is analyzed in the different flow regimes occurring by increasing the Reynolds number. The cavities are effective in the two highly-mixed flow regimes, viz., the steady engulfment and the periodic asymmetric regimes. This presence does not interfere with the formation of the vortical structures that promote mixing by convection in these two regimes, but it further enhances the mixing of the inlet streams in the near-wall region of the mixing channel without any additional cost, leading to better performance than the classical configuration.

Facile nanostructured zinc oxide coating technique for antibacterial and antifouling air filters with low pressure drop

Air filters effectively filtrate external contaminants including pathogenic bioaerosols; however, they also act as culture sites for the pathogenic bacteria captured in nutrient organic pollutants. Although many researchers have applied various antibacterial coatings to filters, the coating application inevitably increased the pressure drop, leading to the low efficiency and high energy consumption of the purification system. Herein, we report a simple nanostructured zinc oxide (ZnO) coating technique to confer a polypropylene nonwoven filter with superior antibacterial, antifouling and anti-biofilm properties without an additional pressure drop. For aerodynamic coating designs, filters were directly immersed into low concentration precursor solutions to enable the sedimentation of the ZnO sol–gel particles on the filter fibers according to fluid dynamic. The precursor concentration affected the surface topology and so properties of the as-fabricated coating. 0.07 M precursor solution produced a rose-like nanostructured coating exhibiting no pressure-drop increase. The large specific surface area and hydrophobic surface killed and then repelled the attached bacteria effectively. As a result, the bare filter promoted the growth and consequent biofilm formation of the surface bacteria in a favorable environment for the growth of microorganisms, while the coated filter successfully suppressed biofilm development.

An Extensive Study on Desorption Models Generated Based on Langmuir and Knudsen Diffusion

Although gas desorption is a known phenomenon, modeling fluid flow in tight gas reservoirs often ignores the governing desorption effect, assuming that viscous transport is the predominant controller, resulting in an erroneous prediction of mass transport and fluid flow calculations. Thus, developing a new model accommodating all the major contributing forces in such a medium is essential. This work introduces a new comprehensive flow model suitable for tight unconventional reservoirs, including viscous, inertia, diffusion, and sorption forces, to account for fluid transport. Based on Langmuir law and Knudsen diffusion effect, three models were generated and compared with different known models using synthetic data. The model was solved and analyzed for different scenario cases, and parametric studies were conducted to evaluate the desorption effect on different reservoir types using MATLAB. Results show that the contribution of the sorption mechanism to the flow increases with the reducing permeability of the medium and lower viscosity of the flowing fluid and an additional pressure drop up to 10 psi was quantified.

A wavy flow channel system for membrane fouling control in oil/water emulsion filtration

The membrane-based process is attractive for the treatment of oil/water emulsion because of its effectiveness in handling micron size oil droplets. However, membrane fouling due to the strong oil droplets/membrane surface interplay remains its major challenge that limits its widespread application. This study reports a new approach for membrane fouling control via a wavy flow channel to enhance the effective area and improve the local mixing. The hydraulic performance of a membrane was used to assess the effectiveness of the system against the traditional straight flow for oil/water emulsion treatment. Results show that the wavy flow channel offers two main advantages: increasing the membrane effective surface area and facilitate swirling flows that effectively promote fouling control. The wavy flow channel showed up to ~58% higher permeability (of 219.1 ± 5.8 L.m−2.hr−1.bar−1) than the reference, in which 18% was due to the enhanced flow property. The energy loss due to additional shear stress and longer flow path only contributed to a 7% additional pressure drop. The energy to overcome the pressure drop was insignificant to the specific energy consumption, which showed that the wavy membrane offered 21% energy saving (0.015 vs 0.019 kWh/m3). This study opens an option in improving membrane filtration performances via a simple module-scale modification suitable for fouling prone pressure-driven membrane systems.

Flow of hydrophobically associating polymers through unconsolidated sand pack: Role of extensional rheology and degree of association

Theoretically, both the polymer’s resistance to flow and retention are the reasons for the additional pressure drop and resistance factor (RF) generated during polymer flow in porous media. In the case of hydrolyzed polyacrylamide (HPAM), the increase in RF at high flux rates, a phenomenon called shear thickening were successfully correlated in our previous works using the combination of shear and extensional rheology alone. Associative polymers that have gained increased attention for enhanced oil recovery (EOR) applications have relatively a higher retention value in porous media than HPAM. No attempts were made in the literature to investigate whether the associative polymer’s flow behavior at various hydrophobicity in porous media could be correlated using the bulk rheology alone. Further, the role of hydrophobicity and concentration on the associative polymer’s shear thickening and extensional behavior were not studied.In this paper, high flux single phase porous media experiments were performed using three different associative polymers of varying hydrophobicity at 1000 ppm and 2000 ppm concentration in the unconsolidated sand pack. Extensional rheology was performed on these polymers using capillary break-up extensional rheometer. Extensional rheological parameters become lower with increasing hydrophobicity at both 1000 and 2000 ppm. Porous media result indicates that extensional rheology is directly correlated with the RF in associative polymer at 2000 ppm but not at 1000 ppm. At 1000 ppm, the highest RF is exhibited by higher hydrophobic polymer that possess least extensional resistance. Unusually higher retention value observed at 1000 ppm explain the increased RF associated higher hydrophobic polymer or else it could be due to the clustered hydrophobic species formation that appears to be active only if the concentration is not high enough to breakage. It is also our observation that higher retention cannot be predicted through bulk rheological measurements and therefore, this work signifies that a combination of retention and extensional rheological parameters are needed to model the flow behavior of associative polymers in porous media at higher fluxes. Moreover, the relative influence of retention and extensional rheology on the flow behavior of associative polymer is strictly a concentration and hydrophobicity dependent.

Effect of oscillation flow induced by lattices on a horizontal gas–solid two-phase flow

This study is focused on reducing the pressure drop, conveying velocity, and power consumption in a horizontal gas–solid flow. Four types of lattice models, which are fixed in the particle inlet, are proposed to easily generate the oscillation of the wake flow to easily convey the gas–solid two-phase flow. A horizontal pipeline with an inner diameter of 80 mm and length of approximately 5 m was used. Polyethylene particles with an average diameter of 2.3 mm and density of 978 kg/m3 were employed as conveying solid materials. The experimental ranges of the average gas velocity and solid mass flow rate were 10–16 m/s and 0.10–0.47 kg/s, respectively. Compared to the nonlattice gas–solid flow, reductions in the total pressure drop, conveying gas velocity, power consumption, and additional pressure loss were achieved in the range of lower gas velocity when using the lattice model. The highest reduction rates of the minimum conveying velocity and additional pressure drop were approximately 5.12% and 15.2%, respectively. In the acceleration region, the particle concentration in the flows with the lattice model was larger than that in the nonlattice flow near the upper part of the pipe and lower than those in the nonlattice flows in the lower part of the pipe. The time-mean axial particle velocity and particle fluctuating velocity in all lattice model flows were higher than those in the nonlattice flow, according to particle image velocimetry measurements, particularly in the upper part of the pipe.

Computational study of rib shape and configuration for heat transfer and fluid flow characteristics of microchannel heat sinks with fan-shaped cavities

Cavities and ribs are usually utilized in the design of microchannel heat sink systems, and their combination may lead to the optimum overall performance. However, it remains unclear how different combination methods contribute to the performance and efficiency of the systems. Computational fluid dynamics simulations were conducted to identify the optimum rib shape and configuration for the systems with fan-shaped cavities. The ribs are rectangular, diamond, hexagonal, or elliptic in cross-section. The effects of rib shape, dimensions, and configuration are investigated, and the optimum comprehensive performance was determined. The results indicated that the shape, dimensions, and configuration of ribs are important factors that affect performance and heat transfer efficiency. The shape and position of ribs must be optimized to minimize pressure drop while maximizing heat removal efficiency. The shape of ribs can be an important factor in obtaining high efficiency of heat removal while limiting the pressure drop across the channels. When the ribs are rectangular in shape, the maximum pressure drop occurs but the maximum relative Nusselt number is achieved. The maximum comprehensive performance factor is achieved when the ribs are elliptic in shape and the Reynolds number is highest. Further improvement in performance can be achieved by choosing particular rib dimensions and configuration. In order to provide appropriate benefit to such a microchannel heat sink system without inducing additional pressure drop that reduces the performance of the system, it is desirable to properly shape and position the ribs relative to the cooling flow and the cavities in a way that takes best advantage of the benefits provided by the combination of cavities and ribs. The effect of trailing edge vortexes on heat transfer performance is significant. A maximum comprehensive performance factor of 1.96 is achieved when the Reynolds number of the laminar flow is 460.