Multiple Inlets Research Articles

The water based Al2O3 nanofluid flow and heat transfer in tangential microtube heat sink with multiple inlets

Micro thermal systems are convenient cooling devices for high heat flux applications. Besides, the nanofluids are used to improve the cooling capabilities. The suspended nanoparticles in the base fluid increase the thermal conductivity, fluid viscosity and fluid density but decrease the effective heat capacity. To analyze the suitability of using the nanofluids for cooling applications, the numerical simulations are made for nanofluid heat transfer and fluid flow in micro-heat sink with straight microtubes and multiple tangential inlet jets. The configurations with five inlet jets is considered and numerical simulations are based on a finite volume method. The Al2O3 water based nanofluid was used in simulations. The heat flux spread through the bottom surface of the heat sink was q=50W/cm2. Re from 15 to 100 was considered to simulate the laminar fluid flow. The analysis is based on thermal and hydrodynamic results obtained for nanofluid and compared with results obtained for water. The results are analyzed on a fixed pumping power, Re or mass flow rate basis. It is observed that the conclusions are strongly dependent on the analysis constraint. Moreover the surface temperature difference is not very much improved by using the nanofluid.

Carbon dioxide capture using solid sorbents in a fluidized bed with reduced pressure regeneration in a downer

The most common technology for postcombustion CO2 capture for existing power plants is the amine solvent scrubber. The energy consumption for capturing CO2 from flue gases using amine solvent technology is 15 to 30% of the power plant electricity production. Hence, there is a need to develop more efficient methods of removing CO2. Here, we show a novel design, obtained using multiphase CFD, and of a fluidized‐bed reduced pressure regenerator, coupled with a fluidized‐bed sorber, which has the potential to reduce the energy consumption. The undesirable core‐annular flow regime in the riser‐sorber is eliminated using multiple jet inlets and large particles leading to a shorter height. Up to 88% of the heat liberated in the riser‐sorber is recovered in the downer‐regenerator. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4519–4537, 2013

Slow invasion of a fluid from multiple inlet sources in a thin porous layer: Influence of trapping and wettability

We study numerically the process of quasistatic invasion of a fluid in thin porous layers from multiple inlet injection sources focusing on the effect of trapping or mixed wettability, that is, when hydrophobic and hydrophilic pores coexist in the system. Two flow scenarios are considered. In the first one, referred to as the sequential scenario, the injection bonds at the inlet are activated one after the other. In the second one, referred to as the kinetic scenario, the injection bonds at the inlet are activated simultaneously. In contrast with the case of purely hydrophobic systems with no trapping, studied in a previous work, it is shown that the invasion pattern and the breakthrough point statistics at the end of the displacement depend on the flow scenario when trapping or mixed wettability effects are taken into account. The transport properties of the defending phase are also studied and it is shown that a one-to-one relationship between the overall diffusive conductance and the mean saturation cannot be expected in a thin system. In contrast with thick systems, the diffusive conductance also depends on the thickness when the system is thin. After consideration of various generic aspects characterizing thin porous systems, the main results are briefly discussed in relation with the water management problem in proton exchange membrane fuel cells.

Advanced Capillary Soft Valves for Flow Control in Self-Driven Microfluidics

Self-driven microfluidic devices enable fully autonomous handling of very small volumes of liquid samples and reagents. However, many applications require an active control mechanism to trigger self-driven flow in microchannels. Here, we report on capillary soft valves (CSVs), which enable stopping a liquid filling front at a precise location inside a microchannel and can resume flow of liquid upon simple actuation. The working mechanism of a CSV is based on a barrier of capillary pressure induced by an abruptly expanding microchannel. We discuss the influence of wetting conditions on the performance of a CSV and the effect of elevated temperatures on a CSV in its closed state. We introduce design features such as pillars and cavities, as well as fabrication techniques for rounded microchannels, which all may broaden the applicability and robustness of CSVs in microfluidic devices. Finally, we present CSV having multiple inlet channels. CSVs further diversify the toolbox of microfluidic functionalities and yet are simple to implement, fabricate and actuate.

A Microfluidic Platform for Controlled Ligand Exposure and Visualization of Cellular Response

We report here a microfluidic device with a unique architecture for capturing and isolating single cells, as well as providing strict control of reagent delivery to the cells. The device contains individualized cell traps with multiple inlet channels to allow flow-focusing of reagents for controlled ligand-receptor interaction studies. In this configuration, a change in relative inlet pressures causes immediate change in the relative widths of the reagent streams which allows timed exposure of cells to ligands of interest. We demonstrate the capabilities of this device by imaging cellular calcium response as a function of ligand pulse width, inter-pulse interval, and frequency. Rat basophilic leukemia (RBL) cells that endogenously express the IgE receptor are loaded with Fluo-4, a calcium indicator dye, and then captured in the device traps. Cells were systematically exposed to various ligand (multivalent crosslinker DNP-BSA) pulse widths (5 seconds to 2 minutes) and calcium response monitored with high-resolution fluorescence imaging. A significant delay between initial ligand exposure and calcium mobilization was observed. The relationship between pulse width, inter-pulse interval, and frequency and the temporal profile of the calcium response is currently under investigation.

Site-specific and regional on-farm rice water conservation analyzer (RiceWCA): Development and evaluation of the water balance model

Rice farming in the Lower Colorado River basin of Texas, US, is a major economic engine and a major water consumer. The Lower Colorado River Authority (LCRA) and the San Antonio Water System (SAWS) sponsored a joint project from 2004 through 2009 to study the feasibility of developing and conserving water to provide sufficient water to farmers in the Lower Colorado River basin, while allowing transfer of water to the city of San Antonio. A major focus of the project was the development of a web-based rice water conservation analyzer (RiceWCA) to evaluate field- and regional-level costs, water savings, and yield benefit associated with implementing on-farm conservation measures, including precision leveling, multiple inlets, conservation tillage, lateral improvement, tailwater recovery, and a production system based on growing high-yielding water efficient cultivars. This paper describes the development and evaluation of the crop development and water balance components of RiceWCA. RiceWCA uses a phenology model to time water management events, including flushing and flush drainage for the main crop, and permanent flood, flood maintenance, and drainage before harvest for the main and ratoon crops. RiceWCA simulates daily water balance for each rice field within the Lower Colorado River basin, as affected by the degree of implementing different conservation measures. The water balance model includes site-specific estimation of soil saturation deficit, evapotranspiration, percolation, seepage, rainfall, irrigation, and tailwater. The water balance model was calibrated and verified using 2000 and 2002 weekly irrigation records for the Lakeside and Gulf Coast irrigation districts, and validated using 2001, 2003, and 2004 weekly irrigation records. Tailwater recovery offers the largest water saving, followed by adoption of high-yielding cultivars, multiple inlet systems, precision leveling, and conservation tillage. Water saving from lateral improvement varies depending on the extent of existing laterals.

Modelling and optimization of IR cell devoted to in situ and operando characterization of catalysts

CFD modelling and tracer experiments were performed in order to improve the design of sample holder used for transmission IR experiments in flow conditions.The complexity of gas velocity field evidenced for the usual circular geometry is avoided with an alternative geometry. A new geometry involving a square pellet, multiple inlets and outlets and specific sample holder proposed in the present study leads to a more homogeneous gas velocity in the vicinity of the catalyst surface as shown by modelling with COMSOL. Experimental measurements of local tracer concentrations in different places of the reactor during transient experiments confirmed more homogeneous tracer distribution in the reactor mainly due to multiple inlets and outlets. Consequences of the presence of dead volumes identified by modelling were also examined and discussed.

Impact of tidal inlet and its geomorphological changes on lagoon environment: A numerical model study

Geomorphological changes of a tidal inlet are governed by complex interactions of tidal currents, waves and sediments. Tidal inlet(s) of the Chilika lagoon (19° 28′–19° 54′ N; 85° 06′–85° 35′ E) on the east coast of India and its geomorphological changes is linked to the contemporary phase of lagoon transformation such as sedimentation (from riverine discharge, land drainage and decay of macrophytes), choking of the outer channel, northward shifting, closing and opening of inlet(s). These transformations are responsible for decrease in salinity, depth and weak lagoon–sea interaction, which in turn are responsible for decline in water area, increase in vegetated area (macrophyte growth) and decrease in fish productivity. The present study investigates the past and present geomorphological changes of Chilika inlet(s) using historical data, satellite data, field observations and numerical modelling techniques. A numerical model was used to simulate the hydrodynamic conditions and salinity distribution in the lagoon for one inlet and multiple inlets and the results are calibrated with observations. The study suggests that tidal inlet(s) and its geomorphological changes have significant impacts on ebb and flood currents at the inlet(s), salinity distribution in the lagoon, sediment and water exchange between the lagoon and sea. Possible impacts of inlet(s) on ecological conditions of the lagoon environment are discussed.

Effects of flow field design on the performance of a PEM fuel cell with metal foam as the flow distributor

In this work, we report the improvements made on the PEM fuel cell with metal foam as the flow distributor. The comparison in polarization curve is made between the PEM unit cell with different metal foam flow field designs and the PEM unit cell with graphite bipolar plate as flow distributor. The experimental results show that after using improved metal foam flow field designs, the fuel cell's performance increases. Our results show that, in the PEM unit cell with single zone metal foam, the convection is weak at side corners. Dividing the metal foam into multiple regions and using multiple inlets effectively improves gas distribution. AC impedance measurement was also performed to study impedance characteristics. The Nyquist and Bode plots confirmed that Ohmic resistance, activation resistance, and mass transfer resistance of metal foam fuel cell are all smaller than that of conventional PEM unit cell.

Effects of hypsometry on the morphodynamic stability of single and multiple tidal inlet systems

The evolution of the cross-sectional areas of tidal inlets draining the same back barrier lagoon is investigated with a simple model. The main new aspect is that hypsometry (cross-sectional area of the inlet and the wetted surface of the lagoon vary during the tidal cycle) is taken into account to determine the morphodynamic stability of the inlets. Results are presented for both a single and a double inlet system. In the double inlet system two inlets drain the same back barrier basin, which is divided into two sub-basins by a topographic high.The advection of the depth-averaged along-channel momentum results in an extra term in the momentum equation. The joint presence of hypsometric terms and this new term instigates a shift of the stable equilibrium cross-section to smaller values. The sole effect of the hypsometry of the inlet cross-section is a larger amplitude of the tidal current, causing a shift of the stable equilibrium cross-section to higher values. Similar conclusions are found in the case of a double inlet system. For this configuration also multiple stable morphodynamic equilibria are found, which strongly depend on the cross-sectional area above the topographic high. It further turns out that the morphodynamic equilibria are sensitive to changes in parameters that break the symmetry of the system, viz. the ratio of the surface areas of the back barrier basins, the ratio of the inlet lengths, the phase difference of the tidal wave and the cross-channel bottom slope of one of the inlets.

A Study of Design Options for a Building Integrated Photovoltaic/thermal (BIPV/T) System with Glazed Air Collector and Multiple Inlets

In this paper, a prototype open loop air-based building integrated photovoltaic thermal BIPV/T system with a single inlet is studied through a comprehensive series of experiments in a full scale solar simulator recently built at Concordia University. A numerical control volume model is developed and validated based on the results from the experiments. Improved designs of the BIPV/T system with multiple inlets and other means of heat transfer enhancement are studied through simulations. Simulation results indicate that the application of two inlets on a BIPV/T collector increase thermal efficiency by around 5% and increase electrical efficiency marginally. An added vertical glazed solar air collector improves the thermal efficiency significantly, and the improvement is more significant with wire mesh packing in the collector.

The tangential micro-heat sink with multiple fluid inlets

The paper presents the thermal and hydrodynamic analysis of the micro-heat sink with straight microtubes and multiple inlet jets. The inlet cross-sections have the rectangular shape and positioned tangentially to the tube axis. Four different configurations are considered: three of them with three inlet jets and one with five inlet jets. The fluid flow regime is laminar and water with variable fluid properties is used as a working fluid. The heat flux spread through the bottom surface of the heat sink is q=100W/cm2. Thermal and hydrodynamic results of the micro-heat sink with multiple inlets are compared with results obtained for single tangential inlet configuration. For all cases, the analysis is made on a fixed pumping power basis. The strong dependence of the position and number of the inlet jets on thermal and hydrodynamic characteristics of the micro-heat sink is observed.

Experimental study on solid circulation in a multiple jet fluidized bed

AbstractParticle image velocimetry was used to investigate the evolution of multiple inlet gas jets located at the distributor base of a two‐dimensional fluidized bed setup. Results were used to estimate the solid circulation rate of the fluidized bed as well as particle‐entrainment into the individual jets. The effects of fluidization velocity, orifice diameter, orifice pitch, particle diameter, and particle density were studied. It was determined from this study that the solid circulation rate linearly increased with an increase in the fluidization velocity until the multiple jet system transitioned from isolated to an interacting system. In the interacting system of jets, the solid circulation increased with fluidization velocity but at a much lower rate. For multiple jet systems, this phenomenon may indicate the presence of an optimum operating condition with high circulation rate and low air input in the bed. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3003–3015, 2012

Slow invasion of a nonwetting fluid from multiple inlet sources in a thin porous layer

We numerically study the process of quasistatic invasion of a nonwetting fluid in 2D and 3D porous layers from multiple inlet injection sources and show that a porous layer acts as a two-phase filter as a result of the repeated convergence of flow paths: The probability for a pore at the outlet to be a breakthrough point is significantly lower than the fraction of active injection points at the inlet owing to the merging within the porous layer of liquid paths originating from different inlet injection points. The study of the breakthrough point statistics indicates that the number of breakthrough points diminishes with the system thickness and that the behavior of thin layers, defined here as systems of typical thicknesses of less than 15 lattice spacing units (≈15 pore or grain mean sizes), is distinct from thicker layers. For thicker systems, it is found that the probability of an outlet pore to be a breakthrough pore scales as l(1-d) where l is the system thickness and d is the space dimensionality, whereas, a power law behavior is not obtained with a thin system. Other properties, such as the invading phase occupancy profiles are studied. We also described a kinetic algorithm that allowed us to compute the occurrence times of breakthrough points. The distribution of these times is markedly different in 2D and in 3D.

Multistability and Complex Routes of Supersonic Inlet Start/Unstart

analyzed. The loops-coupled hysteresis, associated with the interaction among the multiple inlet flow patterns, indicates strong route dependence of multiple flow pattern transitions. The complexity of dynamics behaviors involving loops-coupled hysteresis and complex routes originates from the memory effect of initial states and the existence of multisolution domain. The control of bifurcation system thus depends not only on the instantaneous valueoftheinputbutalsoonthehistoryofitsoperation.Abetterunderstandingofmultistabilityandcomplexroutes of inlet start/unstart may be useful as a guide in thinking about the bifurcation mechanism, designing the control routes, and actively controlling the bifurcation behaviors of inlet start/unstart.

Evaluation of sewage source and fate on southeast Florida coastal reefs

Water, sponge and coral samples were collected from stations impacted by a variety of pollution sources and screened for human enteric viruses as conservative markers for human sewage. While human enteroviruses and adenoviruses were not detected, noroviruses (NoV; human genogroups I and II) were detected in 31% of samples (especially in sponge tissue). Stations near inlets were the only ones to show multiple sample types positive for NoV. Fecal indicator bacteria and enteric viruses were further evaluated at multiple inlet stations on an outgoing tide. Greatest indicator concentrations and highest prevalence of viruses were found at the mouth of the inlet and offshore in the inlet plume. Results suggest that inlets moving large volumes of water into the coastal zone with tides may be an important source of fecal contaminants. Efforts to reduce run-off or unintended release of water into the Intracoastal Waterway may lower contaminants entering sensitive coastal areas.

Negative enrichment of target cells by microfluidic affinity chromatography.

A three-dimensional microfluidic channel was developed for high-purity cell separations. This system featured high capture affinity using multiple vertical inlets to an affinity surface. In cell separations, positive selection (capture of the target cell) is usually employed. Negative enrichment, the capture of nontarget cells and elution of target cells, has distinct advantages over positive selection. In negative enrichment, target cells are not labeled and are not subjected to strenuous elution conditions or dilution. As a result, negative enrichment systems are amenable to multistep processes in microfluidic systems. In previous work (Li, P.; Tian, Y.; Pappas, D. Anal. Chem.2011, 83, 774-781), we reported cell capture enhancement effects at vertical inlets to the affinity surface. In this study, we designed a chip that has multiple vertical and horizontal channels, forming a three-dimensional separation system. Enrichment of target cells showed separation purities of 92-96%, compared with straight-channel systems (77% purity). A parallelized chip was also developed for increased sample throughput. A two-channel system showed similar separation purity with twice the sample flow rate. This microfluidic system, featuring high separation purity and ease of fabrication and use is suitable for cell separations when subsequent analysis of target cells is required.

Applicability of sediment transport models to evaluate medium term evolution of tidal inlet systems

This paper derives local formulae to estimate bed roughness and suspended transport and present a method to calculate net sediment transport at tidal inlet systems, combining field data and a range of well established empirical formulations. To accomplish this, measurements spanning a spring-tidal cycle of mean water levels, waves, near-bed flow turbulence and bed forms were obtained from the Ancão Inlet, Ria Formosa lagoon system, Portugal. High-resolution hydrodynamic data were gathered using acoustic equipments and by measuring sediment properties (grain-size diameter and bed form dimensions) under fair-weather conditions. The results compared favourably with available direct and indirect field observations of sediment transport rates. The approach appears to be robust and widely applicable and so can be applied to the same conditions in any tidal inlet system. This is of particular importance when attempting to understand sediment transport at inlet mouths, and has practical applications in a range of coastal engineering and coastal management areas concerned with navigation safety, coastal erosion, ecosystem health and water quality. The study discusses the applicability of the method on evaluating system flushing capacity, giving important insights on multiple inlet evolution, particularly with regard to their persistence through time. The methodological framework can be applied to assess the long-term stability of single- and multiple-inlet systems, provided that estimates of sediment storage at ebb-tidal deltas are available and sediment transport estimates during storm events are statistically considered.

Long‐term morphological impacts of the opening of a new inlet on a multiple inlet system

ABSTRACTIn this study, the artificial opening of a new tidal inlet in an existing multiple inlet system is shown to significantly modify the adjacent nearshore and backbarrier morphology, as well as both updrift and downdrift shorelines. The study focuses on the dominant Faro‐Olhão and Armona inlets in the Ria Formosa barrier island system of southern Portugal. The equilibrium state and future evolution of the system are inferred using a range of morphological and hydrodynamic indicators, including the evolution of the inlet cross‐section, changes in tidal prism, and changes in the dimensions (length and area) of barrier islands. The results reveal how the morphology of an interconnected two‐inlet bay system and the adjacent coastlines has evolved following the artificial opening and stabilization of Faro‐Olhão inlet since 1929. A clear relationship between barrier island size, inlet cross‐section/width, and tidal prism is demonstrated. Decadal time‐scale changes in the tidal prism of the two interconnected inlets are shown to be the main mechanism responsible for morphological change, and have resulted in the remobilization of ebb‐tidal delta sediments deposited during previous hydraulic configurations. These changes, in turn, have contributed to a narrowing of Armona inlet and an increase in the size of Culatra Island. The work highlights the importance of ebb‐tidal deltas both as sand reservoirs and as conduits through which sand exchange between estuaries or lagoons and the open coast is regulated. It also shows the pivotal role of ebb‐tidal deltas in trapping longshore‐transported sediment and releasing it again during periods of increased wave activity. The findings have implications regarding the accurate assessment of the stability of multiple inlet systems. Copyright © 2011 John Wiley & Sons, Ltd.

Tracer gas experiment for local mean ages of air from individual supply inlets in a space with multiple inlets

We investigate the supply characteristics of incoming air via individual inlets in a ventilated space with multiple inlets. Theoretical considerations are given to determine the relations between the local mean age (LMA) of the total supply air and the individual LMA of each supply air inlet. Tracer gas experiments are conducted in a simplified livestock model with two supply inlets and one exhaust outlet. Transient concentration responses at internal points are measured after tracer gas injection one inlet at a time, and for simultaneous tracer injection at both inlets. The spatial distributions of LMAs and steady concentrations are obtained by tracer injections from each supply inlet, which demonstrate the supply characteristics of the individual inlets in the space. We have found that the overall LMA is the weighted average of the LMA by each inlet, and the weighting factor for the average is the corresponding steady state concentration at a given point. Experiments repeated for various airflow rates show that the nondimensional steady concentrations remain nearly constant regardless of the total airflow rate, but are greatly influenced by the airflow ratio between inlets. The local mean ages are found to increase proportionally with respect to the nominal time constant. Experimental procedures and results are verified by the fact that the total LMA measured at the exhaust is in good agreement with the theoretical nominal time constant of the space.