Inlet Device Research Articles

Adiabatic vertical downward air–water flow pattern map: Influence of inlet device, flow development length and hysteresis effects

Flow patterns for adiabatic vertical downward air–water flow in an 8.8mm diameter channel have been studied. In particular, the influence of the inlet device, the flow history and the development length on the flow pattern have been investigated and assessed. Test results with two inlet devices (highly mixed and unmixed) indicate that the inlet device has a major influence on the flow pattern transitions. Furthermore, the transition boundaries between different flow regimes have been found to depend strongly on the flow’s development length, and display hysteresis effects. Not surprisingly, no existing flow pattern map worked well versus the current observations, nor did they agree with one another, thus pointing the need to better characterize the test section inlet geometry, the influence of the test length and the test procedure to obtain genuine flow pattern observations. Presently, it can be concluded that in each flow pattern region there are important differences in the actual flow structures. A future mechanistic flow pattern map should then not only contain flow pattern transition lines but also physical characteristics which describe the flow regime and inlet device effects. This was qualitatively done in this study by superimposing on the flow pattern maps frames which illustrate the characteristics of the flow for two different inlet devices.

Experimental evaluation and theoretical modeling of oxygen transfer rate for the newly developed hollow fiber bioreactor with three compartments

Bioartificial liver support provides a bridge to transplantation which is at present the only proven specific treatment for acute liver failure. In this paper, a novel multi-coaxial hollow fiber bioreactor so-called "Fibre-in-Fibre FIF Bioartificial liver device" with three compartments is experimentally and mathematically studied. The mathematical model in this paper is an extension of Krogh cylinder model for hollow fibre devices by including one more zone for oxygen transfer, i.e. oxygenation compartment. Three simultaneous linear differential equations were derived for pressure in plasma and cell compartments and flow rate in cell compartment. To validate the model, Oxygen Transfer Rate and hydrostatic pressure experimental measurements for different flow rates, 17-400 ml/min, and different number of hollow fibres pairs are used. Several important parameters of the Michaelis-Menten was investigated, namely, constant Vmax (the maximum oxygen consumption per unit volume of the cell mass), the oxygen partial pressure, the flow rate of the perfusate at device inlet. The results showed that the oxygenation compartment should easily secure Oxygen to the cells in compartment B.

Flow pattern in aquaculture circular tanks: Influence of flow rate, water depth, and water inlet & outlet features

Circular tank geometry is very common in aquaculture because it provides more stable flow patterns, a more homogeneous distribution of dissolved oxygen and metabolites and better self cleaning features. Many works were performed in the last years to determine optimal velocities for maintaining general fish health, but the distribution of velocities inside circular tanks is frequently very heterogeneous. This work is focused on the analysis of the influence of design parameters in the distribution of water velocities inside aquaculture circular tanks. A model is proposed to estimate the distribution of velocities by determining the angular momentum per unit mass next to the tank wall and around the central axis. The model depends on the water inflow and outflow rates, the water inlet velocity, the tank radius, the water depth, and three tank-specific parameters which must be determined experimentally to include the effect of the wall roughness, the characteristics of water inlet devices and the presence of singular elements in the tank bottom producing friction loses.

Non-exhaust PM emission measurements of a light duty vehicle with a mobile trailer

A trailer-based mobile measurement approach for analyzing non-exhaust emissions of a light duty vehicle is presented. Based on a tracer gas experiment which allowed a mapping of the particle dispersion within the wake of the vehicle, emission factors were estimated. A combination of the results from tracer gas experiment, wind tunnel tests and local airflow measurements was taken into account to characterize the vehicle wake and optimize the position of the measurement devices in the wake of the vehicle. Diffuser type inlet devices were employed to correct for anisokinetic sampling. Measurements on unpaved and dust loaded agricultural paved roads as well as more than 800 km of real world driving were conducted with estimated PM10 emission factors varying over several orders of magnitude (10–42,000 mg vehicle−1 km−1 (mg vkm−1)). Emission factors were found to increase with increasing vehicle velocity. The lowest emission factors were measured on motorways. The coefficient of variation for the measurements varied from 10% to 30%.

Influence of the Entrance Configuration on the Performance of a Non-Mechanical Solid Feeding Device for a Pneumatic Dryer

The solids feeder is an important component of a dryer, since it is responsible for introducing the moist material at controlled, specified rates. The purpose of this paper is to investigate the effects of solids feeding configuration on the fluid dynamic behavior of a 53-mm-diameter vertical pneumatic conveyor with a loop of 180°, aiming at further applications in drying granular materials. A non-mechanical solid feeding system constituted by a hopper connected to an inclined pipe was applied to feed type D particles in the conveying line. This simple feeding apparatus was modified through the insertion of different flow restriction devices at the air inlet, namely a reduction nozzle and a Venturi device. This was aimed at studying how the solids flow rates and the fluid dynamics of the whole conveying line are affected by the entrance configuration and inlet devices. The use of inlet devices combined with the non-mechanical inclined valve affected significantly the performance of the valve when operating with type D particles in a pneumatic conveying line. When using inlet devices, an increase in the conveyed solid flow rates at a given air velocity was observed. The reduction nozzle yielded a range of solids loading ratios similar to that of the inclined valve with no inlet device, and introduced some pressure instabilities at the entrance region. The Venturi device allowed operation at a wider range of solids loading ratios and no pressure instability was detected in the conveying line. For the conditions investigated, neither the gas velocity nor the loading ratio affected the extent of entrance length. The inlet devices may be successfully applied to modify and improve the performance of the inclined valve as a solids feeder in pneumatic dryers.

Syringe-vacuum microfluidics: A portable technique to create monodisperse emulsions.

We present a simple method for creating monodisperse emulsions with microfluidic devices. Unlike conventional approaches that require bulky pumps, control computers, and expertise with device physics to operate devices, our method requires only the microfluidic device and a hand-operated syringe. The fluids needed for the emulsion are loaded into the device inlets, while the syringe is used to create a vacuum at the device outlet; this sucks the fluids through the channels, generating the drops. By controlling the hydrodynamic resistances of the channels using hydrodynamic resistors and valves, we are able to control the properties of the drops. This provides a simple and highly portable method for creating monodisperse emulsions.

Spatio-Temporal Structure of Gas-Liquid Interface at Flooding for Two Inlet Devices of Gas Flow

Spatio-Temporal Structure of Gas-Liquid Interface at Flooding for Two Inlet Devices of Gas Flow

Effects of Compact Radial-Vaned Air Separators on Stalling Characteristics of an Axial-Flow Fan

The stall-prevention effect of air separators incorporating radial vanes in place of the existing axial vanes was investigated on a low-speed, single-stage, lightly loaded axial-flow fan for effective and compact air separators of a simplified structure. From the survey, paying attention to several geometrical dimensions of the device, the following conclusions are obtained: (1) Simplified radial vanes made of flat plates could show strong stall-prevention effect comparable to those of the curved-vane type one. The most favorable ones showed no stall up to the fan shut-off conditions. (2) Radial heights of the recirculation passage within the air separator showed significant influences on the stall improvement. It should be larger than some critical size experimentally given in the study. (3) The axial length of the device should be larger than some critical size given experimentally in the study. Too much reduced axial length could give rise to an abrupt loss in the effect. (4) The optimum axial locations of the rotor-tip blade leading edge within the device inlet opening were found to lie near the center of the width of the inlet opening from both aspects of stall improvement and fan efficiency.

Debottlenecking and Computational-Fluid-Dynamics Studies of High-and Low-Pressure Production Separators

Summary Efficient and effective oil/water/gas separation is required for success of many production operations. A major oil producer was experiencing difficulties with the oil/water/gas separation equipment on an offshore platform and improvements were required to meet both present and future production rates. Both high-pressure (HP) and low-pressure (LP) separators on a major oil production platform were studied to determine the design limitations for foamy service and basic sediment and water (BS&W) levels. Computational-fluid-dynamics (CFD) studies were completed to show the volumetric utilization and flow-pattern improvements made with the design changes. Both HP and LP separators showed substantial foam and poor efficiency because of poor inlet-device design, plugging, and other general vessel-design limitations. Debottlenecking efforts determined that, while the inlet device was somewhat ineffective, major improvements could be made from changes to perforated plate baffles, fluid-level adjustments, and weir placement and operations. CFD calculations performed on both vessels indicated similar problems. The perforated plate baffles with improper design lead to countercurrent flow through the baffles, making them less effective in flow control and distribution. Fluid-level settings for the weir height affected the velocity differences between fluid layers and contributed to promotion of recirculation within the vessel, which lead to low volumetric utilization. With adjustments to vessel internal equipment and changes to fluid-phase levels, CFD calculations showed that overall vessel volumetric utilization was improved by 22% for the HP vessel and by 38% for the LP vessel. CFD results also showed the changes to the flow patterns accompanying these improvements. Vessels with the proposed changes were operating effectively with substantially higher throughputs and meeting the expected BS&W levels for operations of the downstream oil-processing equipment. Details about the vessel internals, flow properties, and other changes required to accomplish these improvements will be discussed.

Pierced cylindrical gas inlet device for sulfur dioxide removal from waste gas streams

Configuration of a gas inlet device can significantly affect the performance of a tower for gas purification or separation. In this paper, a pierced cylindrical inlet device is investigated which consists of an evenly perforated wall and is tangentially located at the lower portion of a jet bubble reactor where an absorbent slurry exists. Incoming gas streams are evenly distributed into and flow through the absorbent slurry after leaving the inlet device, therefore, intensive agitation is resulted. Consequently, the gas, liquid, and solid phases mix completely, and the interfacial area for mass transfer within the tower increases dramatically. Results show that the tower achieved 95% SO 2 removal and over 90% dust removal at a pressure drop of about 3 kPa for the entire tower, an incoming SO 2 concentration of 0.12% (v/v) and a gas flux of about 2000 m 3/h. When the depth of immersion of the grid holes increased from 0 mm to 100 mm, the pressure drop within the tower increased from 1.5 kPa to 3 kPa, and removal efficiency of SO 2 increased from 50% to 95%. This gas inlet device overcame the problems of uneven distribution and short-circuiting of gas streams within a typical gas inlet device in a jet bubble reactor, and removal efficiency of SO 2 by the tower was improved considerably. Clogging and scaling within the tower were also avoided. This type of gas inlet device is simple and effective for purification and treatment of waste gas streams.

Effects of flash gas generation at the expansion device inlet on the dynamic characteristics of a refrigeration system

The flash gas generation at the expansion device inlet in multi-air-conditioners causes rapid reduction of refrigerant mass flow rate and irregular distribution of refrigerant into multi-indoor units. The objective of this study is to evaluate the influence of the flash gas generation on the dynamic characteristics of a refrigeration system. The dynamic characteristics of a refrigeration system with an electronic expansion valve (EEV) were measured with time at various levels of flash gas generation, which were expressed as flash gas ratio. In addition, the averaged operating parameters and system COP were investigated with the variation of flash gas ratio. As the EEV inlet condition changed from the subcooled to the two-phase state, the refrigerant flow rate decreased rapidly due to the flash gas generation at the EEV inlet. At two-phase inlet conditions, the system operating parameters, such as mass flow rate, suction and discharge pressures, fluctuated periodically with time. As the flash gas ratio increased, the average COP decreased and the discharge temperature increased, degrading the system performance and reliability more severely.

A study on the interchangeability of LFG–LPG mixed fuels with LFG quality in domestic combustion appliances

The interchangeabilities of LFG–LPG mixed fuels with respect to application in domestic combustion appliances were investigated. Two kinds of mixed fuels (MF(WI) and MF(HV)) were produced so as to have a Wobbe index (WI) and a heating value (HV) nearly equivalent to those of LNG, respectively. In this study, the qualities of LFG used in making mixed fuels were considered by varying CH 4 volume fraction in the LFG composition from 55% to 30%. The fundamental characteristics were estimated through comparisons of flame temperature, burning velocity, and the stability region of various fuels. It was found that All MF(WI)s have very similar stable flame zones regardless of the LFG quality, and these mixed fuels can substitute CH 4 completely without any modification of the air entrainment device. On the other hand, the stable flame zone of MF(HV) is decreased to a lower fuel flowrate with a decrease of CH 4 percentage in LFG. These fuels can substitute CH 4 with some restrictions and the air inlet device must be adjusted to lower the air flowrate entrained by the fuel jet.

Comparing field performances of denuder techniques in the high Arctic

A field evaluation between two annular denuder configurations was conducted during the spring of 2003 in the marine Arctic at Ny-Ålesund, Svalbard. The IIA annular denuder system (ADS) employed a series of five single-channel annular denuders, a cyclone and a filter pack to discriminate between gas and aerosol species, while the EPA-Versatile Air Pollution Sampler (VAPS) configuration used a single multi-channel annular denuder to protect the integrity of PM 2.5 sample filters by collecting acidic gases. We compared the concentrations of gaseous nitric acid (HNO 3), nitrous acid (HONO), sulfur dioxide (SO 2) and hydrochloric acid (HCl) measured by the two systems. Results for HNO 3 and SO 2 suggested losses of gas phase species within the EPA-VAPS inlet surfaces due to low temperatures, high relative humidities, and coarse particle sea-salt deposition to the VAPS inlet during sampling. The difference in HNO 3 concentrations (55%) between the two data sets might also be due to the reaction between HNO 3 and NaCl on inlet surfaces within the EPA-VAPS system. Furthermore, we detected the release of HCl from marine aerosol particles in the EPA-VAPS inlet during sampling contributing to higher observed concentrations. Based on this work we present recommendations on the application of denuder sampling techniques for low-concentration gaseous species in Arctic and remote marine locations to minimize sampling biases. We suggest an annular denuder technique without a large surface area inlet device in order to minimize retention and/or production of gaseous atmospheric pollutants during sampling.

Low volume sampling device for mass spectrometry analysis of gas formation in nickel–metalhydride (NiMH) batteries

Rechargeable nickel–metalhydride (NiMH) batteries have major advantages with respect to environmental friendliness and energy density compared to other battery systems. Research on thermodynamics and reaction kinetics is required to study the behaviour of these batteries, especially under severe operating conditions such as overcharging and (over)discharging. During these processes several reactions take place resulting in the formation of oxygen and hydrogen gas. Hence, the recombination processes should be well controlled to guarantee that the partial oxygen and hydrogen pressure inside the battery are kept low. Mass spectrometry is one of the analytical techniques capable of measuring the composition of gases released inside the battery during the charge and discharge processes. However, the sample gas needs to be withdrawn from the battery during the experiment. The gas consumption must be kept to a minimum otherwise the equilibrium inside the battery will be disturbed. A bench-top quadrupole mass spectrometer with a standard capillary by-pass inlet cannot be used for this purpose as its gas consumption is in the 1–10 ml/min range. In this paper, a new gas inlet device is presented that reduces gas consumption to a value <50 μl/h. The use of a capillary by-pass splitter and a discontinuous sampling procedure allow mass spectrometry to be used as a gas analysis tool in many applications in which small amounts of sample gas are involved. Experiments with standard AA-size NiMH batteries show that hydrogen release dominates during (over)charging at increased charging rates. Beside mass spectrometry, evolved gases are also analysed using Raman spectroscopy. Although some differences are observed, the results of similar experiments show a good agreement.

Instability of automotive air conditioning system with a variable displacement compressor. Part 1. Experimental investigation

A test system is built first in order to investigate the instability of the automotive air conditioning (AAC) system with a variable displacement compressor (VDC), and hunting phenomena caused by the large external disturbance in the AAC system with a VDC and a thermal expansion valve, and in the AAC system with a VDC and a fixed-area throttling device are investigated experimentally in part 1 of this paper. The experimental results indicate that there also exist the hunting phenomena in the AAC system with a fixed-area throttling device. The system stability is found to be dependent on the direction of the external disturbance, and the system is apt to cause hunting when the condensing pressure decreases excessively since it may cause two-phase state at the throttling device inlet and make a large disturbance to the system. The piston stroke length will oscillate only when the oscillation amplitudes of forces acting on the wobble plate are great enough, otherwise the piston stroke length will be kept invariable, and then the system instability rule is also suitable for the AAC system with a fixed displacement compressor. From the experimental results, it is concluded that the two-phase flow at the throttling device inlet or at the evaporator outlet is the necessary condition but not sufficient condition for system hunting. Finally, a new concept, conservative stable region, is proposed based on the experimental results and theoretical analysis.

Modeling the acoustical and airflow performance of natural ventilation inlet and outlet units

One aspect of the trend towards designing green buildings has been the increasing use of natural ventilation for buildings which otherwise might have required mechanical ventilation or even full air conditioning. However, the pressure differentials available to drive the natural ventilation process are small and hence relatively large inlets and outlets with low resistance to flow are required. These apertures constitute significant acoustic weak points on building facades and hence need to be treated to reduce noise ingress. Although there are a number of natural ventilation units available they have frequently been designed from the application of simple principles without any attempt to optimise both their airflow and acoustical performance. In this paper the results of a series of computer modeling exercises are described using acoustic FEM and BEM plus Computational Fluid Dynamics (CFD) which seeks to establish recommendations for the optimum design of natural ventilation inlet and outlet devices for both acoustical and airflow performance.

Thermal stratification in small solar domestic storage tanks caused by draw-offs

Storage tanks with different cold water inlet devices for small Solar Domestic Hot Water (SDHW) systems are compared. The objective of the investigation is to reveal the impact of the cold water inlet device on the thermal stratification in two marketed tanks and to evaluate the possible enhancement in the annual system performance of small solar heating systems. Two different marketed inlet designs are compared, one connected to a small curved plate placed above the inlet tube, the other one connected to a much larger flat plate. The cold domestic water enters the stores in vertical direction from the bottom of the tanks. Temperature measurements were carried out for different operating conditions. It was shown that the thermal stratification inside the two tanks depends differently on the flow rate, the draw-off volume, as well as the initial temperature in the storage tank. To carry out system simulations, a multi-node storage model was used and expanded by an additional input variable to model the mixing behaviour depending on the operating conditions. The inlet device with a comparatively large plate compared to the less favourable design results in an increase of the solar fraction of about 1–3%-points in annual system simulations with a solar fraction of about 60% and fairly large domestic hot water flow rates. This corresponds to a reduction of the auxiliary energy supply of the solar heating system of about 3–7% (58–155 MJ/year) for the investigated solar domestic hot water system.

Inlet and outlet devices for rotary blood pumps.

The purposes of inlet and outlet devices for rotary blood pumps, including inducers and diffusers for axial pumps, inlet and exit volutes for centrifugal pumps, and inlet and outlet cannulas, are to guide the blood into the impeller, where the blood is accelerated, and to convert the high kinetic energy into pressure after the impeller discharge, respectively. The designs of the inlet and outlet devices have an important bearing on the pump performance. Their designs are highly dependent on computational fluid dynamics (CFD) analysis, guided by intuition and experience. For inlet devices, the design objectives are to eliminate separated flow, to minimize recirculation, and to equalize the radial components of velocity. For outlet devices, the design goals are to reduce speed, to minimize energy loss, and to avoid flow separation and whirl. CFD analyses indicate the velocity field and pressure distribution. Geometrical optimization of these components has been implemented in order to improve the flow pattern.

Impact of airflow profile on indoor air quality—a tropical study

The validation of the concentration levels of indoor contaminants and the measurement of ventilation parameters with CFD simulation results often poses considerable difficulty due to the effect of several confounding factors. Whilst a building in dynamic operation with varying operating characteristics in terms of the air-conditioning system and the activities of the occupants renders the possibility of a continuous measurement of IAQ and ventilation data, it is almost impossible to simulate such dynamic changes in the CFD environment. It then becomes imperative that steady-state measurements in buildings be used as representative data for the purposes of CFD simulation. This paper reports the findings of a study, in which the simulation of airflow pattern in an office building in Singapore is based on the indoor environmental conditions and the corresponding ventilation parameters measured on a typical day. Boundary conditions are obtained through hood measurements to determine the airflow rate from each diffuser. The findings of this study clearly support the critical impact of airflow on pollutant pathways in the building as a result of air supply volume, arrangement of air inlet and outlet devices, space design and the presence of heat sources.

A strategy of hypothermic circulatory arrest for difficult heart transplant postventricular assist device

Donor heart and ventricular assist device excision can be extremely difficult at the time of heart transplant. We present a strategy of hypothermic circulatory arrest established with ventricular assist device cannulas for difficult heart transplants. The device inlet or outlet cannulas already in place, or both, are used to complement the safe cannulation sites available. This approach permits controlled excision of the recipient heart and device, easy access to convert to standard ascending aorta and bicaval cannulation, and minimizes the donor graft anoxia time. Two case reports are presented.