Parallel Air Flow Research Articles

The effects of simultaneous electrophoresis and thermophoresis on particulate contamination of an inverted EUVL photomask surface in parallel airflow

The combined influences of electrophoresis and thermophoresis on particle deposition on the inverted critical surface of a flat plate in parallel airflow were investigated by employing the statistical Lagrangian particle tracking approach in an effort to assess the degree of particulate contamination of EUVL photomasks during horizontal transport in cleanroom environments. The numerical method was validated through the comparison with the experimental data, found in the literature, about particle deposition velocity onto a wafer in vertical airflow with and without electrophoresis or thermophoresis. In addition, the validation of the present model was performed via the comparison with the theoretical prediction of particle deposition velocity onto a flat plate under no phoretic forces in parallel airflow. Then, the particle deposition velocity onto the face-down surface of a flat plate in parallel airflow was obtained by varying the temperature of the inverted critical surface in different strengths of uniform electric fields. Injected particles were assumed to be charged with -1 , 0, or +1 elementary unit of charge, in order to consider attractive or repulsive electric force. The degree of particulate contamination of the inverted critical surface was found to be significantly influenced by the combination of electrophoretic and thermophoretic effects.

Particle deposition on face-up flat plates in parallel airflow under the combined influences of thermophoresis and electrophoresis

The deposition velocity is used to assess the degree of particulate contamination of wafers or photomasks. A numerical model was developed to predict the deposition velocity under the combined influences of thermophoresis and electrophoresis. The deposition velocity onto a face-up flat plate in parallel airflow was simulated by varying the temperature difference between the plate’s surface and ambient air or by changing the strength of the electric field established above the plate. Both attraction and repulsion by thermophoresis or electrophoresis were considered. When the plate’s surface was colder than ambient air, the surface of the face-up plate could be at risk of contamination by charged particles even with a repulsive applied electric force. When the temperature of the plate’s surface was higher than the ambient temperature, the degree of particulate contamination on the surface of the face-up plate could be remarkably reduced in the presence of an electric field. The effect of repulsive thermophoresis, however, is expected to be reduced for very fine particles of high electric mobility or for micrometer-sized particles with large gravitational settling speed when the charged particles are influenced by an attractive electric force.

A Mechanistic Study on Minimum Flow Rate for the Continuous Removal of Liquids from Gas Wells

Experimental studies show that liquid drop is deformed from initial sphere shape into oblate spheroid shape in parallel air flow, and experimentally determined values available of critical Weber number Wecrit vary from 2.2 to 60 in low-viscosity liquid. Based on forces equilibrium, the authors deduced a new model to predict minimum flow rate. The model introduces a parameter Ck,Wecrit that describes the effect of liquid drop deformation and the maximum drop size difference on minimum flow rate. A function to predict drop deformation magnitude for different critical Weber number is developed based on energy conservation. The function prediction results are in good agreement with experimental data given in the literature and the predicted result from the DDB model, and the deviation is less than 6%. The Ck,Wecrit calculated by new model changes from 2.44 to 4.79, and the Ck,Wecrit calculated from data from gas field and experiment changes from 1.86 to 5.0. The new model theoretically explains the reasons that the discrepancy of the minimum flow rate is significant and minimum flow rate in some gas wells in China are low.

Statistical Lagrangian particle tracking approach to investigate the effect of thermophoresis on particle deposition onto a face-up flat surface in a parallel airflow

Thermophoresis can affect the particulate contamination of wafers and photomasks. Thermophoretic effect on particle deposition velocity in the cleanroom environment has been intensively investigated for the free-standing wafer situated perpendicular to the top-down airflow, but it has been examined by few studies for the wafers or photomasks in the parallel airflow. In this study, the particle deposition velocity onto a face-up flat surface under the influence of thermophoresis was numerically investigated, when the face-up flat surface was exposed to the parallel airflow. Statistical Lagrangian Particle Tracking (SLPT) model with the aid of commercial codes, i.e. FLUENT and DPM, was employed. The SLPT model was validated by comparing the numerically obtained particle deposition velocities with the theoretically predicted data, with and without considering the thermophoresis, and found to produce correct results. The effects of temperature difference (between the face-up flat surface and the ambient air), parallel airflow velocity, and particle density on the particle deposition velocity onto the face-up flat surface in the parallel airflow were investigated using the SLPT model, when the temperature of the face-up flat surface was either higher or lower than the ambient temperature.

Effect of plate thickness on particle deposition velocity onto a face-up flat plate situated parallel to an airflow

The effect of plate thickness on particle deposition velocity onto a face-up flat plate in a parallel airflow was examined both numerically and experimentally. Plate thickness was varied as 0.05, 0.925, 2.3, and 6.35 mm, by considering flat plates of negligible thickness, 450 mm wafers, 5 in photomasks, and 6 in EUVL photomasks, respectively. Statistical Lagrangian particle tracking (SLPT) model with the use of commercial codes was employed. The SLPT model was validated by comparing the numerically obtained particle deposition velocities with either the theoretically predicted or the experimentally determined particle deposition velocities, for the flat plates of various thicknesses. Then, the effect of plate thickness on particle deposition velocity onto the face-up flat plate in a parallel airflow was investigated by employing the SLPT model. It was found that the effect of plate thickness should be taken into account, when the particle deposition velocity onto a 5 in photomask (2.3 mm thick) or a 6 in EUVL photomask (6.35 mm thick) was considered. However, it was anticipated that the effect of plate thickness was insignificant, when the particle deposition velocity onto a 450 mm wafer was taken into consideration.

Numerical Investigation of Thermophoretic Effect on Particulate Contamination of an Inverted Flat Surface in a Parallel Airflow

Thermophoretic effect on particle deposition velocity onto an inverted flat surface was numerically investigated, by employing the Statistical Lagrangian Particle Tracking (SLPT) model. The SLPT model was verified to be correct, when the numerically obtained particle deposition velocities were compared with the theoretically predicted particle deposition velocities, with and without considering thermophoresis. Temperature difference between flat surface and ambient air, particle density, and airflow velocity were found to affect the particle deposition velocity onto the inverted flat surface under the influence of thermophoresis. Thermal conductivity ratio between air and particle, however, was found to be insignificant in affecting the particle deposition velocity onto the inverted flat surface. Particulate contamination of the inverted critical surface was estimated to be greatly reduced by heating the surface. On the other hand, the face-down critical surface was anticipated to be contaminated by particles when the surface temperature was lower than the ambient temperature, even with the scheme of inverted orientation.

Experimental Investigation of Particle Deposition on Face-up Surfaces of Wafers and EUVL Photomasks Exposed to a Parallel Airflow

It is of great importance to predict the level of particulate contamination of wafers or photomasks in semiconductor manufacturing. Thicknesses of 300-mm-wafers of current mass production, 450-mm-wafers of near-future mass production, and EUVL photomask of next-generation lithography are 0.0775, 0.0925, and 0.635 cm, respectively. In this study, the effect of plate thickness on particle deposition velocity onto face-up wafers or EUVL photomasks situated parallel to an airflow was investigated by comparing experimentally measured and theoretically predicted particle deposition velocities, when the theoretical prediction of Yook et al. (Particle deposition velocity onto a wafer or a photomask in a laminar parallel flow. J. Electrochem. Soc. 157, H692-H698, 2010) was based on the neglect of plate thickness. It was found that the correlation of Yook et al. (2010) could accurately predict particle deposition velocities onto the wafers, owing to negligible thicknesses of wafers. On the other hand, in the case of the EUVL photomask, it was found that the effect of photomask thickness on particle deposition velocity was remarkable, but discrepancy between experimental measurement and prediction using the theory of Yook et al. (2010) became smaller with increasing either particle diffusivity or gravitational settling velocity.

Simultaneous Investigation of Entrained Liquid Fraction, Liquid Film Thickness and Pressure Drop in Vertical Annular Flow

The mechanism of atomization of part of the liquid film to form drops in annular two-phase flow is not entirely understood. It has been observed that drop creation only occurs when there are large disturbance waves present on the film interface. (Woodmansee and Harrantty, 1969, “Mechanisms for the Removal of Droplets From a Liquid Surface by a Parallel Air Flow,” Chem. Eng. Sci., 24, pp. 299–307) observed that ripples on these waves were precursors to drops. Though it has been reported that drops occur in bursts by (Azzopardi, Gas-Liquid Flows Begell House Inc., New York, 2006), all previous drop size or concentration measurements have always been time integrated to simplify data analysis. Dynamic time averaged drop size measurements are reported for the first time in annular flow. Experiments were carried out on a 19 mm internal diameter vertical pipe with air and water as fluids. Spraytec, a laser diffraction-based, drop size measurement instrument, was used in the drop related data acquisition. Simultaneous time-resolved measurements were carried out for drop, film thickness, and pressure drop. Film thickness has been measured using the conductance probes employing a pair of flush mounted rings as electrodes. Pressure drop was logged using differential pressure cell connected to two pressure taps located within the test section. The gas superficial velocity was varied systematically from 13 to 43 m/s at fixed liquid superficial velocities of 0.05 and 0.15 m/s, respectively. Additional tests were carried out with the gas velocity fixed at 14 m/s while the liquid superficial velocity was varied from 0.03 to 0.18 m/s. Signal acquired are presented in form of time series to permit data analysis at different levels. Based on signal analysis, interrelationships between liquid film where the drops are sourced and the contribution of the entrained liquid droplets to the overall pressure drop in the system has been elucidated. Though structures are not clearly visible in the signals acquired, the time series have been analyzed in amplitude space to yield probability density function (Pdf). Beyond gas superficial velocity of 30 m/s, Pdf of drop size distribution becomes monomodal or single-peaked marking transition to mist annular flow.

Polyphenol Oxidase Activity and Colour Changes of ‘Starking’ Apple Cubes Coated with Alginate and Dehydrated with Air

The objective was to study the effect of alginate coating on polyphenol oxidase (PPO) activity and colour of ‘Starking’ apple cubes during dehydration with hot air. Apple cubes were dehydrated at 20oC, 35oC, or 40oC, with a parallel airflow. Analysis of PPO activity, colour (L*, a*, b*) and dry matter were performed along the dehydration process at each temperature. All samples presented a peak in relative PPO activity in the beginning of the drying. Exponential models fitted well the experimental data after the peak. Cubes without coating presented lower PPO activity, suggesting lower browning, than coated samples throughout the dehydration process, for all temperatures. Better results for coated samples were obtained with a perpendicular airflow drying at 40oC, after dipping the whole apple in water at 60oC for 10 min. In order to prevent coated samples from browning, drying by perpendicular airflow preceded by a thermal treatment of the whole apple is required.

Development of Air Flow Equivalent Circuits Analysis Combined with Finite Element Method for High Voltage Air Cooling Inverter Design (Productization of Parallel Air Flow Inverter Carrying Different Units)

To increase the power density of the inverters for power industry, the new air cooling system of high power inverters were developed. Parallel air flow inverters carrying 18 differential units were introduced without unit fan because of easier maintenance and lower cost. Realizing the systems for inverter design, we proposed a useful and epoch-making analysis method named “Air flow equivalent circuits analysis combined with finite element method”. The inverters were divided into a small block and analyzed individually, and their results of the resistances were built into equivalent circuits. The proposed analysis method enables to calculate the wind velocities and pressure drops of the whole inverter panels, which unable to be solved in case of FEM analysis with the numerous mesh for the whole ones. Air flow resistances of merging ducts including the smaller parts could be evaluated in the methods. Therefore, we contribute to decrease the cooling design time within 1 second at the process of mass-produced design.

Optimisation of Spirulina platensis convective drying: evaluation of phycocyanin loss and lipid oxidation

SummaryThe aim of the study was the optimisation of Spirulina platensis drying on convective hot air through the response surface methodology. The responses were thiobarbituric acid (TBA) and phycocyanin loss percentage values in final product. Experiments were carried out in perforated tray drier with parallel air flow, and the wet samples thickness and drying air temperatures were in range of 3–7 mm and 50–70 °C, respectively. The statistical analysis showed significant effect (P < 0.05) for air temperature and samples thickness. In the best drying condition, 55 °C and 3.7 mm, presented the phycocyanin loss percentage and the TBA values of approximately 37% and 1.5 mgMDA kg−1, respectively. In this drying condition, the fatty acids composition of the microalgae Spirulina did not show significance difference (P > 0.05) in relation to fresh biomass. The lipid profile of dried product presented high percentage of polyunsaturated fatty acids (34.4%), especially the gamma‐linolenic acid (20.6%).

A study of steady laminar diffusion flame over methanol pool surface

A numerical study of laminar, boundary layer type diffusion flames established over a liquid fuel pool, under the influence of forced air flow parallel to the pool surface, has been carried out. Burning of a confined methanol pool at atmospheric pressure and under normal gravity conditions is investigated. A numerical model, which solves transient, two-dimensional, mass, momentum, species and energy conservation equations, has been employed to predict the flame characteristics. The gas-phase alone is solved in a decoupled manner using appropriate interface boundary conditions, without considering the effects of liquid-phase transport on the combustion process. A single-step global reaction for methanol–air oxidation, considering carbon-dioxide dissociation, is employed to model the chemical kinetics. An optically thin radiation model has also been incorporated to account for thermal radiation losses by absorbing species in a non-luminous flame. At the outset, the model is validated against the experimental results available in literature. Thereafter, it has been used to investigate the influence of free stream air velocity on fuel mass burning rate, flame stand-off distance, temperature and flow fields. The study brings out the variation in the structure of confined laminar boundary layer type diffusion flames over methanol pool for several air velocities under normal gravity environment.

Unsteady State Heat Transfer from Cylinders to Air in Normal and Parallel Flow

Transient temperature measurements were made to determine the Nusselt number for both normal and parallel air flow over cylinders. The cylinders were fine polymer fibers, and the temperatures were determined with an infrared camera. The experimental results for normal flow agree with the well-established correlation of McAdams. For parallel flow, the results lie between the predictions of previous researchers. Unlike the work described herein, previous investigators used equilibrium conditions as a basis for determining Nusselt numbers. Our transient measurements showed that the Nusselt number is not strongly dependent on the transient character of temperature difference.

Production and biochemical profile of the microalgae Aphanothece microscopica Nägeli submitted to different drying conditions

The production and biochemical profile, consisting of the protein, carbohydrate, lipid and fatty acid fractions of the microalgae Aphanothece microscopica Nägeli, cultivated in parboiled rice effluent, were studied with the objective of evaluating its potential as a source of metabolites of commercial interest. The biomass was produced in a batch cylindrical bioreactor operating isothermally at 30 °C, with the pH adjusted and maintained at 8.0, an inoculum concentration of 100 mg/L and C/N ratio of 50. The biomass was separated by centrifugation and dried in a batch tray dryer with parallel air flow (1.5 m/s) at temperatures of 40, 50 and 60 °C and tray thicknesses of 5 and 7 mm, followed by a biochemical evaluation. The results obtained showed that the parboiled rice effluent was a culture medium with potential for the production of single cell protein, and that the biomass produced represented an important source of protein, carbohydrate and lipids. The drying conditions were shown to significantly affect ( α = 0.05) the macronutrient composition of the biomass with respect to the protein, carbohydrate and lipid contents. The lipid profile showed a predominance of polyunsaturated fatty acids, especially that of gamma linolenic acid, but the drying conditions did not influence the polyunsaturated/saturated ratio of the biomass.

Diffusive model with variable effective diffusivity considering shrinkage in thin layer drying of chitosan

In the thin layer drying of chitosan, a diffusive model considering the material volume change was used, due to the occurrence of shrinkage during the operation. The samples were placed in a rectangular tray with 4 mm of thickness, and inserted in the discontinuous dryer, with parallel air flow at 60 °C of temperature and air speed of 1.5 m/s. The sample shrinkage occurred in the thickness, and the linear shrinkage coefficient was constant. In the model, variable moisture effective diffusivity and equilibrium conditions at the material surface were considered. The dimensionless second order non linear partial differential equation, resulting from the model, was solved numerically by the finite differences technique. A good agreement between the numerical data of the average moisture content, obtained by the model, and the experimental data was observed.

Thermal characterization of porous carbon foam—convection in parallel flow

Experiments are presented to quantify the convective heat transfer that is obtained by passing parallel airflow over a layer of porous carbon foam bonded onto a solid substrate. The increase in heat transfer is shown to be inversely proportional to Reynolds number and decreased from about 28–10% over the Reynolds number range 150,000–500,000. The heat transfer is independent of the effective conductivity over the range of conditions tested herein, and is independent of thickness for carbon-foam layers of thickness greater than 3 mm.

Thermal Analysis of Spirally Wound Lithium Batteries

A two-dimensional thermal model is developed to establish a standard for the simulation of spirally wound cells. It properly deals with the geometric characteristics and the boundary conditions to avoid the distorted simulation results due to improper approximation of the spiral geometry. Furthermore, the flexible architecture makes it possible that the precision of the numerical solutions can be elevated by spending more time on calculation. According to the simulation of lithium batteries under natural convection, the hottest temperatures are in a circular region near the liquid-filled hollow core but not at the exact center. Furthermore, radiation contributes as much as 53.6% to the heat dissipation if the surface emissivity approaches unity. Adopting an air flow parallel to the cylinder axis is effective to suppress the surface temperature, but the hottest temperature inside a battery remains high if a battery has a large radius. The heat dissipation rate of an air flow perpendicular to the cylinder axis is slightly lower than that of a parallel flow, and a battery case with high thermal conductivity is suggested to maintain the temperature uniformity of a battery.

Drying characteristics and heat energy requirement of cornelian cherry fruits ( Cornus mas L.)

In this research, drying characteristics and energy requirement for drying of cornelian cherry fruits ( Cornus mas L.) were reported. Cornelian cherry fruits were dehydrated in a parallel air flow type dryer. The dryer mainly consisted of an electric heater, adjustable forward curved centrifugal fan, corrosion resistant plastic mesh, corrosion resistant metal sheet, sytrafor insulator, drying air inlet and outlet channels as well as thermostat, temperature indicators and wattmeter. Freshly harvested cornelian cherry fruits were dried at 50, 60 and 70 °C temperatures. Selected drying air velocities were 0.3, 0.6 and 0.9 m/s for each temperature. Cornelian cherry fruits were dehydrated from the initial moisture content of 233% (percentage dry basis) to a final moisture content of 8%. During experiments, drying product collected from the plastic mesh were also weighted to note amount of water evaporated. The results showed that drying air temperature significantly influenced the total drying time and air velocity also influenced the total energy requirement for drying. On the contrary, the effect of the drying air velocity on the total drying time was found less. The minimum and the maximum energy requirement for drying of cornelian cherry fruits were also determined as 11.57 kW h/kg and 39.55 kW h/kg for 70 °C, 0.3 m/s and 50 °C, 0.9 m/s, respectively. As a result, to reduce drying energy consumption, it can be recommended that the drying air velocity must not be more than 0.3 m/s for all different temperatures and the most ideal temperature was found 70 °C for this application.

Simulation of flow field of a ventilated and occupied animal space with different inlet and outlet conditions

Simulation of flow field of a ventilated space of a biological object is necessary to determine heat exchange between the object and its environment. In this paper, flow fields of a ventilated space occupied by twenty randomly placed virtual cows are characterized under four different inlet and outlet situations. A three-dimensional turbulence model is used to characterize the flow field. The four inlet and outlet cases are: (1) ceiling-baffle inlet with airflow parallel to the wall with the outlet fan located at the center of the opposite wall, (2) wall-baffle inlet with airflow parallel to the ceiling with the outlet fan located at the center of the opposite wall, (3) the same as in Case 2 but with two inlets and outlets, in which one inlet and one outlet is located in each sidewall, and (4) center-ceiling baffle inlet and an outlet fan located at the center of each sidewall. There is significant variation in the uniformity of the flow field between the four air inlet/outlet locations. Air distribution is more uniform when air enters parallel to the ceiling from two sidewall inlets and exits through two sidewall outlets. The distribution is less uniform when air enters parallel to the ceiling from one sidewall only. Variations in sensible and evaporative heat fluxes are significant between cow locations for the same air inlet/outlet configuration, and for the same cow under the different air inlet/outlet configurations considered.

Experimental investigation of the drying process of automotive base paints

To achieve a better understanding of the heat and mass transfer phenomena in automotive base paints during drying, laboratory scale experiments are carried out. The convective drying of one and two subsequently coated paint layers on steel substrates were examined in an air flow parallel to the sample surface. The evaporation of organic solvents and water is examined by gravimetric and gas-phase FTIR measurements. During the drying process the temperature of the sample is recorded. Experiments are conducted at different humidity (2 g/kg dry air–22 g/kg dry air), air temperature (20 °C–80 °C) and air velocity (0.5 m/s–2 m/s). A metallic industrial paint and a simplified model paint are used in the experiments. The variation of the drying climate shows an influence on the composition of the paint during and at the end of the drying process. This might influence the final coating’s quality.