High Vacuum Level Research Articles

Vacuum drying of food materials modeled and explored using the reaction engineering approach (REA) framework

REA drying kinetics model has been widely examined for different materials and different operating conditions. Vacuum drying, due to its uniqueness, it presents a challenge for setting up the REA parameters, in particular the specification of the equilibrium activation energy value corresponding to each set of environmental condition. Here, the basic kinetic parameters derived from a convective drying run, is used while the effect of vacuum is captured by the equilibrium activation energy. Upon validation against the experimental data, REA is shown to be applicable. A comparison between the vacuum drying and the convective drying of the same material is also made. The vacuum drying at higher vacuum levels has been predicted, showing the expected behavior. It has been shown that REA is flexible and can be used in vacuum drying related design and optimization studies.

Information extraction from Murphy–Good plots of tungsten field electron emitters

This study introduces an easy methodology to test and analyze experimental field electron emission current-voltage data from metallic single-tip emitters; this novel and easy methodology is called the Murphy–Good plots. Tungsten electron emitters were used as an example and were prepared by the electrochemical etching process. The current-voltage characteristics are obtained in high vacuum levels and using a traditional field emission microscope. Murphy–Good plots are used to apply the well-known field electron emission orthodoxy test to the experimental data and then to extract the emitters’ characterization parameters if the test is passed. The novelty in using this type of plots lies in its independency on any correction factors, unlike the traditional Fowler–Nordheim and Millikan–Lauritsen plots, in addition to its simple theoretical form. The results are calculated using a simple web tool that applies the field electron emission orthodoxy test to any type of the current-voltage analysis plots and then to extract the characterization parameters of the emitters.

Influence of microwave vacuum drying process parameters on phytochemical properties of sohiong (Prunus nepalensis) fruit

The microwave vacuum drying of sohiong (Prunus nepalensis) fruit was performed to study the effect of the processing parameters such as microwave power, vacuum level, and citric acid concentration on the phytochemical properties and the color of the dried fruit. The processing parameters were optimized using response surface methodology and the experiments were conducted using Box–Behnken design. The results showed that the processing parameter had a significant effect on the phytochemical properties and color change of the dried fruit. The optimization process revealed that the sohiong slices pretreated with 0.55% of citric acid concentration and dried at 400 W microwave power level, and 690 mmHg vacuum pressure resulted in high-quality dried fruits. The total phenolic content, antioxidant activity, and anthocyanin content under optimum condition were 44.948 mg GAE/g, 89.761%, and 3.739 mg/g dry matter, respectively. Practical applications The study revealed that microwave vacuum drying conducted at a lower microwave power level and higher vacuum level (low absolute pressure) resulted in a high-quality product with retention of anthocyanin, % DPPH scavenging activity, and phenolic components. The microwave vacuum dried fruits had high retention of color with the lowest color change value. In the presence of vacuum, the oxidation of molecules was prevented during drying resulted in dried products with higher nutritional value. The study would allow the scale-up of microwave vacuum drying to obtain dried phytochemical compound rich products, which is of great interest to the pharmaceutical and food industry.

Impact of different manufacturers and gauge sizes on the performance of backflush needle

The present study aimed to identify the factors regulating aspiration rate (AR) of backflush needles and to compare those factors across various backflush needles from different manufacturers. The 27-gauge (27G), 25-gauge, and 23-gauge backflush needles from four different manufacturers, Alcon, MedOne, VitreQ, and DORC, were used for this experiment. AR was measured at four different aspiration vacuum levels: 100, 200, 400, and 650 mmHg. AR was significantly increased as the aspiration vacuum level increased when both aspirating balanced salt solution (BSS) and ethylene glycol; however, 27G products from VitreQ and MedOne were unable to aspirate ethylene glycol at the low aspiration vacuum level of 100 mmHg. When aspirating BSS at the high aspiration vacuum level of 650 mmHg, a smaller gauge number generally resulted in a significantly higher AR. AR, inner diameter, and cross-sectional area in Alcon products were significantly larger in any gauge, and the shaft length of Alcon products was significantly shorter than those of other manufacturers’ products in any gauge. Cross-sectional area negatively correlated with the degree of shaft deflection (r2 = 0.21, p = 0.042). These results imply that AR differs significantly among backflush needles and among companies depending on the shaft cross-sectional area.

Effect of vacuum pressure on small crack propagation in Ti-6Al-4V

In this study, small crack propagation tests are conducted on artificially defected specimens of Ti-6Al-4V under air and vacuum pressures of 100 Pa, 10−2 Pa, 10−4 Pa, and 10−6 Pa. Fracture surfaces between these environments are compared, and the effect of vacuum pressure on the crack propagation process is investigated. The similarities between surface cracks in vacuum and internal cracks in the very high cycle regime are also discussed from the perspectives of crack propagation rate and fractographic characteristics. From the results, it was observed that there was a tendency for the crack initiation life to increase and the crack propagation rate to decrease with a decrease in the vacuum pressure, although no notable distinction was observed in air and under 100 Pa. The fractography exhibited an angular surface with sharp edges in air and under 100 Pa. However, a granular feature with rounded edges was observed below 10−2 Pa and became more pronounced as the vacuum pressure decreased. The window periods, which formed an oxidized surface coverage, were believed to account for the vacuum effect on crack propagation rate and fracture surface features. Both the crack propagation rate and fractographic features of surface cracks under 10−4–10−6 Pa resembled those of internal cracks; therefore, the presumably working vacuum environment around internal cracks was considered to be at a high vacuum level.

Different vacuum levels, vacuum reduction during low milk flow, and different cluster detachment levels affect milking performance and teat condition in dairy cows

Traditionally, machine milking is performed at a constant vacuum supply. The system vacuum has to be set high enough to allow a sufficiently high vacuum at the teat end, despite the inevitable vacuum drop caused by milk flow. This leads to an increased vacuum load on the teat, especially when milk flow ceases at the end of milking. We tested the hypothesis that a milk flow-controlled adaptation of vacuum settings during milking allows even higher vacuum levels than are usually recommended during the period of high milk flow if the vacuum is reduced during low milk flow. Combined with a high cluster detachment flow rate level, increased milking performance is expected without an increased effect on teat tissue. Ten Holstein dairy cows were milked with a bucket milker with the claw vacuum adjusted in the absence of milk flow at a regular (43 kPa) and high (48 kPa) claw vacuum, with and without vacuum reduction during low milk flow (<2 kg/min), and combined with different cluster detachment levels (0.2, 0.6, and 1 kg/min). Each treatment was applied in each cow during 4 subsequent milkings in a randomized crossover design. Both claw vacuum and milk flow were continuously recorded throughout milking. Teat tissue thickness was measured using a cutimeter and teat wall diameter was measured by B-mode ultrasonography at 5 min after the end of milking. Milk yield was not affected by either vacuum settings or detachment levels. Machine-on time in treatments with vacuum reduction was shorter at high than at low vacuum and decreased with increasing detachment levels. Average milk flow was higher at high than at low vacuum and reached highest values in milkings without vacuum reduction at both vacuum levels. The average milk flow was higher at a cluster detachment of 1 kg/min than at 0.2 kg/min. However, both teat tissue thickness and (as a tendency) teat wall diameter at 5 min after cluster detachment were higher in milkings at high vacuum without vacuum reduction compared with all other treatments. In conclusion, high claw vacuum up to 48 kPa increases milking performance because of higher milk flow and reduced machine-on time. Negative effects of high vacuum on teat tissue are prevented by reducing vacuum during low milk flow (<2 kg/min) at the start and end of milking. Additionally, using a high cluster detachment level reduces machine-on time without a loss of harvested milk.

Differential pumping unit for windowless coupling of laser beams to ultra high vacuum

Current laser technology enables table-top high flux XUV sources with photon energies from several tens to several hundreds of eV via high harmonic generation in noble gases. Here we present a compact versatile coupling unit to establish windowless, and thus lossless coupling of such light sources to ultra high vacuum (UHV). The particular coupling unit has been developed to couple a XUV laser source to a heavy ion storage ring. Three-stage differential pumping allows to reduce the input pressure of ~10−6 mbar down to the 10−12 mbar range at the output. The unit particularly reduces the partial pressure of argon, which is used to generate the XUV radiation, by 6 orders of magnitude. Measurements of the pressure distribution inside the different chambers agree well with theoretical simulations.In principle, this unit can also serve for other purposes, where a windowless vacuum coupling is needed, with a transition from High Vacuum (HV) levels to deep UHV, such as coupling to cryogenically cooled detectors, ion traps or to photoelectron emission spectroscopy experiments.

Effects of machine milking on udder health in dairy ewes

• Milking machine settings that increase vacuum fluctuations under the teat must be avoided to reduce the intramammary infection risk. • Although a high milk pipeline causes higher vacuum fluctuations at teat level, no relation with bulk milk SCC have been found. • Milking machine settings that increase teat thickness would reduce the local defence mechanisms and should be avoided. • Post-milking teat disinfection, milking animals with intramammary infections last, and avoiding over-milking for longer than 2 min can affect mammary gland health status by reducing the incidence risk of mastitis. The aim of this article is to review factors associated with machine milking that would increase mastitis incidence risk and the effects of milking machine, milking management and routine in sheep. Machine milking settings that increase vacuum fluctuations under the teat or teat thickness and help to disseminate infectious agents would increase the risk of intramammary infection. Vacuum fluctuations are caused by a low effective reserve, low air and milk line diameters, low milk tube diameters, sudden air leakages caused by high milking cluster weight, teatcup slippage, excessive liner mouthpiece diameter or inadequate machine stripping. The milk line height (low vs mid line) has no relation with SCC if the rest of the settings are adequate, although higher vacuum fluctuations have been recorded in high line. The settings that increase teat thickness include an excessively high vacuum level, lack of effective massage on the teat (high pulsation ratio), liners too soft, hard, narrow or old, and overmilking for longer than 2 min. Regarding milking management, the reduction of milking frequency to 1 milking per day has an effect on yield and SCC due to a concentration effect, and some milking practices such as post-milking teat disinfection or milking animals with intramammary infections last, despite the drawbacks in overall farm management (identification and separation of infected animals), can lower the risk of mastitis incidence.

CT-severity index can predict the severity of acute pancreatitis similar than other scoring systems

An investigation on the Consolidation by Atmospheric Pressure (CAPing) of a gas atomized commercial T15 tool steel powder is presented. The study was carried out over a range of temperature between 1150 and 1250 °C using loose powder encapsulated in Pyrex glass bottles. The densification mechanisms during CAPing process are subjected to several factors, such as sintering temperature and time, powder particle size and vacuum level. The results indicated that the densification of this powder can be enhanced by decreasing powder particle size and increasing the vacuum level, temperature and time of sintering. Glass penetration is a special characteristic of this process. At some conditions, the highly fluid glass may penetrate deeply throughout the powder aggregate and prevents it from densifying. This study has showed that during CAPing of T15 tool steel powder, there is a competition between the densification and the glass penetration rates. At high temperature (1250 °C) and high vacuum level (10−5tor), the pore closure rate is higher than glass penetration rate and this leads to full density of the material within only 1.5 h. However, at lower temperatures and vacuum conditions, the powder material needs much longer time to reach higher densities. Finally, it can be said that this process offers the possibility of closing the residual porosity and a good control of structural refinement, as well as a substantial production cost savings which could prove a crucial decision making parameter for industrial exploitation of the process.

(Invited) High Performance Carbon Nanotube –Laminated Perovskite Solar Cells

Recently, perovskite solar cells (PSCs) have got much attention since the big jump of the power conversion efficiency (PCE) from about 3.9% [1] to 23.3% [2] in less than a decade that is comparable to the developed Si and CIGS-based counterparts in more than 40 years. Accordingly, tremendous efforts have been devoted on increasing durability of the produced devices at low cost. PSC commonly invented by sandwiching the perovskite layers between two charge selective transport layers. Then, the two conducting electrodes are placed outside of charge selective layers, one is facing the light usually transparent conducting oxide, and the other is a noble metal like gold or silver. The metal electrode typically prepared by thermal evaporation at high vacuum level that’s substantially increase the cost as well for the cost of noble metal. Moreover, these metals either react with the PSC components or migrate into the device at environmental temperature and operational conditions that is subsequently reduces the overall performance and stability [3]. Single-walled carbon nanotubes (SWCNTs) displayed superb physical, properties in terms of conductivity, light absorption, thermal, mechanical, and chemical ones. SWCNTs could be incorporated into the PSC system [4]. SWCNTs is a favorable electrode material, owing to its abundance, hydrophobicity, and mechanical robustness [5]. The application of SWCNT as the top electrode expressively enhances the stability of PSCs by removing the ion migration, and considerably reduces the fabrication cost as it can be easily deposited onto devices by a simple mechanical transfer [6]. We recently showed that the trifillic acid-treated SWCNTs can have a great applicability with 2D/3D FACsPbI3 system reaching PCE of 17.6% with enhanced stability [7]. The conductivity of SWCNT film could be increased as the work function is tuned by using a vapor-assisted doping of trifluoromethanesulfonic acid (TFMS). We extend this work on the MAPbI3 system showing better performance. In this presentation, we will present our latest results on doping of SWCNT electrodes with diluted solution of TFMS having a new record of PCE for the SWCNT-based PSCs. Our devices showed higher PCE of more than 18 % with a J SC of 22.67 mA cm-2, V OC of 1.104 V, and FF of 0.724 through the optimization of hole transport layer concentration as shown in figure 1. Additionally, we will show the possibility of introducing our new 1D heterostructures by wrapping of various SWCNT with BN and TMD layers using chemical vapor deposition into the solar cells and devices field. These SWCNT-based heterostructures are expected to have a broad interest and impact in fabricating BN-protected or gated SWNT devices and building more sophisticated 1D material systems [8]. These new structures are expected to give extra functionality, durability, and great applicability in electronic, optoelectronic, and energy devices.

The effects of cobalt elements addition on Ti2Ni phases, thermodynamics parameters, crystal structure and transformation temperature of NiTi shape memory alloys

By adding cobalt into NiTi-based shape memory alloy, the change of phase transformation, microstructure, and magnetic property of alloys has been investigated in austenite and martensite phases. NiTi and NiTiCo alloys with various rates of cobalt element, 2-6at.%, were prepared by arc-melting furnace, which had a high-vacuum level to avoid contamination, and then samples homogenized at 1323 K for 24h. Subsequently, at room temperature each crystal structure, the microstructural phases, change in chemical composition ratio, and magnetization of the alloys, were investigated by using XRD, optical microscope, SEM-EDX, and PPMS equipment, respectively. The results of these measurements showed that, at room temperature, NiTiCo alloys with cobalt compositions of 0, 2, and 3 (at.%) exhibit the austenite phase, while the rest of the alloys show the martensite phase. Also, the enthalpy change for the first three alloys increased with increasing cobalt addition, however its value decreased suddenly for NiTiCo alloys with 4, 5, and 6 (at.%) cobalt doping.

Consolidation by atmospheric pressure of T15 tool steel powder

An investigation on the Consolidation by Atmospheric Pressure (CAPing) of a gas atomized commercial T15 tool steel powder is presented. The study was carried out over a range of temperature between 1150 and 1250 °C using loose powder encapsulated in Pyrex glass bottles. The densification mechanisms during CAPing process are subjected to several factors, such as sintering temperature and time, powder particle size and vacuum level. The results indicated that the densification of this powder can be enhanced by decreasing powder particle size and increasing the vacuum level, temperature and time of sintering. Glass penetration is a special characteristic of this process. At some conditions, the highly fluid glass may penetrate deeply throughout the powder aggregate and prevents it from densifying. This study has showed that during CAPing of T15 tool steel powder, there is a competition between the densification and the glass penetration rates. At high temperature (1250 °C) and high vacuum level (10−5tor), the pore closure rate is higher than glass penetration rate and this leads to full density of the material within only 1.5 h. However, at lower temperatures and vacuum conditions, the powder material needs much longer time to reach higher densities. Finally, it can be said that this process offers the possibility of closing the residual porosity and a good control of structural refinement, as well as a substantial production cost savings which could prove a crucial decision making parameter for industrial exploitation of the process.

Large-scale cross-sectional study of relationships between somatic cell count and milking-time test results in different milking systems

Milking-time testing (MTT) is a method for evaluating the vacuum conditions in the teatcup during milking. The purpose is to evaluate the possible impact of the milking and milking equipment on udder health and milk quality. The method is commonly implemented by herd health advisory services, but results are interpreted empirically due to lack of scientific documentation on relationships between MTT result variables and objective measures of udder health.The current study was conducted to increase our understanding of associations between cow-level differences in composite milk somatic cell count (CMSCC) and MTT results in dairy cows milked in 3 different milking systems; automatic milking systems (AMS), milking parlors, and pipeline milking systems. Data from 7069 cows (predominantly Norwegian Red breed) in 1009 herds were used in a cross-sectional study. Multilevel linear regression models with a random intercept at herd level were used to describe relationships between CMSCC (on logarithmic scale) and the following MTT explanatory variables: average vacuum level in the short milk tube and mouthpiece chamber in the main milking and overmilking periods, the duration of these two periods, and vacuum stability, measured by sudden vacuum drops in the short milk tube. The models were corrected for the herd effect, mastitis history and differences in milk yield, lactation stage and parity between cows. Separate models were run for AMS, milking parlors, and pipeline milking systems, because this approach allowed for comparison between systems and for evaluation of the herd effect independently of milking system.The models described 8–10 % of the variation in CMSCC, indicating that MTT could only explain a relatively small proportion of a large total variation in CMSCC. In most observations, vacuum levels in the short milk tube during main milking were within the range recommended by the International Organization for Standardization. The results from our multivariable models showed decreasing CMSCC with increasing vacuum level in the short milk tube during the main milking period in AMS and milking parlors. Similarly, decreasing CMSCC was also associated with increasing duration of the main milking period in all 3 systems. These relationships are important for the interpretation of MTT results under practical conditions; finding high vacuum levels and long milking durations in a MTT is not associated with elevated CMSCC. In AMS herds, we also found indications that the relationships were different for cows where a case of mastitis had been treated before the MTT.

Interaction of electrons with residual gas molecules and its effect on gas bremsstrahlung radiation in electron storage rings

High energy electrons on interaction with residual gas molecules present in the vacuum chamber of electron storage rings produce gas bremsstrahlung radiation. Extensive studies have been carried out in past to evaluate dose rate from gas bremsstrahlung using various simulation techniques with air as target gas. From these studies, empirical relations were deduced to evaluate gas bremsstrahlung dose rate. However storage rings at ultra high vacuum level contains primarily hydrogen and hydrocarbon gases as residue. In this work, effect of residual gas composition in vacuum chamber on gas bremsstrahlung dose rate in electron storage rings of energy range 1–3 GeV has been studied using FLUKA Monte Carlo code. Simulation study was performed to investigate effects on energy distribution, angular distribution and absorbed dose rate of gas bremsstrahlung due to various composition of residual gas normally encountered in vacuum chambers of storage rings. The gas bremsstrahlung dose rate was found to depend on effective atomic number and molecular mass of the residual gas molecules. From the study, a new empirical formula for the estimation of gas bremsstrahlung dose rate is proposed.

Heat Treatment for a Superconducting Cavity

Imperfections on the surface of a superconducting material, niobium, have serious effects on the performance by increasing the surface resistance. Cold working of niobium to fabricate a cavity degrades the crystallinity of the niobium surface only to increase the surface resistance. Hydrogen is a well-known impurity that lowers the quality factor in the form of Q-disease. High-temperature heat treatment with a high vacuum level was carried out to remove impurity gases from the niobium surface of a cavity, and to anneal the cavity to increase the crystallinity. Optical images were taken to confirm the effect of the heat treatment on the microstructure. Grains did not grow much after the heat treatment, and the crystallinity was increased. Diffraction analyses based on X-ray diffraction (XRD) and the full widths at half maximum (HWHMs) of the XRD peaks confirmed that the annealing was successfully performed. The residual gas analysis (RGA) confirmed that a very large of amount of hydrogen, which is known as a major impurity causing the quality degradation of the superconducting cavity, was removed during the heat treatment.

A 3D-printed miniature magnetron gauge for ultra-high vacuum environments

Miniaturized magnetron gauges are necessary for monitoring vacuum level in miniature vacuum chambers. This paper addresses the challenges of designing the magnetron cavity and configuring the electric and magnetic fields within it while meeting the contradictory constraints of small size and high vacuum level that make electron confinement and accumulation difficult. The resulting gauge has an internal volume of 0.3 cm3 and is designed for and fabricated by advanced 3D printing – including direct metal laser sintering of 316 L stainless steel. Additionally, it is capable of directly attaching to a standard vacuum electrical feedthrough. A particle tracing simulation is used to assess the electron confinement for a range of operating conditions. Experimental characterization shows that the operating pressures extend from 10 nTorr (1.33 μPa) to 1 mTorr (133 mPa). The gauge current is repeatable over the characterized pressures at various values of supply source voltage, VS, from −1000 V to −2500 V, and ranges from ≈1 nA to ≈100 μA over these pressures and voltages. The effects of VS and pressure are examined and compared to prior work. This gauge is at least 30× smaller than commercially available magnetron gauges (e.g., a typical inverted magnetron transducer has an internal volume of 15 cm3).

High-vacuum clothesline technique for elevation and repositioning of posteriorly dislocated intraocular lens

We describe a technique to simplify the retrieval process of an intraocular lens (IOL) that has fallen into the posterior segment of the eye. A high-vacuum level setting is used to achieve fixation of the IOL to the vitrectomy tip, permitting the IOL to be elevated into the anterior segment. The clothesline technique is then used to secure the IOL partially within the anterior chamber for subsequent suture fixation or explantation. This technique simplifies the elevation, repositioning, and/or explantation of a posteriorly dislocated IOL and eliminates the need to perform more complex and potentially traumatic maneuvers.

Machine milking parameters for an efficient and healthy milking in dairy camels (Camelus dromedarius)

The effect of vacuum level and pulsation rate on machine milking efficiency in lactating dromedary camels were studied in 2 separate experiments. In the first experiment, a total of 14 multiparous camels in early (n=7) and late (n=7) lactation were used to study the effects of vacuum level (45 and 50 kPa) and pulsation rate (52 and 60 pulsations/min) on milk fractionation and flows traits. At the morning milking, volumes of machine milk (MM), machine stripping milk (MSM) and residual milk (RM) were recorded at two different days. For the second experiment, another 10 multiparous dromedary camels at mid stage of lactation were used to evaluate teat condition and udder health during 10 weeks. Milk samples were collected weekly at each milking and analysed for major milk constitutes and udder health. The 50 kPa vacuum level and 60 pulsations/min decreased (P<0.05) the MSM (from 15.2 to 5.9%) and RM (from 44.1 to 29.8%) compared to 45 kPa and 52 pulsation rate. Moreover, milking camels at high vacuum level resulted in significantly more milk in a shorter time with higher milk flows rate at early stage of lactation. No subclinical mastitis was detected in any of udders quarters as indicated by the CMT (<1), SCC (387×103±86 cells/mL) and bacteriology (coliform=0 and total flora=32097±396 ufc/mL) test. There were no differences in teat diameters, texture and color before and after milking. In conclusion, dromedary camels are readily to milk efficiently at 50 kPa and 60 pulsations/min without affecting negatively teat condition or udder health.

Variability of vacuum in goat clusters under different controlled conditions of pipeline height, vacuum and pulsation settings and flow rate

Teat-end mean vacuum is directly related to teat health and milking process (liner adhesion on teat, proper flow rate). Moreover, vacuum fluctuations (cyclic and irregular) increase the risk of bacterial transmission from one teat to the other. Goat sector is yet missing references on factors linked with milking machine and animal, which influence teat-end vacuum. A laboratory experimentation was performed using a milking simulation device, used for International Committee for Animal Recording (ICAR) tests. The influence of six different parameters on vacuum levels in cluster was studied: pipeline height, working vacuum, pulsation type, pulsation rate and ratio and flow rate. The data analysis was based on vacuum stability calculation: vacuum loss and cyclic vacuum fluctuations.In high line, due to a complex milk flow in long milk tube, teat-end vacuum fluctuations are about 4kPa higher than in low line. An increase of flow rate also leads to higher vacuum fluctuations. This relation seems to be linear; however, this hypothesis should be confirmed through another specific experiment. Contrary to other publications, in low line, vacuum fluctuations are slightly intensified by alternate pulsation, compared to simultaneous one (+1.3kPa). A farm experiment should be carried out, in order to check these results with real field situation and to analyze the effects of these vacuum fluctuations levels on milking incident frequency and udder health. Vacuum loss analysis reveals that high working vacuum level, especially when associated with low flow rates, may lead to teat-end average vacuum over 38kPa. This point out the interest of reducing overmilking and measuring teat-end vacuum during milking, to help farmers define their proper working vacuum level, with regards to mammary health.

Modeling of U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ hollow-fiber membrane for oxygen permeation

Abstract A mathematic model is developed for the perovskite-type mixed ionic-electronic conducting (MIEC) membrane, which makes it possible to simulate the process of oxygen separation in the U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3 − δ hollow-fiber membrane. The model correlates the oxygen permeation flux to the measurable variables. The trends of calculated results for purge operation coincide well with the experimental data, therefore the model is considerable for flux prediction under vacuum operation. Higher oxygen separation efficiency can be achieved with vacuum operation than purge operation. Parameter study with vacuum operation reveals that oxygen permeation flux increases with higher vacuum levels, and vacuum pressure of around 1.013 × 10 3 Pa is the optimal. Also, vacuum operation on the lumen side is much more efficient to achieve higher oxygen permeation flux compared with compression mode on the shell side.