Effect Of Upstream Pressure Research Articles

Stable metal-organic frameworks based mixed matrix membranes for Ethylbenzene/N2 separation

To remove volatile organic compounds (VOCs) from air, N2 or other waste gas streams in industrial processes is significant to the environmental protection and human health, as well as gain the opportunity to reuse these valuable chemicals. Mixed matrix membranes (MMMs) based on metal-organic frameworks (MOFs) have been proved to have potential application in this field. In this work, MIL-101 and UiO-66 are selected to construct MMMs for efficient ethylbenzene separation because of following factors: (1) the high ethylbenzene adsorption capacities; (2) the three-dimensional channels with large pore size; and (3) the ideal hydrothermal stability of structures. [email protected] and [email protected] MMMs have been prepared in an environment-friendly way and evaluated for the ethylbenzene/N2 separation performance. SEM, TGA, FITR and XRD results indicate that continuous MMMs with different filler loading ratios have been fabricated successfully. The results show that [email protected] and [email protected] with the MOF loading radio of 20 wt% possess ethylbenzene/N2 permselectivity of 284 and 100 respectively at 25 °C, 0.05 MPa and moderate feed ethylbenzene concentration (1000 ppm), which increased by 10.5 and 3.0 times compared with the pristine Pebax membrane. Effects of upstream pressure, feed concentration, and operating temperature on separation performance have been investigated for ethylbenzene/N2 separation. Due to the selective adsorption capacity to ethylbenzene, as well as the large pore size of MIL-101(Cr), [email protected] can be applied as efficient membrane materials in ethylbenzene capture system for high concentration region at ambient temperature.

Experimental study of supercritical CO2 leakage behavior from pressurized vessels

The accidental leakage is one of the main risks in supercritical CO2 transportation and storage system. A new experimental facility was built to study the leakage behavior of supercritical CO2 flow. The leakage flow and jet flow behaviors of supercritical CO2 from pressurized vessels were experimentally investigated. The upstream temperature was examined ranging from 34.9 to 100.5 °C. The effects of upstream pressure were tested ranging from 8.1 to 11.0 MPa. The effects of nozzle geometry structure were tested by using six nozzles with length-diameter ratio (L/D) ranging from 1 to 15. The supercritical CO2 leakage mass flow rate decreases with the increase of upstream temperature and L/D, and increases with the increase of upstream pressure. An empirical correlation with geometric and thermal parameters is developed based on a large amount of experimental data. The experimental data of leakage flow and empirical correlation could be used for safety assessment and theoretical model validation.

Experimental investigation of mass flow rate difference between forward flow and reverse flow of sub-cooled R-22 through stepped short tube orifices

An expansion device of two capillary tubes with a by-pass check valve is popularly used in domestic heat pump systems. In order to reduce the manufacturing cost and improve reliability of the heat pump systems, a stepped short tube orifice consisting of two serial-connected short tube orifices with different diameters is employed as an alternative. The effects of upstream pressure, downstream pressure, upstream degree of sub-cooling and the geometric sizes of stepped short tube orifices on mass flow rate difference between forward flow and reverse flow of R-22 through stepped short tube orifices were investigated in this study. The results showed that there was a distinguishing mass flow rate difference between forward flow and reverse flow of R-22 through stepped short tube orifices under upstream pressure ranged from 1460kPa to 1940kPa, downstream pressure ranged from 420kPa to 680kPa and degree of sub-cooling ranged from 2 to 12°C. The mass flow rate difference is about 10kg/h between forward flow and reverse flow of R-22 through the stepped short tube orifice with sizes of D1=0.8mm, D2=1.0mm, L1=3mm, L2=6.5mm at the upstream pressure of 1940kPa, downstream pressure of 500kPa and the degree of sub-cooling ranging between 2°C and 12°C.

Experimental and numerical investigations on spray structure under the effect of cavitation phenomenon in a microchannel

In this study, the effect of upstream pressure on cavitation flows inside a microchannel with an inner diameter of 152 μm and resulting spray structure were experimentally and numerically investigated. The effects of bubble number density on two-phase flow hydrodynamics were studied using the numerical approach, where transient model was utilized to obtain the changes in vapor quality inside the microchannel and velocity field near the inlet and outlet of the nozzle. Spray visualization was carried out at a distance of 4.5 mm from the tip of the microchannel using the high speed visualization system. The experimental results showed that the spray cone angle increased with upstream pressure, and beyond the upstream pressure of 50 bar, the liquid jet flow changed to the cloudy spray flow. The bubble collapse was recorded at upstream pressures of 100 and 120 bar, where the cavitation bubbles extended to the outlet of the microchannel, and their collapse took place around the spray.

Flash spray characteristics of a coal-liquid carbon dioxide slurry

Liquid carbon dioxide (LCO2) could potentially be utilized in coal gasification plants for effectively transporting coal particles, replacing conventional carriers such as water (H2O), particularly in wet-fed gasifiers. However, it is essential to understand the atomization behavior of LCO2 leaving an injector nozzle under both coal-free and coalfed conditions. We examined the atomization behavior of a coal-LCO2 slurry during the throttling process. The injector nozzle was mounted downstream of a high-pressure spray system. The effect of upstream pressure on flash atomization and devolatilization behavior was presented. Compared with the coal-LCO2 mixture, the spray pattern of the coal-water mixture was significantly different, since it evidenced a Rayleigh-type breakup mode. This difference indicates that the coal-water slurry did not transport the coal as effectively as the coal-LCO2 slurry.

Influence of Orifice Shape on Reaction Rate by Hydrodynamic Cavitation

Hydrodynamic cavitation is expected to apply to the decomposition of chemicals and the disinfection in wastewater. In this study, the effects of upstream pressure, hole diameter and shape of orifice plate on the reaction rate of I3- formation were investigated. The reaction rate increases with increasing upstream pressure of orifice plate. The reaction rates have maximum values, when hole diameters of orifice plate are 2.7 mm at the upstream pressure of 0.9 MPa gauge and 3.0 mm at 0.7 MPa gauge. The reaction rate increases in the order of triangle < square < hexagon < circle shaped hole of orifice plate at the same hole area.

Characteristics of turbulent flow distribution in branch piping system

Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall information only. However, detailed analysis is required to find effects of design parameters on the flow distribution. For this aspect, three-dimensional turbulent flow analysis was performed to assess turbulence model performance and effects of upstream pressure and branch pipe geometry. Three different turbulence models of standard k-ɛ model, realizable k-ɛ model and standard k-ω yield similar results, indicating small effects of turbulence models on flow characteristics analysis. Geometric variations include area ratio of main and branch pipes, branch pipe diameter, and connection shape of main and branch pipes. Among these parameters, area ratio and branch diameter and shape show strong effect on flow distribution due to high friction and minor loss. Uniform flow distribution is one of common requirements in the branch piping system and this can be achieved with rather high total loss design.

Permeability, Solubility, and Diffusivity of Methane and Butane in Diphenylsiloxane-Dimethylsiloxane Copolymer Membranes

Permeation and sorption of methane and n-butane gases in polydimethylsiloxane (PDMS) and diphenylsiloxane-dimethylsiloxane (DPh-DM) block copolymer membranes were studied at room temperature and different upstream pressures. The membranes were prepared via room temperature vulcanization of vinyl terminated siloxanes through platinum catalyzed hydrosilylation reactions by mixing stoichiometric amounts of polymer, crosslinker, and catalyst, and casting of the mixture solutions with hexane. Composite membranes of polysiloxanes on a polyacrylonitrile microporous support were synthesized for permeation experiments and single layer dense films were used in sorption experiments. The effect of upstream pressure on permeability, solubility, and diffusivity of these membranes was evaluated. It was found that selectivity of the DPh-DM copolymer membrane for n-C4H10 relative to CH4 was up to 19% higher than that in PDMS membrane. Both solubility and diffusivity selectivities had positive contributions in permselectivity improvement. The improvement in selectivity was attained with less than a 6% decrease in permeability of n-C4H10. Up to 11% improvement in selectivity was also obtained in mixed gas experiment.

Role of Different Parameters in the Optimization of Hydrodynamic Cavitation

AbstractLow pressure setups (up to 150 psi) for creating hydrodynamic cavitation are investigated in this study. The decomposition of chloroform in water is used as a model reaction. The effects of upstream pressure, fluid velocity, Cavitation number, Cv, and β0 on the conversion are compared with regard to the effectiveness (conversion per pass) with changing flow conditions and scale‐up terms within three different setups. The values of Cv and β0 are seen to be significant parameters in optimizing the hydrodynamic cavitation. Moreover, the optimal values of these parameters shift to smaller values with increasing pipe diameter. The influence of a new orifice plate specific parameter, δ, on the collapse conditions, is also described.

Experimentation and correlation of R744 two-phase flow through short tubes

Refrigerant-744 flow through a short-tube orifice was investigated. The flow of R744 through a short-tube orifice is greatly different from that of a conventional refrigerant such as R134a. R744 flow depending upon upstream pressure, upstream superheating, downstream pressure, and short-tube geometries were examined. A correlation for mass flow rate prediction was developed based on a large amount of experimental data. Ten sharp-edged short tubes and three chamfered tubes with lengths between 8.02 and 25.42 mm and diameters between 0.83 and 1.53 mm were tested to investigate the flowing characteristics of R744. The dependence upon upstream temperature was examined for condensing temperatures ranging from 35.3 to 45.5 °C. The effects of upstream pressure and downstream pressure were tested respectively. The high pressure was varied from 7.55 to 10.24 MPa, and the low pressure ranged from 3.03 to 5.02 MPa. A specially designed short tube was used in the tests to study the flow inside the tube. Experimental results indicated that choked flow existed in all cases. The R744 flow was strongly affected by the diameter of the tube; it was proportional to the upstream pressure but was insensitive to the inlet and exit chamfering.

Oxygen/nitrogen separation by polycarbonate/Co(SalPr) complex membranes

An oxygen carrier, cobalt di-(salicylal)-3,3′-diimino-di- n-propylamine (Co(SalPr)), was added into a polycarbonate membrane for improving its oxygen/nitrogen selectivity. Both the oxygen permeability and oxygen/nitrogen selectivity increased when only 3 wt% of Co(SalPr) was added. The permeability kept increasing but the selectivity decreased when more than 3 wt% of Co(SalPr) was added. The oxygen to nitrogen solubility ratio decreased when 3 wt% of Co(SalPr) was added. Further increase in Co(SalPr) content led to an increase in oxygen/nitrogen solubility ratio. It was astonishing to know that the effect of Co(SalPr) content on the oxygen/nitrogen solubility ratio was totally opposite to that on the oxygen/nitrogen selectivity. A membrane gas transport model which combines the dual mobility model with pore model was adopted to explain the above phenomenon. The specific volume measurement implied that the pore diffusion was responsible for this behavior. The contribution of sorption-diffusion type transport was also investigated by examining the transport behavior of the 3 wt% Co(SalPr) containing membrane through which the pore diffusion is relatively low. The effect of upstream pressure on the oxygen permeability and solubility implied that the diffusivity of Henry's mode was much higher than that of Langmuir's mode. It was also found that the effects of upstream pressure and operating temperature on the oxygen/nitrogen selectivity were both in accordance with those on the Henry's mode solubility ratio. The above information suggested that in addition to the pore diffusion the ratio of Henry's mode diffusion dominated the O 2/N 2 separation instead of the overall O 2 to N 2 solubility ratio.

Effect of Upstream Pressure on the Flux of Single Permeant in Pervaporation

The effect of the upstream pressure on the pervaporation flux of water was studied both theoretically and experimentally. The increase in the pervaporation flux with an increase in the upstream pressure was predicted using newly developed transport equations that allow the pressure change across the membrane and include both liquid and vapor phase transport. The conventional solution-diffusion model, on the other hand, fails to predict the effect of the upstream pressure, particularly when an assumption is made that the pressure of the permeant inside the membrane is constant across the membrane and is equal to the upstream pressure. The pervaporation flux of water through a polydimethysiloxane membrane and an aromatic polyamide membrane was found, experimentally, to increase with an increase in the upstream pressure.

Permeation equations developed for prediction of membrane performance in pervaporation, vapor permeation and reverse osmosis based on the solution-diffusion model.

General permeation equations based on the solution-diffusion model were proposed for pervaporation (PV), vapor permeation (VP) and reverse osmosis (RO) on two different assumptions about the pressure gradient inside a membrane: a flat gradient (case 1) and a linear gradient (case 2). With these equations the permeation properties in PV, RO and VP can be estimated once the transport parameter of a membrane is known.The effect of upstream pressure on selectivity and flux in RO and PV was estimated by sample calculations for water- and ethanol-selective membranes in ethanol–water system. Flux and selectivity in RO is smaller and, reaching that in PV at infinite pressure. This ultimate value is different in cases 1 and 2, and in the latter the molar volume ratio of the permeants becomes important. The effect of downstream pressure in PV was also estimated and compared with the case of vacuum-enhanced membrane distillation (MD) with a porous membrane. With increasing pressure the separation factor approaches that of vapor–liquid equilibrium in both PV and MD. With decreasing pressure that in MD is governed by the ratio of diffusion coefficients inside the membrane. Since the Knudsen diffusion coefficient of water is larger than that of ethanol, the separation factor decreases in ethanol–water separation with decreasing downstream pressure. This was verified by experiment, using PTFE membranes.