Maximum Mass Flow Rate Research Articles

Study on the heat transfer performance of coaxial casing heat exchanger for medium and deep geothermal energy in cold regions

To accurately assess the heat transfer performance of a medium-depth coaxial casing heat exchanger, this study introduced the concepts of the annual stabilized mining stage and the effective thermal influence distance for each layer of non-homogeneous thermal storage. The study area was stratified into six layers based on the geothermal temperature gradient fitting results. The findings revealed that the maximum injected circulating fluid temperature for the mid-depth coaxial casing geothermal system was 37 °C, with a maximum mass flow rate of 16.67 kg/s. When the injected circulating fluid temperature increased from 2 °C to 25 °C, the duration of the annual stabilized exploitation stage extended from 23 to 26 years. Similarly, increasing the injected circulating fluid mass flow rate from 2.78 kg/s to 16.67 kg/s prolonged the maintenance period in the annual stable mining stage from 22 to 28 years. The study further indicated that the effective thermal influence distance for each layer of thermal storage was significantly impacted by varying injection circulating fluid temperatures. These results offered theoretical insights into the heat transfer performance of medium-depth coaxial casing geothermal systems under both short- and long-term operational conditions.

Performances of the ITER Pressure Suppression System during unstable steam condensation regimes

Abstract The paper deals with the qualification of the main safety system of the nuclear fusion reactor ITER: the Vacuum Vessel Pressure Suppression System (VVPSS). This safety system manages the Loss of Coolant Accident (LOCA), that could occur in the Vacuum Vessel (VV), avoiding a significant increase of the internal pressure that could breach the primary confinement barrier. Steam condensation occurs at sub-atmospheric pressure. This condition is original respect the usual applications of steam direct condensation in nuclear fission reactors. An extensive experimental research program, funded by ITER Organization, on reduced scale experimental rigs (scale 1/22 and 1/10) have been carried out at the University of Pisa. Unstable condensation regimes occurred during some tests at about 500 g/s of steam mass flow rate (10 % of the maximum steam mass flow rate foreseen for the relevant accidental scenarios). In these conditions, high intensity vibrations of the whole experimental rig occurred. These events can be classified as ‘Chugging’ or Condensation Induced Water Hammer (CIWH). 
The performed tests have been analysed elaborating the images of the video-cameras located in the pool and comparing the steam jet shape with the acceleration values recorded by an accelerometer mounted on the sparger structure.
These elaborations permitted to evaluate the dynamic of bubble collapse, the volume of the developed external bubbles, the collapse frequency as function of thermal-hydraulic parameters. 
Moreover, the paper emphasizes the beneficial effects of non-condensable gases on the unstable condensation regimes. In fact, the non-condensable gas inhibits the occurrences of Water Hammer inside the sparger and eliminates the thermal stratification inside the water pool increasing the turbulence.

Optimization design method based on parameter reduction and active subspaces: Redistribution of chordwise loading at blade tips in a transonic axial-flow fan

In practical optimization design, an excessive number of design variables have a highly detrimental influence on the efficiency and accuracy of the final design scheme and expose the optimization problem to the curse of dimensionality. Therefore, incorporating only the most essential variables into an optimization design problem facilitates obtaining accurate and cost-efficient solutions. Reported here is an optimization design method based on parameter reduction and active subspaces, and it is used to redistribute the tip load in a transonic fan. Specifically, a coupled design strategy is developed to reduce the number of parameters needed to describe the three-dimensional blade shape, which leads to far fewer design variables being involved in the optimization design. Moreover, active subspaces are used to perform sensitivity analysis and establish low-dimensional surrogate models. After the coupled design, a blade is represented effectively by only three parameters, each of which has a significant influence on the fan performance. Three one-dimensional active subspaces are established for maximum mass flow rate, maximum total pressure ratio, and maximum efficiency, based on which the linear surrogate models are obtained. Next, the chordwise tip blade loading is optimized, after which the rotor efficiency at the design point is increased by 1.1%, while the total pressure ratio remains nearly unchanged. Finally, the flow field is analyzed to understand the mechanism for this performance improvement, and the results show that the optimized blade loading reduces the aerodynamic losses caused by shock-induced flow separation and the interaction between shocks and tip leakage flows.

Parameter study of waste shiitake substrate/waste polyethylene Co-gasification using Aspen Plus kinetic modeling

Waste Shiitake Substrate, a major agricultural waste in Taiwan, is typically packaged in plastic bags (Waste Polyethylene, PE) during mushroom cultivation process. Consequently, these plastic bags become additional waste that requires proper disposal. In recent years, Taiwan has produced over 150,000 tons of waste shiitake substrate annually, with approximately 1580 tons of plastic bags used for mushroom cultivation. Up to now, there has not been an effective method for handling this waste. This study aims to develop a co-gasification process using the complementary characteristics of WSS and PE. Unlike traditional direct combustion, the co-gasification approach can convert these wastes into cleaner bioenergy. This study aims to develop an Aspen Plus model for a laboratory-scale 1 kWth bubbling fluidized bed gasifier. This model incorporates kinetic reactions and tar formation during co-gasification. The model accurately predicted the experimental results. Different variables were investigated, including gasifier temperature, blending ratio (BR) of the two fuels, mixing ratio (MR) of the gasifying agent, and equivalence ratio (ER). The results showed that hydrogen production correlated positively with the steam-to-carbon ratio in the gasification medium, whereas carbon monoxide (CO) was more affected by the feedstock type and equivalence ratio, with CO reaching its peak at an equivalence ratio of 0.2. When gasifying using only waste shiitake substrate (BR = 0%), at an ER of 0.2, a gasification furnace temperature of 950 °C, and an MR of 100% (pure CO2), the maximum CO mass flow rate in the syngas is obtained. Waste plastics contain significant amounts of volatile matter and no oxygen, leading to increased production of CH4, CO, and H2 during co-gasification with the addition of waste plastic. For plastics, high temperature and low ER conditions promote the production of CO, H2, and CH4 because of the significant tar content, thereby enhancing the Cold gas efficiency (CGE). When the gasification temperature is 950 °C, with 80% polyethylene (BR = 80%) and an ER of 0.1, the highest HHV is achieved. These results can serve as a reference for determining the operational conditions for the scale-up of gasification systems.

Effect of applying serpentine channels and hybrid nanofluid for thermal management of photovoltaic cell: Numerical simulation, ANN and sensitivity analysis

Regarding the importance of thermal management of solar PV cells to achieve higher efficiency and electricity output, a novel configuration by use of serpentine channels for cooling is proposed and numerically investigated in the present article. Moreover, a hybrid nanofluid, (MWCNT)-Fe3O4/water, is employed as the coolant to investigate its potential in further improvement of thermal management. Computational Fluid Dynamics (CFD) is applied to numerically simulate the systems and investigate the impacts of different factors. Performance of the proposed configuration is compared with cooling channels with simple structure without nanofluids. Simulations results revealed that the employment of serpentine channels leads to modification in the thermal management of the cell compared with the simple channel. The maximum improvement rate in this condition compared with simple channels is around 9.63 % that is obtained in case of maximum mass flow rate of coolant and solar radiation intensity. Despite increment in pressure loss by using the serpentine channel compared with the simple channel, 2.6 ×10−3 W and 9.3 ×10−4 W, respectively, in mass flow rate of 0.003 kg/s for water, increase in the generated electricity is much more in this case. Furthermore, numerical results show that applying the hybrid nanofluid with 0.1 % concentration can cause slight reduction in the temperature compared with using water. Moreover, Group Method of Data Handling (GMDH) and Multilayer Perceptron (MLP) neural network as intelligent methods used for estimation of the cell temperature and the maximum error for the developed model is approximately 1.1 % and 0.098 % for the GMDH- and MLP-based models, respectively. Finally, sensitivity analysis is implemented and it is shown that solar radiation intensity is the most influential factor on the cell temperature in condition of using serpentine channels while mass flow rate of the coolant has the minimum relevancy factor and consequently effect on the temperature of the solar cell.

Exploring sustainable agriculture: Investigating the impact of controlled release fertilizer damage through bonded particle modeling

Controlled release technology of chemical fertilizers is an important cornerstone for the efficient development of sustainable agriculture. Damage to the coating layer and fragmentation of particles during the application of controlled release fertilizers can lead to the loss of their controlled release properties, making the development of effective damage reduction operations a key focus in the study of such agricultural materials. Therefore, this paper employs the bonded particle model (BPM) method within the discrete element method (DEM) framework to investigate the mechanism of coating damage in controlled-release fertilizers. It establishes a classification of damage types based on the level of damaged particles as an effective analytical approach. Furthermore, a comparative analysis is conducted between the discrete element particle model (DEPM) method and the bonded particle model method in terms of their performance in discharge mechanics and flow characteristics. The results indicate that the breakage rate of fertilizer discharge is influenced by both the formation of a steady state and the depletion of the fertilizer load within the container, with an average breakage rate of 1.511% over the total period. Differences in the average maximum compression force and mass flow rate between the discrete element particle model group and the bonded particle model group were 60.355 N and 1.998 g/s, respectively, reflecting limitations imposed by the fertilizer models on expected damage deformation behaviors. This study elucidates the process and potential impacts of fertilizer particle damage and deformation, revealing the strengths and limitations of two simulation model approaches under different application conditions, providing insights for sustainable agricultural production and technological innovation in fertilization equipment.

Mathematical and Experimental Simulation of Operating Modes of Capillary Emitter of Electrostatic Colloidal Microthruster

This work experimentally and theoretically analyzes the dynamics of the process of ion emission from a capillary emitter filled with an ionic liquid as a working fluid. Such emitters can be used in the energy system of low-mass satellites as a source of jet propulsion. The dependence of the thrust of a micromotor on the electrical power supplied to it was experimentally studied, which made it possible to determine the most efficient operating modes of the microthruster. This is of interest from the point of view of increasing the energy efficiency of the latter in conditions of limited power availability of low-mass satellites. It was found that the characteristic “electric field voltage – emitter thrust” is non-monotonic with a pronounced maximum, which imposes restrictions on the magnitude of the electric field in the emitter. To explain the limit of emission intensity, a diffusion-convective model of ion movement inside the capillary was constructed. The main idea of the proposed model is the assumption that the intensity of ion emission is determined by their concentration at the outlet of the capillary, and the velocity of the emitted ions is higher than the velocity of flow of the ionic liquid in the capillary as a continuous medium. Moreover, the acceleration of ions at the outlet of the emitter increases nonlinearly with increasing external forces. The decrease in the concentration of ions as they are emitted must be compensated by their diffusion inside the capillary and convective flows, the velocity of which is limited. The constructed system of equations is analyzed numerically. For the system of Navier – Stokes equations, the projection method proposed by Chorin is applied. Based on the known velocity field, density, and concentration distribution, a time step is taken for the equations of motion. Then, taking into account the found velocity, a time step is taken for the convective diffusion equations and the density field is recalculated. The created code made it possible to confirm the possibility of the existence of a maximum mass flow rate of ions, i.e., micromotor thrust, which is in qualitative agreement with the experimental data. The main factor on which the magnitude of the maximum and its position depend is the degree of nonlinearity of the coefficient responsible for the acceleration of ions at the outlet of the capillary.

Improving heat transfer in indirect liquid-based battery thermal management systems through turbulator-equipped conical flow paths

To guarantee the safe operation of Li-Ion Cells (LICs) in various applications, such as electric vehicles, an efficient Battery Thermal Management System (BTMS) is necessary. The design of BTMSs, as documented in the literature, typically involves the use of cooling channels with uniform and smooth configurations. However, these configurations encounter the challenge of temperature non-uniformity in the battery module, which stems from elevated coolant temperatures along the flow direction. In this study, a 3D numerical analysis is conducted to develop a novel indirect liquid-based cooling system for the BTMS of a module with cylindrical LICs. The study explores the effects of conical cooling channels, both with and without twisted turbulators, across various coolant mass flows during a 2C discharge process of LICs. Within the studied ranges, diverging cooling channels improve the overall thermal and hydraulic performance of the BTMS by an average of 40%, increasing the heat transfer coefficient by a maximum of 32.6%, and decreasing pressure drop by up to 35.1%. The application of turbulators proves effective in reducing the maximum temperature difference within the LICs, demonstrating a decrease of approximately 34.2% at the minimum mass flow rate and 74.4% at the maximum mass flow rate. This emphasizes the more substantial impact of turbulator utilization at higher coolant mass flow rates. An increased coolant flow rate leads to a significant enhancement of the heat transfer coefficient, ranging from 70.5% to 79.0% for the BTMS incorporating turbulators. Moreover, the study highlights a more pronounced impact of increasing mass flow rates in the BTMS designed with converging cooling channels compared to those designed with diverging channels. Finally, the results of this analysis demonstrate that the proposed system is capable of efficiently regulating the temperature of the entire battery module, ensuring that it consistently maintains a normal and safe operational range suitable for vehicular applications (below 40 °C).

Mean-line analysis and optimal design of turbines using a proper algorithm for choked conditions

Compressible flow turbines usually work under choked conditions, requiring an analysis for the performance estimation. The Mean-line modeling is a fast and accurate method extensively used for the analysis and design purposes. However, it has not already been well-investigated for axial flow turbines specially in choked conditions. The present study investigates the issue from three novel aspects. First, a detailed study is accomplished on the inconsistencies of Mean-line method respect to the physics of real flows. It is discussed that the conditions related to maximum mass flow rate through a nozzle and the Mach number one at the throat are different. In fact, the latter condition is not quite physical. Second, a complete algorithm is utilized to implement the aforementioned considerations for the analysis of turbines. This algorithm includes an innovative Blade Solution Algorithm (BSA) and Turbine Solution Algorithm (TSA). The BSA solves the blade rows of turbine using the basic laws of Physics and real-gas properties. In the TSA, a robust and efficient procedure is presented so the solution of turbine converges in wide ranges of boundary conditions with minimum iterations. The results demonstrate that the algorithm generate close maps to the previous studies. Eventually in the third part, since a fast and robust Mean-line algorithm is crucial in optimization, the code is utilized for a design based on optimization using the Genetic Algorithm. In this procedure, all geometrical parameters are optimized as decision parameters rather than the use of old and approximate correlations. This is done along with novel constraints, which not only maximizes efficiency, but also puts the output power, mass flow rate and turbine size in appropriate ranges. The optimization results in a 3.5% rise in efficiency.

Optimization of multi-staged Tesla valve using response surface methodology

The multi-stage Tesla valve (MSTV), which consists of multiple identical TVs in series, enhances the effectiveness of the TV. To further improve the performance of the MSTV, an improved MSTV has been proposed by designing each arch channel in the typical MSTV as two separate arch channels: the inner arch channel and the outer arch channel. Response surface methodology is used to optimize the improved MSTV, with the maximum mass flow rate in forward flow and the minimum mass flow rate in reverse flow as two optimization objectives. The non-dominated sorting genetic algorithm is employed to obtain the Pareto solution set, resulting in the optimized design for the improved MSTV (named short-baffle improved MSTV). Theoretical simulations and experimental research are conducted on a typical MSTV, an improved MSTV, and a short-baffle improved MSTV, and their flow resistance ratios (FRRs) are obtained. The FRR of the short-baffle improved MSTV has improved by an average of 8.70% compared to that of typical MSTV. At low inlet pressures, the increase in FRR is approximately 1.4% higher than that at high inlet pressures. The research results indicate that the FRR of the shot-baffle improved MSTV is greater than that of a typical MSTV, and to some extent, the performance of an MSTV is enhanced under low inlet pressure.

Gravity-driven powder flow and the influence of external vibration on flow characteristics

The controlled and homogeneous flow of dry granular powders through hoppers is essential for applications, namely, packaging of food grains, fertilizers and additive manufacturing processes such as directed energy deposition for better product quality. One of the major issues encountered in the granular flows through hoppers is flow stagnation due to the well-known arching phenomenon. Vibration-assisted granular flow through hoppers is one of the mechanisms used for better mass flow control. In this work, the influence of external mechanical vibration on the powder flow is investigated experimentally and using discrete element simulations. First, the mass flow rate through the hopper increases with an increase in vibration amplitude and then decreases, signifying the existence of an optimal amplitude of vibration. The DEM simulations explained the underlying mechanisms for the existence of an optimal amplitude of vibration corresponding to the maximum mass flow rate. A range of vibration amplitudes from 0 mm to 3.5 mm is used to study the flow behaviour; the maximum flow of around 33 g/s to 35 g/s is observed for 0.75 mm to 1.25 mm vibration amplitude for the hopper-particle combination studied in this work. The work also reports the influence of vibration frequency, hopper, and particle dimension on the flow characteristics. The research facilitates the effective use of mechanical vibration to enhance powder flow that can further be extended to non-spherical and multi-material particles.

Flow physics of annular and semi-annular fanjet and integration scheme with aircraft wing

Aerodynamic forces created on the lifting body, like an aircraft wing, can be optimized by modifying the flow field around it. These aerodynamic forces directly influence fuel consumption, thus the economy of flight. Various techniques have been developed and tested on wings for improving aerodynamic efficiency. The present work deals with the integration schemes of fanjets with aircraft wings for the same reason. Fanjets, like bladeless fans, can induce and entrain surrounding air for generation of lift and thrust; however, they are not yet integrated with the wing for modification of aerodynamic forces. In this novel research, the flow physics of the fanjet is explored by varying various geometric parameters. With an increase in the fanjet radius, the mass flow rate decreases, whereas the drag increases. A similar trend was observed for an increase in the jet width. For variation in the angle of attack, the maximum mass flow rate and minimum drag were observed at an angle of 0°. A similar analysis was carried out for semi-annular fanjets. Based on the results, the preferred selection for geometric parameters of annular and semi-annular fanjets was documented for integration with the aircraft wing.

Mass-Flow Simulation in Air-Intake Models at Subsonic Mach Numbers Using Diffuser of Wind Tunnel As Passive Ejector

In order to ensure adequate mass-flow rate at low Mach numbers through air-intake models in a blow-down wind tunnel, the diffuser of the wind tunnel was used as a passive ejector. The ejector action was accomplished by interconnecting the exit plane of the intake model to a low-pressure region downstream of the choked second throat of the tunnel. Due to the reduced back-pressure, there was a significant acceleration of the entry flow, as indicated by nearly doubling of the inlet velocity. Measurements indicate that for an aircraft air-intake model, as well as a submerged air-intake model, the maximum mass flow rate achievable through the control plug was accomplished even at the lowest Mach number of 0.30, obviating the need for using an active ejector system.

Experimental study on energy-exergy performance of single-phase natural circulation loop using mono/hybrid nano-oils

Thermal/vegetable oil-based mono/hybrid nanofluids (Nano-oils) may be potential working fluids in single-phase natural circulation loops for medium temperature applications due to their favorable thermophysical properties (high thermal expansion coefficient and low viscosity) and high Prandtl number; however, not studied yet. Hence, the present study investigates the different nano-oils in a natural circulation loop. Therminol-VP1 and soybean-based mono/hybrid nano-oils with different nanoparticles (Al2O3, CuO, SiC, and MWCNT) are used at a volume fraction of 0.1%. The influence of power input and loop inclination on the energy-exergy performance parameters (Effectiveness, Entropy generation rate and Induced mass flow rate) are presented. The use of nano-oil shows enhanced heat exchanger effectiveness and lower entropy generation rate, whereas the induced mass flow rate may increase or decrease depending on nanoparticle shape and power input. Al2O3+MWCNT nano-oil exhibits superior performance, with a maximum mass flow rate reduction of 8%, effectiveness enhancement of 36%, and entropy generation reduction of 20% as compared to base oil. Therminol-VP1 shows quick flow establishment than soyabean oil. The usage of nano-oil is more beneficial at the higher power input. Loop inclination reduces the mass flow rate while increasing the effectiveness and entropy generation; however, mass flow reduction is much lower for counter-clockwise inclination.

Numerical simulation of fuel supply of multi-tandem fuel tanks in flight vehicle

Multi-tandem fuel tanks have a complex structure, low flow rate between tanks, and, unlike single-fuel tanks, uneven pressure distribution, which makes their fuel supply and pressurization difficult to control. This paper uses a volume-of-fluid model based on the finite-volume method to track the fuel motion in different states of a flight vehicle and obtains the liquid-surface sloshing and the liquid flow in the connecting pipe. The model uses the dynamic meshing technique combined with the pressure at the solid wall to track the motion of the one-way stop valve diaphragm in the connecting pipe, thereby better predicting the fuel transfer in the connecting pipe. The calculation covers the whole process of flight vehicle erection, standby, flight, pumping, and pressurization and provides the distribution of pressure in different fuel tanks and the fuel flow characteristics in the connecting pipe. The calculation results are consistent with the experimental results, which verifies the accuracy of the model. By calculating different working cases, the results show that the different states of the flight vehicle strongly affect the sloshing of the liquid in the fuel tank, the pressure distribution, and the opening and closing of the valves. The maximum mass flow rate through the three valves, pressure at the bottom of the tank, and pressure at the pumping port all increase after the pressurization in the fuel tank. The flow of fuel between different tanks can be increased by changing the structure of the connecting pipe, which affects the pressure at different locations in the tank and at the pumping port.

Performance Optimization of Nozzle-Diffuser Piezoelectric Micropump with Multiple Vibrating Membranes by Design of Experiment (DOE) Method

During recent years, microfluidics based microelectromechanical systems (MEMSs) have found multiple applications in biomedical engineering. One of their most important implementations is fluid transfer in microliter and nanoliter scales. Nowadays, micropumps are extensively used in various medical applications such as drug delivery. In this study, the performance of a piezoelectric micropump is investigated and optimized. This micropump consists of a pump chamber and three deformable walls in a nozzle-diffuser shape, which are used to create pressure gradient between the inlet and outlet. The performance of the micropump is evaluated by transient Computational Fluid Dynamics (CFD) simulation using dynamic mesh. Then its performance is optimized using the Design of Experiment (DOE) method based on mean net outlet mass flow rate and flow reversibility at the pump outlet. The results indicate an improvement of 34.5% in mean net outlet mass flow rate and a significant decrease in reversibility. The maximum mean net outlet mass flow rate and the minimum reversibility corresponding to the optimum geometries are 95.82 mL/min and 0.05%, respectively.

Determination of hydrogen production performance with waste exhaust gas in marine diesel engines

Steam-methane reformers are one of the most effective environmental systems used to obtain hydrogen with the effect of temperature. This study investigated hydrogen production efficiency numerically with exhaust waste heat. Two different scenarios were studied parametrically at five various engine loads. In this study, steam methane reactor temperature change, hydrogen, CO and CO2 formation amounts were determined according to each exhaust temperature and mass flow rate. As a result of the study, the temperature changes for the scenario 1 and scenario 2 conditions of the steam methane reformer were examined and it was found that the maximum temperature change was 26.7% at the 25% engine load condition. The maximum hydrogen production mass flow rate in proportion to the temperature was approximately 7020 g/h in scenario 2 at 25% engine load condition. Radical CO formation showed that system performance is not realized efficiently enough. The study's significant finding is that increasing the temperature and using catalysts throughout the system increases hydrogen production.

Effects of Radiator Angle and Sidepod Profile on Aerodynamic Performance of a Race Car

In Formula Society of Automotive Engineers (FSAE) cars engine heat management serves as an important factor for the performance of the vehicle. Therefore, a proper design of sidepod is crucial for optimal cooling of the engine since sidepods are designed to direct the airflow through the radiator. Also, since sidepods play an important role in the aerodynamic performance of the vehicle, factors such as drag and lift must also be considered along with the cooling of the engine. This paper brings forth the methodology carried out to design the sidepods effectively. First the optimal radiator angle is determined on which the maximum mass flow rate of air through the radiator core is observed. Angles are varied from 50, 70 and 90 degrees on various orientations with respect to the car. Fixing this radiator angle, various inlet and outlet areas of the sidepod are analyzed. Choosing the model with least drag and lift coefficient the sidepod is analyzed by sealing it at various sides. Finally, the effects of gills are also analyzed for better optimization of the sidepod. The models are designed in Solidworks and the CFD simulations are carried out in Simscale. Half car simulation is performed with symmetry conditions in order to reduce the cell count. The results of the analysis showed that the radiator angled forward with a diverging type sidepod yields in the better cooling of the engine.

Physicomechanical properties of raw and comminuted pine and poplar shavings: energy consumption, particle size distribution and flow properties

The aim of this study was to assess the energy consumption during milling and cutting-milling of pine and poplar shavings and the determination of particle size distribution (PSD) characteristics and mechanical properties of these materials. Cutting-milling process required less energy (in kJ·kg–1) than milling but maximum mass flow rate of shavings was significantly higher and thus the effective power requirement of the knife mill during cutting also was higher. Comminution of plastic poplar shavings was more energy-consuming than harder pine shavings. These features influenced PSD, which was approximated with four mathematical models: Rosin–Rammler-Sperling-Bennett (RRSB), normal, logistic and lognormal. On the basis of the best fitting (Radj2) for RRSB, detailed PSD parameters were calculated and all PSDs were described as ‘mesokurtic’, ‘fine skewed’ and ‘well-graded’. In comparison to milled shavings, cut-milled shavings had higher density, but were less compressible and had lower unconfined yield strength. However, cut-milled shavings had higher flowability because of lower cohesion and internal friction angles, because after cutting-milling particles were more spherical than elongated particles after milling. Cut-milled poplar shavings had more favourable mechanical parameters and better PSD characteristics, but required more energy for comminution than pine shavings.

Analysis of fluid-structure interaction in a directional permeability membrane in pressure-driven flow

Finite volume and finite element analysis of fluid-structure interaction is performed to understand the behavior of a directional permeability membrane in pressure-driven flow. The membrane is comprised of two flexible porous sheets separated by a spacer. The porous sheets each have a different thickness with pores that are offset from each other. The design allows flow when the thicker sheet is on the high pressure side, but prevents flow if the pressure gradient is reversed. Flow through the membrane is studied for a pressure range of 0.01–0.1 m H2O in forward flow to understand the complex fluid motion and dependence of membrane deformation on sheet thickness, downstream pore diameter, and initial gap between the sheets. In forward flow, maximum mass flow rate of 0.2 g s−1 (or flow rate of 12.024 ml min−1) can be obtained at 0.1 m H2O pressure head. Reverse flow conditions are modeled to study the effect of design parameters on the required closing pressure, indicating that as little as 0.0325 m H2O of pressure head is required for closing.