volume flow rate
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Author(s):  
Chems Anwar ◽  
Abdeslam Benamara ◽  
Abdelhak Kaci

This preliminary work deals with potential use of additive manufacturing to print a bio-based composite. For this, mixture of clay and flax fibers was used. First, we proceeded to the optimization of the printability conditions by ensuring that the water dosage allows a good extrusion with a continuous volume flow rate. Moreover, the yield stress obtained must allow to deposit several layers without loss of stability. This criterion was verified and then we printed a square element of 20 cm length where 4x4x16cm3 specimens were cut and used to evaluate bending strength. We have shown that under some conditions we are able to print with different layers this composite. To improve the limit height of a printed element, additional tests are necessary to increase the resistance of this type of composite. This study will be continued by Optimizing mix design using other additives and introducing of reinforcement.


2022 ◽  
Vol 10 (1) ◽  
pp. 57
Author(s):  
Lei Jiang ◽  
Ling Bai ◽  
Peng Xue ◽  
Guangjie Peng ◽  
Ling Zhou

The slurry pump is one of the most important pieces of equipment in mineral transportation and separation systems, and it has complex two-phase flow characteristics and wear mechanisms. By employing numerical and experimental methods, the solid–liquid two-phase flow characteristics and wear patterns were investigated in this study. A two-way coupling discrete phase model (DPM) method was used to predict the flow pattern and the wear location and shows good agreement with the experimental observations. The pump performance characteristics of numerical results under pure water conditions were consistent with the experimental results. The effects of particle parameters and operating conditions on the internal flow field and wear were compared and discussed. The results show that the wear degree increased with the increase in volume flow rate and solid volume fraction. With the increase in particle size, the wear range at the impeller inlet became significantly smaller, but the wear degree became obviously larger. This study provides a basis for reducing the wear and improving the hydraulic performance of slurry pumps.


Author(s):  
Martin Kriegel ◽  
Anne Hartmann ◽  
Udo Buchholz ◽  
Janna Seifried ◽  
Sigrid Baumgarte ◽  
...  

There is uncertainty about the viral loads of infectious individuals required to transmit COVID-19 via aerosol. In addition, there is a lack of both quantification of the influencing parameters on airborne transmission and simple-to-use models for assessing the risk of infection in practice, which furthermore quantify the influence of non-medical preventive measures. In this study, a dose–response model was adopted to analyze 25 documented outbreaks at infection rates of 4–100%. We show that infection was only possible if the viral load was higher than 108 viral copies/mL. Based on mathematical simplifications of our approach to predict the probable situational attack rate (PARs) of a group of persons in a room, and valid assumptions, we provide simplified equations to calculate, among others, the maximum possible number of persons and the person-related virus-free air supply flow necessary to keep the number of newly infected persons to less than one. A comparison of different preventive measures revealed that testing contributes the most to the joint protective effect, besides wearing masks and increasing ventilation. In addition, we conclude that absolute volume flow rate or person-related volume flow rate are more intuitive parameters for evaluating ventilation for infection prevention than air exchange rate.


Author(s):  
Hamidou Benzenine ◽  
Said Abboudi ◽  
Rachid Saim

In this paper, a two-dimensional numerical study of heat exchange by forced convection of an incompressible laminar flow in a solar air heater duct (SAH), which is equipped with a shoulder attached to the absorber, was performed. The impact of three locations of this shoulder and their three heights on friction losses, as well as the drag coefficient, the variations of velocity, and temperature at the exit section of the SAH, were analyzed for a volume flow rate in the range [20-80 m3/h.]. The results obtained numerically prove that the insertion of a shoulder on the absorber improves the heat transfer and the dynamics of the flow very significantly. An average temperature difference (inlet-outlet) of the collector of 23.51 °C at 29.94 °C and 50.64 °C at 67.53 °C is acquired respectively for the high and the low flow rates. This paper also showed that the height of the shoulder used can ensure an acceleration of the flow with an axial variation of the order of 1.25 up to 2.5 times (> twice) compared with the simple case.


Axioms ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 344
Author(s):  
Guanqiang Dong ◽  
Mingcong Deng

Heat exchangers are commonly used in various industries. A spiral-plate heat exchanger with two fluids is a compact plant that only requires a small space and is excellent in high heat transfer efficiency. However, the spiral-plate heat exchanger is a nonlinear plant with uncertainties, considering the difference between the heat fluid, the heated fluid, and other complex factors. The fractional order derivation model is more accurate than the traditional integer order model. In this paper, a parallel fractional order derivation model is proposed by considering the merit of the graphics processing unit (GPU). Then, the parallel fractional order derivation model for the spiral-plate heat exchanger is constructed. Simulations show the relationships between the output temperature of heated fluid and the orders of fractional order derivatives with two directional fluids impacted by complex factors, namely, the volume flow rate in hot fluid, and the volume flow rate in cold fluid, respectively.


2021 ◽  
Vol 2021 (6) ◽  
pp. 5360-5365
Author(s):  
TOMAS BLEJCHAR ◽  
◽  
SYLVA DRABKOVA ◽  
VACLAV JANUS ◽  
◽  
...  

The energy efficiency of systems, equipment, and sensors is nowadays intensively studied. The new generation of microelectronic sensors is very sophisticated and the energy consumption is in the microwatts range. The energy to power the microelectronic devices can be harvested from oscillating flow in small size channels and so replaceable batteries could be eliminated. Piezoelectric elements can convert energy from oscillation to electrical energy. This paper focuses on the simulation of periodic flow in the fluidic oscillator. CFD simulations were performed for several values of the flow rate. Experimental measurement was carried out under the same conditions as the CFD experiment. The main monitored and evaluated parameters were volume flow rate and pressure loss. Fluid oscillations were analysed based on CFD simulations and the theoretical maximum energy available for the deformation of piezoelectric elements and transformable into electrical energy was evaluated.


Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1530
Author(s):  
Makhsuda Juraeva ◽  
Dong-Jin Kang

A new passive micro-mixer with mixing units stacked in the cross flow direction was proposed, and its performance was evaluated numerically. The present micro-mixer consisted of eight mixing units. Each mixing unit had four baffles, and they were arranged alternatively in the cross flow and transverse direction. The mixing units were stacked in four different ways: one step, two step, four step, and eight step stacking. A numerical study was carried out for the Reynolds numbers from 0.5 to 50. The corresponding volume flow rate ranged from 6.33 μL/min to 633 μL/min. The mixing performance was analyzed in terms of the degree of mixing (DOM) and relative mixing energy cost (MEC). The numerical results showed a noticeable enhancement of the mixing performance compared with other micromixers. The mixing enhancement was achieved by two flow characteristics: baffle wall impingement by a stream of high concentration and swirl motion within the mixing unit. The baffle wall impingement by a stream of high concentration was observed throughout all Reynolds numbers. The swirl motion inside the mixing unit was observed in the cross flow direction, and became significant as the Reynolds number increased to larger than about five. The eight step stacking showed the best performance for Reynolds numbers larger than about two, while the two step stacking was better for Reynolds numbers less than about two.


2021 ◽  
Vol 11 (23) ◽  
pp. 11542
Author(s):  
Robert Stefan Vizitiu ◽  
Andrei Burlacu ◽  
Cherifa Abid ◽  
Marina Verdes ◽  
Marius Costel Balan ◽  
...  

One of the biggest challenges the world is facing these days is to reduce the greenhouse gases emissions in order to prevent the global warming. Since a significant quantity of CO2 emissions is the result of the energy producing process required in industry or buildings, the waste heat recovery is an important aspect in the fight for preserving the planet. In this study, an innovative waste heat recovery system which can recover waste heat energy from cooling liquids used in industry or in different processes, was designed and subjected to experimental investigations. The equipment uses heat pipes to capture thermal energy from the residual fluids transiting the evaporator zone and transfer it to the cold water transiting the condenser zone. The efficiency of the heat exchanger was tested in 9 scenarios, by varying the temperature of the primary agent to 60, 65 and 70 °C and the volume flow rate of the secondary agent to 1, 2 and 3 L/min. The temperature of the secondary agent and the volume flow rate of the primary agent were kept constant at 10 °C, respectively 24 L/min. The results were later validated through numerical simulations, and confirmed that the equipment can easily recover waste thermal energy from used water with low and medium temperatures at very low costs compared to the traditional heat exchangers. The results were promising, revealing an efficiency of the equipment up to 76.7%.


2021 ◽  
pp. 112972982110609
Author(s):  
Erik Mulder Pettersen ◽  
Jørgen Avdal ◽  
Stefano Fiorentini ◽  
Øyvind Salvesen ◽  
Jonny Hisdal ◽  
...  

Background: Controversy exists regarding surveillance of arteriovenous fistulas for hemodialysis to increase patency. A significant reduction in volume flow rate (VFR) should lead to diagnostic evaluation and eventually intervention. Several methods are available for VFR measurements, but all of them are associated with low reproducibility. VFR trend analysis is suggested as an improved solution. It is therefore a need to find user-friendly, cost and time-effective modalities. We present a novel Doppler ultrasound device (earlybird) which could bridge this gap. It includes an easy-to-use and light-weight single element transducer. Methods: In an experimental and clinical setting, we compared earlybird to duplex ultrasound to assess VFR. In a closed circuit of blood-mimicking fluid, 36 paired calculations of calibrated, duplex ultrasound and earlybird VFR was measured. In addition, 23 paired recordings of duplex ultrasound and earlybird VFR was measured in 16 patients with underarm arteriovenous fistulas. Pearson correlation, intraclass correlation coefficient, root-mean-square and Bland-Altman plots were analyzed. Results: Strong correlation ( r = 0.991, p < 0.001), and excellent level of agreement (ICC = 0.970 (95% CI 0.932 - 0.985), p < 0.001) between earlybird and the calibrated VFR was found in the experimental setup. This was confirmed in the clinical setting, with a strong correlation ( r = 0.781, p < 0.001) and moderate to good level of agreement (ICC = 0.750 (95% CI 0.502–0.885), p < 0.001) between earlybird and duplex ultrasound VFR measured at the arteriovenous fistulas outflow veins. In the Bland-Altman plot-analysis for the experimental setup, we found smaller limits of agreement, a smaller consistent and proportional bias, as well as greater accuracy of earlybird than DUS when compared to the calibrated VFR. Conclusion: Earlybird is a feasible tool for VFR measurements and could be a future promising device for easy assessment and surveillance of AVF for hemodialysis.


2021 ◽  
Vol 15 (4) ◽  
pp. 254-259
Author(s):  
Paweł Dzienis

Abstract In the present paper, the influence of bubble size on liquid penetration into the capillary was experimentally and numerically studied. In the experiment, bubbles were generated from a glass capillary (with an inner diameter equal to 1 mm) in a glass tank containing distilled water, tap water or an aqueous solution of calcium carbonate. These liquids differ in the value of their surface tension, which influences the bubble size. During experimental investigations, air pressure fluctuations in the gas supply system were measured. Simultaneously, the videos showing the liquids’ penetration into the capillary were recorded. Based on the videos, the time series of liquid movements inside the capillary were recovered. The numerical models were used to study the influence of bubble size on the velocity of liquid flow above the capillary and the depth of liquid penetration into the capillary. It was shown that the air volume flow rate and the surface tension have the greatest impact on the changes of pressure during a single cycle of bubble departure (Δp). The changes in pressure during a single cycle of bubble departure determine the depth of liquid penetration into the capillary. Moreover, the values of Δp and, consequently, the depth of liquid penetration can be modified by perturbations in the liquid velocity above the capillary outlet.


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