scholarly journals Unsteady Unidirectional MHD Flow of Voigt Fluids Moving between Two Parallel Surfaces for Variable Volume Flow Rates

2012 ◽  
Vol 2012 ◽  
pp. 1-12
Author(s):  
Wei-Fan Chen ◽  
Hsin-Yi Lai ◽  
Cha'o-Kuang Chen
Keyword(s):  
Velocity Profile ◽  
Volume Flow Rate ◽  
Linear Acceleration ◽  
Mhd Flow ◽  
Volume Flow ◽  
Magnetic Field Effects ◽  
Piston Motion ◽  
Transform Method ◽  
Flow Rates ◽  
Parallel Surfaces

The velocity profile and pressure gradient of an unsteady state unidirectional MHD flow of Voigt fluids moving between two parallel surfaces under magnetic field effects are solved by the Laplace transform method. The flow motion between parallel surfaces is induced by a prescribed inlet volume flow rate that varies with time. Four cases of different inlet volume flow rates are considered in this study including (1) constant acceleration piston motion, (2) suddenly started flow, (3) linear acceleration piston motion, and (4) oscillatory piston motion. The solution for each case is elaborately derived, and the results of associated velocity profile and pressure gradients are presented in analytical forms.

Validation of a third-generation Doppler system for studies of detailed aortic flow

1984 ◽  
Vol 247 (5) ◽  
pp. H847-H856
Author(s):  
J. A. Rumberger ◽  
C. F. Fastenow ◽  
D. L. Laughlin ◽  
M. L. Marcus
Keyword(s):  
Velocity Profile ◽  
Volume Flow ◽  
Aortic Diameter ◽  
Doppler Velocity ◽  
Third Generation ◽  
Flow Rates ◽  
Doppler System ◽  
Aortic Hemodynamics

A multigated, third-generation Doppler velocity system has been developed and validated for detailed studies of aortic hemodynamics. The Doppler system employs a single 3-mm, 5-MHz crystal applied to the aorta at a fixed angle with respect to the flow axis and is capable of measuring velocity profile, blood vessel diameter, and integrated volume flow on a continuous, real-time basis. This represents a major developmental advance over existing first-generation, continuous-wave and second-generation, single-gated pulsed Doppler systems. Validation studies have been performed in vitro and in dogs. Aortic diameter was measured simultaneously with the volumetric Doppler system and with sonomicrometer probes. During changes in aortic diameter between 8 and 18 mm (n = 18), produced by temporary pulmonary artery occlusion or epinephrine infusion, quantitative agreement between the Doppler and sonomicrometer probes was found (r = 0.96). Velocity profile measurements and axial velocity values made with the Doppler system compared favorably with hot-film anemometry studies in vitro and in vivo. Although the current system is nondirectional, measurements of phasic aortic volume flow and absolute-time-averaged changes in flow rates showed an excellent correlation with chronically placed electromagnetic flow probes over a broad range of flow rates in vivo (1-5 l/min, n = 36, r = 0.95). This third-generation Doppler system should prove useful in clinical and research studies of detailed aortic hemodynamics.

scholarly journals Effects of Arterial Pco2 and Cerebrospinal Fluid Volume Flow Rate Changes on Choroid Plexus and Cerebral Blood Flow in Normal and Experimental Hydrocephalic Cats

1983 ◽  
Vol 3 (3) ◽  
pp. 369-375 ◽  
Author(s):  
S. Nakamura ◽  
G. M. Hochwald
Keyword(s):  
Blood Flow ◽  
Cerebrospinal Fluid ◽  
Cerebral Cortex ◽  
Choroid Plexus ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Brain Blood Flow ◽  
Choroidal Blood Flow ◽  
Flow Rates

The effect of changes in brain blood flow on cerebrospinal fluid (CSF) volume flow rates, and that of changes in CSF volume flow rates on brain blood flow were determined in both normal and kaolin-induced hydrocephalic cats. In both groups of cats, blood flow in grey and white matter, cerebral cortex, and choroid plexus was measured with 105Ru microspheres during normocapnia, and again with 141Ce microspheres after arterial Pco2 was either increased by 300% or decreased by 50%. Blood flow measurements were also made during perfusion of the ventricular system with mock CSF and repeated during perfusion with anisosmotic mannitol solutions to alter CSF volume flow rate. In 30 normal and 26 hydrocephalic cats, blood flow to the cerebral cortex, white matter, and choroid plexus was similar; only blood flow to the caudate nucleus was greater in normal cats. The weight of the choroid plexus from hydrocephalic cats decreased by 17%. Blood flow in the choroid plexus of all cats decreased by almost 50% following hypercapnia or hypocapnia, without a change in the CSF volume flow rate. There was no change in cerebral or choroidal blood flow when CSF volume flow rate was either increased by 170% or decreased by 80%. These results suggest that choroid plexus blood flow does not limit or affect the volume flow rate of CSF from the choroid plexus. CSF volume flow rate can be altered without corresponding blood flow changes of the brain or choroid plexus. Choroid plexus blood flow and the reactivity of both brain and choroidal blood flow to changes in arterial Pco2 were not affected by the hydrocephalus. The lower CSF formation rate of hydrocephalic cats can be attributed in part to the decrease in the mass of choroid plexus tissue.

Unsteady Unidirectional Flow of Bingham Fluid Through the Parallel Microgap Plates with Wall Slip and Given Inlet Volume Flow Rate Variations

2013 ◽  
Vol 29 (2) ◽  
pp. 355-362
Author(s):  
Y.W. Lin ◽  
C.-I. Chen ◽  
C.-K. Chen
Keyword(s):  
Flow Rate ◽  
Volume Flow Rate ◽  
Flow Behavior ◽  
Linear Acceleration ◽  
Wall Slip ◽  
Transformation Method ◽  
Bingham Fluid ◽  
Volume Flow ◽  
Unidirectional Flow ◽  
Flow Motion

AbstractIn this paper, Laplace transformation method is used to solve the velocity profile and pressure gradient of the unsteady unidirectional flow of Bingham fluid. Between the parallel microgap plates, the flow motion is induced by a prescribed arbitrary inlet volume flow rate which varies with time. Due to the rarefaction, the wall slip condition is existed; therefore, the complexity of solution is also increased. In order to understand the flow behavior of Bingham fluid, there are two basic flow situations are solved. One is a suddenly started flow and the other is constant acceleration flow. Furthermore, linear acceleration and oscillatory flow are also considered. The result indicates when the yield stress τ0 is zero; the solution of the problem reduces to Newtonian fluid.

Influence of two-phase suction injection on performances of the scroll refrigeration compressor with a high-temperature shell

2021 ◽  
pp. 095440892110302
Author(s):  
Shuaihui Sun ◽  
Wang Zhe ◽  
Li Liansheng ◽  
Bu Gaoxuan
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Coefficient Of Performance ◽  
Two Phase ◽  
Flow Rates ◽  
Injection Volume ◽  
Discharge Temperature

The two-phase suction injection can reduce the discharge temperature of scroll refrigeration compressors, which work under a high-pressure ratio. The heat transfer along the pipe axis from the shell affects the two-phase suction injection significantly for the compressor with a high-temperature shell. In this paper, the suction mixing and heat transfer model was developed to calculate the heat transfer along the pipe axis from the high-temperature compressor shell. Then the model was coupled with the two-phase compressor model to obtain the compressor performance under different suction injection volume flow rates. The compressor with two-phase suction injection was tested under different injection volume flow rates to validate the model. The results indicated that the discharge temperature decreased by 2 °C when the mass injection ratio increased by 1%. As the injection volume flow rates increased, the total mass flow rate increased due to the reduction of the specific volume of the suction fluid; the input work decreased because of the reduction of specific work and the improvement of the motor's electric efficiency. The cooling capacity decreased since the cooling capacity of the injection refrigerant was wasted for cooling the suction process and the compressor shell, especially at high injection volume flow rates. The coefficient of performance reached the maximum value at the injection volume flow rate of 0.015 m3·h−1 and became lower than the coefficient of performance without injection when the injection volume flow rate raised to 0.035 m3·h−1. Hence, the two-phase suction injection can reduce the discharge temperature efficiently at low injection volume flow rates with a slight improvement of coefficient of performance.

Three-dimensional multiphase flow modeling of membrane humidifier for PEM fuel cell application

2019 ◽  
Vol 30 (1) ◽  
pp. 54-74
Author(s):  
Seyed Ali Atyabi ◽  
Ebrahim Afshari ◽  
Mohammad Yaghoub Abdollahzadeh Jamalabadi
Keyword(s):  
Flow Rate ◽  
Volume Flow Rate ◽  
Three Dimensional ◽  
Cross Flow ◽  
High Volume ◽  
Volume Flow ◽  
Dew Point ◽  
Multiphase Model ◽  
Flow Rates ◽  
Content Type

Purpose In this paper, a single module of cross-flow membrane humidifier is evaluated as a three-dimensional multiphase model. The purpose of this paper is to analyze the effect of volume flow rate, dry temperature, dew point wet temperature and porosity of gas diffusion layer on the humidifier performance. Design/methodology/approach In this study, one set of coupled equations are continuity, momentum, species and energy conservation is considered. The numerical code is benchmarked by the comparison of numerical results with experimental data of Hwang et al. Findings The results reveal that the transfer rate of water vapor and dew point approach temperature (DPAT) increase by increasing the volume flow rate. Also, it is found that the water recovery ratio (WRR) and relative humidity (RH) decrease with increasing volume flow rate. In addition, all mixed results decrease with increasing dry side temperature especially at high volume flow rates and this trend in high volume flow rates is more sensible. Although the transfer rate of water vapor and DPAT increases with increasing the wet inlet temperature, WRR and RH reduce. Increasing dew point temperature effect is more sensible at the wet side is compared with the dry side. The humidification performance will be enhanced with increasing diffusion layer porosity by increasing the wet inlet dew point temperature, but has no meaningful effect on other operating parameters. The pressure drop along humidifier gas channels increases with rising flow rate, consequently, the required power of membrane humidifier will enhance. Originality/value According to previous studies, the three-dimensional numerical multiphase model of cross-flow membrane humidifier has not been developed.

scholarly journals A comparison of UK domestic water services sizing methods with each other and with empirical data

2017 ◽  
Vol 38 (6) ◽  
pp. 635-649 ◽  
Author(s):  
Jess Tindall ◽  
Jamie Pendle
Keyword(s):  
Empirical Data ◽  
Cold Water ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Design Flow ◽  
Water Volume ◽  
Practical Application ◽  
Domestic Water ◽  
Flow Rates ◽  
Water Service

Evidence suggests that domestic cold water service sizing methods in many countries around the world tend to overestimate the actual peak water volume flow rate. Oversizing domestic water service systems does waste materials and money, but it also increases the length of time that it takes for water to pass through the system which can increase water temperatures with the associated risks that presents. This paper compares the three commonly used UK domestic cold water service sizing methods and reveals variance in the methods, the design flow rates calculated and the amount of diversity applied by each method. BS EN 806 returns the lowest design flow rates of the three methods and also applies significantly greater diversity. Empirical domestic cold water service volume flow rate data from two case study buildings revealed that all three UK sizing methods significantly overestimated the peak water volume flow rates but that BS EN 806 was the closest. Additional empirical data from seven more buildings have been used to validate the data from this study and add confidence to the findings. This research provides useful evidence to help engineers select the most appropriate UK domestic cold water service sizing method and to anticipate the likely range and fluctuation of domestic cold water service flow rates. Practical application: Engineers tend to be conservative by nature and generally err on the side of caution to ensure that there is never any cause for customer complaint about their designs. This is understandable but there can be negative consequences if the full implications of such decisions are not fully understood. This paper reveals significant oversizing compared to empirical data from each of the three UK domestic water service sizing methods and highlights the reasons for this. The practical application of this paper lies in the presented results data and analysis which will help engineers make this important choice between the available sizing methods.

scholarly journals A Novel Non-Intrusive Vibration Energy Harvesting Method for Air Conditioning Compressor Unit

2021 ◽  
Vol 13 (18) ◽  
pp. 10300
Author(s):  
Chuan Choong Yang ◽  
Noor Fiqri Razqi Bin Noor Hanafi ◽  
Noor Hazrin Hany Bt Mohamad Hanif ◽  
Ahmad Faris Ismail ◽  
Hsueh-Hsien Chang
Keyword(s):  
Flow Rate ◽  
Air Conditioning ◽  
Volume Flow Rate ◽  
Piezoelectric Sensor ◽  
Volume Flow ◽  
Vibration Energy ◽  
Compressor Unit ◽  
Flow Rates ◽  
Air Volume ◽  
Custom Made

The purpose of harvesting vibration energy is to obtain clean and sustainable energy by converting vibration energy from ambient sources into a voltage output. In this work, a piezoelectric sensor, PZT-5H is attached to a 3D printed and custom-made mounting to be placed at an air conditioning condenser unit, to harvest vibration energy. The configuration of the harvester is non-intrusive, in which the harvester did not intrude into compressor unit operation. Temperature (20 °C, 22 °C, and 24 °C) and air volume flow rates (3 levels of air volume flow rate at 245 L/second, 274 L/second, and 297 L/second) were taken into consideration in this investigation. An accelerometer was first used to investigate the optimum vibration frequency in Hertz, and six locations were identified. Next, the piezoelectric sensor was mounted at these six locations, and the output root-mean-square (RMS) voltage from the piezoelectric sensor was obtained. The analysis of variance (ANOVA) indicated that temperature and air volume flow rates factors were significant. It was found that the location identified with the highest amount of vibration at 830.2 Hz from accelerometer measurement, was also the highest amount of RMS voltage, at 510.82 mV, harvested by the piezoelectric, from the temperature of 20 °C and air volume flow rates at high level (air flow volume flow rate at 297 L/second). From this work, it is feasible to utilize this novel method of harvesting waste vibration energy from the air conditioning compressor unit.

scholarly journals Experimental Studies of Ethyl Acetate Saponification Using Different Reactor Systems: The Effect of Volume Flow Rate on Reactor Performance and Pressure Drop

2019 ◽  
Vol 9 (3) ◽  
pp. 532
Author(s):  
Ekaterina Borovinskaya ◽  
Valentin Khaydarov ◽  
Nicole Strehle ◽  
Alexander Musaev ◽  
Wladimir Reschetilowski
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Experimental Studies ◽  
Chemical Processes ◽  
Volume Flow ◽  
Reactor Performance ◽  
Flow Rates ◽  
Flow Energy ◽  
Mass And Heat Transfer

Microreactors intensify chemical processes due to improved flow regimes, mass and heat transfer. In the present study, the effect of the volume flow rate on reactor performance in different reactors (the T-shaped reactor, the interdigital microreactor and the chicane microreactor) was investigated. For this purpose, the saponification reaction in these reactor systems was considered. Experimental results were verified using the obtained kinetic model. The reactor system with a T-shaped reactor shows good performance only at high flow rates, while the experimental setups with the interdigital and the chicane microreactors yield good performance throughout the whole range of volume flow rates. However, microreactors exhibit a higher pressure drop, indicating higher mechanical flow energy consumption than seen using a T-shaped reactor.

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