Increment Of Flow Rate Research Articles

Performance evaluation of a multi-stage plate-type membrane humidifier for proton exchange membrane fuel cell

The influence of channel dimension and altering dry air inlet conditions such as temperature and humidity on the humidification efficiency of a multi-stage plate-type membrane humidifier for kW-scale proton exchange membrane fuel cells is analyzed in terms of the dew point approach temperature, water recovery ratio, pressure loss, and the coefficient of performance. Investigating the effect of channel dimension reveals that the width and depth of the channel significantly affect the humidification performance. The results show that the increase of dry air inlet temperature and humidity leads to improving the dew point approach temperature, decreasing the water recovery ratio, slight increasing the pressure drop, and consequently decreasing the coefficient of performance. The minimum dew point approach temperature and maximum water recovery ratio occur at the flow rate of 30 L/min. The highest water recovery ratio, 73%, is achieved at the temperature of 50 °C and relative humidity of 40%. Moreover, the pressure loss increases with the increment of air flow rate and the coefficient of performance declines with the increase of air flow rate. Thus, it is recommended to select the minimum possible flow rate, dry air inlet temperature, and relative humidity as the efficient operating condition.

Experimental investigation on Al2O3-R123 nanorefrigerant heat transfer performances in evaporator based on organic Rankine cycle

This paper presents an experimental investigation of variation tendency of heat transfer coefficient, log-mean temperature difference and differential pressure of pure R123 and 20 nm Al2O3-R123 nanorefrigerants with four various volume concentrations, 0.03%, 0.13%, 0.18%, 0.23% flowing inside the evaporator of organic Rankine cycle system under the conditions of various heat source temperatures and flow rates. Heat source temperatures are in the range of 50–90 °C at an interval of 10 °C, and heat source flow rates are 0.7 m3/h, 1.3 m3/h and 1.8 m3/h. Results show an increment of heat transfer coefficient along flowing direction for both pure R123 and four Al2O3-R123 nanorefrigerants with the increment of heat source temperature and flow rate, and that of four nanorefrigerants are higher than that of pure R123. There is no optimum value of heat transfer coefficient when operation condition is changed for the loading carrying capacity increasing with the increasing intensity of operation condition. Meanwhile, suspending nanoparticles and increasing heat source temperature can change the variation tendency of heat transfer coefficient along flowing direction except pure R123 and 0.18 vol% nanorefrigerant. In addition, 0.13 vol% as a whole is the optimum volume concentration for both log-mean temperature difference and differential pressure.

Nonlinear Flow Characteristics of a System of Two Intersecting Fractures with Different Apertures

The nonlinear flow regimes of a crossed fracture model consisting of two fractures have been investigated, in which the influences of hydraulic gradient, surface roughness, intersecting angle, and scale effect have been taken into account. However, in these attempts, the aperture of the two crossed fractures is the same and effects of aperture ratio have not been considered. This study aims to extend their works, characterizing nonlinear flow through a system of two intersecting fractures with different apertures. First, three experiment models with two fractures having different apertures were established and flow tests were carried out. Then, numerical simulations by solving the Navier-Stokes equations were performed and the results compared with the experiment results. Finally, the effects of fracture aperture on the critical pressure difference and the ratio of hydraulic aperture to mechanical aperture were systematically analyzed. The results show that the numerical simulation results agree well with those of the fluid flow tests, which indicates that the visualization techniques and the numerical simulation code are reliable. With the increment of flow rate, the pressure difference increases first linearly and then nonlinearly, which can be best fitted using Forchheimer’s law. The two coefficients in Forchheimer’s law decrease with the increasing number of outlets. When increasing fracture aperture from 3 mm to 5 mm, the critical pressure difference increases significantly. However, when continuously increasing fracture aperture from 5 mm to 7 mm, the critical pressure difference changes are negligibly small. The ratio of hydraulic aperture to mechanical aperture decreases more significantly for a fracture that has a larger aperture. Increasing fracture aperture from 5 mm to 7 mm, that has a negligibly small effect on the critical pressure difference will however significantly influence the ratio of hydraulic aperture to mechanical aperture.

A comprehensive exergy analysis of a prototype Peltier air-cooler; experimental investigation

Abstract Thermoelectric coolers have been abundantly investigated from the viewpoint of the first law of thermodynamic. However, extremely few exergy analysis have been probed for thermoelectric air-coolers. Because of the importance of exergy consideration in each thermodynamic process, this paper experimentally focuses on the effect of various parameters on exergy destruction and the second law performance through a thermoelectric air cooler. The effects of flow and thermodynamic parameters including air flow rate, incoming air temperature, water flow rate, incoming water temperature, DC voltage/ampere etc. on exergetic characteristics are clarified in this study. Interesting meaningful curve behavior was observed for exergetic performance of thermoelectric cooler. Indeed, curve behavior of exergetic performance is descending-ascending and therefore a critical value of DC voltage was found in which the amount of second law performance has a minimum/maximum value. Increment of air flow rate improved the exergetic performance of Peltier-air cooler. Besides, higher air inlet temperature reduced exergy destruction of thermoelectric module (TEM) which means that Peltier air cooler is appropriate for regions with warmer weather in comparison with moderate climates.

An Experimental Investigation on Flame Pulsation for a Swirl Non-Premixed Combustion

Flame pulsation has a significant effect on combustion, and understanding its oscillatory behavior is important to the combustion community. An experiment was performed to analyze the pulsation characteristics of a swirl non-premixed flame under various parameters. The results showed that as fuel mass flow rate increased, the puffing frequency increased due to the decreased flame radiation fraction, and the puffing amplitude became smaller resulting in a more stable flame. With an increase in combustor pressure, the flickering frequency declined because of the increasing soot radiation, while the flickering amplitude uniformly increased, leading to more deteriorative flame stability. With an increment in mass flow rate of primary air, the puffing frequency decreased due to the enhanced mixing between fuel and primary air. Also, the puffing amplitude had an oscillating relationship with the mass flow rate of primary air. When the exit velocity of the injector was increased, the flickering frequency diminished nearly linearly because of the improving swirl intensity, and the flickering amplitude was approximately unaffected by injector exit velocity. Moreover, the measured puffing frequencies summarized over all cases varied within the range of 3–22 Hz, the predicted values from theoretical models based on non-swirl flame also fell within this range. The puffing frequency of swirl combustion was more sensitive to the variation in operating conditions than that of non-swirl combustion. Additionally, the obtained correlations indicated that the Strouhal number St was proportional to Fr−1.4 (the Froude number) and Re−2.9 (the Reynolds number), respectively.

Experimental study on the heat gain of water in hybrid solar collector integrated with fin-and-tube heat exchanger with respect to air and water flow rate

Solar assisted heat pump system is the system using solar thermal energy that can lead to the improvement of performance of heat pump by transferring solar thermal energy obtained from solar collector to evaporator of the heat pump for evaporation of refrigerant. In traditional system, solar collector can get a thermal energy only from solar radiation. So, the collector is hard to be used when the solar radiation is not enough such as cloudy day or night even though these collector take up much space. Thus the hybrid solar collector that has fin- and-tube heat exchanger have been developed for getting a thermal energy from not only solar radiation but also ambient air. Due to the fin-and-tube heat exchanger, this collector can get a thermal energy from ambient air for heating chilled water by evaporation of refrigerant in heat pump system. At this time, heat gain of water from ambient air by the collector needs to be confirmed before combining with real heat pump system. Thus, in this study, heat gain of water in the hybrid solar collector was investigated experimentally with respect to air and water flow rate on the various temperature difference between inlet air and water. As a results, heat gain of water was shown maximum value of 900W and it was increased with increment of air and water flow rate. Also, heat gain of water was changed linearly with increment or decrement of temperature difference between inlet air and water on the specific air and water flow rate. Furthermore, relationship between heat gain of water and operating conditions was also confirmed that can be used for decision of collector area and heat pump capacity for designing solar assisted heat pump integrated with this collector.

Energy and exergy analysis of the PVT system: Effect of nanofluid flow rate

Solar energy is one of the promising resources to fulfil the energy demands to some level in place of fossil fuels to avoid environmental pollution. The efficiency of solar technology, e.g. photovoltaic panels, thermal systems or a combination of both technologies as photovoltaic thermal is a concern to increase at an optimum level. A three-dimensional numerical analysis of PVT systems using water and MWCNT-water nanofluid has been completed with FEM based software COMSOL Multiphysics®. A numerical investigation has been validated by the indoor experimental research at different mass flow rates of 30 to 120 L/h while keeping solar irradiation fixed at 1000 W/m2, inlet fluid and ambient temperature at 32 and 25 °C, respectively. Percent improvement of electrical efficiency of PV with nanofluid cooling at flow rate 120 L/h is obtained about 10.72 and 12.25% of numerical and experimental cases respectively. Optimization of the nanofluid for weight concentration is achieved at 0.75% MWCNT-water. Solar cell temperature reduces about 0.72 °C experimentally and 0.77 °C numerically per 10 L/h flow rate increment. Approximately 7.74 and 6.89 W thermal energy is enhanced per 10 L/h flow rate increment in numerical and experimental studies respectively. Percentage increment of thermal efficiency is found as 5.62% numerically and 5.13% experimentally for PVT system operated by water/MWCNT nanofluid with compared to water.

Experiment and numerical simulation on seepage failure of sand caused by leakage of underground water pipe

Underground water pipe leakage accident is a serious threat to the city road and people's life safety, the internal mechanism is necessary to carry out related study. In this paper, numerical simulation technology and model test device was used for researching on the effect of different factors on the seepage failure of sand. The research shows that the evolutionary process of sand seepage failure induced by underground water pipe leakage can be divided into three stages: unfluidized stage stable cavity stage and fluidized stage. At the initial stage, the pressure distribution at different height reaches a peak with the increment of water pressure and flow rate. When the water pressure and flow rate is beyond the peak, cavity would occur at leakage hole. Under the action of seepage force, the cavity would dissipate at the surface of soil, and the distribution of fluidized bed pressure would maintain a stable state. Moreover, the smaller the leakage diameter, the greater the critical water pressure is. In a numerical test of a wedge angle of 62 degrees, F (upward drag force) is equal to the W (weight of wedge), which indicates the cavity reaches a force balance. The wedge with an angle of 62 degrees is significant to the sample model used in numerical simulation.

Performance improvement of the R744 two-phase ejector with an implemented suction nozzle bypass

In this study, the concept of an R744 ejector with a bypass duct of a suction nozzle was presented. The design of the geometry and bypass positioning in a mixing section, and the idea of regulation, as well as integration, with a suction nozzle duct was described. A preliminary numerical analysis of the proposed bypass geometry was also presented. The computational platform ejectorPL integrated with an extensively validated mathematical model of transcritical R744 two-phase flow was used. Motive nozzle inlet and suction nozzle inlet conditions reflecting gas cooler and evaporator conditions characteristic of large systems, such as supermarket refrigeration units, were examined. Three different separation pressures in liquid receivers were assumed for two bypass geometries and six bypass inlet positions. The bypass positioning as a function of a mixer length was presented. Uniquely positive results were obtained for the lowest pressure conditions. Namely, the increment of the suction mass flow rate was substantial and equal to 36.9% for the bypass angle of 19°. Hence, the bypass implementation resulted in distinct potential of an efficiency improvement from 22.2% to 30.4%. A higher pressure lift case did not result in any improvement of the ejector work. The influence of the bypass geometry on the overall ejector efficiency was preliminarily characterised. Finally, the pressure distribution in the bypass type ejector was described.

Linear Quadratic Optimal Controller Design for Constant Downstream Water-Level PI Feedback Control of Open-Canal Systems

The key point of PI feedback control is how to design appropriate controller parameters. This paper combined the linear quadratic optimizing control theory to design an online controller for constant downstream water-level operation which could respond to different working condition properly and rapidly avoiding complex controller parameters adjusting. Based on the Integrator-Delay (ID) model simplified from Saint-Venant Equations, we established the discretized linear time invariant system of canals. Then transferred it into the state-space equations and obtained the state-feedback equation. Water level deviations and flow rate increments were chosen to form the objective function and this paper recommended values ofQandRweight matrices among it should be set according to the optimum quadratic form indicators correspondingly. This controller was applied to two practical canal systems which had diverse scales. Results showed the system under control quickly regained stability; optimizing the objective function with recommended weight matrices could well balance demands on water level deviations and flow rate changes; dynamic performances of water movements and gate movements were acceptable. Through simulations, we preliminarily proved the practicability of this online PI controller implementing LQR. This work proposed an available solutions for the design and operation of water conveyance systems around the world.

Experimental investigation of urea injection parameters influence on NOx emissions from blended biodiesel-fueled diesel engines.

The present work submits an investigation about the effect of urea injection parameters on NOx emissions from a four-stroke four-cylinder diesel engine fueled with B20 blended biodiesel. An L9(34) Taguchi orthogonal array was used to design the test plan. The results reveal that increasing urea concentration leads to lower NOx emissions. Urea flow rate increment has the same influence on NOx emission. The same result is obtained by an increase in spray angle. Also, according to the analysis of variance (ANOVA), urea concentration and then urea flow rate are the most effective design parameters on NOx emissions, while spray angle and mixing length have less influence on this pollutant emission. Finally, since the result of confirmation test is in good agreement with the predicted value based on the Taguchi technique, the predictive capability of this method in the present study could be deduced.

Influence of Medium Parameters and Acrylate Ionic Terpolymer Concentration on the Toms Effect

The influence of the solution ionic strength (up to 1.89 M), temperature (up to 413 K) and acidity (pH down to 1.65) on the drag reduction DR and flow rate increment ΔQ of an aqueous solution of the terpolymer containing 71.6 mol % acrylamide, 10.5 mol % acrylonitrile, and 17.9 mol % sodium 2-acrylamido-2-methylpropanesulfonate was studied by capillary turbulent viscometry. The intrinsic performance and the optimum concentrations of the terpolymer under these conditions were determined. The temperature dependence of the flow rate increment for the terpolymer solution passes through a maximum. The turbulence drag reduction for water flows at temperatures exceeding 373 K was demonstrated.

Luminescent Properties of SiC Thin Film Deposited by VHF-PECVD: Effect of Methane Flow Rate

Bulk silicon carbide (SiC) as light emitter is less efficient due to its indirect bandgap. Therefore, nanosized SiC thin film fabrication approach enable emission wavelength shifts due to spatial confinement. The result of luminescent study of SiC thin film deposited via very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) are presented. Precursor gasses used were silane and methane. Methane flow rate was varied from 8 sccm to 20 sccm while other parameters were maintained. Raman spectral analysis denotes the quantum confinement effect occurrence in proportion to the methane flow rate increment. The luminescence properties of the deposited SiC thin film ranging from highly green emission (~518 nm) to highly UVB emission (~294 nm) dominant luminescence. Broad blue emission band shifted toward higher wavelength with smaller FWHM as methane flow rate is increased. This results enable the possibility of luminescent SiC thin film applications in photonics and electronic integration as blue light sources.

Antiturbulent properties of sulfomethylated polyacrylamide under the conditions of thermal, salt, and acid aggressions

Nonionic polyacrylamide with the weight-average molecular mass of 7 MDa was modified by sulfomethylation. The composition of sulfomethylated polyacrylamides was determined by iodometric titration, Fourier IR spectroscopy, thermal gravimetric analysis, and elemental analysis. The sulfomethylated acrylate polymers containing ≥19.9 mol % sulfo groups are resistant to brines containing up to 70 g L–1 CaCl2 at temperatures of up to 140°С and to hydrothermal treatment at 180°С. As shown by capillary turbulent rheometry under the conditions of thermal, salt, and acid aggressions, at the optimum concentrations of sulfomethylated polyacrylamide in the medium, с opt = 0.025–0.085%, the maximal extent of a decrease in the hydrodynamic resistance, DRmax, remains on the level of 71–80%, and the flow rate increment, ΔQ, is on the level of (22.01–28.85) × 10–6 m3 s–1.

Enhancement of aerodynamic performance through high pressure relief in the engine room for passenger car using cfd technique

High pressure acting on the vehicle’s body plays an important role in deciding the aerodynamic drag. An idea has been suggested to enhance the aerodynamic performance for small passenger car by relieving the high pressure in the engine room. The high pressure inside the engine room can be released to the outside of the vehicle through a hole perforated on the wheel house liner. About 1 % of the drag coefficient can be improved with the 1.88 % of the radiator air mass flow rate increment by installing the top hole with slots on the wheel house liner. Flow simulations are performed at the driving velocity of 110 km/h with the moving wall condition of the same velocity. The tire is rotating to catch more precise flow physics around a tire and wheelhouse liner.

Experimental research on stability enhancement for centrifugal compressors using active control casing treatment system

Centrifugal compressors are widely used in many fields, where they become unstable when operated at the edge of the surge line. This paper presents a method, which is based on the active control casing treatment to enhance the operating stability of the centrifugal compressor. To investigate the effect of the active control casing treatment system on the performance of a centrifugal compressor, a test rig with rotating speed of 15,000 r/min was built up. The experimental results show that the active control casing treatment system can significantly decrease the surge flow rate and extend the envelope of stable operation via injecting gas (so-called the control gas) into the casing of the centrifugal compressor. The tested maximal enhancement ability is 30.55% at the condition of 10,586 r/min when the flow rate of the control gas is 2.5 m3/min. It was found that the enhancement ability increases with the decrease of the rotating speed of the centrifugal compressor. The increment of the control gas flow rate results in a smaller surge flow rate of the centrifugal compressors.

Effect of deposition efficiency on microstructure and property of 316L stainless steel fabricated by laser engineered net shaping

Laser engineered net shaping is a promising technique to fabricate high-performance components with complex geometry rapidly. Excellent properties of fabricated specimen and high deposition efficiency are both important for this additive manufacturing method, but few researches have been done on the relationship between them. In this paper, single-bead multilayer structures of 316L stainless steel are fabricated by laser engineered net shaping (LENS). Using the same laser power and scanning speed, different deposition efficiencies are achieved by adjusting powder flow rate and layer increment. Microstructures and mechanical properties of the deposited structures under different deposition efficiencies are discussed. The results show that, for certain laser power and scanning speed, the deposition efficiency increases from 12.41 mm3/s to 22.62 mm3/s with the increase of the powder flow rate and layer increment , which increases by 86.3% compared with the initial process. Laser energy consumed by depositing unit effective volume reduces from initial 98.84 J/mm3 to 53.06 J/mm3 and the energy efficiency increases by 46.32%. Microstructures of the specimen consist of columnar dendrite and the dendrite length increases obviously with the deposition efficiency. Property test shows that properties of the specimen under different deposition efficiencies are consistent and do not decrease with the deposition efficiency. Tensile strength and yield strength are stable in 510 MPa and 290 MPa, respectively. The elongation rate is around 40% while the micro-hardness is about 180 HV, all of which have reached the same level of forging. The results illustrate that the deposition efficiency and mechanical property can be optimized, which achieves fabrication of high performance parts with low energy consumption and high efficiency.

Properties of Pervious Concrete Containing Scrap Tyre Tubes

There is a huge quantity of waste tyre tubes generated every year due to the increasing of motorcycle user. Therefore, recycling of the waste tyre tubes is become mandatory. The aim of this research was to study the properties of pervious concrete containing scrap tyre tube (STT) rubber particles with percentages of 3%, 5% and 7% of the cement content. The properties studied are void content, compressive strength measured at 7, 14 and 28 days, flexural strength and flow rate which were determined at 28 day. The experimental results showed that, there were increased in void content and flow rate of pervious concrete containing STT. Both compressive strength and flexural strength of pervious concrete containing STT showed a lower value compared to the control mix without STT. The reductions of the mechanical strengths are likely due to the increase of void content. Overall, pervious concrete which contains 7% STT has shown an increment of mechanical strengths and flow rate compared to other STT pervious concrete. Nonetheless, the results indicate that there are potentials for use of STT in pervious concrete, especially for use in pervious concrete applications such as pavements, driveways and parking lots.

Exergo-environmental and exergo-economic analyses and multi-criteria optimization of a novel solar-driven CCHP based on Kalina cycle

The present research proposes and optimizes the performance of a novel solar-driven combined cooling, heating, and power (CCHP) Kalina system for two seasons—winter and summer—based on exergy, exergo-economic, and exergo-environmental concepts applying a Non-dominated Sort Genetic Algorithm-II (NSGA-II) technique. Three criteria, i.e. daily exergy efficiency, total product cost rate, and total product environmental impact rate associated with the exergy of the system for each season are considered simultaneously for multi-objective optimization. The outcomes reveal that increments in turbine inlet pressure and mass flow rate of the vapour generator lower the environmental impact of system products as well as the total product cost rate in both seasons. The optimum value of daily exergy efficiency, total product environmental impact rate, and total product cost rate indicate improvements by 2.56%, 15.7%, and 15.3% respectively in summer and 36.34%, 7.39%, and 4.93% respectively in winter, relative to the base point.

Thermal analysis of photovoltaic-thermal (PVT) single slope roof integrated greenhouse solar dryer

In this research paper, a hybrid photovoltaic-thermal (PVT) single slope roof integrated greenhouse solar dryer under natural and forced mode has been tested for climatic condition of New Delhi, India. Thermal modelling of PVT dryer has been experimentally validated under natural and forced mode without load condition. Further, characteristic curves have also been discussed on the basis of thermal efficiency, overall thermal efficiency, overall exergy efficiency and solar cell efficiency including the effect of packing factor and mass flow rate. The thermal energy decreased and the electrical energy increased by 76.39% and 88.73% respectively with increment in packing factor of PV module. It was also found that with increment in mass flow rate, the thermal energy increased by 89.44% and 65.70% for natural and forced mode respectively.