Mass Flow Rate Ratio Research Articles

Numerical Study of Different Steady-State Flow Rigs for the Tumble Motion Characterization of a Four-Valve Cylinder Head

It is widely accepted that in-cylinder airflow structure strongly affects the performance and combustion of internal combustion (IC) engines. In order to enhance turbulence levels at the time of combustion, modern spark ignition engines (SI) usually employ a tumbling motion inside the cylinder. The tumble generated during the intake phase is mainly controlled by the cylinder head, inlet valves and ports configuration. The use of steady-state flow rigs is a common method to characterize the tumble generating ability of a given configuration. The purpose of this study is to perform CFD numerical simulations of two widely used tumbling measuring steady-state flow rig configurations, in order to compare and correlate the tumble ratios obtained from each one of them. A typical modern four-valve shallow pentroof cylinder head is considered and the flow is simulated for various inlet valve lifts. The results highlight the mass flow rate and tumble ratio differences between the two configurations.

Atomisation and vacuum drying studies on Malaysian honey encapsulation

Malaysian honey is rich in nutrients and bioactive compounds, which can be a healthy alternative to refined sugar in food production. However, liquid honey’s viscous and sticky nature makes it unpreferable in industrial handling. This study, an atomization system coupled with vacuum drying to produce honey powders to overcome the problem. Three types of Malaysian honey, namely Acacia, Gelam, and Tualang, were encapsulated in Ca-alginate gel beads using the atomization system. The density viscosity, and surface tension of the honey-alginate solutions were measured, and the concentration of honey and alginate influenced the physical properties of the solutions. Honey-encapsulated gel beads in the size range of 2.16-2.92 mm were produced using the atomization system with the air-liquid mass flow rate ratios of 0.22-0.31, Weber number (We) of 112-545, and Ohnersorges number (Oh) of 0.35-10.46. Gel bead diameter can be predicted using a simple mathematical model. After vacuum drying, the honey gel powder produced was in the size range of 1.50-1.79 mm. Results showed that honey gel powders with good encapsulation efficiency and high honey loading could be produced using the atomization system and vacuum drying.

Experimental Investigation into the Heat and Mass Transfer in an Indirect Contact Closed Circuit Cooling Tower

The heat and mass transfer coefficients of the indirect contact closed circuit cooling tower, ICCCCT, were investigated experimentally. Different experiments were conducted involving the controlling parameters such as air velocity, spray water to air mass flow rate ratio, spray water flow rate, ambient air wet bulb temperature and the provided heat load to investigate their effects on the performance of the ICCCCT. Also the effect of using packing on the performance of the ICCCCT was investigated. It was noticed that these parameters affect the tower performance and the use of packing materials is a good approach to enhance the performance for different operational conditions. Correlations for mass and heat transfer coefficients are presented. The results showed a good agreement with other published works. Correlations are showed that the spray heat transfer coefficient is a function flow rates of spray water and air as well as spray water temperature while mass transfer coefficient is a function of spray water and air flow rates only.

Experimental research on the detonation behavior in annular combustors utilizing liquid hypergolic propellants

The development of rotating detonation engine utilizing hypergolic propellants is necessary for practical application of detonation-based rocket engines, but this liquid-liquid rotating detonation has been rarely researched due to its difficulty of well atomization and mixing in very short time. This study aims to experimentally investigate the propagation characteristics of rotating detonations using non-premixed hypergolic propellants in annular combustors. Here the monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO) have been used as oxidizer and fuel, respectively. Twenty-four unlike impinging elements have been used for injection and mixing of liquid propellants. The orifice diameter is 0.4 mm for oxidizer and 0.3 mm for fuel. Three typical combustion modes such as deflagration mode, one-wave rotating detonation mode and two-wave collision mode have been captured by dynamic pressure transducers and the high-speed camera. The influence of many factors, such as mass flow rate, mixing ratio, annular combustor width and chamber throat, on rotating detonation behaviors have been investigated. The propagation velocity of rotating detonations is around 1328 m/s∼1405 m/s, including one-wave rotating detonation mode and two-wave collision mode. When the mass flow rate and mixing ratio is not appropriate, the hypergolic combustion becomes obviously unstable and combustion modes vary very quickly, especially at the start-up stage. The chamber throat plays a negative role on rotating detonation which suppresses the detonation propagation and can lead to detonation fail. Besides, the wider annular combustor width is beneficial for rotating detonation propagating, which can eliminate the negative influence of the chamber throat on the detonation propagation. In addition, increasing mass flow rate would lead to higher injection velocity and thus better impinging injection, atomization and mixing, which is positive for increasing the stable operation range of mixing ratio for rotating detonations.

Industrial-scale experimental study of internal-mixing air-blast nozzle for sludge atomization

The atomization of sewage sludge is a key step in its drying process. This study conducts an industrial-scale experimental study to investigate the performance of a self-developed internal-mixing air-blast nozzle for atomizing sewage sludge. The size of atomized droplets is calculated using image processing technology. Using the specific size and characteristic size of the droplets, the droplet distribution and the droplet motion behavior in spray field are investigated at various air-to-liquid mass flow rate ratio (ALR). The larger the ALR, the smaller the atomization droplets. By installing outlet diffusers and impaction pins, the atomization angle can be increased and the distribution of droplets in the spray field can be improved. The outlet diffuser with an outlet angle of 90° and the square impaction pin exhibit optimal effect. Experiments with real scale and industrial grade have a significant reference value for industrial applications of sludge atomization.

Numerical investigation of an inertization system for a radiative coil coating oven

In this work the inertization of a radiative curing oven for coil coating is numerically investigated. Inertization chambers (IC) — comprised by a confined impinging slot jet and an exhaust slot — are applied at the curing oven openings to prevent external air from entering and toxic solvents from exiting the oven, avoiding simultaneously the contamination of the external surroundings and the development of explosive conditions within the oven. The influence of the main IC operating parameters — extracted-to-injected mass flow rate ratio (Ψ), coil plate-to-jet velocity ratio, injection Reynolds number, and oven pressure — on the safety of the sealing process is investigated considering the validated k-kl-ω transition RANS model. To guarantee safety conditions regarding the IC placed at the metal strip entrance, the corresponding range for Ψ was found to be between 0.8 and 1.6 considering oven pressures ranging from −20 to 20Pa. For the IC placed at the metal strip exit and considering high coil velocities, safety conditions can only be observed with negative oven pressures. Overall, this procedure found a Ψ range between 0.8 and 1.2 that complies with the restrictive safety criteria for a realistic oven operation with typical coil velocities and oven pressures ranging from −20 to 10Pa.

Two-evaporator refrigeration system integrated with expander-compressor booster

Two-evaporator refrigeration systems are commonly used in many practical applications where two different temperatures are required. Improving the performance of these systems can contribute to energy efficiency. Expansion recovery has been extensively utilized in order to maintain higher performance and the most commonly used method is adopting an ejector instead of expansion valve. In this work, different from the previous studies, an expander-compressor booster is introduced to the system instead of an expansion device to improve coefficient of performance (COP) and second law efficiency of the two evaporator refrigeration system. Parametric studies are conducted for different mass flow rate ratios, condensing, evaporating, superheating temperatures on COP and relative increment in COP (COP*) values are plotted. An internal heat exchanger (IHX) is also added to evaluate whether it helps or worsens the system performance. Moreover, the impact of different refrigerants (R134a, R1234yf, R290, R717, R32 and R410A) on the results is discussed. The results for R1234yf showed that the expander-compressor booster increases the performance of the system and second law efficiency by 38% when mass flow rate ratios are identical. This increment can be increased at lower mass flow rate ratios. Addition of the IHX contributes the COP*. It has also been observed that the refrigerant type has a significant impact on the results.

Numerical and experimental investigation of a Mg/N2O powdered fuel rocket engine

Powdered metal fuel rocket engines, utilizing high energy density metal powder as fuel, have great potential in the development of propulsion systems for upper-stage rockets, and thrusters for attitude or trajectory control. The main challenges of this rocket engine technology currently lie in the realization of stable powder fuel supply, quick engine start-up, and high combustion efficiency. In this paper, we present a computational analysis of the reactive flow in a Mg/N2O powdered metal fuel rocket engine. Consideration in this work includes effects of a flame holder, mass flow rate ratio and entry angle of N2O on combustion efficiency. Based on the numerical simulation results, an experimental Mg/N2O powdered metal fuel rocket engine was designed, and working processes of the engine were investigated through hot fire tests with Mg powder as fuel and N2O as oxidant. A ground test system, consisting of a high-precision test bench, a fuel feed unit, an oxidant feed unit, and a measurement and control unit, was established. The test results show that the combustion of Mg powder and N2O can be sustained.

Multiobjective optimization of a pressurized water reactor cogeneration plant for nuclear hydrogen production

In this paper, energy, exergy, economic analysis and multiobjective optimization of a pressurized water reactor (PWR) nuclear cogeneration plant for hydrogen production through high-temperature steam electrolysis (HTSE) are carried out. HTSE requires energy in the form of both heat and electrical work. A novel parameter, namely the heat/total energy ratio, is defined, and used as a decision variable in optimization. In addition to energy ratio, hydrogen production capacity, reactor thermal power, live steam temperature, reheating mass flow rate ratio, reheating temperature and steam extraction location are considered as the decision variables to simultaneously optimize the thermal efficiency, thermal-to-hydrogen efficiency, utilization factor, exergy efficiency and total revenue of the cogeneration plant. The analysis and optimization focus on the secondary cycle of the PWR and the effects of hydrogen and electricity prices and ambient conditions are also taken into account since these prices have a significant impact on the optimum design. For a hydrogen price of 4 $/kg and an electricity price of 0.1 $/kWh, when equal preference is given to all objective functions, the optimum production capacity is 6.778 kg/s. The energy ratio has an optimum value if the optimization focuses exclusively on the thermal efficiency and total revenue.

Gas atomization of A2 tool steel: Effect of process parameters on powders' physical properties

In this study, powders of the A2 tool steel were produced by close-coupled gas atomization using argon gas aiming their use in additive manufacturing (AM) technologies. The effects of melt overheating and gas atomization pressure on their physical properties were analyzed. The powders were separated into different particle size ranges, and a complete morphological characterization was carried out. The effect of back pressure was verified due to a substantial increase in the gas-to-melt mass flow rates ratio (GMR) with increasing gas pressure. Atomization gas pressure showed a slightly more significant influence on particle size distribution; however, the melt overheating effect was also significant. As the GMR increases, the median particle size decreases to a certain threshold. Above this, particle size cannot be considerably reduced with increasing GMR.

Fundamental optimization of steam Rankine cycle power plants

This paper introduces a mathematical model for the design and fundamental optimization of steam Rankine cycle (SRC) power plants. The model assumes that the plant irreversibilities are predominant in the heat exchangers, thus exergy destruction in the turbine, pump, fittings, tubes and other internal components are neglected. The NTU-effectiveness method was utilized to model the heat exchangers, and water was considered as the working fluid, which changes phase in both heat exchangers. Acknowledging that entropy is generated in any physical system, the fundamental optimization problem selected the dimensionless net power output, and second law efficiency as the objective functions to be maximized, after the identification of plant geometric and operating parameters to be optimized based on the intersection of asymptotes method, subject to a fixed total heat exchangers area realistic physical constraint, i.e., for a finite size plant. As a result, two levels of optimization were identified: i) the working fluid to hot stream mass flow rate ratio, M, and ii) the steam generator, xH, and condenser, xL, area fractions of the plant fixed total heat exchangers area. The model was experimentally validated for a heat recovery driven power plant. Sharp maxima were obtained in both levels, which is illustrated with a base case by ∼ 60 % second law efficiency variation in comparison to the obtained maximum for 0.05 < M < 0.25 in the first optimization level, and ∼ 30 % for 0.2 < xH < 0.7 in the second optimization level, so that (xf,H,xfg,H,xg,H)2wo=(0.14,0.13, 0.23), with (M,xH)2wo=(0.16,0.5), in the base case considered in this study. The two-way optima results sensitivity to several plant geometric and operating parameters were thoroughly investigated. The optimized parameters are shown to be robust with respect to several system’s design and operating conditions. Therefore, the herein reported fundamental optimization results are important for whatever actual SRC power plant.

Optimization of operation mode and design parameters of a finely-dispersed metallic liquid-alloy generator

During the process of designing new devices for the high-speed metallization process, there appears the necessity to define the stable operation range and search for the optimum values of the operation mode and design parameters. This paper describes a process of optimization of a device made for depositing low-melting metal coatings, based on the rocket chamber operation principle. The paper presents an analysis of the objective function surface response metallizer operation performance. On the basis of this analysis the optimal values of fuel mass flow rate and excess oxidant ratio were determined. The choice of fuel and oxidizer throttling orifice cross-section areas was substantiated, the value of the throat cross-section for the metallizer flow-path was found. The expected performance of the designed device was also determined.

Influence of engine heat source conditions on a small-scale CO2 power generation system

Employing a CO2 power generation system to recover waste heat from engines can reduce fuel consumption and CO2 emissions by producing additional electric power. Nevertheless, the fluctuation in engine operating conditions would cause variations in waste heat sources and affect system performances largely. Hence, an experimental performance test at various engine conditions was implemented by the construction of a small-scale (10 kW) CO2 power generation system. Key components, including the turbine expander and printed circuit heat exchanger, were specifically designed and constructed. The steady-state and transient performances of critical components and the integrated system were carried out. Experimental results of the turbine expander at varying engine conditions revealed the potential for long-term and stable operation under dynamic mass flow rate, inlet temperature, and pressure ratio. The maximum total generation power and efficiency reached 11.55 kW and 58.92%. The printed circuit heat exchanger used to exploit engine exhaust gas showed satisfactory performances in balancing the trade-off between heat transfer and pressure drop. The total pressure drop of engine exhaust gas was lower than 4 kPa determined by both exhaust mass flow and temperature, considering all the variable engine conditions. Despite that a performance penalty was observed at the off-design operation of the integrated system because of the decrease in the waste heat input, the maximum net power and thermal efficiency reached 10.57 kW and 6.59%, respectively, at the engine condition of 1100 rpm, 1200 N m, with a relative improvement of 6.3% in engine brake thermal efficiency.

On using artificial neural network models for a thermodynamically-balanced humidification-dehumidification system: Design and rating analysis

This research focuses on rating and sizing a thermodynamically-balanced humidification-dehumidification (HDH) system with zero, single, and double extractions of humid air from the humidifier to the dehumidifier. In order to implement thermodynamic balancing appropriately, optimal thermal design is essential to be estimated via a reliable and straightforward model. Thus, this study suggests an artificial neural network to predict the system performance and size parameters. The artificial neural network is trained, tested, and validated using a rich data set created to cover possible operating ranges. The considered performance parameters are gained output ratio, water-to-air mass flow rate ratio, recovery ratio, seawater and air temperatures, energy effectiveness, and critical enthalpy pinch, and the design parameters involve humidifier volume and dehumidifier area. Four inputs are used: seawater inlet temperature, heating temperature, enthalpy pinch, and extractions count. The developed model works best for inlet temperature, heating temperature, enthalpy pinch, and extractions count within 20 – 40 °C, 60 – 80 °C, 1 – critical enthalpy pinch in kJ kgd-1, and 0 – 2 extractions, respectively. The results indicate that the developed artificial neural network has high accuracy in predicting the performance and design parameters, demonstrating minimum accuracy of 98.3%, 96.4%, and 98.9% for zero, single, and double extractions, respectively. Furthermore, the generated neural network is validated against numerical and experimental data from the literature, showing a maximum discrepancy percentage of less than 4%. Thus, the neural network provided by this study is helpful for HDH desalination engineers, designers, researchers, and scientists.

Combustion behavior study and flame zone analysis of biogas-fueled gas turbine combustor under O2/CO2 and O2/H2O oxidizing modes

Environmental problems resulting from the increment of greenhouse gases have raised the tendency toward using renewable energy sources alongside carbon-capturing technology via oxyfuel combustion. In this regard, numerical simulation on the feasibility of using renewable biogas in the gas turbine combustor under two combustion modes, namely, O2/CO2 and O2/H2O, at high operating pressure is investigated in the current research. Considering that conventional air-based combustion systems are not suitable for oxyfuel combustion regimes, the modification of the gas turbine combustor will be addressed to provide the necessary conditions for proper operation at higher power densities on an industrial scale. In this study, the focus is on investigating the influences of the primary diluent mass flow rate ratio (PDR) and the O2 content in the oxidizer composition on combustion and thermal behaviors of biogas flame such as distribution of reaction zone and temperature, combustion species, pattern factor, combustion efficiency, CO pollutant emission, and as well as flame stability in different combustion modes. The results indicated that the PDR parameter plays an essential role in the combustion stability within the gas turbine combustor due to its direct exposure to the vortices created in the recirculation zone. Moreover, combustion instabilities were observed for biogas flame at PDR = 15% in both combustion modes and in O2/H2O case at PDR < 25%. It was also found that CO emissions decrease significantly with increasing PDR, so in higher PDR values, CO pollutant levels were observed at 39 ppm and 21 ppm in O2/CO2 and O2/H2O cases, respectively.

Reactive Sputtering Process Study for Vanadium Oxynitride Films

In this study, vanadium oxynitride thin films were deposited by reactive magnetron sputtering using pure vanadium targets, Ar as a plasma carrier, and a mix of N2 and O2 as reactive gases. Various ratios of mass flow rates between two reactive gases were maintained as a constant during the process. To obtain crystalline phases of oxynitrides, rapid thermal annealing in Ar atmosphere at 600 °C and 700 °C for 5 min was conducted after the deposition. This study aims to define the range of the process parameters of magnetron sputtering to deposit vanadium oxynitride thin films. The assessment for the characterization of films utilizes the surface profiler, scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, four-point probe, Hall analyzer, and UV-visible-NIR spectrometer. Experimental results reveal that the annealed films can be oxynitrides when the oxygen flow rate is below 0.25 sccm, and the ratio of oxygen/nitrogen is no more than ~1/10. The annealed vanadium oxynitride films, in terms of their properties, are closer to vanadium nitrides than to oxides, due to the intended low supply of oxygen during deposition. For instance, the film is more metallic than semi-conductive with dark appurtenance and high optical absorbance across the spectrum between 200 and 900 nm. For practical purposes, the deposition conditions of O2:N2 = 1/20, O2 &lt; 0.25 sccm, and 600 °C annealing are recommended to obtain vanadium oxynitride films with relatively lower resistivity (10−2 Ω cm) and optical transmittance (&lt;15%) through films.

Evaluation of a heat pump coupled two-stage humidification-dehumidification desalination system with waste heat recovery

Humidification and dehumidification (HDH) desalination technology has attracted wide attention in the field of small-scale dispersed fresh water demand, because of its advantages such as simple configuration, low investment, and utilization of low-grade renewable energy and waste heat. In this paper, a heat pump coupled two-stage humidification-dehumidification desalination system with waste heat recovery is proposed, where the waste heat is used to heat the feed seawater of the first-stage humidifier, and the brine leaving the bottom is further heated by the condenser of heat pump and then taken as the feed of the second-stage humidifier, while the evaporator of heat pump is used to recover the heat of humid air from the first-stage dehumidifier. Performance evaluation of the proposed system with various working fluids are conducted regarding the fresh water production mpw, gained output ratio (GOR), recovery ratio (RR), specific entropy generation stot, and unit cost of fresh water production Zpw, and parametric studies are performed to identify the key operating parameters. Results show that the largest entropy generation occurs in evaporator, followed by the first-stage humidifier and condenser. Taking R22 as the working fluids is corresponding to the largest mpw, while the lowest Zpw and stot, and the highest GOR are obtained by R600. Higher spraying temperature of the first humidifier T4 is conducive to improving the mpw and Zpw, but leading to a larger stot. The GOR increases first and then decreases with the rise of T4, and the peak value is 4.57 at T4 = 340.65 K. The mass flow rate ratio of the first stage MR1 has significant effects on the system performance. When MR1 is about 3.5, the mpw, GOR and RR reach the peak. However, the bottom value of Zpw is 8.74 $/m3 corresponding to the MR1 of 2.2–2.5. With the increase of compression ratio (CR) of heat pump subsystem, the mpw, GOR and RR climb up first and then decrease, while Zpw and stot get raised.

AERATED CIRCULAR AND ELLIPTICAL LIQUID JETS IN A GASEOUS CROSSFLOW

In this study, the atomization of an effervescent atomizer with an elliptical and circular orifice was investigated experimentally in the gaseous crossflow. The shadowgraph technique was used to visualize the near field of the spray atomization. To measure the spray penetration height in crossflow, image processing was performed on the shadowgraph images based on two different approaches: (i) a threshold analysis of average spray images and (ii) standard deviation images of spray. By comparing these two approaches, it is found that the penetration heights obtained from the standard deviation images were much higher since these images were able to capture small droplets more accurately. Moreover, based on the standard deviation images of spray, an empirical correlation for the spray penetration height was developed as a function of gas-liquid mass flowrate ratio, liquid-air momentum flux ratio, orifice aspect ratio, and downstream location. The laser diffraction technique was used to analyze the particle size of the aerated elliptical and aerated circular jets in a gaseous crossflow. For each orifice shape, the effect of gas-liquid ratio and downstream location on the Sauter mean diameter (SMD) was studied. The results show that the aerated circular jet penetrates higher into the gaseous crossflow than the aerated elliptical jet. Besides, the aerated circular jet in crossflow mainly generates smaller drop sizes compared to the aerated elliptical jet.

Experimental Performance Investigation of a Nanofluid Based Parabolic Trough Concentrator in Malaysia

Abstract— Concentrating solar energy system is a potential solar thermal technology, wherein parabolic trough concentrators (PTC) are becoming growingly popular. In this research, both analytical and experiment analyses have been done. The experiment has compared with analytical results. to examine the effect of different operating parameters. Water and water-carbon nanotube (w-CNT) are used to explore the performance of PTC system. Optimum receiver diameter is found 51.80 mm for the maximum efficiency of the collector. During optimization, mass flow rate and concentration ratio are found to be influencing on the thermal efficiency and heat removal factor. Investigations show improvement in heat transfer for added nanoparticles. Heat transfer rate is better in laminar flow than in turbulent flow. After analytical analyses, an experiment has been done using water and carbon nanotube and compared with analytical results. Results show that for every 1oC increase in outlet temperature heat gain and thermal efficiency with water increase at the rate of 0.02 kJ/s and 1.6% respectively. On the other hand, for w-CNT as HTF, for every 100 W/m2 increase in irradiance, heat gain augments at a rate of 0.23 kJ/s and thermal efficiency upsurges by around 7%. Flow rate of working fluids and solar irradiance are found to have respective negative and positive impact on thermal efficiency of the parabolic trough collector.

Performance analysis of a pilot-scale modified air heated and dual heated humidification-dehumidification desalination system

Humidification-dehumidification (HDH) desalination systems offer an effective decentralized solution to meet the potable water demands of small and medium - size communities. Amongst many HDH configurations, the modified air heated and dual heated HDH cycles have demonstrated promising results in several studies based on small lab-scale setups, where the pilot scale experimental data are lacking in literature. In this study, the performance of both modified air heated and dual heated cycles are experimentally investigated using a new pilot-scale system to benchmark the performance for scaling-up the HDH system. The concept of heat rate ratio is explored practically in a new approach by splitting up the energy supply between water and air streams in the dual heated cycle. Both cycles operate in closed-air open-water cycle. In the modified air heated layout, humid air is heated after the humidifier, whereas in the dual heated mode, both water and air are heated simultaneously before and after the humidifier. The effects of changing the mass flowrate ratio on the performance dynamic indices, including productivity, gained output ratio, product cost, recovery ratio, top system temperature, specific energy consumption, and heat capacity ratio of both configurations are investigated. Results indicate that the dual heated system performs better than the modified air heated cycle, with a maximum freshwater production rate of 117.2 kg/day and 72.7 kg/day for dual the heated and modified air heated cycles, respectively. Dual heated system also recorded peak recovery ratio of 2.24 % while modified air heated cycle attained a highest RR of 1.26 %. Furthermore, the estimated peak gained output ratio for modified air heated and dual heated cycles are 0.53 and 0.74, respectively. The dual heated cycle also recorded the lower freshwater cost of 0.055 $/kg, while the best product cost for the air heated cycle is 0.079 $/kg of freshwater.