The Efficiency of Pd Addition and Sr Substitution on La1−xSrxMnO3 to Remove Ventilation Air Methane in a Catalytic Flow Reversal Reactor

Ventilation air methane (VAM) is the main cause of greenhouse gas emissions in coal mining. Catalytic flow reverse reactor (CFRR) is widely used in VAM to mitigate methane emissions. In this study, palladium (Pd) and La1−xSrxMnO3 were used as catalysts in a CFRR. Different types of catalysts were prepared by loading La0.8Sr0.2MnO3, La0.9Sr0.1MnO3, and 0.1%Pd-La0.9Sr0.1MnO3 on a cordierite honeycomb reactor coated with γ-Al2O3 to compare their performances. In addition, this study compared the performance of the three catalysts in an 800 °C reactor based on different methane inlet concentrations, inlet speeds, and conversion times. The results showed: (1) 0.1% addition of Pd increased methane conversion. (2) La0.8Sr0.2MnO3 had higher efficiency at lower methane inlet concentrations, whereas La0.9Sr0.1MnO3 was more efficient at higher methane concentrations. This study demonstrates that a higher Sr loading is worth implementing only when the methane concentration of VAM is lower than 0.6%. (3) To achieve a higher methane conversion efficiency, the inlet velocity of methane should also be considered.

A Comprehensive CFD Assessment of Wheat Flow in Wheat Conveying Cyclone Validation and Performance Analysis by Experimental Data

Cyclone is often used in the Industry due to its low maintenance costs, simple design, and ease of operation. This work presents both experimental and simulation evaluation on the effect of inlet velocity and mass flow rate on the performance of a wheat conveying cyclone. According to the great importance of the pressure drop and separation efficiency on the separation phenomenon in the cyclone, a comprehensive study has been conducted in this regard. A computational fluid dynamics (CFD) simulation was realized using a Reynolds stress turbulence model, and particle-air interactions were modeled using a discrete phase model. The result showed a good agreement between the measured value and CFD simulation on the pressure drop and tangential velocity with a maximum deviation of 6.8%. It was found that the separation efficiency increased with inlet velocity up to 16 m s−1 but decreased slightly at a velocity of 20 m s−1. The pressure drop increased proportionally with inlet velocity. However, optimum performance with the highest separation efficiency (99%) and acceptable pressure drop (416 Pa) was achieved at the inlet velocity of 16 m s−1 and mass flow rate of 0.01 kg s−1.

Development of flow control methods in free and impinging jets

Submerged and impinging jets with harmonic perturbations added to the inlet velocity profile and with nozzle vibrations are simulated numerically at different Reynolds (Re) and Strouhal (St) numbers by solving the Navier–Stokes equations. The effects of Re, St and forcing amplitudes on flow behavior and jet splitting phenomena are studied.

Analysis on Inlet Nozzle Design Geometry of Tesla Turbine

Tesla turbine is a bladeless turbine that uses a set of discs arranged at a certain distance to rotate and one of the parameters controlling turbine performance is the inlet parameter. The purpose of this study is to optimize the design of the inlet nozzle and analyse its effects on the flow of the fluid. A total of four nozzle designs have been proposed using CATIA while the Solidworks Flow Simulator is used to analyse the fluid flow at various inlet velocities. Then, the most efficient design is then fabricated via 3D printing and put to test by connecting it with the actual Tesla turbine model. Through the results obtained from the analysis, it is observed that Design 4 is the most efficient of all tested nozzles and the highest RPM and output voltage achieved from the nozzle is 7940 RPM and 13.56 V. The difference in velocity and pressure increases as the area of the nozzle outlet reduces, whereas nozzle efficiency decreases as the inlet velocity increases. The result of this study is a source material for increasing the effectiveness of an alternative power turbine in generating electricity by manipulating the inlet design geometry.

Effect of Mainstream Velocity on the Heat Transfer Coefficient of Gas Turbine Blade Tips

This study experimentally investigated the effects of cascade inlet velocity on the distribution and the level of the heat transfer coefficient on a gas turbine blade tip. The tests were conducted in a transient turbine test facility at Korea Aerospace University, and three cascade inlet velocities—30, 60, and 90 m/s—were considered. The heat transfer coefficient was measured using the transient IR camera technique with a linear regression method, and both the squealer and plane tips were investigated. The results showed that the overall averaged heat transfer coefficient was generally proportional to the inlet velocity. As the inlet velocity is increased from 30 m/s to 60 m/s and 90 m/s, the heat transfer coefficient increased by 11.4% and 25.0% for plane tip, and 26.6% and 64.1% for squealer tip, respectively. However, the heat transfer coefficient near the leading edge of the squealer tip and the reattachment region of the plane tip was greatly affected by the cascade inlet velocity. Therefore, heat transfer experiments for a gas turbine blade tip should be performed under engine simulating conditions.

Recovery and effective utilization of waste heat from the exhaust of internal combustion engines for cooling applications using ANSYS

The exhaust gases from an internal combustion (IC) engine carry away about 75% of the heat energy which means only 25% of heat energy is operated for power production. A recovery unit at the exhaust outlet port can ensure heat exchange between different temperature fluids through conjugate heat transfer phenomena. This study represents heat recovery from exhaust gases that are emitted from IC engines which can be utilized in various applications such as vapor absorption refrigeration systems. In the present work, a new type of perforated fin heat exchanger for waste heat recovery of exhaust gases is designed using SolidWorks, and the flow field design of the heat recovery system is optimized using ANSYS software. Various parameters (velocity, pressure, temperature, and heat conduction) of hot and cold fluid have been analyzed. Inlet velocity of cold fluids including refrigerant (LiBr solution), water, and graphene oxide (GO) nanofluid have been adopted at 0.03 m/s, 0.165 m/s, and 0.3 m/s, respectively. Inlet velocity of hot fluid is taken as 2 m/s, 4 m/s, and 6 m/s, respectively, to develop a test matrix. The results showed that maximum temperature reduction by the exhaust is achieved at 104.8°C using graphene oxide nanofluids with an inlet velocity of 0.3 m/s and exit velocity of 2 m/s in the heat recovery unit. Similarly, temperature reduction by exhaust gases is acquired at 102 °C using water and 96.34 °C by using a refrigerant (LiBr solution) with the same exit velocity (2 m/ s). Furthermore, maximum effectiveness of 0.489 is also obtained for GO nanofluid when compared with water and the refrigerant. On the other hand, the refrigerant has the maximum log mean temperature difference from all fluids with a value of 224.4 followed by water and GO.

Thermal Performance Characteristics of a Microchannel Gas Heater for Solar Heating Applications

In the present article, the heat transfer and fluid flow of the air in a compact microchannel gas heater (MCGH) was experimentally quantified. To understand the effect of heat flux value (HFV), and inlet velocity on the heat transfer coefficient (HTC), wall temperature, friction factor, Nusselt number, average pressure-drop value (PDV) and performance index (PI), a microchannel gas heater was constructed and tested with pressurized air. The results showed that the HTC was 20 W/(sqmK) to 70 W/(sqmK), corresponding to inlet velocities 6.7 m/s and 16.7 m/s, respectively within HFV < 1 kW/m2. Also, the highest PI was 1.19 meaning that the HT rate can be increased by 19% at u = 15 m/s in comparison with the reference case (at u = 13.3 m/s). Likewise, the HTC was intensified once the inlet velocity is increased. It was also identified that increasing the HFV has a strong effect on wall temperature, however, slightly changes the HTC. By increasing the heat flux value from 200 W/sqm to 1000 W/sqm, the HTC increased only by 4.7% which was associated with the poor thermophysical properties of air flowing inside MCGH. Two main mechanisms of wall slip and viscous heating were identified as main contributors to the heat transfer enhancement in MCGH.

Effects of inlet velocity profiles for thermal stripping phenomena in T-junctions

This paper investigates the effects of different inlet velocities on thermal stripping phenomena within a T-junction. The computational flow domain is modelled using the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model implemented within the commercial CFD code STAR-CCM+ 12.04. The computational model is validated against the OECD-NEA-Vattenfall T-junction Benchmark data. The influence of flat and fully developed inlet velocity profiles is then assessed. The results are in good agreement with the experimental data. The different inlet velocity profiles have a non-negligible effect on the mean wall temperature. The mean velocity shows lower sensitivity to changes in inlet velocity profiles, whose influence is confined mainly to the recirculation zone near the T-junction.

Characteristics Analysis of Fluid-Structure Coupling Vibration of spray bar for High gap sprayer

With the progressive improvement of the level of mechanization of agricultural production, the high-gap rod sprayer has gradually become an important component of agricultural production equipment. The stability of spray rod has an important influence on the life and operation quality of spray rod. Therefore, considering the stability of the spray rod of high gap sprayer, a fluid-solid coupling vibration simulation model of the spray rod of high gap sprayer is established in this paper. The influence of inlet velocity, inlet pressure, fluid density and fluid viscosity on the flow rate and dynamic pressure in the pipe was analyzed by fluent. The results show that the exit velocity increases with the increase of the inlet velocity, but when the velocity reaches a certain value, backflow occurs. With the increase of inlet pressure, the dynamic pressure increases, and the local energy loss and the energy loss along the path also increase. The velocity and dynamic pressure decrease with increasing density.