Papers by Keyword: Laminar

Abstract: Microchannels based on Micro Electromechanical Systems (MEMS) have garnered a great lot of interest over the past 40 years from the fields of microfluidics and biomedicine. In order to address the problem of heat dissipation in incredibly small integrated circuits with up to 790 W/cm² of huge heat dissipation capabilities, Tuckerman et al. [1] first proposed the microchannel heat rejection idea in 1981. These channels are typically at the microscale, with characteristic dimensions on the order of micrometers 10^-6 m or smaller as shown in Figure 1 [2]. These channels often exist at the microscale and have characteristic diameters of micrometres 10^-6 m or less. Microchannels display distinct fluidic behaviour as a result of their small size. Because the flow is normally laminar and the Reynolds number is low, the flow pattern is predictable. Capillary forces and other surface forces become comparatively more important. As a result, fluid behaviour in microchannels is greatly influenced by surface wetting characteristics and channel surface roughness.

Abstract: Monosodium Glutamate (MSG) [1] was invented more than 100 years ago from its first invention in 1908 by Japanese biochemist Kikunae Ikeda, who was trying to isolate and duplicate the savory taste of kombu, an edible seaweed used as a base for many Japanese soups. From 2016, most MSG worldwide is produced by bacterial fermentation in a process similar to making vinegar or yogurt. Sodium is added later, for neutralization. During fermentation, Corynebacterium species, cultured with ammonia and carbohydrates from sugar beets, sugarcane, tapioca (cassava tuber) or molasses, excrete amino acids into a culture broth from which L-glutamate is isolated. In this process, Monosodium Glutamate companies buy cassava [2] pulps from farmers that contain a lot of sand and impurities. In order to increase the productivity with lowest expense, the filtration of sand and solid impurities’ is performed by separation cyclone. In this paper, we study all the measure to design a system of effective pump, cyclone to extract as much as possible all of solid impurities included sand out of cassava slurry before providing to the bacterial fermentation in a process.

Abstract: Several features of heat transfer on enclosing surfaces are discussed including temperature distributions in a room heated by a floor heater. Numerical analyses on radiative and convective heat transfer were carried out against several partial floor heating. Partial floor heating produces different types of temperature distribution between the heated and non-heated places, which is a remarkable characteristics found out in this study. In the heated places, the temperature distribution is almost the same as that of typical floor heating. However, in the non-heated places, air temperature differs by 6 °C (3.6 °Difference) between a point near the floor surface and a point well above that. Heating efficiency of partial heating slightly depends on the set place as well as its Area. Moreover, convective heat exchange constitutes approximately half of the total heat exchange

Abstract: This work studied fluid flow in the hydroponics systems to create 4 prototypes of the hydroponics systems; horizontal (traditional), inclined-flow, vertical-droplet and vertical-bowl systems, for a household application with initial conditions as low investment cost and easy installation. Red Oak was used to plant in all prototypes to investigate the prototype productivity. Fluid in the experimental investigation was the plant nutrient solution. All variables; fluid and ambient temperatures, fluid pH and sunlight intensity were measured 2 times a day from 4 systems placed in the same area and environment during 15 days of the experimental period in July 2013,. From results, the solution temperatures affected the productivity less than the fluid flow patterns did. The vertical-droplet system could not be used to grow Red Oak because the plants died during the experiment period. The vertical-bowl system could provide the highest productivity. We noticed that the fluid in the vertical-bowl system flowed transitionally while the flow in the other systems was laminar. Therefore, the fluid flow patterns could affect the productivity in the hydroponics systems.

Abstract: The explosive welding is a non-conventional technique gaining popularity due to its ability to join dissimilar metals. The technique is very successful in achieving area joining by using the controlled energy of explosives which creates a metallurgical bond between two similar or dissimilar materials. This paper explains the technique of explosive welding for joining SS304 and AA6061 using pure aluminum (2 mm) as an interlayer. The joining was done in two stages. The explosive used is a mixture of Trimonite and salt having velocity of detonation (VOD) in the range of 1500-1600 m/sec. Ultrasonic testing showed good bonding over more than 80%. Micro-hardness variations as compared to parent materials have been evaluated along with microstructure study done to analyze the interface characteristics. SEM/EDS also have been used to check the presence of any possible brittle phases. Both the interfaces are found to be laminar, continuous, uniform and free from micro-cracks.

Abstract: At a macro scale level, mixing is generally achieved by a turbulent flow, which makes possible of segregating the fluid in small domains, thereby leading to an increase in the contact surface and decrease in the mixing path. At low Reynolds number, the viscous effects dominate inertial effects and a completely laminar flow occurs. In the laminar flow system, fluid streams flow parallel to each other and the velocity at any location within the fluid stream is variant with pressure when boundary conditions are constant and due to the change in surface area–to-volume tension and diffusion, do not simply scale linearly from large to small devices. This makes the use of microfluidic as a mixing device difficult. Thus, the study posed to bridge this gap by created geometrically enhanced Micromixer for homogenous mixing.

Abstract: The present study focuses on the derivation of carbonaceous material from rich premixed propane/air mixture using a laminar flame burner. The presence of Nickel catalyst (Ni) and the effect of equivalence ratio on the synthesis of carbon nanotubes (CNTs) were investigated. Samples were collected from the flame synthesized wire mesh and analyzed using a Field emission scanning electron microscope (FESEM). FESEM imaging shows that the CNTs obtained were of the multi-walled type. The presence of nickel catalyst results in the production of CNTs and the rich equivalent ratio of φ = 2.2 produces the highest yield of CNT in terms of weight and coverage area on the wire mesh.

Abstract: Wall shear stress (WSS) is one of the important variables in microfluidic devices. In this paper WSS distribution for a microfluidic device in Forward Facing Step (FFS) configuration has been investigated using Reynolds number 500 and step height 1μm. Numerical simulation was performed usingAnsys-CFX software with the assumption of Newtonian fluid and laminar condition. The simulation result showed that wall shear stress distribution increased after the fluid passing through the step.

Abstract: A numerical investigation of two-dimensional unsteady, viscous and laminar compressible flow past an asymmetric biconvex circular-arc aerofoil in supersonic regime is carried out. The focus of the present work is to investigate the effects of variation of Mach number, at two different angles of attack, on the flow and force characteristics on NACA 2S-(50)(04)-(50)(20) aerofoil. The value of Reynolds number is taken as 5x10⁵. The computations are carried out at Mach numbers of 1.25, 1.5 and 2.0 at an angle of attack of α=0° and α=10°. It is found that the aerofoil works well in the supersonic flow and, unlike the conventional symmetric biconvex aerofoil, generates finite lift at α=0° due to stronger shock waves at the lower surface. Moreover, the L/D ratio at α=10° is always found to be more than 2.5.

Abstract: In the present work, laminar cross flow forced convective heat transfer of nanofluid over tube banks with various geometry under constant wall temperature condition is investigated numerically. We used nanofluid instead of pure fluid ,as external cross flow, because of its potential to increase heat transfer of system. The effect of the nanofluid on the compact heat exchanger performance was studied and compared to that of a conventional fluid.The two-dimensional steady state Navier-Stokes equations and the energy equation governing laminar incompressible flow are solved using a Finite volume method for the case of flow across an in-line bundle of tube banks as commercial compact heat exchanger. The nanofluid used was alumina-water 4% and the performance was compared with water. In this paper, the effect of parameters such as various tube shapes ( flat, circle, elliptic), and heat transfer comparison between nanofluid and pure fluid is studied. Temperature profile, heat transfer coefficient and pressure profile were obtained from the simulations and the performance was discussed in terms of heat transfer rate and performance index. Results indicated enhanced performance in the use of a nanofluid, and slight penalty in pressure drop. The increase in Reynolds number caused an increase in the heat transfer rate and a decrease in the overall bulk temperature of the cold fluid. The results show that, for a given heat duty, a mas flow rate required of the nanofluid is lower than that of water causing lower pressure drop. Consequently, smaller equipment and less pumping power are required.