Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session M28: Industrial Applications II |
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Chair: Simon Song, Hanyang University Room: 32A |
Tuesday, November 20, 2012 8:00AM - 8:13AM |
M28.00001: Flow and Heat Transfer Characteristics of the Staggered Slotted Semi Cylinders in a Cross Flow Heat Exchangers Sedat Yayla, Seyfettin Beyin, Alparslan Oztekin Transient 3-D dimensional turbulent flow simulations are conducted to examine flow and heat transfer characteristics in inline and staggered slotted semi-cylinders placed in a rectangular cross sectioned fin tube heat exchanger. Both Reynolds averaged Navier's equation and Large Eddy simulations model are employed to conduct simulations using Fluent-ANSYS. Predictions of transient simulations are compared against the results of the PIV flow visualization observations at Reynolds number 1500 and 4000. Measured and predicted velocity and the vorticity field in the wake of cylinders agree well with each other at both Reynolds number. The effect of the angle between the slotted semi cylinders and the flow direction is investigated for various values of Reynolds number in both laminar and turbulent flow regimes. Transient nature of the three dimensional flow structures with flow separation, reattachment and vortices are characterized. The effects of the flow structure on the heat transfer characteristics are determined by calculating the heat transfer coefficient along the surface of the semi cylinders. [Preview Abstract] |
Tuesday, November 20, 2012 8:13AM - 8:26AM |
M28.00002: High speed imaging in icing windtunnel tests Dennis De Pauw, Percival Graham, Ali Dolatabadi The detailed visualization and behavior of a spray impinging on a hydrophilic, and superhydrophobic aerodynamic shape in isothermal room and icing conditions can provide deep understanding of in-flight icing. A superhydrophobic coating has a very low surface energy so it can be used to counteract the ice accumulation. It also reduces the adhesion strength of ice to the surface which ensures easier removal of the ice during flight. The focus of the experiments primarily lies on the fundamental study of multiple droplet, i.e. spray, impact on a NACA 0012 airfoil in room and icing conditions. Under such conditions, important icing features such as rivulets and runback flow are observed. This provides us with the basics of ice formation on an aerodynamic surface. The study also focuses on the comparison between aluminum and superhydrophobic surfaces for ice accumulation in conditions which approach flight conditions. All the experiments are carried out in a small scale icing windtunnel using high speed photography with frame rates ranging from five thousand to fifty thousand frames per second. [Preview Abstract] |
Tuesday, November 20, 2012 8:26AM - 8:39AM |
M28.00003: Development of MEMS-based thermal flow sensors for high sensitivity and wide range of flow rate Woong Kang, Hae Man Choi, Yong Moon Choi We have proposed and demonstrated a novel design of MEMS-based thermal mass flow sensor for high sensitivity and wide flow range. Thermal mass flow sensors are able to measure small amount of gas flow such as process control gas via heat transfer phenomena between heater and thermopiles. To understand characteristics of the correlation between sensing performance and geometry of sensor components like heater and thermopile, various designed models were fabricated by using MEMS technology considering manufacturing efficiency. A evanohm R alloy heater and chromel-constantan thermopiles were formed on a Si$_{3}$N$_{4}$/SiO$_{2}$/Si$_{3}$N$_{4}$ sandwich type membrane for thermal performance enhancement. Characteristics tests between flow rate, heat power and sensitivity for fabricated models were conducted in low pressure gas flow standard system of KRISS (Korea Research Institute of Standard and Science) with MFC (Mass Flow Controller). Finally, the optimum geometry based on the non-uniform distribution of heater and thermopiles was determined according to characteristics comparison of designed and fabricated models. The developed thermal mass flow sensor can be adopted for low range flow rate (0 -- 200 sccm) and also high one (up to 10 SLM) with high sensitivity. [Preview Abstract] |
Tuesday, November 20, 2012 8:39AM - 8:52AM |
M28.00004: Experimental Investigation of Flow and Thermal Patterns in the Rotated Arc Mixer Ozge Baskan, Michel Speetjens, Guy Metcalfe, Herman Clercx Thermal patterns emerging during the downstream evolution of temperature fields in industrial inline mixers have been studied numerically yet experimental observation remains outstanding. This research concerns a comparative analysis between experimental and numerical studies on the evolution of the temperature fields of a representative configuration, namely the Rotated Arc Mixer (RAM), and its correlation with the flow field. The RAM is an inline mixer that is composed of a stationary inner cylinder with consecutive apertures and a rotating outer cylinder inducing transverse flow at the apertures. Design of the experimental facility is based on a 2D time-periodic simplification of the 3D spatially-periodic RAM, where the cross-sectional progression is represented by the temporal evolution. The setup consists of a circular test section with apertures on the circumference and motor-driven belts imitating the rotating cylinder. Constant circumferential temperature is achieved by an enclosing annular hot-water reservoir. The 2D flow and temperature fields are measured by 2D Particle-Imaging Velocimetry and Infrared Thermography. Preliminary results have exposed a clear correlation between temperature and flow fields: thermal patterns evolve in accordance with the time-periodic flow patterns and become persistent ultimately. [Preview Abstract] |
Tuesday, November 20, 2012 8:52AM - 9:05AM |
M28.00005: Novel Model to Predict Minimum Coating Thickness for High Speed Slot Coating Ilhoon Jang, Simon Song Recently slot coating is often applied to printed electronics for a flat display and in battery industry due to advantages such as the fast production rate and cost effectiveness. The accurate prediction of minimum coating thickness, closely related to coating stability, is a key issue in slot coating. It is because trial-and-error should be minimized when determining operating conditions of slot coating of which inks with metallic nano-particles are very expensive. So far, the viscocapillay model is known to provide good physical insight in a range of a low or moderate coating speed. However, its predictions are inaccurate for high coating speed since it doesn't consider the inertia of the ink flow arising at the high speed coating. In this study, we propose a novel model which accounts for the inertial effects. We performed detailed numerical analysis on ink flows of a slot coating to find out the cause of inaccurate prediction at a high speed coating and minimum coating thicknesses under various operating conditions. We found that the novel model prediction and numerical results are in excellent agreement in a wide coating speed range and that the new model can be applicable to an operating Reynolds number of an order higher than the viscocapillary model. [Preview Abstract] |
Tuesday, November 20, 2012 9:05AM - 9:18AM |
M28.00006: Macro analysis of the electro adsorption process in a capacitive demonization cell during water desalination at developing and fully developed concentration regimes Carlos Rios Perez, Onur Demirer, Rebecca Clifton, Rachel Naylor, Carlos Hidrovo Capacitive deionization has become a desalination technique of large interest because of its added capability of energy recovery during the regeneration of the adsorbing electrodes. As in any separation practice, adequate modeling of the mass transport mechanisms present in the salt extraction process is crucial for the adequate dimensioning of the desalination cell and selection of the operation parameters. In this regard, this paper presents a simplified one-dimensional model of the concentration variation within a capacitive deionization cell. This model was solved at two distinctive regimes: developing, and fully developed convective diffusion layer. These solutions were used to estimate the net electro-adsorption rates by comparing the predictive variation of the minimum ratio of outlet to inlet solution concentrations with the corresponding measured values at various flow rates. A very good agreement between anticipated and measured outlet solution concentration transients validated the model and methodology to estimate the adsorption rates. This good concurrence between model and experiments evidence the capability of the proposed model to accurately simulate the effects of electrode saturation on the net electro-adsorption rate. Finally, the model and methodology presented were tested with experiments using brackish water concentration solutions. [Preview Abstract] |
Tuesday, November 20, 2012 9:18AM - 9:31AM |
M28.00007: Near-Critical CO2 Flow Measurements and Visualization Farzan Kazemifar, Dimitrios Kyritsis Carbon dioxide capturing and sequestration is one of the proposed solutions for reducing greenhouse gas emission. This technique will be used in big industrial plants with very high CO2 emissions. Handling such large flow rates requires high pressure and low temperature (in order to maximize density and minimize volumetric flow rate) which brings us close to the critical point of CO2 at approximately 74 bar and 31\r{ }C. This necessitates studying near-critical CO2 flows. In our experiment setup CO2 is compressed to supercritical pressures using a hydraulic accumulator. Pressurized CO2 then flows through the test section, which is a 2-ft long stainless steel tube with ID = 0.084 in. The flow rate is controlled by a needle valve downstream of the test section and the mass flow rate is measured using a coriolis mass flow meter. Temperature and pressure are monitored using two K-type thermocouples and pressure transducers at the inlet and exit of the test section. The pressure difference across the pipe is measured separately using a differential pressure transducer. In another set of experiments, the aforementioned test section is replaced with an optically accessible test section. In this setup high-speed imaging is used to visualize the flow inside the test section. We studied the recorded data in order to identify distinct flow regimes based on pressure drop as a function of pressure, temperature and mass flow rate. [Preview Abstract] |
Tuesday, November 20, 2012 9:31AM - 9:44AM |
M28.00008: Study of fluid parameters in high pressure descaling valves Param Adhikari, Yogendra Panta Our work is focused on the high pressure valves used for descaling purposes in steel mills. A reverse flow operation was set in one of such valves due to piping constraints. Computational approaches are being utilized to understand the fluid phenomena at such high pressures. Though the valve geometry accounts for the complete fluid flow path, a study has been initiated from an axisymmetric model of the valve core. The highly energized fluid from the descaling pump sets off a static pressure of 5000 psi at the valve inlet. It is responsible for continuous fluid flow rate of up to 208 gpm for fully open position. A Shear Stress Transport turbulence model is utilized to study pressure at nearly closed position of the poppet part while Renormalization Group Turbulence model is compared with Shear Stress Transport turbulence model for full opening position. A very low pressure developed below the poppet seat suggests the onset of cavitation zones which may lead to leakage. A full 3D model is studied after a complete studies of fluid phenomenon in the axisymmetric geometry. Using ANSYS Fluent, a commercial CFD software package, the poppet valve assembly was processed for modeling, meshing and setting up of physical parameters. Computational results show the cavitation intensities higher at small openings than at larger openings which is further verified by literature research and currently comparing with experiments. [Preview Abstract] |
Tuesday, November 20, 2012 9:44AM - 9:57AM |
M28.00009: Electrowetting climbing of inclined water surfaces Junqi Yuan, Sung Kwon Cho It is well known that some small insects easily climb the inclined air-water interfaces simply by distorting the interfaces. This presentation will talk about bio-mimicking of the insect-climbing principle by electrically controlling the contact angle (so called electrowetting) and thus distorting the adjacent interfaces. For an experimental proof, we fabricated a small floating object whose sidewalls were covered with electrowetting electrodes. In response to the external voltage applied to the electrodes, the surfaces of the sidewalls can be switched from hydrophobic to hydrophilic states, resulting in interface distortions. It is confirmed that the interface distortions generate lateral forces that allow the floating object to climb inclined water surfaces. Detailed results along with effects of many parameters will be presented and discussed. [Preview Abstract] |
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