A method to estimate the moisture diffusivity (Dm) of fish-sausage is given as a function of local moisture content. The correlation of the moisture diffusivity is determined by matching the time history of the numerically estimated average moisture content and that obtained from an experiment. The simulation is based on a semi-two dimensional heat and mass transfer analysis with shrinkage and variable thermal properties. The data of the sausage's properties and its shrinkage during the course of drying are obtained from the experiment. The drying air conditions are 50±2oC of temperature and 0.67±0.02 m/s of velocity with 5.1-6.2% of RH. The size of the specimen is approximately 70, 100 and 10 mm of width, length and thickness, respectively. The calculated result of the drying curve using obtained Dm, local gives an error less than ±1.5%.
Radiation emission characteristics of an open-cellular porous burner, where methane-air premixed combustion occurs, were investigated experimentally and theoretically. In the analysis, we assumed that the chemical kinetics of gas-phase reactions are governed by a single-step Arrhenius rate expression. The energy liberation due to combustion and the effects of radiation were considered in the energy equations for the gas and solid phases. To evaluate the radiative transports in the solid-phase energy equation, the equation of transfer for the radiation field in a porous burner was solved using Barkstrom' s finite difference method and the P1 approximation. Three kinds of Ni-Cr open-cellular porous material with different porosities and pores per inch (PPI) were examined. Radiant output from the porous burner was measured based on a two-color radiometry. Calculated results of the forward radiative heat flux and the burner surface temperature were favorably compared with experimental data: satisfactory agreement between theory and experiment was obtained, and thereby the validity of the present theoretical model for predicting the radiation from a porous burner was confirmed. Moreover, it is found that there is only a little difference between predicted results of Barkstrom' s method and these of the P1 approximation.
A new technique is developed for the measurement of the solidification rate for a latent-heat storage material that consisted of spherical n-paraffin particles and water (emulsion slurry). This method utilizes the correlation between the optical characteristics of the slurry and the solidification rate of the paraffin particles. From experiment, it was shown that the increase in the solidification rate of the particles causes the rise in the transimissivity and the drop in the reflectivity of the slurry. Each paraffin particles has a conical crater on the surface when it solidifies. Based on these observations, a new radiative transfer model has been developed for a transparent particle with a conical crater and a three-dimensional radiative transfer model for a particulate medium by the Monte Carlo method. The analytical results for the slurry using the model well agreed with the experimental ones. From the analysis, it was shown that the crater on the particle surface makes the forward scattering weak and scattering in the backward and the lateral direction strong. Therefore, it was concluded that the rise in the transmissivity and decrease in the reflectivity of the slurry by the increase in its solidification rate is caused by the craters on the particle surfaces due to their phase-change.
Plant shoot configurations evolve so that maximum sunlight may be obtained. The objective of this study is to develop a compact light-condensing system mimicking a plant shoot configuration that is applicable to a light source from a large area. In this paper, the relationship between the position of a light source (the sun) and the rate at which light is absorbed by each leaf was investigated in detail for plant shoot models of a dogwood (simple leaf) and a ginkgo tree (lobed leaf). The rate of light quantum received in each leaf model is reported to an analysis program that uses cross entropy (CE). The analyses showed that the peak amount of light received in the plant-shoot-light-condensing system was during February (vernal equinox) and October (autumnal equinox). Similarly, the rate of light quantum received in each leaf was measured with the CE. The results found that the plant-shoot-light-condensing system that maximizes the amount of light received has differences in the light received in each leaf. Furthermore, the light-condensing characteristics of the ginkgo biloba model are better than the dogwood model. The light-condensing characteristics of a leaf are influenced by the size, a lobe, shape, and the length of the branch.
The ignition-chamber GDI engine combustion system and its fuel injection strategy were presented and studied by multi-dimensional fluid dynamic (CFD) code and experiment. The CFD research result shows that the ignition-chamber combustion system and its fuel injection strategy can ensure that there is flammable mixture with appropriate concentration distribution near the spark plug to enhance the ignition reliability. The performance of the GDI engine with the ignition-chamber combustion system was investigated basing on the existing experiment condition. The result shows that the ignition-chamber combustion system has the potential of decreasing emissions and enhancing the combustion speed and stability.
This study describes use of a thermoelectric power converter to transform waste heat into electrical energy to power an RF receiver and transmitter, for use in harsh environment wireless temperature sensing and telemetry. The sensing and transmitting module employs a DS-1820 low power digital temperature sensor to perform temperature to voltage conversion, an ATX-34 RF transmitter, an ARX-34 RF receiver module, and a PIC16f84A microcontroller to synchronize data communication between them. The unit has been tested in a laboratory environment, and promising results have been obtained for an actual automotive wireless under hood temperature sensing and telemetry implementation.
Acoustically-coupled combustion oscillation is studied for premixed flame with pilot fuel to be used in gas turbine combustors. Premixed gas is passed through swirl vanes and burnt with the centrally injected pilot fuel. The dependencies of pressure, fuel to air ratio, premixed fuel rate, inlet velocity and air temperature on the combustion oscillation are investigated. Two kinds of oscillation modes of ∼100Hz and ∼350Hz are activated according to inlet velocities. Fluctuating pressures are amplified when the premixed fuel rate is over ∼80% at elevated pressures. The fluctuating pressure peak moves to a higher premixed fuel ratio region with increased pressure or fuel to air ratio for the Helmholz type mode. Combustion oscillation occurs when the pilot fuel velocity is changed proportionally with the flame length.
An investigation of the effect of radiation on NOx emission was conducted for low temperature diesel engine combustion by using advanced numerical models in a Computational Fluid Dynamics code. The Discrete Ordinates Method (DOM) model was used for the prediction of radiation, which is mainly radiated from soot emissions. The advanced numerical model was able to predict the pressure and heat release rate for a wide range of Start Of Injection (SOI) timing cases. It was found that the influence of the radiation was larger on soot formation than on NOx formation. However, the influence of the radiation on the emissions was smaller than the influence of the wall temperature on emissions. The reaction-induced interaction between NOx and soot emissions was found to be very small, only up to 2.5 % difference of engine-out NOx concentration.
In this article, we demonstrate a novel micro optical viscosity sensor (MOVS) based on a laser-induced capillary wave with a focus control system that enables in situ monitoring of viscosity and surface tension changes in microliter-order liquid samples such as body fluids, polymer coating materials, lubricants, heavy oils and so on. The microfabricated sensor consists of two deep trenches (depth of 273 μm) holding photonic crystal fibers (PCFs), and three shallow trenches (depth of 125 μm) holding collimating lensed fibers (CLFs) for the probing laser. The capillary wave is excited by two pulsed laser beams generating optical interference, and the rapid motion of the capillary wave, which contains information regarding the viscosity and surface tension of the sample, is monitored by detecting the first-order diffracted beam of the probing laser irradiated onto the sample surface. In order to apply this sensor in manufacturing and clinical settings, the distance between the liquid level and the sensor must be properly adjusted because the sample surface is strongly influenced by evaporation and outside vibration disturbances under such conditions. In the MOVS, the specular reflection of the probing laser is detected by a symmetrically placed collimating lensed fiber. Maximizing the signal of specular reflection by using a piezo stage connected to the MOVS and PID controller, the focal points of the fibers (PCFs and CLFs) are adjusted on the sample surface. The high-reproducible measurement results under evaporation and outside disturbance indicate the validity of MOVS for in situ application.
Micro- and nano-scale systems are explained and are categorized in terms of heat and fluid flow phenomena. Some typical applications of nano- and micro-machines are presented. Heat and fluid flow phenomena of nano-micro spatio-temporal systems are described as follows. Micro-systems: · The size of the micro-machine element ranges from 1 µm to 1 mm. · The fluid motion and heat transfer can be treated as a continuum, and is described by Navier-Stokes equations and Fourier's law. Nano-systems: · The fluid cannot be treated as a continuum. · Discontinuity and wave characteristics of fluid and energy have to be considered.
In the present study, Large-Eddy Simulation (LES) modeling for turbulent spray combustion flows has been developed in conjunction with the Eulerian/Lagrangian method for the gas phase and dispersed phase representation and flamelet approach for combustion modeling. Moreover, a new thermal energy coupling model is proposed to estimate the thermal interaction between the gas phase and the dispersed phase. The governing equations for the gas phase are the mass and momentum conservation equations and the mixture fraction transport equation. The governing equations for spray droplets are the mass, momentum, and thermal energy equations for each droplet. We applied the numerical procedure to a laboratory-sized spray combustor and found that procedure can predict key features of turbulent spray combustion phenomena, such as the temperature distribution of the combustion gas, individual droplet behavior, and droplet vaporization phenomena. Moreover, the flame temperature drop caused by the thermal impact from the spray droplets is expressed properly by employing the coupling model.
A coated surface with high reflectance in the near infrared (NIR) region and low reflectance in the visible (VIS) region can both stay cool in the sun and retain its appearance by reducing the glare of reflected sunlight. To design such coatings, an optimization method that embraces both thermal and aesthetic effects is introduced. White pigments are widely used in designing cool coatings due to their relatively high reflectance of sunlight. However, using white pigments may produce glare, which can cause visual discomfort. It is possible to control these effects by controlling the size of pigment particles, volume concentration of pigments and coating thickness. Among the various white pigments that are available, we chose titanium dioxide, zinc oxide and alumina for this study. Radiative heat transfer in an anisotropic scattering, monodisperse pigmented layer was analyzed using the radiation element method by ray emission model (REM2). Both collimated and diffuse solar irradiations were considered. The CIE (International Commission on Illumination) colorimetric system was used for color analysis. Finally, the optimum values of particle size, volume fraction of pigment, and coating thickness were obtained and compared for the three mentioned pigments.
A non-linear least-squares curve-fitting procedure is proposed to analyze three-omega voltage data from a fine wire in a gas sample using the three-omega method. The method uses both three-omega components of the voltage arising from a sinusoidal heating current to determine the thermal conductivity of the surrounding medium. The proposed procedure is tested against simulated data and some experimental data for air at atmospheric pressure. Treating the technique as an absolute method and assuming a known sample heat capacity, the thermal conductivity of air has been measured at room temperature to within 11% of a reference value. Practical application of the method may require a calibrated effective wire length and wire diameter. An average wire temperature rise of around 10 K to ensure the three-omega components is enough for accurate measurement.
This study presents a simple multi-fluid model for Helmholtz energy equations of state. The model contains only three parameters, whereas rigorous multi-fluid models developed for several industrially important mixtures usually have more than 10 parameters and coefficients. Therefore, the model can be applied to mixtures where experimental data is limited. Vapor-liquid equilibrium (VLE) of the following seven mixtures have been successfully correlated with the model: CO2 + difluoromethane (R-32), CO2 + trifluoromethane (R-23), CO2 + fluoromethane (R-41), CO2 + 1,1,1,2- tetrafluoroethane (R-134a), CO2 + pentafluoroethane (R-125), CO2 + 1,1-difluoroethane (R-152a), and CO2 + dimethyl ether (DME). The best currently available equations of state for the pure refrigerants were used for the correlations. For all mixtures, average deviations in calculated bubble-point pressures from experimental values are within 2%. The simple multi-fluid model will be helpful for design and simulations of heat pumps and refrigeration systems using the mixtures as working fluid.
A high-frequency (20kHz) standing wave was applied to the unburned mixture upstream of a methane-air lifted jet flame using a bolt-clamped Langevin transducer (BLT) to improve stability. The flow field near the flame was visualized using acetone planar-laser-induced fluorescence (PLIF). The standing wave decreased the lifted flame height and increased the blow-off limit. The upstream flow field of the center jet then bent. This phenomenon appeared when there was a density difference between the center jet and the surrounding secondary flow. When the density of the center jet was less than that of the co-flow, the center jet was redirected to the pressure anti-node side. Conversely, when the density of the center jet was greater than that of the co-flow, the center jet was redirected to the pressure node side. This redirection tended to stabilize the laminar lifted flame.
In this study, we attempted to clarify the electrical characteristics of diamond films synthesized by combustion flame and consequently synthesizing a suitable diamond film for use in electronic device applications. When the film contains amorphous carbon, the electrical resistivity (volume resistivity) decreases, i.e., the electrical characteristics of the diamond film worsen. To decrease the content of amorphous carbon in the diamond film, we utilized methods to detect two parameters: optimal equivalent ratio and optimal substrate temperature. These methods can decrease the amount of amorphous carbon effectively, thereby systematically changing the factors influencing the optimal synthesis for improving the film's electrical characteristics. We have successfully developed a method for producing high-quality diamond films with excellent electrical characteristics and high electrical resistivity (1010 to 1013 Ωm) at room temperature.
This experimental study is performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition (u'/SL0=1.4), in order to clarify basically the influence of the addition of hydrogen to lean and rich methane or propane mixtures on its local burning velocity. The mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen δH are prepared. A two-dimensional sequential laser tomography technique is used to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. Some of the key parameters of local flame properties quantitatively measured are the local flame displacement velocity SF, curvature and stretch of turbulent flames. Additionally, the Markstein number Ma was obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It was found that the trends of the mean values of measured SF with respect to δH, the total equivalence ratio Φ and fuel types corresponded well its turbulent burning velocity. The trend of the obtained Ma could explain the SF of turbulent flames only qualitatively. The local burning velocity at the part of turbulent flames with positive stretch and curvature using this Ma, SLt, attempted to be estimated quantitatively. As a result, a quantitative relationship between the estimated SLt and the SF at positive stretch and curvature of turbulent flames could be observed only for mixtures with Le > 1 or Ma >0.
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Edited and published by : The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan Produced and listed by : Showa Joho Process Co., Ltd.(Vol.8 No.3-) Sanbi Printing Co., Ltd.(Vol.1 No.1-Vol.8 No.2)