bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Tectonic Belts in Tibet and Their Control on Earthquakes
Authors: Tonglin Han
Published: September 2010

Abstract A series of nearly N‐S‐trending active tectonic belts are found in Tibet. The earthquakes there mostly belong to shallow‐focus ones, and are characterized by high frequency, high intensity and short recurrence intervals. The epicentres are mainly located near the boundary faults along the active tectonic belts. They are most concentrated, with small earthquake magnitudes, at the turning or intersecting parts of the boundary faults, and are less concentrated, but with big earthquake magnitudes, in other parts of the boundary faults. The mechanic properties of the seismic fracture belts are generally related to their strike: the NW‐trending ones are of dextral strike‐slip nature and the NE‐trending ones are of sinistral strike‐slip nature, while the nearly N‐S‐trending ones exhibit the nature of tensional normal faults. In the region the earthquake‐controlling structures are considered to be the active tectonic belts, while the seismogenetic structures are the boundary faults in the active tectonic belts.
On the Origin of Petroleum Hydrocarbon Gases
Authors: Zhigao He
Published: September 2010

Abstract The compositional variation of oil‐soluble gaseous hydrocarbons in high‐pressure in‐place oil from more than 40 oil wells in the Northern Jiangsu oil field, China, was studied. Samples in which the effects of the factors of pressure and biodegradation had been got rid of were chosen as the representatives that could really reflect the original composition of hydrocarbon gases. Such samples were compared compositionally with their corresponding hydrocarbons formed by decarboxylation of volatile low‐molecular fatty acids. Thus highly correlative regularities were found to exist between them. The numerical values of both are graphically expressed. The two curves on the diagram are very similar. These two sets of values have a simple correlation coefficient of 0.9935, which presents their genetic relation.

Based on the study of the formation of gaseous hydrocarbons from decarboxylation of volatile fatty acids, the following regularities of the isomers are revealed:

1) n‐butyric acid + isobutyric acid = propane;

2) 1 2 isopentanoic acid (2‐methyl‐butyric acid) + n‐pentanoic acid = n‐butane; and

3) 1.2 isopentanoic acid (3‐methyl‐butyric acid) = isobutane.

The thermodynamics of decarboxylation was analysed and the enthalpy change ΔH, entropy change ΔS and Gibbs free energy change AG in the following reaction were calculated:

CH3COOH(l)—CH4(g) + CO2(g).

Thus the author considers that the reaction for the formation of hydrocarbons due to the decarboxylation of fatty acids is an exothermic one with increased entropy and decreased free energy as well as a spontaneous one. According to the CRC rule, the resultant Gibbs free energy change Δ G is approximately −41.84 kJ/mol, which is well within the range of the energy levels of biophysiological changes.

According to the changes in odd‐carbon preference in n‐alkanes of petroleum and sediments and the analysis of fatty acids and amino acids, it is considered that hydrocarbon gases do not originate from pyrolysis or thermal degradation but from decarboxylation of organisms. But this biological reaction is not ordinary biochemical reaction in the artificial fermentation for generating marsh gas. On the basis of the change tendency of the fatty acid content in the fermentation liquor for marsh gas generation and the change tendency of the carbon isotopes in methane and carbon dioxide in the marsh gas, it can be judged that the biochemical reaction for forming hydrocarbon gases is a special biological one occurring after the fermentation.
On Late Triassic Floras in China and Principles for Palaeophytogeographic Regionalization
Authors: Ge Sun
Published: September 2010

Abstract

A new scheme of Late Triassic palaeophytogeographic regionalization of China is put forward on the basis of three principles given as follows:

1. The palaeophytogeographic regionalization should be based on the characters of the various floras themselves. These characters include the types of the dominant floras, compositional patterns of various communities and existence of dominant genera or those genera and species characteristic of a region.

2. The palaeogeographic positions of the floras in geologic time should be considered.

3. The distribution of the floras was Influenced in three directions—latitudinal, longitudinal and vertical—in geological time.

Formerly, a number of Chinese palaeobotanists based the palaeophytogeographic regionalization only on the factor of latitude, and neglected the characters of the floras themselves and the effect of their three‐directional zonation. However, the discovery of the Tianqiaoling flora (located at latitude 43. 5°N in NE China) rich in fossils of Dipteridaceae and Cycadophyta, indicating tropic or subtropic conditions, and a comprehensive consideration of assigning the floras of southern Tibet on the basis of palaeomagnetism, plate tectonics, etc., suggest that the palaeophytogeographic regionalization is a rather complicated subject. As the climatic conditions controlling, the growth of vegetation changed in three directions, one should consider not only the effect of latitudinal change (which usually causes temperature variations from south to north), but also the effect of longitudinal change (which usually brings about variations in humidity from sea to inland) and moreover the effect of vertical or elevation change (which also leads to variations in temperature and humidity). At the same time, it is also necessary to take into consideration the actual palaeogeographic positions of the floras in geologic time.

Therefore, it is suggested that the Late Triassic floras in China should be grouped into three floristic regions, namely, (1) the Northern Floristic Region with the Danaeopsis‐Symopteris flora, (2) the Southern Floristic Region with the Dictyophyllum‐Clathropteris flora, and (3) the Yarlung Zangbo River Floristic Region. It is inferred here that the floral characters of the 3rd region are similar to those of the Dicroidium‐Lepidopteris flora growing on Gondwana land at that time.
The Devonian‐Carboniferous Boundary in Shallow‐Water Facies Areas of China as Based on Conodonts
Authors: Qiang Ji
Published: September 2010

Abstract

Traditionally, the lower boundary of the Aikuanian (Yanguanian) Stage has always been considered as the lower boundary of the Carboniferous in China, marked by the occurrence of the coralCystophrentis.

In recent years, some biostratigraphical research results have shown that theCystophrentiszone is only distributed in the lower part of the Menggong'ao Formation (or the Gelaohe Formation) and that there is an interval zone namely theCystophrentis‐Pseudouraliniainterval zone, wedged in just between theCystophrentiszone and thePseudouraliniazone in the upper part of the Menggong'ao Formation (or the Gelaohe Formation ). According to the current study of the conodont biostratigraphy, the coralCystophrentiszone appears to be of latest Devonian age. So the lower boundary of the Aikuanian Stage is much lower than the lower Devonian‐Carboniferous boundary and should no longer be regarded as the lower boundary of the Carboniferous in China. In this paper, two proposals for the Devonian‐Carboniferous boundary in the shallow‐water facies areas of China are put forward: 1) that the boundary is marked by the first appearance of the conodontSiphonodella (Eosiphonodella) simplex, and 2) that the boundary is recognized by the extinction of the coralCystophrentisor the brachiopodTenticospirifer.

In addition, 4 species are newly estabished here:Icriodus obovatussp. nov.,Polygnathus lepidussp. nov.,Polygnathus paucidentatussp. nov. andPolylophodonta jianghuaensissp. nov.
Tectono‐Geochemistry of Superimposed Mineralization in the Bainaimiao Ore Field, Inner Mongolia
Authors: Dongxu Li , Ganglio Wu
Published: September 2010

Abstract

Combining geomechanics with geochemistry, this paper makes a rather systematic study on the stratigraphic division, tectonic evolution and ore genesis of the Bainaimiao ore field and, on such a basis, puts forward some new ideas. It has been emphatically pointed out that, in addition to the prominent E‐W structural zone that controls the Cu‐Mo deposits, there also exist N‐S and NE structures which dominate Pb‐Zn and Au mineralizations respectively. The formation of the copper deposit was attributed to the superimposition of three successive stages of mineralization related to volcano‐sedimentation and metamorphic and magmatic hydrothermal activities respectively.
REE Geochemistry of Skarns in the Tongshan Copper Deposit, Guichi, Anhui Province
Authors: Ruilong Qiu
Published: September 2010

Abstract

This paper presents REE abundance pattern and REE geochemistry of granodiorite porphyry, skarns, as well as late hydrothermal alterations in the Tongshan copper deposit, Guichi County and, in the light of their similarities and variations, deals with the genesis of the skarns and the transformation process of the post‐skarn hydrothermal alterations. On such a basis, the inference is drawn that the skarn‐forming solution was produced by further fractionation of residual magma, thus belonging to a transitional fluid between residual magma and hydrothermal solution which, with the continuous variation of its components during the metasomatism, tended to become a hydrothermal solution.
The Late Ordovician Wufengian Sediments and the Ordovician‐Silurian Boundary in Western Zhejiang Province
Authors: Jiaju Qian
Published: September 2010

Abstract The Late Ordovician Wufengian sediments in western Zhejiang include three facies: 1) graptolite shale facies, composed of two parts— the upper part the Yankou Formation, with the Diplograptus bohemicus (graptolite) zone and Dalmanitina sp. (trilobite), and the lower part the yuqian Formation with four graptolite zones: (4) the Paraorthograptus yuqianensis zone, (3) the Climacograptus venustus zone, (2) the Dicellograptus szechuanensis zone and (1) the Pseudoclimacograptus anhuiensis zone; 2) mixed facies, consisting of the Wenchang Formation in its upper part and the Changwu Formation in its lower; and 3) shelly limestone facies, whose upper and lower parts are separately the Wenchang Formation and Sanjushan Formation, containing Taeniolites, Proheliolites, etc. In this region the Dalmanitina‐Hirnantia bed is well exposed, and Da. and H. are associated with Diplograptus bohemicus, belonging to the late Late Ordovician.

The Ordovician‐Silurian boundary is drawn as follows: (1) for the graptolite facies, it lies between the Diplograptus bohemicus zone and Glyptograptus persculptus zone; (2) for the graptolite‐shelly limestone facies (brachiopod fauna), it is placed between the top of the Diplograptus bohemicus zone and the base of the horizon with the Eospirifer fauna; and 3) for the shelly facies (brachiopod fauna), it is drawn between the top of the horizon with the Dalmanitina‐Hirnantia fauna and the base of the horizon with the Eospirifer fauna.
The Genesis and Evolution of Alpine‐Type Ultrabasic Rocks in Western Junggar, Xinjiang
Authors: Ligui Peng
Published: September 2010

Abstract The alpine‐type ultrabasic rocks of the studied area have undergone plastic deformation under a temperature about 800–1200°C, a pressure about 0.9–1.68 GPa and differential stress of 0.2–0.35 GPa in relatively dry conditions, forming ultrabasic mylonite with porphyroclastic and mylonitic textures. Primary crystallized silicate melt inclusions and melt‐fluid inclusions are discovered in porphyroclastic minerals and ore‐forming chrome spinel. These rocks are formed under relatively stable physico‐chemical conditions through liquid immiscibility of silicate melts, at 1200°– 1300° C and 1.1–1.38 GPa, equivalent to a depth of 40–50 km. No inclusion has been found in recrystallized secondary olivine and pyroxene, indicating that the plastic deformation happened after the formation of the rocks.
Genesis of Podiform Chromite Deposits——Evidence from the Luobosa Chromite Deposits, Tibet
Authors: Xibin Wang , Peisheng Bao
Published: September 2010

Abstract Taking for example the Luobosa chromite deposit in Tibet combined with other deposits of the same type in the world, the paper discusses the genetic mechanism of podiform chromite deposits. The study indicates that chromite and dunite‐harzburgite are both the products of different degrees of partial melting of the same primary pyrolite (spinel lherzolite) and that chromite and dunite are the end product of higher degree of partial melting.

The melting mechanism lies in the conversion of the two subgroups of pyroxenes (Cpx and Opx) into olivine and spinel respectively as a result of their incongruent melting, accompanied by regulation and reformation of accessory chrome spinel and such rock‐forming minerals as Ol, Opx and Cpx, thus resulting in the close association of chromite deposits and dunite. The results of this study are of general significance for understanding the genesis of chromite deposits of the same type in the world.
Typification and synonymy of names inSantolina(Asteraceae: Anthemideae) published by Hoffmannsegg and Link
Authors: Rivero‐Guerra Aixa O.
Published: September 2010

During recent studies in theSantolina rosmarinifoliaL. aggregate, nomenclatural problems with the the namesS.impressaandS.semidentatapublished by Hoffmannsegg and Link were revealed. Here, both names are neotypified andS. rosmarinifoliavar.cinereaPau & Merino andS.zamoranaLosa are lectotypified. The criteria used to recogniseS.impressaandS.semidentataand their diagnostic characters are discussed. Revision of the lectotypes ofS.rosmarinifoliavar.cinereaPau & Merino and ofS.zamoranaLosa suggests that both names are synonyms ofS.semidentata. The full synonymy ofS. impressaandS. semidentatais provided.
Measurement of Entropy Generation in Microscale Thermal-Fluid Systems
Authors: Saffaripour Meghdad , Culham Richard
Published: September 2010

A new nonintrusive and whole field method for the measurement of entropy generation in microscale thermal-fluid devices is presented. The rate of entropy generation is a measure of the thermodynamic losses or irreversibilities associated with viscous effects and heat transfer in thermal-fluid systems. This method provides the entropy generation distribution in the device, thus enabling the designers to find and modify the areas producing high energy losses characterized by large entropy production rates. The entropy generation map is obtained by postprocessing the velocity and temperature distribution data, measured by micro particle image velocimetry and laser induced fluorescence methods, respectively. The velocity and temperature measurements lead to the frictional and thermal terms of entropy generation. One main application of this method is optimizing the efficiency of microchannel heatsinks, used in cooling of electronic devices. The minimum amount of entropy generation determines the optimum design parameters of heatsinks, leading to highest heat removal rates and at the same time, the lowest pressure drop across the heatsink. To show the capability of this technique, the entropy generation field in the transition region between a 100 μm wide and a 200 μm wide rectangular microchannel is measured. This method is used to measure thermal and frictional entropy generation rates in three different flow area transition geometries. The results can be used to determine which geometry has the highest thermal and hydraulic efficiencies.
Performance of Aluminum and Carbon Foams for Air Side Heat Transfer Augmentation
Authors: Garrity Patrick T. , Klausner James F. , Mei Renwei
Published: September 2010

The air side heat transfer performance of three aluminum foam samples and three modified carbon foam samples are examined for comparison with multilouvered fins often found in compact heat exchangers. The aluminum foam samples have a bulk density of 216 kg/m3 with pore sizes of 0.5, 1, and 2 mm. The modified carbon foam samples have bulk densities of 284, 317, and 400 kg/m3 and machined flow passages of 3.2 mm in diameter. The samples were placed in a forced convection arrangement using a foil heater as the heat source and ambient air as the sink. A constant heat flux of 9.77 kW/m2 is applied throughout the experiments with the mean air velocity ranging from 1 to 6 m/s as the control parameter. The steady volume-averaged momentum equation and a two-equation nonequilibrium heat transfer model are employed to extract the volumetric heat transfer coefficients. Pressure drop measurements are correlated with the Darcy–Forcheimer relation. Empirical heat transfer correlations for the aluminum and carbon foam samples are provided. Using a hypothetical heat exchanger considering only the thermal resistance between the ambient air and the outer tube wall, the air side performance for each sample is modeled based on the local heat transfer coefficients and friction factors obtained from experiments. The performance of each sample is evaluated based on a coefficient of performance (COP, defined as the ratio of the total heat removed to the electrical input of the blower), compactness factor (CF, defined as the total heat removed per unit volume), and power density (PD, defined as the total heat removed per unit mass). Results show the carbon foam samples provide significant improvement in CF but the COP and PD are considerably lower than that for comparable multilouvered fin heat exchangers.
A Semi-Empirical Heat Transfer Model for Forced Convection in Pin-Fin Heat Sinks Subjected to Nonuniform Heating
Authors: Feng S. S. , Kim T. , Lu T. J.
Published: September 2010

This paper presents a cost effective semi-empirical analytical model for convective heat transfer in pin-fin heat sinks subjected to nonuniform heating set by a circular hot gas impinging jet. Based on empirical correlations taken from the open literature, temperature variations in the heat sink are obtained from the finite volume solution of the semi-empirical model. Based on a purpose-built experimental setup, measurements of a substrate temperature are performed using an infrared camera. These, along with the convective fluid temperature measured at the exit of the pin-fin array, are compared against analytical model predictions, with overall good agreement achieved. Subsequently, the influences of the convection Reynolds number, substrate thickness, and thermal conductivity of material on the distribution of substrate temperature are quantified by the validated model. It is demonstrated that the present model is capable of predicting local thermal behaviors such as the footprints of the pin fins. In addition, with the spreading resistance captured accurately, the model can be used for the design optimization of pin-fin/substrate systems subjected to nonuniform heating.
Influence of Inter- and Intraband Transitions to Electron Temperature Decay in Noble Metals After Short-Pulsed Laser Heating
Authors: Hopkins Patrick E.
Published: September 2010

This work examines the effects of photonically induced interband excitations from the d-band to states at the Fermi energy on the electron temperature decay in noble metals. The change in the electron population in the d-band and the conduction band causes a change in electron heat capacity and electron-phonon coupling factor. In noble metals, due to the large d-band to Fermi energy separation, the contributions to electron heat capacity and electron-phonon coupling factor of intra- and interband transitions can be separated. The two temperature model describing electron-phonon heat transfer after short-pulsed laser heating is solved using the expressions for heat capacity and electron-phonon coupling factor after intra- and interband excitations, and the predicted electron temperature change of the intra- and interband excited electrons are examined. A critical fluence value is defined that represents the absorbed fluence needed to fill all available states at a given photon energy above the Fermi level. At high absorbed laser fluences and pulse energies greater than the interband transition threshold, the interband and intraband contributions to thermophysical properties differ and are shown to affect temporal electron temperature profiles.
Analytical Solution to Nonlinear Thermal Diffusion: Kirchhoff Versus Cole–Hopf Transformations
Authors: Vadasz Peter
Published: September 2010

The Kirchhoff transformation is the classical method of solution to the nonlinear thermal diffusion problem with temperature dependent properties. It essentially converts the nonlinear problem into a linear one if the thermal diffusivity is approximately constant. Unfortunately, with the only exception of an exponential dependence of the thermal conductivity on temperature, all other thermal conductivity functions produce an inconvenient form for the inverse transform. This paper shows that the Kirchhoff transformation is a particular consequence of the more general Cole–Hopf transformation. However, the classical presentation of the Kirchhoff transformation in terms of a definite integral is more restrictive than the result obtained from the Cole–Hopf transformation and it is this restrictiveness that causes the practical inconvenience in the form of the inverse transform. It is shown that a more compact and practically convenient form of the inverse transform can be obtained by using directly the result from the Cole–Hopf transformation, hence, making its application more attractive.
Analytical Solution Under Two-Flux Approximation to Radiative Heat Transfer in Absorbing Emitting and Anisotropically Scattering Medium
Authors: Xia Xin-Lin , Li Dong-Hui , Sun Feng-Xian
Published: September 2010

Radiative transfer in absorbing, emitting, and highly anisotropically scattering media is widely encountered in high temperature applications such as pulverized coal firing furnaces and high temperature thermal protection materials. Efficient and effective solution methods for the transfer process are very crucial, especially in thermal radiation related reverse problems and optimization designs. In this study, the analytical solution for radiative heat transfer in an absorbing, emitting, and anisotropically scattering slab between two parallel gray walls are derived under the two-flux approximation. Explicit expression for the radiative heat flux in a slab is obtained under two-flux approximation. The reliability and adaptability of an analytical solution is examined in case studies by comparing with the Monte Carlo results. Comparative studies indicate that the analytical solution can be used in radiative transfer calculation in an absorbing emitting and anisotropically scattering slab. It is much more applicable in a forward and isotropic scattering slab than in an absorbing one, especially in a forward scattering slab. Because of simplicity and high computing efficiency with the analytical solution, it may be useful in reverse radiative transfer problems, in optimization design, and in developing some numerical schemes on radiative heat transfer.
Formation Mechanism and Characteristics of a Liquid Microlayer in Microchannel Boiling System
Authors: Zhang Yaohua , Utaka Yoshio , Kashiwabara Yuki
Published: September 2010

Experiments were performed using the laser extinction method to measure the thickness of the liquid film formed by growing flattened bubbles in a microchannel for gap sizes of 0.5 mm, 0.3 mm, and 0.15 mm. Water, ethanol, and toluene were used as test fluids. A high-speed camera was also used to simultaneously measure the bubble growth process. It was confirmed that the gap size and bubble forefront velocity determined the initial microlayer thickness. The variation trend of the microlayer thickness relative to the velocity of the interface was divided into two regions: region I, where the velocity is small and the thickness increases linearly with increasing velocity, and region II, where the thickness is almost constant or decreased slightly with increasing velocity. Furthermore, a nondimensional correlation for investigating the effects of test materials and gap sizes on microlayer thickness is presented. An analysis of the results showed that the boundaries of the two regions correspond to a Weber number of approximately 110, and in the region where the Weber number was smaller than 110, the thickness of the microlayer was thinner for the liquid whose value of ρ0.62ν0.42σ−0.62 was relatively small. However, for the region where Weber number was larger than 110, the smaller the kinematic viscosity of the liquid, the thinner the microlayer became.
Calibration of a Computational Model to Predict Mist/Steam Impinging Jets Cooling With an Application to Gas Turbine Blades
Authors: Wang Ting , Dhanasekaran T. S.
Published: September 2010

In heavy-frame advanced turbine systems, steam is used as a coolant for turbine blade cooling. The concept of injecting mist into the impinging jets of steam was experimentally proved as an effective way of significantly enhancing the cooling effectiveness in the laboratory under low pressure and temperature conditions. However, whether or not mist/steam cooling is applicable under actual gas turbine operating conditions is still subject to further verification. Recognizing the difficulties of conducting experiments in an actual high-pressure, high-temperature working gas turbine, a simulation using a computational fluid dynamic (CFD) model calibrated with laboratory data would be an opted approach. To this end, the present study conducts a CFD model calibration against the database of two experimental cases including a slot impinging jet and three rows of staggered impinging jets. The calibrated CFD model was then used to predict the mist cooling enhancement at the elevated gas turbine working condition. Using the experimental results, the CFD model has been tuned by employing different turbulence models, computational cells, and wall y+ values. In addition, the effects of different forces (e.g., drag, thermophoretic, Brownian, and Saffman’s lift force) are also studied. None of the models is a good predictor for all the flow regions from near the stagnation region to far-field downstream of the jets. Overall speaking, both standard k-ε and Reynolds stress model (RSM) turbulence models perform better than other models. The RSM model has produced the closest results to the experimental data due to its capability of modeling the nonisotropic turbulence shear stresses in the 3D impinging jet fields. The simulated results show that the calibrated CFD model can predict the heat transfer coefficient of steam-only case within 2–5% deviations from the experimental results for all the cases. When mist is employed, the prediction of wall temperatures is within 5% for a slot jet and within 10% for three-row jets. The predicted results with 1.5% mist at the gas turbine working condition show the mist cooling enhancement of 20%, whereas in the laboratory condition, the enhancement is predicted as 80%. Increasing mist ratio to 5% increased the cooling enhancement to about 100% at the gas turbine working condition.
Entropy-Based Design of Liquid-Repellent Nanochannels Destined to Energy Absorption Systems (EAS)
Authors: Suciu Claudiu Valentin
Published: September 2010

Entropy production is a key parameter to evaluate the maximal efficiency of engineering systems. Recently, liquid penetration/exudation in/from non-wetted nanoporous solids was employed to develop ecological energy absorption systems (EAS). Dissipation is based on the well-known fact that external work must be done to spread a liquid on a lyophobic surface. Minimization of the entropy production is usually required to obtain high-efficiency engineering systems. However, enhancement of the EAS nano-damping ability requires oppositely maximization of the entropy generated through interfacial, frictional and thermal instabilities. A model of the entropy production during water flow inside of a liquid-repellent silica nanopore is proposed. A mixture of hydrophobized nanoporous silica and water is introduced inside of a compression-decompression chamber. Using a thermo-camera, the temperature distribution on the external surface of the test chamber is recorded versus the working time and the positions of main heat sources are identified. Such experiments allow determination of the overall dissipation, generated heat, and the heat flux at the wall of silica nanochannel. Then, the test rig is introduced inside of an incubator that allows temperature adjustment in the range 0∼50 °C and the thermal effects on the hysteresis and damping performances are evaluated. From such tests one determines the variation of the solid surface tension on the nanochannel wall versus temperature. Entropy (heat) production in the nanochannel is estimated and compared with experimental data to validate the proposed model.
Transient Electroosmotic Flow in Slit Microchannel Containing Salt-Free Medium
Authors: Chang Shih-Hsiang
Published: September 2010

A theoretical study on the transient electroosmotic flow through a slit microchannel containing a salt-free medium is presented for both constant surface charge density and constant surface potential. The exact analytical solutions for the electric potential distribution and the transient electroosmotic flow velocity are derived by solving the nonlinear Poisson-Boltzmann equation and the Navier-Stokes equation. Based on these results, a systematic parametric study on the characteristics of the transient electroosmotic flow is detailed. The general behavior of electroosmotic flow in a planar slit is similar to that in a capillary tube; however, the rate of evolution of the flow in a tube with time is faster by a factor of about 2.4 than that in a slit with its width equal to the tube diameter.
Data Acquisition and Physical Interpretation With Respect to Micro Channel Flows: A Delicate Issue
Authors: Gloss D. , Herwig H.
Published: September 2010

This study is meant as a warning and an encouragement alike, when it comes to data aquisition, processing and interpretation in micro sized devices. In our study we start with the raw data gained from radial channel flow between two opposing discs with flow from the centre to the edge. Processing these data with certain concepts of Knudsen number, or more general “micro effects” in mind, is shown to be not at all straightforward. Depending on how critically these data are looked upon and how deep the experimental device is analysed very different “results” are gained.
Analysis of Multi-Layer Mini- and Micro- Channel Heat Sinks in Single Phase Flow Using One and Two Equation Porous Media Models
Authors: Hassell Bryan , Ortega Alfonso
Published: September 2010

Research in liquid cooled mini- and micro-channel heat sinks is growing due to the potentially high heat fluxes that can be dissipated with such devices. Deterministic mini- or micro-channel heat sinks with rectilinear channels are derivatives of more generalized porous structures. The present paper is devoted to an examination of the application of one and two equation porous media theory for modeling the thermal-fluid behavior of stacked multi-layer micro- or mini-channel heat sinks. One surface of the heat sink is exposed to high heat flux, while the other is insulated. The objectives of the paper are to examine generalizations of the geometric scaling that is elucidated by adopting a porous media approach, and the unification of models for apparently dissimilar geometries. This paper examines the relative accuracy and computational efficiency of one and two equation approaches. The error between the two models and the experimental data are examined by an error map given as a function of conductivity ratios, Darcy number (Da) and Reynolds number (Re).
Sound Propagation Through a Gas in Microscale
Authors: Sharipov Felix , Kalempa Denize
Published: September 2010

A sound wave propagation through a rarefied gas is investigated on the basis of the linearized kinetic equation by taking into account the influence of the receptor of sound waves on the solution of the problem. In order to do so, a plate oscillating in the normal direction to its own plane is considered as a sound wave source while a stationary one is considered as being the receptor of sound waves. The distance between the plates can be of the order of the molecular mean free path. It is assumed a fully established oscillation so that the solution of the kinetic equation depends on time harmonically. The main parameters of the problem are the oscillation speed parameter, defined as the ratio of intermolecular collision frequency to the sound frequency, and the Knudsen number, defined as the ratio of the molecular mean free path to a characteristic scale of the gas flow. The problem is solved over a wide range of both parameters and the amplitudes and phases of all the macrocharacteristics of the gas flow are calculated.
The Synthesis and Characterizations of Narrow-Dispersed Copper Nanoparticles
Authors: Yu Wei , Xie Huaqing , Chen Lifei , Li Yang , Zhang Chen
Published: September 2010

A controlled synthesis method for preparing narrow-dispersed copper nanoparticles, using water and ethylene glycol as the reaction mediums respectively, has been reported. In order to obtain pure-phase copper nanoparticles using water, the reaction time of 8h is essential. Owing to the reduction property of ethylene glycol, the reaction rate using ethylene glycol is higher. In addition, the amount of reduction agent can reduce largely. Polyvinyl pyrrolidone plays great role on the size of copper particles, and the increasing of polyvinyl pyrrolidone concentration attributes to the smaller dimension particles. The mean diameter is about 4 nm when the concentration of polyvinyl pyrrolidone is 0.5 mmol/L. Polyvinyl pyrrolidone acts as the polymeric capping agents in the reaction, preventing the agglomeration of the copper nanoparticles. When water is the reaction medium, Cu2+ complex is reduced to Cu+ complex firstly, and the further reduction of Cu+ forms the pure copper nanoparticle.
The Study of Intelligent Fuzzy Weighted Input Estimation Method Combined With the Experiment Verification
Authors: Lee Ming-Hui , Chen Tsung-Chien , Yu Tsu-Ping
Published: September 2010

The innovative intelligent fuzzy weighted input estimation method (FWIEM) can be applied to the inverse heat transfer conduction problem (IHCP) to estimate the unknown time-varying heat flux as presented in this paper. The feasibility of this method can be verified by adopting the temperature measurement experiment. The experiment modular may be designed by using 4 copper samples with different thicknesses. Furthermore, the bottoms of the samples are heated by applying the standard heat source, and the temperatures on the tops are measured by using the thermocouples. The temperature measurements are then regarded as the inputs into the presented method to estimate the heat flux in the bottoms of samples. The influence on the estimation caused by the processing noise covariance Q, the weighting factor γ, the sampling time interval Δt, and the space discrete interval Δx, will be investigated by utilizing the experiment verification. The results show that this method is efficient and robust to estimate the unknown time-varying heat input.
Experimental and Numerical Investigation of Droplet Transport in a Diffuser/Nozzle Structure
Authors: Liu Jing , Nguyen Nam-Trung , Yap Yit Fatt
Published: September 2010

This paper investigates the droplet behavior in serially connected diffuser/nozzle structures using experimental and simulation methods. The serial structures act as diffusers in the expanding flow direction, and as nozzles in the converging flow direction. The opening angle of the structures is 45 degree. The test devices were fabricated in polydimethylsiloxane (PDMS) using soft lithography technique. The droplets under investigation were formed using T-junctions. Mineral oil with 2%w/w surfactant Span 80 and de-ionized (DI) water with fluorescent dye work as the carrier phase and the dispersed phase, respectively. The droplet behavior was captured using a CCD camera. The corresponding pressure drops across the test section were measured in both diffuser and nozzle flow direction using an external pressure sensor connected to the pressure port integrated on the device. The pressure drops across the test structure of two cases, with and without droplet, were analyzed and compared. The experimental results showed a linear relationship between the pressure drop and the oil flow rate. Furthermore, rectification effect was observed in the test device. The pressure drop in the diffuser configuration is higher than that of the nozzle configuration. Numerical models were employed to study the dynamics of the pressure drop across the diffuser/nozzle structures as well as the deformation of the droplet, which is modelled using level-set method. Corresponding to the experiments, two cases with and without were investigated and compared.
Effect of Partition Wall Thickness on Heat Transfer Characteristics of a Gas-to-Gas Counterflow Microchannel Heat Exchanger
Authors: Koyama K. , Hong C. , Asako Y.
Published: September 2010

Effect of partition wall thickness on heat transfer characteristics of a two-stream counterflow gas-to-gas microchannel heat exchanger has been numerically investigated. The flow passages of the microchannel heat exchanger are plane channels of 100 μm in height and 20 mm in length. The partition wall thickness ranges from 20 μm to 200 μm. The material of the partition wall is assumed to be stainless steel. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian method. The computations were performed for a wide range of flow rate to investigate effect of partition wall thickness on heat transfer characteristics of the microchannel heat exchanger. The computational results are presented in form of temperature distributions, bulk temperatures, total temperatures, and heat flux variations along the channels. We have concluded that the partition wall thickness affects significantly heat transfer characteristics of a microchannel heat exchanger.
Experimental Investigation of Gaseous Flow in a Micro-Tube
Authors: Yoshida Yasuhiro , Hong Chungpyo , Asako Yutaka , Suzuki Koichi
Published: September 2010

Experimental investigations on nitrogen gas flow characteristics were performed for a micro-tube. The micro-tube was fabricated in a stainless steel block by electrical discharge machining (EDM). The tube diameter was 326 μm and the ratio of length to diameter was 200. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 1.4. The outlet pressure was fixed at atmospheric conditions. The pressure was locally measured at five locations along tube length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. The result shows that f·Re is a function of Mach number and higher than incompressible value, 64 due to the compressibility effect. The values of f·Re were compared with f·Re correlation in literature. In additional experiments, Mach number at the micro-tube exit was measured by using a Shadowgraph system which visualizes the shock wave of the gas. The micro-tube with 400 μm in diameter was used for the experiment. The super sonic flow was observed since Mach number at the micro-tube exit was beyond unity. The experimental results for laminar flow were compared with the numerical results obtained by the arbitrary-Lagrangian-Eulerian method. The both results are in excellent agreement.
Laser-Induced Fluorescence Detection of Copper Ion With a Rhodamine Derivative by a Capillary Electrophoresis Microchip
Authors: Yu Yong , Yang Meng , Shen Feng
Published: September 2010

A capillary electrophoresis microchip system with a confocal LIF detector was successfully constructed. RBPhOH, a new fluorescence dye synthesized from rhodamine B, was first investigated in a glass microchip for the selective and sensitive determination of copper ion by LIF method. The influences of the pH value, concentration of running buffer, detection voltage, and sample loading time on the response of LIF detector were studied. RBPhOH dissolved in 20 mM pH 6.0 Tris containing 10% acetonitrile could detect copper ions with a detection limit of 1.34×10−7 mol L−1 (S/N=3), an order of magnitude lower than those of conductivity detectors.
The Numerical Simulation of a Passive Interdigital Micromixer With Uneven Lamellar Width
Authors: Fan YanFeng , Hassan Ibrahim
Published: September 2010

In this paper, a passive micromixer with interdigital structure is proposed and investigated using numerical simulations. The micromixer contains three layers to achieve the interdigital flow structure. The height of mixing channels is fixed as 0.2 mm. The total width of inlets is 0.9 mm. The mixing regime is rectangular in shape. The Reynolds number, measured at the entrance of straight channel, ranges from 5 to 60. Grid independence is performed to minimize the influence of numerical diffusion on simulation results. The grid size is selected as 6 μm, which can be considered as optimal. The interdigital micromixers with straight downstream channels are designed and simulated. In order to achieve better mixing near the inner walls, uneven lamellae width of each species is applied to create a larger concentration gradient near the inner walls. The results show that the micromixer with uneven lamellar width is able to enhance the mixing near the inner walls. A new passive micromixer with the uneven interdigital inlets is also designed to improve the mixing efficiency at high Re. The simulation results show that this new micromixer has a mixing efficiency larger than 80%, and a maximum pressure drop of 2.7 KPa.
Thermal Bubble Dynamics Under the Effect of Acoustic Vibration
Authors: Qu Xiaopeng , Qiu Huihe
Published: September 2010

The effect of acoustic field on the dynamics of micro thermal bubble is investigated in this paper. The micro thermal bubbles were generated by a micro heater which was fabricated by standard Micro-Electro-Mechanical-System (MEMS) technology and integrated into a mini chamber. The acoustic field formed in the mini chamber was generated by a piezoelectric plate which was adhered on the top side of the chamber’s wall. The dynamics and related heat transfer induced by the micro heater generated vapor bubble with and without the existing of acoustic field were characterized by a high speed photograph system and a micro temperature sensor. Through the experiments, it was found that in two different conditions, the temperature changing induced by the micro heater generated vapor bubble was significantly different. From the analysis of the high speed photograph results, the acoustic force induced micro thermal bubble movements, such as forcibly removing, collapsing and sweeping, were the main effects of acoustic enhanced boiling heat transfer. The experimental results and theoretical analysis were helpful for understanding of the mechanisms of acoustic enhanced boiling heat transfer and development of novel micro cooling devices.
3-D Visualization of Flow in Microscale Jet Impingement System
Authors: Won Yoon Jin , David Milnes , Wang Evelyn N. , Goodson Kenneth E. , Kenny Thomas W.
Published: September 2010

This paper presents our recent work on the reconstruction of three-dimensional (3-D) flow fields in a microscale jet impingement cooling flows. We use micron-resolution PIV to capture successive two-dimensional (2-D) “slices” of the flow field in a 3-D structure, and compare with models of flow near microscale jets. This approach is specifically constructed to determine the z-component of the flow velocities, which play a key role in enhancing heat transfer at the impingement surface. These new results will enable a predictive design capability for microjet impingement cooling structures for high power electronics.
Transport Phenomena in Novel Microstructures for Use in Thermal Separation Processes
Authors: Wiesegger Lukas E. , Knauss Ralf P. , Winkler Thomas , Maikowske Stefan , Brandner Ju¨rgen J. , Marr Rolf J.
Published: September 2010

In the present work novel microstructures are developed and studied by means of analytical and numerical methods. These microstructures form part of a demonstration microdevice to carry out a distillation without chemical reaction, two for the liquid and gaseous phase distribution/collection, and one for the liquid/gas mass transfer (“μTU-I,-II”). A solution for the 3D velocity field for the velocity component w in flow direction can be given for the rectangular and semicircular microchannel by using a lubrication approximation which gives good realistic values for the Reynolds number at low flow rates comparing to the common 2D approaches. The μTU-I is studied using the CFD code (6.3 FLUENT ® - 3ddp) by the approach of the VOF model. The simulations are performed with the test system methanol/water (distillation). By varying the flow rates of both phases and the contact angle, the condition until the occurrence of flooding of the microunit “μTU-I” is determined. The flooding and the optimum operating conditions of a new optimized configuration “μTU-II” -microunit are also investigated by means of numerical simulation (CFD). It can be shown that longitudinal instability is generated. Based on several concepts for liquid and gaseous phase distribution/collection by the Forschungszentrum Karlsruhe, novel microstructures (“Liquid-Distribution-Collection-Microstructure”, “Vapor-Distribution-Collection-Microstructure”) for both phases are developed, studied and optimized by using CFD. The results of all studies are verified based on the demonstration device in the laboratory.
Dynamic Optimization of an Evaporator by a Nonlinear Model Predictive Controller for Operation at Modular Micro Rectification
Authors: Knauss Ralf , Wiesegger Lukas E. , Marr Rolf , Brandner Ju¨rgen J.
Published: September 2010

Arranging micro-structured equipment to plants whole production processes can be realized with maximum efficiency in tightest space. Unit operations are thereby represented as individual functional modules in shape of micro devices. In a multi unit operation plant a correspondingly large number of manipulable variables have to be coordinated. Due to the design of micro-scaled devices plants form sophisticated systems, while for a fully optimized control still no common satisfying solutions exist. A system of modular, discontinuous phase contacting, micro rectification consists of unit operations heating, cooling, mixing and separating. Heat exchangers, mixers and cyclones for phase separation can be arranged to a counter-current rectification system with maximum mass-transfer efficiency every unit. Operating an electrical heated evaporator for modular rectification purposes a strong coupling of mass flow with the vapor fraction and the outlet temperature can be observed [4]. Operating at a predefined state for mass flow, temperature and vapor fraction may only be possible with difficulties using traditional methods of linear control technology. For dynamic optimization of the multivariable micro-structured evaporator principle of Nonlinear Model Predictive Control (NMPC) was generically formulated in C++ and implemented to LABVIEW 7. Every discrete time step an objective function is generated from nonlinear process models in the form of grouped NARX-polynomials. Optimal sequences of control actions for plant operation are evolved. The resulting constrained cost function is non-convex making detection of relative local optimum a difficult task. This obstacle can be gone around using heuristic optimization algorithm in combination with traditional techniques. Based on experimental results it was demonstrated that NMPC keeps the coupled variables mass flow and temperature energy saving with minimal control activity in the entire two-phase region on their set-points.