Nanofluid multi-phase convective heat transfer in closed domain: Simulation with lattice Boltzmann method

The lattice Boltzmann method is applied to simulate the thermal field and flow field of nanofluid natural convection in a square cavity. The heat transfer characteristics of nanofluid are compared with that of water to explore nanofluid heat transfer mechanism. The flow field shows different characters at different Rayleigh number and the average Nusselt number is obtained changing with Rayleigh number.     

An accurate dual-gate HFET nonlinear model for millimeter-wave MMIC design

An accurate nonlinear model for dual-gate HFETs is presented in this paper. Because of the complexity of the global equivalent circuit, the dual-gate transistor is modeled as two single-gate devices in cascode configuration. A good agreement between the measured and simulated performance is obtained, and its validity is proved as it was used for the design of an MMIC mixer at V-band. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 315–320, 1998.     

Strength,durability, and micro-structural properties of concrete made with used-foundry sand (UFS)

This paper presents the design of concrete mixes made with used-foundry (UFS) sand as partial replacement of fine aggregates. Various mechanical properties are evaluated (compressive strength, and split-tensile strength). Durability of the concrete regarding resistance to chloride penetration, and carbonation is also evaluated. Test results indicate that industrial by-products can produce concrete with sufficient strength and durability to replace normal concrete. Compressive strength, and split-tensile strength, was determined at 28, 90 and 365 days along with carbonation and rapid chloride penetration resistance at 90 and 365 days. Comparative strength development of foundry sand mixes in relation to the control mix i.e. mix without foundry sand was observed. The maximum carbonation depth in natural environment, for mixes containing foundry sand never exceeded 2.5 mm at 90 days and 5 mm at 365 days. The RCPT values, as per ASTM C 1202-97, were less than 750 coulombs at 90 days and 500 coulombs at 365 days which comes under very low category. Thereby, indicating effective use of foundry sand as an alternate material, as partial replacement of fine aggregates in concrete. Micro-structural investigations of control mix and mixes with various percentages of foundry sand were also performed using XRD and SEM techniques. The micro-structural investigations shed some light on the nature of variation in strength at the different replacements of fine aggregates with foundry sand, in concrete.     

Hydrogeological Behavior of a Store-and-Release Cover: A Comparison Between Field Column Tests and Numerical Predictions With or Without Hysteresis Effects

Non-hysteretic numerical codes are often used to design store-and-release (SR) cover systems. Hysteretic and non-hysteretic predictions were compared using field measurements with instrumented column tests, consisting of fine-grained SR material (phosphate limestone waste) with high hysteretic behavior (hysteretic ratio ≈11) placed over a capillary break layer. Transient unsaturated water flow was then predicted using a one-dimensional code (HYDRUS-1D) under semi-arid climatic conditions over 1 year. Non-hysteretic simulation based on the main wetting curve of the SR material and hysteretic simulation were validated with the measured data. The compared results showed better agreement between measured and predicted values for non-hysteretic simulation during wet periods, whereas the hysteretic scenario showed better agreement with field measurements during dry periods. The influence of hysteresis effects on the complex transient unsaturated water flow of the tested scenarios and conditions is considered minor.     

Multidentate Cyclohexylphosphonic Acid as Corrosion Inhibitor for Structural Steel in 3.5% NaCl Solution: An Experimental and Computational Study

Protection of Metals and Physical Chemistry of Surfaces - The inhibition effect of cyclohexylphosphonic acid (CHPA) on the corrosion of structural steel (EN 10027) in 3.5% sodium chloride solution...     

Performance analysis of Vernier slotted doubly salient permanent magnet generator for wind power

This paper presents the impact results of the variation of the rotor and the stator tooth pitches (Vernier effect), on the waveform of the back-electromotive force (EMF) generated by the low speed Doubly Salient Permanent Magnet machine (DSPM). The rotating electrical machines with and without Vernier effect are designed and optimized using genetic algorithms combined with finite element method. The optimization of machines parameters is focused on the maximization of the mass to torque ratio. The results show that the machine with Vernier effect has better performances. The obtained Vernier slotted doubly salient permanent magnet generator is then integrated into an autonomous wind energy conversion system. Simulations tests are carried out through Matlab/Simulink. The results show that the proposed machine is a valid and inexpensive alternative for directly coupled wind turbines.     

Optimizing reactors selection and sequencing: Minimum cost versus minimum volume

The present investigation targets minimum cost of reactors in series for the case of one single chemical reaction, considering plug flow and stirred tank reactor（s） in the sequence of flow reactors. Using Guthrie＇s cost correlations three typical cases were considered based on the profile of the reaction rate reciprocal versus conversion. Significant differences were found compared to the classical approach targeting minimum total reactor volume.