In order to analyze the boiling and capillary limitations of two-phase heat transport devices, the existing models developed by Chi and Peterson and the existing experimental data carried out with various micro channel wick structures from literature were collected for benchmark. It was found that the dominant parameters for boiling and capillary limitations were the nucleation sites and structure geometries of the micro channels, and important parameters were considered to modify the models empirically. It was also found that for micro channel structures the inclined angle is sensitive to the capillary limitations and not to boiling limitations. By properly estimating the nucleation sites and empirical coefficients for micro channels needed by the newly modified models, the boiling and capillary limitations can be accurately predicted, and hence the applicability of the modified models is confirmed. Based on this, a numerical analysis was then carried out to investigate the trends of boiling and capillary limitations of the micro channel wick structures. Effects of the channel geometries and arrangement were taken into account, including the aspect ratio and structure size of the micro channels. Furthermore, the effects of inclined angle and contact angle were also analyzed. The present results can provide a design reference of performance trends of micro channel wick structures.

The possibility of cooling enhancement of flat plate heat pipes (FPHPs) by tilting was examined experimentally in this study. All of the FPHPs were made of Al and were partially filled with acetone. They had the same size of 120 mm (length) by 36 mm (width) by 2.5 mm (thickness) and the same liquid filling ratio of 25.1%. The effects of six tilting angles of -30°, -15°, -10°, 0°, 45°, and 90° were explored. The results showed that the thermal resistance decreased and the effective thermal conductivity increased when the tilting angle was increased. By increasing the tilting angle from 0° to 45° and further to 90°, the maximum effective thermal conductivity increased by a factor of 1.205 from 4561 W/mK to 5497 W/mK and of 1.212 to 5530 W/mK, respectively. The corresponding maximum heat transport capability increased by a factor of 2.89 from 39.8 W to 115 W and of 3.27 to 130 W. Hence, by proper tilting into positve angles, cooling enhancement of the FPHPs can be greatly achieved.

In this paper, the dynamic stall of S809 airfoil that widely used in horizontal axis wind turbine, in different reduced frequencies is investigated. The simulation was carried out numerically handling Navier-Stokes equations. For this purpose, the segregated solver with SIMPLE algorithm was chosen to solve the momentum equations. The effect of turbulence on the flow field is taken into account using Shear Stress Transport (SST) K-ω turbulence model. The obtained numerical results are compared with experimental and a few numerical results. The results indicate that the K-ω SST model is in good agreement with experimental results for both steady and unsteady conditions. Furthermore, a non-dimensional parameter, relating the acceleration of unsteady free stream velocity and acceleration of pitch motion (known as reduced frequency), is also investigated. In addition, the results show that any increase in the reduced frequency increases the instantaneous aerodynamic characteristics of oscillating airfoil.

A mathematical model has been developed to determine the best geometry of a compact heat exchanger in this research study. Accordingly, an objective function was introduced to define the optimized structure of the exchanger. Two main targets were pursued in this regard. First was the rate of existing discrepancy between the possible heat transfer rate in the exchanger and the maximum rate. Second was possible heat transfer consideration between exchanging gasses and incoming air of the furnace. A sample shell and tube heat exchanger of existing tube in a processing industry has been studied and the calculations have been performed to solve the relevant equations. In addition, a comprehensive code to design an optimized compact heat exchanger for heat recovery of the furnaces has been presented. Then, data gathering and model synchronization caused to a preliminary evaluation of model quality. Thus, for increasing accuracy level of mentioned research, along with measurements’ correction program, model modification has been done and new results were calculated. Optimization model analysis showed that by using this approach, not only significant heat conservation can be achieved, but also suggested procedure might be completely economical.

The generalized differential quadrature (GDQ) method is used to investigate the transient response of magnetostrictive functionally graded material (FGM) circular cylindrical shells. The effects of control gain value, thermal load temperature and power-law index on transient responses of dominant normal displacement and thermal stress are analyzed. With velocity feedback and suitable product values of coil constant by control gain in the magnetostrictive FGM shells can reduce the transient amplitude of displacement into a smaller value.

Using the method of Laplace transform, an analytical solution of unsteady rotating electroosmotic flow (EOF) through a parallel plate microchannel is presented. The analysis is based upon the linearized Poisson-Boltzmann equation describing electrical potential distribution and the Navies Stokes equation representing flow field in the rotating coordinate system. The discrepancy of present problem from classical EOF is that the velocity fields are two-dimensional. The rotating EOF velocity profile and flow rate greatly depend on time t, rotating parameter ω and the electrokinetic width K (ratio of half height of microchannel to thickness of electric double layer). The influence of the above dimensionless parameters on transient EOF velocity, volume flow rate and EO spiral is investigated.

Combined free and forced convection Couette-Hartmann flow of a viscous, incompressible and electrically conducting fluid in rotating channel with arbitrary conducting walls in the presence of Hall current is investigated. Boundary conditions for magnetic field and expressions for shear stresses at the walls and mass flow rate are derived. Asymptotic analysis of solution for large values of rotation and magnetic parameters is performed to highlight nature of modified Ekmann and Hartmann boundary layers. Numerical solution of non-linear energy equation and rate of heat transfer at the walls are computed with the help of MATHEMATICA. It is found that velocity depends on wall conductance ratio of moving wall and on the sum of wall conductance ratios of both the walls of channel. There arises reverse flow in the secondary flow direction near central region of the channel due to thermal buoyancy force. Thermal buoyancy force, rotation, Hall current and wall conductance ratios resist primary fluid velocity whereas thermal buoyancy force and Hall current favor secondary fluid velocity in the region near lower wall of the channel. Magnetic field favors both the primary and secondary fluid velocities in the region near lower wall of the channel.

This paper deals with studying fluid flow and heat transfer of nanofluid through a forward facing step channel which is affected by a uniform magnetic field transverse to fluid flow. All the channel walls are assumed to be in constant temperature and the fluid temperature at the channel inlet is less than that of the walls. Also, the nanofluid is considered as a single-phase Newtonian fluid and the proper correlations were utilized to determine the thermophysical properties of nanofluid. Therefore, a code has been developed and two-dimensional continuity, momentum and energy equations were solved, using CFD technique. The computations were conducted for different values of the Reynolds and Hartmann numbers, and contraction ratio and an extensive range of nanoparticles volume fraction. The results indicated that flow separation and reattachment phenomena, in vicinity of the step edge, could be influenced strongly by magnetic field and the average Nusselt number is increased significantly by increasing nanoparticles volume fraction and Hartmann number.

The journal bearings which are designed for heavy-duty operations could experience different lubricant density due to high bearing loads. In the present work, hydrodynamic behaviour of finite length journal bearings under laminar and isoviscous flow with variable density are investigated. For this purpose, three-dimensional continuity and momentum equations along with a proper density-pressure relation are solved numerically, using CFD technique. Also, an appropriate cavitation model based on mass conservation is involved in the computation. Because of complex geometry of journal bearing, a conformal mapping is employed to generate an orthogonal grid and the governing equations are transformed in the computational domain. Since the degree of oil compressibility can be depended to the type of lubricant, typical mineral and synthetic oils treatments are modelled, separately. Results indicate that the oil compressibility effect leads to increasing load carrying capacity such that this increase is slightly more for the synthetic oil.

This paper proposes a systematic methodology to obtain a closed-form formulation for dynamics analysis of a novel spherical robot that is called a 3(RPSP)-S parallel manipulator. The proposed manipulator provides high rotational displacement of the moving platform for low angular displacement of the motors. The advised robot is suitable for repetitive oscillatory applications (for example, wrist and ankle rehabilitation and table of autopilot and gyroscope life test, etc.). First, we describe the structure of the proposed manipulator and solve the inverse kinematics problem of the manipulator. Next, based on the principle of virtual work, a methodology for deriving the dynamical equations of motion is developed. The elaborated approach shows that the inverse dynamics of the manipulator can be reduced to solving a system of three linear equations in three unknowns. Finally, a computational algorithm to solve the inverse dynamics of the manipulator is advised and several trajectories of the moving platform are simulated and verified by a special dynamics modeling commercial software (MSC ADAMS).

Simulation of the 3-D, fully developed turbulent channel flows laden with various mass loading ratios of particles is made using an Eulerian-Lagrangian approach in which the carrier-fluid flow field is solved with a low-Reynolds-number k-ε turbulence model while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. Effects of inter-particle collisions and particle-wall collisions under different extents of wall roughness on particle dispersion are addressed in the study. A cost-effective searching algorithm of collision pair among particles is developed. It is found that the effects of inter-particle collisions on particle dispersion cannot be negligible when the ratio of the mean free time of particle to the mean particle relaxation time of particle is less or equal to O(10). In addition, the wall roughness extent plays an important role in the simulation of particle-wall collisions particularly for cases with small mass loading ratios.

This study investigated four electrolytes (tap water, mineral water, seawater, and Al2O3 nanoparticles emulsified in deionized water) to prepare nanofluids for enhancing their microgeneration and heattransfer capabilities by conducting thermoelectric performance experiments on power generation facilities. This study first performed a two-step synthesis process by using emulsion-ultrasonic technology for fabricating an Al2O3 nanofluid to determine the optimal suspended stability for the alumina nanofluid used as an electrolyte according to the Zeta potential, pH value, thermal conductivity, and viscosity. The alumina nanofluid was then compared with the other aqueous solutions to determine the characteristics of the effects of the output currents, voltages, resistances, and temperature distributions at different operating temperatures, distances, and electrode areas. Finally, the emulsifying effect of the alumina nanofluid between 0 wt % and 2 wt % demonstrated the most favorable stability, particle fraction, thermal conductivity, and stable current output.

A new approach for the analysis of stress intensity factors (SIFs) for cracked plane plate is proposed based on the wavelet finite element method using the scaling functions of B-spline wavelet on the interval (BSWI). The performance of the method is investigated through the comparison of the results with the available numerical examples in the literate. It is shown that the solution quality is much better than that of the traditional adaptive finite element method. Though the method is applied to plane structures in this paper, it can be extended to solving problems for other classes of structures.

This paper analytically investigates the reaction phenomenon in micro-combustors using a two-dimensional model. The length of micro-combustor is considered at finite length that makes a better physical model than other works. The micro-combustor medium is divided into three integral zones composed of preheat, reaction and post flame where the governing equations are solved using the matching conditions of neighboring zones. The reaction zone thickness is considered as a variable and predicted by an iterative solution. In order to validate the model, normalized magnitude of maximum temperature is compared with published computational data for different values of Peclet number that shows an acceptable agreement that confirms the accuracy of the predicted data. Since a higher wall temperature causes the reaction to be faster, increasing the normalized wall temperature will result to reduce reaction zone thickness.

Based on the conformal mapping, this paper provides a closed form solution for the degenerate scale of the hypocycloid hole in plane elasticity. In the derivation, we assume the vanishing displacements along the boundary in the degenerate scale problem. Some functions in the boundary condition are decomposed into three parts with particular behavior. Even the displacements are vanishing along the boundary of an exterior region, the displacements and stresses are not equal to zero in the exterior region. This is a particular feature in the degenerate scale problem.

In the present paper the propagation of torsional surface waves is discussed in an inhomogeneous elastic layer lying over a fluid saturated porous half space. The inhomogeneity in rigidity and density in the inhomogeneous layer plays an important role in the propagation of torsional surface waves. The presence of fluid in the pores diminishes the velocity. Further, it is seen that if the layer becomes homogeneous and the porous half space is replaced by a homogeneous half space, the velocity of the torsional surface waves coincides with that of Love wave. The effect of inhomogeneity factors and porosity factor on the phase velocity of torsional surface wave is delimitated by means of graphs.