A PROPOSED METHODOLOGY TO EVALUATE SPECIFIC APPLICATIONS OF EXTENDED SURFACES IN INDUSTRIAL EQUIPMENT

The concept of Passive Cooling fits into a number of technological options involving constructive elements, whereby the heat exchange area of a surface being cooled by a surrounding fluid medium occurs. Thus, the increase in area results in an increase in the surface heat dissipation rate for the refrigerant, inferring only a single cost, i.e. the construction cost. Among the available technical possibilities, the use of extended surfaces, known as fins, stands out. The present work focuses on the use of fins on three very common electrical devices in the industrial environment, which present a great need for cooling.They are: three-phase transformer, frequency inverter and induction electric motor. The study is dedicated to a theoretical evaluation of the use of the fin profiles used in these equipments, since the manufacturers do not make their design data available to the public. Thus, a methodology was developed for this evaluation, including comparison of the results between the original profiles of these equipments with an alternative profile of similar design. Within the process of calculating the heat dissipation rates by the fins, the axial temperature distribution profiles were numerically determined using the Finite Difference discretization method, together with the Gauss-Seidel iterative method for the resolution of the discretized equations. The computational code was developed using MatLab® software. The results of the present work attested to the proper use of the original profiles employed by the manufacturers.

Optimization design of heat dissipation structure of inserts supporting run-flat tire

Inserts supporting run-flat tire is a key technology in the field of vehicle active safety. When the vehicle is under zero driving condition, the deformation of the inserts supporting run-flat tire due to compression can cause the tire to be crushed, and loss of adhesion between the tire and rim can lead to separation. These situations can reduce the cruising ability of the vehicle. Under zero driving condition, the insert, which is the main support body for the tire, could rub against the inner part of the tire sharply, thereby generating heat in the tire. Heat in the tire is difficult to dissipate and can accumulate rapidly under this condition. As the temperature of the tire and insert increases, the inserts supporting run-flat tire could fail to support the vehicle. To improve heat dissipation of the insert, a finite element model of the inserts supporting run-flat tire under the condition of zero rolling is established. The steady-state temperature field of the inserts supporting run-flat tire is analyzed using ANSYS Workbench. The insert temperature field and heat flux are solved. The optimization design of axial heat dissipation holes and surface heat dissipation grooves based on experimental and simulation results of the insert is presented. Finally, the optimization structure of the insert is verified using a thermal–mechanical coupling simulation method. The conclusions are of great significance for optimizing inserts supporting run-flat tire and improving zero rolling ability of tire.

Patterned surface charges coupled with thermal gradients may create giant augmentations of solute dispersion in electro-osmosis of viscoelastic fluids

Augmenting the dispersion of a solute species and fluidic mixing remains a challenging proposition in electrically actuated microfluidic devices, primarily due to an inherent plug-like nature of the velocity profile under uniform surface charge conditions. While a judicious patterning of surface charges may obviate some of the concerning challenges, the consequent improvement in solute dispersion may turn out to be marginal. Here, we show that by exploiting a unique coupling of patterned surface charges with intrinsically induced thermal gradients, it may be possible to realize giant augmentations in solute dispersion in electro-osmotic flows. This is effectively mediated by the phenomena of Joule heating and surface heat dissipation, so as to induce local variations in electrical properties. Combined with the rheological premises of a viscoelastic fluid that are typically reminiscent of common biofluids handled in lab-on-a-chip-based micro-devices, our results demonstrate that the consequent electro-hydrodynamic forcing may open up favourable windows for augmented hydrodynamic dispersion, which has not yet been unveiled.