Analysis of suspension and heat transfer characteristics of Al2O3 nanofluids prepared through ultrasonic vibration

Nanofluids that contain nanoparticles with excellent heat transfer characteristics dispersed in a continuous liquid phase are expected to exhibit superior thermal and fluid characteristics to those in a single liquid phase primarily because of their much greater collision frequency and larger contact surface between solid nanoparticles and the liquid phase. One of the major challenges in the use of nanofluids to dissipate the heat generated in electronic equipment such as LEDs is nanoparticles’ precipitation due to their poor suspension in the fluid after periods of storage or operation, thereby leading to deterioration in the nanofluids’ heat transfer rate. In this study, ultrasonic vibration was employed to prepare Al₂O₃ nanofluids with a surfactant, a dispersant, and a combination of the two to evaluate their suspension and heat transfer characteristics. The experimental results show the Al₂O₃ nanofluid prepared with a non-ionic surfactant with a hydrophile lipophile balance (HLB) value of 12 to have the lowest nanoparticle precipitation rate and, accordingly, the highest degree of emulsification stability. Moreover, the nanofluids prepared with both the dispersant and surfactant had the greatest dynamic viscosity and lowest degree of thermal conductivity. Both the precipitation rate and dynamic viscosity of the nanoparticles increased, and their thermal conductivity coefficient decreased, the longer they remained in the Al₂O₃ nanofluids. Further, an increase in operating temperature caused an increase in the thermal conductivity coefficients of all of the Al₂O₃ nanofluids considered.     

Thermal Stresses in Multilayer Gun Barrel with Interlayer Thermal Contact Resistance

A hybrid numerical method of the Laplace transformation and the finite difference is applied to solve the transient heat transfer problem of a gun barrel, in which the interlayer thermal contact resistance between the steel cylinder and the chrome coating is taken into account in the boundary conditions. The general solutions of the governing equations are first solved in the transform domain. Then the inversion to the real domain is completed by the method of Fourier series technique. The transient distributions of temperature and thermal stresses for the gun barrel in the real domain are calculated numerically.     

Analysis for diving regulator applying local heating mechanism of vapor chamber in insert molding process

This paper aims to use the local heating mechanism, along with the excellent thermal performance of vapor chamber, to analyze and enhance the strength of products formed after insert molding process. In the insert molding process, the metal insert is firstly placed into the mold, and then formed into an embedded plastic product named diving regulator by injection molding. These results indicate that, the product formed by the local heating mechanism of vapor chamber can reduce the weld line efficiency and achieve high strength, which passed the standard of 15.82 N-m torque test, with a yield rate up to 100%.     

An innovative eigenvalue problem solver for free vibration of Euler–Bernoulli beam by using the Adomian decomposition method

This paper deals with free vibration problems of Euler–Bernoulli beam under various supporting conditions. The technique we have used is based on applying the Adomian decomposition method (ADM) to our vibration problems. Doing some simple mathematical operations on the method, we can obtain ith natural frequencies and mode shapes one at a time. The computed results agree well with those analytical and numerical results given in the literature. These results indicate that the present analysis is accurate, and provides a unified and systematic procedure which is simple and more straightforward than the other modal analysis.