Boiling-condensation heat transfer in ultrathin flat pipes are complicated and difficult to observe. In this study, a visualization experiment simulation analysis an limited enclosed space were carried out. Width of the ul?trathin was 1 mm, with anhydrous ethanol as working medium. The oriented vertically heating section on bottom cooling top. Flow characteristics photographed using high speed ...

Experimental measurements of local heat tra nsfer coefficients and pressure drop are made for forced conv ection boiling and condensation for R134a-oil mixtures inside a horizontal tube. The results are compared with the experime ntal data of pure Rl34a. Average convection boiling and cond ensation heat transfer coefficients decreased about 20% at a 10\ o il mass fraction, and boiling and conde...

Experiments are conducted with a perfluorinated dielectric fluid, Fluorinert FC-77, to investigate the effects of channel size and mass flux (225–1420 kg/ms) on microchannel flow boiling regimes by means of high-speed photography. Seven different silicon test pieces with parallel microchannels of widths ranging from 100 to 5850 lm, all with a depth of 400 lm, are considered. Flow visualizations...

Thermal management has become a critical issue for high heat flux electronics and energy systems. Integrated two-phase microchannel liquid-cooling technology has been envisioned as a promising solution, but with great challenges in flow instability. In this work, silicon nanowires were synthesized in situ in parallel silicon microchannel arrays for the first time to suppress the flow instabilit...

The oscillating heat pipe (OHP) is a new member in the family of heat pipes, and it has great potential applications in energy conservation. However, the fluid flow and heat transfer in the OHP as well as the fundamental effects of inner diameter on them have not been fully understood, which are essential to the design and optimization of the OHP in real applications. Therefore, by combining th...

We present results from direct numerical simulations of two types of technologically important phase change processes: directional solidification of a binary alloy and film boiling. We use a two-dimensional finite-difference/front-tracking method which allows us to accurately follow the evolution of the interface between the phases. The method is general in the sense that discontinuities in mat...

Mixtures of ethylene glycol and water are used in cooling the engines in automotive applications. Heat is transferred essentially under subcooled flow boiling conditions as the mixture flows over the hot surfaces, which are at temperatures well above the local saturation temperature of the mixture. Very little information is available in the literature on the subcooled flow boiling characterist...

Performance enhancement of the two-phase flow boiling heat transfer process in microchannels through implementation of surface micro- and nanostructures has gained substantial interest in recent years. However, the reported results range widely from a decline to improvements in performance depending on the test conditions and fluid properties, without a consensus on the physical mechanisms resp...