Visualization of pool boiling heat transfer of magnetic nanofluid

To increase heat transfer, ferrofluids have been utilized to study the effective parameters of pool boiling. Changes and possible enhancement of pool boiling heat transfer of magnetic fluids is a function of magnetic field and concentration of nanoparticles. To the best knowledge of the authors, no systematic experiments have been conducted to visualize the phenomena during the boiling of ferrofluids with different concentrations. In this study an experimental investigation has been conducted, by designing and fabricating a novel hele-shaw vessel with glass sides, to explore via visualizations some details in the pool boiling of ferrofluids. Boiling patterns of ferrofluids at various concentrations have been visualized -both in the presence of a constant magnetic field and without any magnetic field. Pure water tests were performed as a baseline, and the experimental program has been conducted at four different concentrations, namely 30, 40, 50, and 500 ppm. The primary focus of the visualization is to study how different concentration of ferrofluid affects the boiling ebullition cycle through a high-speed camera. The results showed that in the boiling process of ferrofluids with a low concentration (10 to 50 ppm), the rising bubbles lead to enlarge the active nucleation sites and create cavities. The formation of cavities changes the solid layer of the surface to a porous medium and enhances the wettability of the surface and boiling heat transfer coefficient. In the ferrofluid boiling with high concentration (500 ppm), bubbles rising is hindered by nanoparticles.