01. Experimental/Computational Fluid Dynamics

Electrical devices are expected with higher demand for faster data processing and smaller size, which results in higher heat flux in a device. One of the promising methods is to use liquid cooling. Recently, colloidal liquid dispersed with insoluble nano-sized solid particles are expected to enhance the heat transfer with higher thermal conductivity of the solid material without increasing the resulting fluid viscosity leading to higher pressure loss. In the present work, we investigate convective flow in a rectangular channel. The channel consists of a horizontally placed square channel with the bottom wall heated at a constant temperature. The flow is driven by streamwise pressure gradient and expected to be fully developed at the test section. The flow was found to exhibit three-dimensional convection in the test section. Our aim is to investigate the characteristics and formation mechanism of the three-dimensional convective flow. The test channel with a square-shaped cross-section was fabricated based on PDMS with a channel height of 0.8 mm with the aspect ratio of 12.5. The high aspect ratio ensures the two-dimensionality of the flow. The channel was attached to a glass plate coated with thin electrically conductive layer functioning as a heater. Velocity fields were measured with a microscopic particle tracking velocimetry. Repeating the measurements at multiple planes in the depth direction yielded the velocity distributions. The resulting velocity distributions exhibit two-dimensional fully developed flow without heating, while three-dimensional S-shaped convective flow when the bottom wall was heated. The S-shaped flow consists of upward secondary flow along the side walls and downward flow at the channel center. In the final paper, we report on the three-dimensional structure of the convective flow at different temperature conditions. We will also discuss on possible mechanisms of the formation of the three-dimensional flow structures observed at the experiment.