Thermal-Buoyancy Driven Flows around a Japanese Kyusu*

The Japanese teapot also known as the kyusu has a unique design for its handle, allowing for a cool to touch pouring. The handle acts as a fin and the traditional hollow, cylindrical design is hypothesized to be cooled by a thermo-buoyancy driven flow. Though fins are ubiquitous in practical heat transfer applications, the underlying heat transfer mechanism for these geometries are not well understood. Analytical solutions are only available for simple fins, often with assumptions of constant cross section, one-dimensional and steady state. Infrared thermography was used for investigation of spatial distribution of the temperature in the pot handles. Four different kyusu designs were studied: ceramic, black with a tapered hollow handle, white, porcelain with a solid handle, orange, clay with a hollow variable cross section handle, and clear glass with a hollow handle. Simplified models, such as solid cylinders, hollow cylinders of uniform and varying cross-sectional geometry, and 3D models of actual handle designs were used for analysis and comparison with data. Temperature profiles were compared against each other for the different handle designs. The hollow ones maintained a degree of temperature variation in length while the solid handle acted primarily as a fin of uniform temperature. The experimental data was also used to develop a computational fluid dynamics model of the thermo-buoyancy driven flow in the hollow handle cases. Previously unreported recirculation was found to be the primary mechanism for the convective cooling.