Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7056172 | International Journal of Heat and Mass Transfer | 2016 | 6 Pages |
Abstract
We report an experimental study of external natural convection from a Joule heated horizontal platinum wire immersed in water in a relative large cavity. Through that the platinum wire was used both as a heater and a thermistor for measuring a small temperature increment, our experiments were performed with much lower Rayleigh numbers in a range from 10â5 to 10â2 for water. Contrary to the general expectation, it is found that a local minimum Nusselt number happens at a critical Rayleigh number, which are about 5.0 Ã 10â4 and 1 Ã 10â4 for the platinum wires with diameters of 50.8 μm and 20.1 μm, respectively. The Nusselt number decreases rather than increases as usual with Rayleigh number before reaching the critical value, and the temperature of platinum wire fluctuates wildly over time at the critical condition. Corresponding experiments by using silicon oil instead of water, however, did not show such phenomena, which indicate that natural or free convection from a micro object may be fluid dependent.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Fluid Flow and Transfer Processes
Authors
Chuanshan Dai, Jue Wang,