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홍봉환(Hong Bong Hwan),황상동(Sang Dong Hwang),조형희(Hyung Hee Cho) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Experimental study is conducted to investigate the cooling performance of impinging jet from mictotube using Joule-Thomson effect to apply practical applications. And also the heat transfer characteristics of a impinging jet itself and the impinging jet with Joule-Thomson effect are tested to make a comparative study of the two different general ideas. For this propose, two kinds of copper microtubes which have 200㎛ and 300㎛ in inner diameter respectively were tested and N₂was used as a working fulid. In case of impinging jet without Joule-Thomson effect, heat transfer coefficients distributions were similar to those of normal impinging jet. But in impinging jet with Joule-Thomson effect, the heat transfer coefficients decrease as jet-to-surface increases contrary to the case of the normal jet. As a result, much higher heat transfer coeffcients are obtained with Joule-Thomson effect than those of the normal jet without J-T effect.
홍봉환(Bong Hwan Hong),황상동(Sang Dong Hwang),조형희(Hyng Hee Cho) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
An experimental study is conducted to investigate the cooling performance of micro-tubes using Joule- Thomson effect. For this purpose, two kinds of copper micro-tubes which have different tube length, are tested. One is 120 ㎜ long and the other is 280 ㎜ long and all of these have 150 ㎛ in inner diameter. N₂ and CO₂ are used as the tested working fluids and the inlet pressure to expand the working fluids are changed from 3 ㎫ to 9 ㎫. Stronger Joule-Thomson effect was obtained with CO₂ than N₂ and linear temperature gradient region appeared along the micro-tube. The temperature distribution caused by Joule-Thomson effect varied with the inlet pressure along the micro-tube appeared different characteristic for the different tube length. It is considered that the pressure gradient along the tube and its exit has a different characteristic. Cooling performance of an aluminum circular hot plate on which has twenty 500 ㎛×500 ㎛ channels, is tested for application with CO₂. As a result, uniform temperature distributions along the circumference direction are obtained. However, non-uniform temperature distributions are obtained along radial direction.