Study on nucleate boiling heat transfer by measuring instantaneous surface temperature distribution by infrared radiation camera

赤外線放射温度計を用いた瞬時表面温度分布測定による核沸騰熱伝達に関する研究

小泉 安郎; 高橋 和希*

Koizumi, Yasuo; Takahashi, Kazuki*

核沸騰熱伝達素過程解明を目的として圧力0.101MPaの下、水を用いてプール核沸騰熱伝達実験を行った。伝熱面には銅のプリント基板を使用した。直流電流を直接通電することにより伝熱面加熱を行った。プリント基板伝熱面中心部分の銅薄膜背面のベークライト板部分を剥ぎ取り、銅薄膜背面を剥き出し状にした。その背面の瞬時温度分布を赤外線放射温度計で測定した。また、気泡挙動を高速度カメラで撮影した。孤立気泡領域では、休止期間時伝熱面温度はほぼ一様であった。沸騰気泡生成が始まると気泡直下に伝熱面温度の大きな低下が発生した。伝熱面からの気泡離脱後、伝熱面温度は気泡発生前の一様な分布に回復した。気泡中心から1.8mmを越えると伝熱面温度は気泡生成の影響を受けない。中熱流束、高熱流束域では、熱流束が大きくなっているにも拘わらず気泡生成による温度変動域は大きくなっていない。この傾向は温度変動変動幅は孤立気泡域のそれに近い。

Pool nucleate boiling heat transfer experiments were performed for water at 0.101 MPa to examine the elementary process of the nucleate boiling. Heat transfer surface was made from a copper printed circuit board. Direct current was supplied to heat it up. The Bakelite plate of the backside of a copper layer was taken off at the center portion of the heat transfer surface to expose the back side of the copper layer. The instantaneous variation of the backside temperature of the heat transfer surface was measured with an infrared radiation camera. Bubble behavior was recorded with a high speed video camera. In the isolated bubble region, surface temperature was uniform during waiting time. When boiling bubble generation started, a large dip in the surface temperature distribution was formed under the bubble. After the bubble left from the heat transfer surface, the surface temperature distribution returned to former uniform distribution. Surface temperature was not affected by the bubble generation beyond 1.8 mm from the center of the bubble. In the intermediate and high heat flux region, the variation of surface temperature and heat flux did not become large even though the heat flux increased. The heat flux variation was close to that at the isolated boiling region.