Study on flow boiling heat transfer in horizontal-rectangular-narrow-flat channels

水平矩形狭隘流路内流動沸騰熱伝達に関する研究

小泉 安郎; 太平 晃貢*

Koizumi, Yasuo; Ohira, Koji*

流路の微小化の流動沸騰熱伝達への影響を把握するため、流路巾W=3mm、流路間隙=1.25mm0.163mmの範囲の矩形流路に対し、単相流と二相流熱伝達実験を行った。単相流熱伝達では、水力等価直径1.06mm以下で流路微小化の影響が現れ、熱伝達係数は通常サイズでの値より小さくなった。二相流に対しては、沸騰が始まると直ぐにチャーン流、次いで環状流へ流動状態が遷移した。測定された限界熱流束は、多くの実験結果でクタテラーゼプール沸騰限界熱流束相関式の値より大きくなったが、流路間隙が極端に小さい場合では、限界熱流束は本相関式の値よりも小さくなった。これらの結果を基に、熱伝達相関式に対して、流路微小化の影響を取り入れる修正法を提案した。

In this study, to examine the channel narrowing effect on the two-phase flow boiling heat transfer, single-phase flow and flow boiling heat transfer experiments were performed for a thin rectangular channel of the width W = 3 mm and the height = 1.25 mm 0.163 mm. When the hydraulic diameter became smaller than 1.06 mm, for the single-phase flow conditions, the heat transfer coefficient became smaller than that for a conventional size channel. In the flow boiling, churn flow appeared even at a low heat flux and a flow pattern was mainly the churn flow or/and the annular flow. The critical heat flux was higher than the value of Kutateladze correlation for the pool boiling. However, when the flow channel height became extremely narrow, measured critical heat flux became lower than the Kutateladze value. based on these results, the modification method to incorporate the channel narrowing effect into the heat transfer coefficient correlation was proposed.