三好 弘二 （Koji Miyoshi）
要約
T 字管の高低温水合流部における衝突型逆流の流動様式を対象に，温度および圧力が分岐管内面近傍の熱伝達率に与える影響を調べた．逆流による分岐管内面の熱疲労を想定し，数値シミュレーションにより，分岐部のコーナー位置から分岐管軸に沿った内面近傍の熱伝達率の特性を明らかにした．数値シミュレーションでは，主管と分岐管を含む流体・構造熱連成解析による非定常計算を行った．分岐管側の熱伝達率は，壁近傍の流体温度と管内面温度の値を使用し，パワースペクトル法にて求めた．その結果，高温・高圧条件では壁近傍の流速が増加することで，熱伝達率が増加する傾向があり，その増加比の最大値は 2.3 であることが求められた．また，分岐部のコーナー位置近傍の熱伝達率を推定する式を提案した．熱伝達率は分岐部から上流にいくに従い減少する傾向があることから，その推定式を用いることで分岐管内面において保守的な疲労評価が可能である．
キーワード 熱疲労，T 字管，衝突型逆流，数値シミュレーション，熱伝達率
Abstract
This study investigates the influence of temperature and pressure on the heat transfer coefficient near the inner surface of the branch pipe, focusing on the flow pattern of impinging penetration in the mixing region of hot and cold water in a T-junction. To evaluate the thermal fatigue of the branch pipe caused by the
penetration, the characteristics of the heat transfer coefficient near the inner surface along the branch pipe axis from the corner of the junction were clarified through numerical simulation. In the numerical simulation, unsteady calculations were performed using fluid-structure thermal coupled analysis, including the main and branch pipes. The heat transfer coefficient on the branch pipe was determined using the fluid temperature near the wall and the pipe inner surface temperature, based on the power spectrum method. The results showed that under high-temperature and high-pressure conditions, the near-wall velocity increased, leading to an enhancement of the heat transfer coefficient, with a maximum increase ratio of 2.3. A predictive correlation was also proposed to estimate the heat transfer coefficient near the corner of the junction. Since the heat transfer coefficient tends to decrease upstream from the junction, the proposed correlation enables a conservative fatigue assessment on the inner surface of the branch pipe.
Keywords Thermal fatigue, T-junction, Impinged penetration, Numerical simulation, Heat transfer coefficient
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