유동 방향에 직각으로 놓인 원관에서 원주 방향의 열전도가 열관류계수에 미치는 영향

Abstract

본 논문에서는 국소열전달계수의 비균일성으로 유발되는 관벽에서의 온도 구배가 열관류계수에 미치는 영향을 조사하였다. 판벽에서의 열전도의 외부 유체로의 대류 열전달에 대한 상대적인 크기를 나타내기 위한 무차원 변수?과 관 외부의 대류 열저항과 관 내부에서의 대류 열저항의 비를 나타내는 무차원 변수?의 함수로 열관류계수의 변화를 표시하였으며, β가 1정도일 경우 관벽의 온도를 균일하다고 가정하여 계산된 전열량은 온도 구배를 고려할 겨우보다 10%이상 크게 나타나나, β가 10이상인 경우에는 그 차가 5%미만임이 밝혀졌다.

The effect of peripheral wall conduction on overall heat transfer coefficient of a tube in a tranverse flow was investigated. Non-dimensional parameters,?and?, which denote the relative magnitude of heat conduction to that of convective heat transferand the ratio of thermal resistance at the outside of the tube to that inside, respectively, were used. It was found that heat transfer rate obtained assuming uniform temperature around the tube is about 10% higher than that calculated considering temperature gragient when βis order of unity and that the difference is less than 5% if βis larger than 10.

The effect of peripheral wall conduction on overall heat transfer coefficient of a tube in a tranverse flow was investigated. Non-dimensional parameters,?and?, which denote the relative magnitude of heat conduction to that of convective heat transferand the ratio of thermal resistance at the outside of the tube to that inside, respectively, were used. It was found that heat transfer rate obtained assuming uniform temperature around the tube is about 10% higher than that calculated considering temperature gragient when βis order of unity and that the difference is less than 5% if βis larger than 10.