山多能源宇院 SHANXI INSTITUTE OF ENEROY Ot r=R h Or const )r=R =const tw- 即：常物性流体在热充分发展段的表面传热系数保持不变 44 ( ) w f r R q h t t r t q  = −        = − =  const t t r t t t t t r w f r R r R w f w = −         − =         − −   = = const h t t r t w f r R = = −         − =  即：常物性流体在热充分发展段的表面传热系数保持不变