Text this: Cooling of liquid in a tube under rotation

導出完成 — 

 _    _     _____    _____       ___    __    __  
| \  / ||  |  ___|| |  __ \\    / _ \\  \ \\ / // 
|  \/  ||  | ||__   | |  \ ||  | / \ ||  \ \/ //  
| .  . ||  | ||__   | |__/ ||  | \_/ ||   \  //   
|_|\/|_||  |_____|| |_____//    \___//     \//    
`-`  `-`   `-----`   -----`     `---`       `