In the given formula for overall heat transfer coefficient in Rising film evaporators, What is the term hOD? ( frac{1}{U}= frac{1}{ho}+ frac{1}{h_{OD}}+( frac{Do}{Di})( frac{1}{h_{ID}})+ ( frac{Do}{Di})( frac{1}{hi}) )

• A. Outside dirt coefficient
• B. Inside dirt coefficient
• C. Outside film heat transfer coefficient
• D. Inside film heat transfer coefficient