OVERALL HEAT TRANSFER COEFFICIENT

OBJECTIVES

-- To calculate overall heat transfer coefficient

-- To develop a mathematical equation useful in designing a heat exchanger

 

 

 

 

 

 

 

 


q = UA(Ta - Tb)           (1)

 

Heat transfer through individual layers

 

q = hiA(Ta - T1)

                    

q = hoA(T2 -  Tb)

 

Adding above three equations

 

 

From (1)

 

 

Similar expression obtained when an overall thermal resistance is calculated

 

 

 


RT = Rconv1 + Rcond + Rconv2

 

Then

 

 

 

 

 

 

 

 

 


In cylindrical coordinates: