Calculation of shell-side heat transfer coefficient (condensing film heat transfer coefficient) (h_o): The Kern method is discussed here to calculate the individual heat transfer co-efficient of the condensing fluid by trial and error calculation.

i. Assume, h_o(assm) in the range from 100 to 300 BTU.h^-1.ft^-2.°F^-1. The film coefficient of condensing hydrocarbons generally varies in this range. Air-free condensing steam has a coefficient of 1500 BTU.h^-1.ft^-2.°F^-1.

 

ii. Calculate the tube wall temperature ( T_w ):

                                                                                           (1.11)  

or

                                                                                                       (1.12)  

Where, ( d_i tube ID and d_o tube OD)

= Average temperature of the cold fluid

T_cc =Calorific temperature of the cold fluid

 

iii. Calculate condensate film temperature,                                                    (1.13)  

T_v =Condensation temperature (For pure fluid compound T_v is the saturation temperature. Average of condensation over a temperature range also can be used for non-isothermal condensation).

 

iv. Calculate all thermophysical property of the condensing fluid at film temperature ( T_f ).

v. Recalculate, h_o(cal) from j_H factor.

Now again set, h_o(assm) = h_o(cal) and continue the calculation till h_o(assm) ≈ h_o(cal).

 

vi. Calculate the overall heat transfer-coefficient ( U_d ) including the dirt factors.