6.6.3 Drain cooling section
In this section the condensate formed in the condensing section has further heat removed by transfer to the incoming feedwater.
The equation for the calculation of the surface area is as before. The LMTD is found using the temperatures shown in Fig 3.51 (c).
The heat transfer coefficient is found by the methods given in BEAMA 1968  or ТЕМА 1978 . The velocity of the drains condensate across the tubes is important in determining the heat transfer coefficient, so again baffle pitch is important and the subject of an iterative process during the design.
A typical figure for the heat transfer coefficient in the drain cooling section will be about 1900 W/m2K.
Again, tube length is found from the drain cooling surface as explained above.