It can be seen that heat and mass transfer in cooling towers is a complex process, involving
not only thermodynamically problems, but also problems related to for example
aerodynamics. To derive the equation for the heat transfer a lot of simplifications are made.
For a more correct formulation attention has to be paid to varying values of the heat and mass
transfer coefficients. Temperature and humidity differences will change along the tower, and losses due to windage will occur. When modelling the droplet, the shape of the droplet should
be considered. Though, in most advanced calculations it is taken to be spherical. Even Lewis
factor, which describes the relation between heat and mass transfer, is often considered unity.
Mostly the droplets and the air are assumed to move vertically, which is not always the case
in reality