Direct Expansion Example



This calculation mode has an additional report into the printout tempaltes:


It is possible to set the frost thickness, just go to the "Air Side Details" tab on the left side of the screen:


Considerations on the frost thickness in coil:


Considering the impact of ice thickness (freezing) in heat exchangers and why does the heat exchanger capacity increase instead of decreasing?


When we use the thickness of the ice, we get two effects:


  1. ice increases thermal resistance, which reduces the heat transfer coefficient.


  1. ice reduces air permeability, so with the same flow rate, the cross velocity increases, thus increasing the heat transfer coefficient on the air side. As a rule, it is the coefficient in the heat exchanger that is the binding factor.


The sum of these two impacts results in increased or decreased capacity.


If the airflow rate is determined by an additional fan, the presence of ice will increase the pressure drops on the air side by changing the balance point to a lower one, thus reducing capacity.