wet and dry efficiency of recuperative air to air heat exchanger

[CmAnD]

I would be very grateful if somebody can explain me how to calculate dry and wet efficiency of recuperative air to air heat exchanger.
I only have this equation for heat exchanger efficiency stated in DIN EN 308 standard.

n=(Tsupplyair-Tfreshair)/(Textractair – Tfreshair).

Please tell me if you need some additional information for this problem.

Thank you in advance.