In Indirect Evaporative cooling the water and hot air travels in different channels .Water and hot air doesn’t come in direct contact with each other and that is why it is called Indirect evaporative cooling.It additionally uses a heat exchanger called DAMA.
The DAMA heat exchanger is a cross-flow, plate-type polymeric exchanger. Warm, primary air flows in enclosed channels and gives up its heat to water films flowing down the other side of the polymeric plates. A secondary air stream flowing in the direction opposite to the water, evaporates water before it is exhausted outside. Thus, the primary air is cooled without any moisture addition.