A heat exchanger assembly, an indirect evaporative heat exchanger including the heat exchanger, and methods of operating the same. The heat exchanger assembly includes at least one tube, a plurality of sections, and a plurality of nozzles. The at least one tube is configured to (i) have a process fluid flow therethrough in a first direction and (ii) have a scavenger cooling medium flow over the outer surface of the tube in a second direction. The second direction intersects the first direction. The plurality of sections is aligned in the first direction. The plurality of nozzles are located above the at least one tube. At least one nozzle of the plurality of nozzles is (i) located in each of the plurality of sections and (ii) configured to selectively discharge coolant onto the portion of the tube in that section of the heat exchanger.