Indirect evaporative cooling is recognized as an alternative air-cooling solution with low carbon potential and considerable energy efficiency. An indirect evaporative cooler (IEC) can handle both of the sensible and latent cooling loads because of possible condensation when it is used as a precooling unit in an air-conditioning system in hot and humid regions. Cross flow and counter flow, as two basic flow configurations of an IEC, differ in condensation behavior that affects their cooling performance. In this paper, a novel 2-D model of cross flow IEC considering condensation is established and validated. The performance of the cross flow and counter flow IEC is thoroughly compared under the same configuration. The channel gap and height to length ratio (H/L) are optimized to provide references for the design and operation of the IEC under condensation conditions. Results show that under the same operating conditions, the condensation ratio of counter flow IEC is 2-15% higher than that of the cross flow IEC, leading to 2-7% decrease of wet-bulb effectiveness. The difference in the total heat transfer rate between the two configurations is less than 5% when the number of transfer units (NTUp) is lower than 3.1. For cross flow IEC, there is an optimal value in H/L among 0.4-0.8 considering the cooling capacity and energy consumption. (C) 2018 Elsevier Ltd. All rights reserved.