A run-around membrane energy exchanger (RAMEE) is a novel energy recovery system which can avoid carryover of desiccant solution while transferring both heat and moisture between non-adjacent supply and exhaust air streams. In this study, an analytical model for a flat-plate counter-cross-flow liquid-to-air membrane energy exchanger (LAMEE) is compared with experimental test results and numerical simulations for a single LAMEE and a RAMEE system under various operating conditions. Agreements are obtained among the analytical, experimental and numerical results. The effectiveness of a RAMEE system under balanced and unbalanced airflow conditions is evaluated by using the analytical model. Optimization studies for exchanger size and solution flow rate in RAMEE systems are investigated. Results show that RAMEE systems with equal-sized supply and exhaust exchangers can achieve the highest effectiveness in most conditions for both balanced and unbalanced airflow. Optimization control of the solution flow rate can enhance annual energy recovery rate up to 7%. (c) 2013 Elsevier B.V. All rights reserved.