Liquid-to-air membrane energy exchangers (LAMEEs) can avoid the problem of desiccant droplets carryover by using semi-permeable membranes to separate the air and desiccant solution streams. The aim of this study is to test and compare the heat and moisture transfer performances between the air and desiccant solution inside a novel 3-fluid LAMEE and a 2-fluid LAMEE under air heating and humidifying conditions. The effect of flow maldistribution on the deterioration of the 3-fluid LAMEE's performance is estimated, and an experimental study of the feasibility of membrane pre-tension to reduce flow maldistribution caused by membrane deflections in flat-plate LAMEEs is presented. Unlike heat exchangers where the lowest possible outlet hot fluid temperature is equal to the inlet cold fluid temperature, experimental data show that the outlet desiccant solution (hot fluid) temperature in the 2-fluid LAMEE may be lower than the inlet air (cold fluid) temperature. This is attributed to the effect of the phase change energy associated with the air humidification process. (C) 2016 Elsevier Ltd. All rights reserved.