The results of indoor experiments with model regenerators of open cycle solar absorption dehumidifying and drying system consisting of regenerator, heat exchanger, dryness storage tank and dehumidifier are described. It has been difficult, in the past outdoor experiments, to identify the performance of regenerator because of strong variation in ambient conditions, especially wind speed. The influences by air volume and air velocity with the constant temperature of regenerating surface and controlled flow rate of solution on the regenerating performance were examined by the indoor experiment with the model regenerator of open-end type under the steady state conditions. The results showed that the influence of the air volume on evaporation rate could hardly be observed with different heights of the air space and regeneration rate with higher air velocity turned out greater in the case of a given air space. Furthermore, we proposed a new method to obtain the concentration of LiCl solution used as liquid desiccant continuously and easily without extracting solution during operating hours in reference to the standard concentration curves for LiCl solution prepared beforehand by measuring electric conductivity of LiCl solution. In the actual experiments, concentration value could be obtained by this method and continuously recorded. The relationships among non-dimensional numbers calculated from the results of experiments were slightly different from the general mass transfer equations for the laminar and turbulent flow of forced convection as found in literatures in the air velocity range higher than 0.5m/s, but considerable deviations were found in the lower air velocity range.