The ways to increase dehumidification capacity during the dehumidification operation reheated by refrigeration cycle on room air conditioners using R 410A was investigated, keeping electric power consumption lower, noise level lower and outlet air temperature constant. The indoor heat exchanger is divided into a condensing part and an evaporating part by a dehumidification valve which is located between these two heat exchangers. The cooled and dehumidified indoor air is heated by the condensing part. The noise occurred from the two-phase refrigerant flow passing through this valve. So the compressor rotational speed was increased properly to increase dehumidification capacity. Moreover a new dehumidification valve was developed to reduce the refrigerant flow noise. This valve has two expansion processes and each expansion process has plural notch throttles. As the result, 1.5 times dehumidification capacity was gained, keeping lower electric power consumption, lower noise level and constant outlet air temperature.
