PURPOSE: To increase enthalpy efficiency by applying a process for increasing hydrophilic property on heat exchanging surfaces.

CONSTITUTION: A process for increasing hydrophilic property is applied on the surface of wall plates 6 to make heat exchanging surfaces 60. The wall plate 6 is constituted by bonding non-woven cloths 62 whose material is synthetic resin on both surfaces of a hard vinyl chloride sheet 61, for example. In case a total heat exchanger is used in winter, an air intake port is connected to a first inlet port 14, connected with a water spray device 5, while a second outlet port 18 is connected to an indoor air discharging port. Water drips are deposited to the wall plate 6 of a first communicating gap 2 by sprinkled water from spray nozzles 51, and the surface of the wall plate is hydrophilic, therefore, the water drips are spread to a wide range. Low-enthalpy air, which flows into the heat exchanger from the first inlet port 14 of the heat exchanger, is changed to a direction approaching to a saturated condition by the sprinkled water from the spray nozzles 51 and the wall plates 6 whose surfaces are wetted. According to this method, the amount of heat, absorbed from high-temperature side, is not consumed for increasing temperature and is received as latent heat, therefore, the temperature rise of the low-enthalpy air becomes smaller remarkably than by sensible heat heating and a temperature difference between high-enthalpy side air may be increased.