Heat-storage type floor heating by hot water from a heat pump driven 8 h by night electricity was studied.The phase change material (PCM) used for heat storage was Na2SO4.10H2O package.Properties of the PCM are: m.p. 32°, solidification point 30°, heat storage 43.0 W·h/kg (ΔT = 10°).The floor heating room was a 40 m2, and without window, Na2SO4·10H2O package was used as a phase change material for heat storage.Hot water panels laid under PCM packages (26 m2) were placed on a stage 1.2 m above the floor.The total heat storage was 28.5 kW.The heat pump was operated in an 8 h ON-16 h OFF cycle so that three times the heat extraction was needed as compared with continuous operation.For this reason, a wet film type vertical tube with a CFC flashing pump at the bottom was developed.From exptl. results, the thermal balance of the system was calculated and the applicability for practical use was discussed.
