HEAT STORAGE-TYPE FLOOR HEATING-SYSTEM WITH HEAT-PUMP DRIVEN BY DISCOUNT ELECTRICITY SUPPLIED AT NIGHT

Heat storage-type floor heating by hot water from a heat pump driven 8 hrs by night electricity was studied. The phase change material (PCM) used for heat storage was Na2SO4 . 10H(2)O package. Properties of the PCM are; melting point 32 degrees C, solidification point 30 degrees C, heat storage 43.0 W . h/kg (Delta T=10 degrees C). The floor heating room was a 40 m(2), and without window, Na2SO4 . 10H(2)O package was used as a phase change material for heat storage. Hot water panels laid under PCM packages (26 m(2)) 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 hrs ON-16 hrs OFF cycle so that three times the heat extraction was needed as compared with continuous operation. For this reason, a Net film type vertical tube with a CFC flashing pump at the bottom was developed. From experimental results, the thermal balance of the system was calculated and the applicability for practical use was discussed.