地窓を利用した夜間自然換気による潜熱蓄熱材の蓄冷効果に関する研究

Abstract

1. Introduction In this paper, we focused on introduction of phase change material(PCM) into a house to secure a cold storage with night natural ventilation. We conducted measurement in order to understand indoor thermal characteristics in a room with night natural ventilation for introducing PCM on the floor of a house to maximize cooling effect. Measurement was mainly conducted for on a room of the full-scale house where it has two openings at floor level. We measured vertical air temperature distribution and inflow wind speed to understand indoor thermal characteristics. And heat flow was also measured on the floor and under the floor to reveal cold storage mechanism. 2. Categorization We categorized measurement results according to weather condition on each day as follows. 1) Day of large air temperature difference between indoor and outdoor(ΔT) with high inflow wind speed, 2) Day of large ΔT with low inflow wind speed, and 3) Day of small ΔT with high inflow wind speed. 3. Measurement summary on indoor thermal characteristics Vertical air temperature distribution of indoor was influenced by inflow wind speed and ΔT. In case that inflow wind speed was lower than 0.1m/s, cold air accumulated along the floor was not mixed with the air at upper area of indoor. In case that inflow wind speed was over 0.1m/s and under 0.3m/s, inlet air mixed with indoor air. At this time, mixing height was determined by ΔT and inflow wind speed. In case that inflow wind speed was over 0.3m/s, indoor air was entirely mixed with outdoor air, thus vertical air temperature distribution tended to be disappeared. 4. Measurement summary on cold storage Cold storage tended to be proportional to ΔT. Cold storage accelerated as the condition of large ΔT and low inflow wind speed because cold air accumulated along the floor was not mixed with upper air of indoor. In case that air temperature near the floor was 2°C lower than phase change temperature of PCM for solidification, latent cold storage begun to progress. Cold storage ratio of latent heat was averagely 70%, and total cold storage tended to change approximate 1.5 times depending on outdoor air temperature. 5. Conclusion Indoor thermal characteristics and cold storage rate were changed by ΔT and inflow wind speed. In some cases, latent cold storage efficiency of PCM on the floor with night natural ventilation was confirmed. In the future, considering the daily life activity of residents, we are going to research passive cooling effect of PCM including the day time. Also, in order to develop a numerical simulation tool for designing a passive cooling house with PCM including a calculation model of vertical air temperature distribution, we will determine the parameter of turbulence diffusion coefficient by CFD simulation.