Study Of Radiant Floor Cooling And Heating System With Double Layer Phase Change Energy Storage And The Thermal Performance

With the continuous improvement of living conditions, people’s demand on the indoor thermal environment gradually raises, which has resulted in the increasing building energy consumptions. In the largest proportion of building energy consumption is heating and air conditioning energy consumption. The mature radiant heating and cooling mode has become popular, which is of obvious advantages such as comfort, energy saving and health. Meanwhile, in order to regulate the unbalancedness of power consumption by policy, the country has implemented the peak and valley electric charges to encourage residents to use low power at night. Thus the peak load shifting is realized. In view of the above background, the terminal equipment of radiant combined with phase change energy storage technology was designed to achieve the purpose to accumulate energy at night and release it during the day using the high thermal storage density of phase change material to meet the indoor thermal environment.First, the phase change energy storage technology has been integrated to mature heating floor and cooling ceiling to form phase change energy storage heating floor and phase change energy storage cooling ceiling with suitable phase change material. Reasonable simplifying assumption has been made for these phase change energy storage radiant terminal equipment and 2D unsteady heat transfer model has been set up. The winter operating condition for phase change energy storage heating floor and the summer operating condition for phase change energy storage cooling ceiling were simulated by FLUENT. The results turned out that the phase change material being added to the radiant terminal equipment could satisfy the thermal demand of indoor environment during the day with the release of stored energy at night using low-cost electric. Furthermore, these two terminal equipment in the energy release process of their own operating condition could remain the radiant surface temperature stable. Indoor thermal comfort has taken place with small temperature difference.Only the above two sets of equipment using together can meet the requirements of winter and summer, radiant terminal equipment with the integration of heating and cooling was put forward to satisfy the both seasons. Two radiant floor types with double layer phase change energy storage have been designed differ in the location of two kinds of phase change material, one structure is that the cold storage material is upper and the hcat is down called the cold above heat double layer phase change energy storage floor, the other is the opposite, called the heat above cold double layer phase change energy storage floor. The simulation and analysis of these two floors in winter operation and summer operation were carried out in detail. Contrast to previous results of the terminal equipment of single layer phase change energy storage, the best of winter heating conditions is the heat above cold double layer phase change energy storage floor, the temperature of floor is about 27 ℃ and the feat flux is about 75 W/m2during the discharge. The best of summer cooling conditions is phase change energy storage cooling ceiling, the temperature of which is 20 ℃ and flux is over 55 W/m2 during the discharge. The best equipment for both winter and summer is phase change energy storage heating floor and phase change energy storage cooling ceiling using together. In terms of the integration of heating and cooling terminal equipment, the cold storage phase change process is very fast and the cold is difficult to release when the cold storage layer is down, which surface temperature is 25 ℃ all the time without cooling effect. Based on the above analysis, the more suitable radiant terminal equipment is the cold above heat double layer phase change energy storage floor, which heating operation could be improved by elevating the temperature of the water supply.The test rooms A(cold above heat) and B(heat above cold) with two different radiant floor types with double layer phase change energy storage were built for the winter and summer experiments, focusing on the temperature in floor structure layer and the longitudinal temperature of the room. Experimental Results shown that the heating effect is better when the heat storage layer is upside, and the cold storage layer is upside the cooling is better, which matched the simulation conclusion.The indoor temperature of room A and room B is above 16.5 ℃ in winter operation and below 27 ℃ in summer in the discharge, which can meet the requirements of radiation and proved that the integration of heating and cooling design is reasonable. The indoor vertical temperature difference is within 0.5 ℃ in winter and 3 ℃ in summer, meeting thermal comfort requirements. The appropriate radiant floor with the integration of heating and cooling could be chosen according to the regional climate characteristics in the practical application.