Simulation Of Floor Heating System Using Seasonal Thermal Storage By PCM With Stable Supercooling

A floor heating system using phase change material module is established to achieve seasonal thermal storage. Particularly, this system can store solar energy in summer and release in winter due to the stable supercooling behavior of phase change material. In this paper, the charging processes, stable supercooling and discharging process are mainly simulated. Additionally, the effects of parameters (such as different collecting area of solar heat, fluid mass flow rate, phase change temperature and the amount of phase change unit) on the system are analyzed.At the first stage (the charging process), the simulation results show that, during the period of Na2S2O3·5H2O charging processes, when the mass flow rates are 50 kg/hr,60 kg/hr and 70 kg/hr, the corresponding charging time are 58,51 and 46 days, respectively; during the period of NaCH3COO·3H2O charging processes, when the mass flow rates are 50 kg/hr,60 kg/hr and 70 kg/hr, the corresponding charging time are 111,95 and 82 days, respectively, i.e. compared with mass flow rate of 50 and 60 kg/hr,70 kg/hr needs the shortest time to complete the charging process. In addition, under the same operating conditions, For Na2S2O3·5H2O, one module charging time is 30 hours; while for NaCH3COO·3H2O, the charging time is 32 hours. At the second stage (the process of supercooling), it takes 20 hours to cool down the phase chenge module from overheating temperature to environment temperature (14℃) for Na2S2O3·5H2O, and for NaCH3COO·3H2O it takes 17 hours.At the third stage (the dsicharging process), when the supercooled salt is activated, the temperature of PCM can reach up to phase change temperature quickly, the liquid rate of Na2S2O3·5H2O (S) changed from 1 to 0.665, and the S of NaCH3COO·3H2O changed from 1 to 0.557. During the period of floor heating using phase change material, the temperature fluctuations of floor layer and room are smaller with five PCM unit, i.e. it is available to determine the heat release rate of phase change heat storage module according to the number of PCM units in one module. In addition, three operation modes are used in the radiant floor heating system. The results show that, the mode of single use of Na2S2O3·5H2O needs 82 modules and the mode of single use of NaCH3COO·3H20 needs 87 modules. For high and low phase change temperature modules with hierarchical discharge operation,it needs 35 modules of Na2S2O3·5H2O and 50 modules of NaCH3COO·3H2O. Under the same conditions, high phase change temperature materials can reach higher room tempreture.Based on the analysis of the effect of different parameters and different stages, a system is established to meet the heating load during winter, and provide evidence and reference for engineering application in future.