Flow And Heat Transfer Characteristic Of Radiant Floor Heating System With Micro-Encapsulated Phase Change Material Slurry

With the development of society,the shortage of energy becomes more and more serious.Phase change energy storage material can effectively solve the contradiction between the demand and supply of energy in time and space.The PCM was microencapsulated and the Micro-encapsulated phase change material slurry was prepared.It has a wide application prospect in the fields of energy utilization due to its high energy storage density and high apparent specific heat.Therefore,the flow and heat transfer characteristics of micro-encapsulated phase change material slurry in radiant floor heating systems were studied by numerical simulation in this paper.Firstly,the validity of the micro-encapsulated phase change material slurry model was validated by comparing the experimental data of temperature and pressure drop.The complex boundary conditions were simplified,and a three-dimensional model of a radiant floor heating system was established.Then,comparing the heat transfer,pressure drop and comprehensive evaluation factors,the effects of material,volume fraction,inlet velocity of different micro-encapsulated phase change material slurries on the performance of radiant floor heating system were analyzed.In addition,the influence of different tube spacing,thickness of filling layer and diameter of buried pipe on the performance of radiant floor heating system were analyzed.Finally,using the Box-Behnken design conditions,the volume fraction of micro-encapsulated phase change material slurry,inlet velocity of radiant floor heating system,tube spacing,thickness of filling layer and diameter of buried pipe were optimized by response surface methodology,and the best factor ratio was obtained by Numerical Optimization.The main conclusions of this research are as follows:（1）By comparing different volume fractions of micro-encapsulated phase change material slurries and inlet velocities.It was found that both volume fraction and inlet velocity had a positive effect on the radiant floor heating system.When the velocity was constant,there was a volume fraction,which could make the system performance best.In addition,different volume fractions had different optimal velocities.When the volume fraction was 10%,20%and 30%,the optimal entrance velocity was 0.5 m·s^-1,0.9 m·s^-1and 1.1 m·s^-1,respectively.（2）By simulating different pipe spacing,thickness of filling layer and buried pipe spacing,it was found that the comprehensive evaluation factor increased first and then decreased with the increase of pipe spacing.The heat transfer decreased with the increase of the thickness of filling layer,the pressure drop of the system was maintained in a certain range.With the increase in the thickness of the filling layer,the performance evaluation factor was gradually reduced.The diameter of buried pipe has an important influence on the thermal performance of the radiant floor heating system.The heat transfer and comprehensive evaluation factors increased with the increase of pipe diameter,while the pressure drop and performance evaluation factors decreased with the increase of pipe diameter.（3）The parameters were optimized by response surface method and the best combination of factors was obtained.Forty-six simulated working conditions with five factors and three levels were designed,andηof each working condition was calculated.The best factor ratio was volume fraction=35%,velocity=1.3 m·s^-1,pipe spacing=0.25 m,thickness of filling layer=0.04m,diameter of pipe=0.025 m,which obtained by Numerical.By simulating the radiant floor heating system with the best combination of factors,it was found that theηof MPCMS was 124%higher than that of water.To sum up,this paper optimizes the structural parameters of micro-encapsulated phase change material slurry in radiant floor heating systems,and the optimized radiant floor heating system can significantly improve thermal performance and heating efficiency.It can provide a reference for the development and optimization of micro-encapsulated phase change material slurry in radiant floor heating systems.