Research On Ventilation Performance And Influencing Parameters Of PCM Based Solar Chimney Coupled With EAHE

With the industrialization and urbanization,the problem of energy shortage has become increasingly prominent in the world.As one of the three major energy consumption departments,building has a huge energy saving potential.The energy consumption of HVAC system accounts for more than 50% of building energy consumption.In order to reduce building energy consumption and environmental pollution,in recent decades,many renewable energy sources have been introduced into HVAC system,among which solar energy and geothermal energy have great application potential,attracting the attention of many researchers.Solar chimney which uses solar energy to promote indoor ventilation and earth to air heat exchanger which uses soil to pretreat air have been widely used all over the world.The solar chimney-earth to air heat exchanger coupling system combines the above two systems.While the earth to air heat exchanger pretreats the outdoor fresh air,it uses the suction function of the solar chimney to save the energy consumption of the fan,greatly reduces the energy consumption of the fresh air system,and achieves energy-saving benefits.However,due to the poor heat storage capacity of the envelope structure or metal plate as the heat storage medium,the chimney effect of the coupling system is weakened at night or rainy days,and the system efficiency is reduced,or even difficult to operate.In order to solve the above problem,based on previous studies,a solar chimney with phase change material and earth to air heat exchanger coupling system is proposed in this paper.In this paper,the theoretical model of solar chimney with phase change material and earth to air heat exchanger coupling system is established,and the ventilation and heat transfer effect of this coupling system is studied by using MATLAB and TRNSYS.The results show that the change of ventilation rate is obvious after adding phase change material and the night ventilation of the coupling system increases significantly,but the daytime ventilation decreases,the maximum ventilation rate decreases by 18%,and the time to reach the maximum ventilation rate is delayed.Moreover,buried pipe outlet air temperature decreases in the daytime and increases slightly at night.The maximum value of the outlet air temperature also decreases,and the fluctuation range of indoor temperature decreases.At the same time,the time when the room temperature reaches the maximum value is delayed.The phase difference between indoor load and ventilation rate is reduced,which is conducive to the use of ventilation rate to eliminate indoor load.In order to further study the ventilation and heat transfer performance of the coupling system,the control variable method is used to analyze the influence of five parameters,namely phase change latent heat,thermal conductivity,phase change temperature,phase change temperature difference and specific heat capacity,on the ventilation and heat transfer performance of the coupling system.The results show that the above five parameters have great influence on the ventilation rate of the system,but little influence on the indoor temperature.With the increase of latent heat and thermal conductivity,the ventilation rate of the coupling system decreases in the daytime and increases at night,and the effect of "peak shaving and valley filling" by phase change materials is more obvious.When the phase change temperature increases,the airflow rate initially decreases at afternoon,and then increases at night.The phase change temperature does not change the maximum ventilation rate of the system in the daytime,but significantly enhances the night ventilation rate.The effect of phase change temperature difference and specific heat capacity on the ventilation rate is not significant.The research in this paper proves that phase change materials can improve the ventilation and heat transfer effect of solar chimney-earth to air heat exchanger coupling system,improve the applicability of the system.This is of great significance to promote the more extensive and effective application of solar and geothermal joint ventilation technology,and to promote the development and utilization of renewable energy and the development of energy-saving buildings.