Study On Energy Consumption Of Floor Radiant Cooling Combined With Underfloor Air Supply System In Tall Space

The energy consumption of tall space buildings is getting higher and higher with the rapid development of tall space buildings,and the air distribution mode has great influence on the indoor comfort and energy consumption of air conditioning system in tall space.Take the phenomenon of thermal stratification into consideration,the application of floor radiant cooling and underfloor air supply system contributes to energy saving and the improvement of indoor comfort.In this paper,the application characteristics of complex system are researched.Firstly,the mathematical model for floor radiant cooling and underfloor air supply system was established by the method of the combination of numerical simulation and experimental data.Taking a waiting hall in hot summer and cold winter zone as the research object,the load calculation method based on the indoor temperature stratification under the composite system was proposed,the indoor temperature stratification under different roof temperatures was simulated,and the CFD simulation results were coupled to the Room Air module in Energy Plus.The results show that the reduction rate of the cooling load is about11.57% compared with the complete air conditioning.The indoor temperature and humidity regulation characteristics of the compound system under the maximum cooling load were simulated.The results demonstrate that under the maximum cooling load,based on the design requirements of indoor temperature and humidity,the temperature distribution horizontally under the composite system is more uniform;the average relative humidity of the Z=0.1m section of the composite system is higher than that of the whole air system;the average relative humidity of the Z=1.1m section and the Z=2m section is 0.6% and 1.1% lower than that of the total air system,respectively,and the humidity distribution is more uniform.By adjusting the cooling capacity proportion of the composite system,the influence of cooling capacity ratio of the composite system on indoor humidity and comfort under the maximum cooling load was explored.The results show that when the air supply speed is constant,the air supply temperature is 23°C,or when the the air supply temperature is constant,the air supply speed is 0.23 m/s,the indoor workspace has the highest comfort degree and the ratio of floor radiant cooling is about 0.6.Considering two conditions of constant air volume and variable air volume of the air supply system,the dynamic response characteristics of the indoor thermal environment of the composite system were studied,and the floor surface temperature under the maximum cooling load was set as the floor boundary condition.The results indicate that the indoor temperature and humidity can satisfy the control requirements under two systems,and the latter requires more fresh air.The floor radiant cooling capacity changes dynamically,and the ratios of floor coolingcapacity to sensible heat load and total cooling load are approximately 0.68 and 0.44 at the peak of indoor cooling load.The energy analysis modules of the floor radiant cooling system and underfloor air supply system were added,the energy consumption models of the floor radiant cooling terminal system,the underfloor air supply terminal system,the fans and the pumps were analyzed.The influence of temperature difference of floor radiant cold water on the performance of the water chilling unit was mainly researched.Meanwhile,the energy consumption of composite system under variable air volume and constant air volume were studied compared with all air system.The research results demonstrate that when the outlet temperature of the cold water of the floor radiant chiller is constant,the energy efficiency ratio of the unit increases with the increase of the temperature difference between the inlet and outlet water,but there is a peak.The composite system has the lower energy consumption under the combination of floor radiation and variable air volume control mode.Under this control mode,the ratio of the energy consumption of the floor radiant cooling system to the total energy consumption is 63.18%,and the energy consumption cooling season is reduced by 28.83% compared to the all air system base on the indoor temperature and humidity requirements.The research results of the thesis can provide ideas for the study of the thermal environment of tall space buildings.