Analysis Of Thermal Environment And Energy Consumption Of Independent Temperature And Humidity Control Air Conditioning System

As a new type of air-conditioning system,the temperature and humidity independent control air-conditioning system is attracting widespread attention due to its advantages of energy saving,improved indoor thermal comfort and air quality.The temperature and humidity independent control air conditioning system has flexible forms,and the difference in indoor thermal environment and energy consumption of different forms is a problem that designers and users are very concerned about.In order to provide basis for the engineering application of the heat and humidity control system,taking the radiant(Radiant Ceiling Cooling,Radiant Floor Cooling system)and convection type(Dry Coil system)temperature and humidity independent control air-conditioning system as the research,combined with the method of field test and simulation,the indoor thermal environment and energy consumption of different forms of temperature and humidity independent control air-conditioning system are evaluated,and the reasons for the difference of them are analyzed.It aims to provide a research basis for the engineering design of the heat and humidity control system.The paper firstly evaluates and analyzes the differences in the indoor thermal and humid environment of the temperature and humidity independent control air-conditioning systems 、the fan coil system and the radiant and convection system through the indoor heat thermal environment experiment of different temperature and humidity independent control air-conditioning system,and analyzes the reasons for the difference.Compare the indoor thermal and humid environment of each system at different indoor set temperatures(24,26 ℃).Then use Energy Plus software to establish different types of temperature and humidity independent control air-conditioning system models,simulate the air conditioning energy consumption of them,and analyze the energy saving potential of the radiant system.The results show that:The indoor temperature and humidity parameters of the temperature and humidity independent control air-conditioning system fluctuate less,and that of the fan coil system fluctuate more.The main reason is that the former can separately handle indoor temperature and humidity,and the heat capacity of the radiating terminal is much greater than that of air,and the ability to resist temperature fluctuations is greater than air.The speed of the indoor temperature thermal response of each system is in order: fan coil,dry coil,radiant ceiling,and radiant floor cooling system.The main reason is that the heat transfer method and the heat dissipation per unit time of the indoor terminal of each system are different.The fan coil has the largest heat dissipation per unit time,the dry coil and the radiant ceiling are second,and the radiant floor unit heat dissipation per unit time is the smallest.The indoor vertical temperature field of different cooling systems is stratified,the vertical temperature gradient of the floor radiation room is the largest,and the maximum indoor vertical temperature difference of each system is less than 2 ℃,which meets the requirements of the standard ISO 7730-2005.The main reason is that the supply air of the fan coil is fully mixed with the indoor air,and the vertical temperature gradient is small.The indoor cold air of the radiant ceiling system sinks naturally,and the vertical temperature gradient is also small.However,the cold air radiated from the floor surface accumulates on the floor surface,which prevents the cold air from rising upwards,so the temperature gradient in the floor radiation room is the largest.However,the cold air on the radiation surface of the radiant floor system accumulates on the floor surface,which prevents the cold air from rising upward,so the temperature gradient in the floor radiation room is the largest.The indoor average radiant temperature and operating temperature of the radiant system are lower than that of the convection system,and the operating temperature of the radiant system meets the thermal comfort range specified by ISO 7730-2005.The main reason is that the radiant heat transfer at the radiating terminal can effectively reduce the temperature of the inner surface of the envelope structure,thereby reducing the action temperature.The overall indoor thermal comfort PMV—PPD and the local thermal comfort of the radiant and convection system meet the level I indicators in the "Evaluation Standards for Indoor Thermal and Humid Environment of Civil Buildings"(GB/T50785-2012),comprehensive from the perspective of indoor temperature distribution,the indoor vertical and horizontal temperature difference of the radiant ceiling is the smallest,and the indoor thermal comfort is the highest.It can be found that the radiant floor cooling is 7.8% more energy-efficient than the dry coil system,and the radiant ceiling cooling is 14.4% more energy-efficient than the dry coil system through the design daily energy consumption comparison.The main reason is that the temperature difference between the supply and return water at the terminal of the dry coil is large,and the return water temperature is low.Therefore,the energy consumption of the fan and the chiller is higher than that of the radiant system,and the energy consumption of the pump is lower than that of the radiant system.The overall energy consumption is greater than Radiant system.Under different indoor set temperatures(24,26 ℃),there is no new change in the distribution of indoor temperature and humidity of each air-conditioning system.However,due to the low air temperature in the convection system at 24 ℃,the thermal comfort only meets the level II evaluation index in the standard,but meets the level Ⅰ evaluation index at 26 ℃.It shows that when the indoor temperature setting of the convection system in summer is too low,which will not only increase the system energy consumption,but also reduce the indoor thermal comfort.Considering comprehensively the energy consumption and thermal environment of different types of temperature and humidity independent control air-conditioning systems,the radiant ceiling cooling system has the highest indoor thermal comfort and the lowest energy consumption,but there is a problem that the indoor thermal response is slow,so in the actual project,the ceiling can be considered a fan coil is installed at the radiation place to strengthen the convective heat transfer effect of the radiant ceiling and increase the indoor air thermal response speed.In areas with hot summers and cold winters,when the water supply temperature is 18 ℃,the capillary light pipe and the 40 mm thick radiant floor of the structural layer can work well.The radiation surface temperature is higher than the surrounding air dew point temperature,and no condensation will appear on the radiation surface.This paper studies the indoor thermal environment and energy consumption of the radiant and convection temperature and humidity independent control air-conditioning system,and aims to provide a reference for the practical application of the temperature and humidity independent control air-conditioning system.