Modeling Of Humidity Stratification And Energy-Saving Potential Analysis In Displacement Ventilation

As a kind of energy-efficient system,the displacement ventilation system can not only ensure the high air quality in the room,but also reduce the energy consumption compared with the traditional hybrid ventilation system.The unique airflow organization in placement ventilation can form significant temperature stratification and contaminants stratification in the room,which make highly ventilation efficiency.There is also moisture stratification phenomenon in the displacement ventilation room as well as temperature stratification,which means that the displacement ventilation has a stronger dehumidification capacity,and also provides a new space for energy conservation.Therefore,this paper studies the humidity distribution in the displacement ventilation through numerical simulation.and establishes a three-node model to predict indoor humidity distribution for two different building types,office and classroom;then analyses the factors affecting indoor humidity distribution.Finally,taking the construction project in Changsha as an example,this model is used to optimize the design method of displacement ventilation system and analyses the energy-saving potential of the system before and after optimization with EnergyPlus The results are as follows:(1)According to the mass conservation of indoor water vapor transport process,a three-node model was established for predicting indoor humidity distribution.The optimum value of model parameter I_o(the ratio of indoor moisture dissipation into the working area)was 0.8 through the deviation analysis between the calculated and simulated values;(2)The influence of heat dissipation on indoor humidity distribution is studied.The results show that with the increase of heat dissipation,the corresponding air humidity at the same height increases in varying degrees.At the same time,the fact that as the heat dissipation increasing,the stronger momentum of the plumes and their impingement on the ceiling resulting in backflow can have significant effects on the stratification height;(3)By comparing the three cases with different radiation panel temperature corresponding to 26??22?and 18?respectively,it is found that as the temperature decrease,the temperature and humidity distribution in the room tends to be more uniform;(4)The model was used to optimize the system design,and the results show that ignoring the indoor humidity stratification will lead to the refrigeration unit design capacity is larger,while the system design capacity can be reduced by about 6%after optimization.Compared with the dynamic energy consumption of the system before and after optimization,it is found that all the energy consumption of chiller reheater and pump have been significantly reduced after optimization and the energy saving rates are 12.4%,17.8%,19.4%,respectively.the overall energy saving of system is about 11.6%.the fact that the great energy-saving potential is important to popularize the application of displacement ventilation in China further.