Study On Air Diffusion Based On Desktop Task Air-conditioning

Some study indicates that people live in the comfortable conditioning environment for a long time; it may cause a series of health problems such as sick building syndrome (SBS). In the face of the abuse that the traditional air-conditioning exits, the refrigeration and air-conditioning enter a new develop phase since 1980s, the sign of the new phase is the transform that the comfortable air-conditioning turns to health air-conditioning. The task air-conditioning (TAC) systems have become more and more regarded by people for it creates good local micro-environment to realize the individual comfort and save energy through adopting the individual adjusting to control temperature, humidity, speed and air quality in the task area.At present, the analysis and investigation of the thermal comfort and indoor air quality (IAQ) based on desktop task air-conditioning need more improvement, a rational set of air supply parameters have not been established. The research based on predecessors'researches, through experiment investigation and CFD numerical simulation to analyze the thermal comfortable in the task area and discuss the air supply parameters combination of the desktop task air-conditioning.The main research productions of the paper are:①Through experiment study, we found that there is speed stratification in the vertical direction because of the supply air jet concentrated in the desktop task air conditioning system, and the higher speed is concentrated within the range of 0.2m as the center of the place with a draught, the fluctuation and change of velocity caused by the air jet mainly concentrate in the 1.1 meters high plane which faces the breath of the user; And there is a certain temperature gradient in vertical direction in the task area, it is within 1℃and not great, it would not have great impact to the human in the task area; At the same time, the study found the uneven coefficient of the speed and temperature in the different sections in the task area is small, air diffusion in the working area is even.②Having studied the influence of personnel thermal comfort in the task area that the supply flow rate, supply temperature and ambient temperature of the desktop task air-conditioning system have made, through the analysis of variance to find that in supply flow rate, supply temperature and ambient temperature three parameters, the supply flow rate has made the most distinct influence to the air diffusion in the task area. The experiment result has also verified the rationality of the numerical simulating result of the desktop task air-conditioning system.③Many operating modes of desktop task air-conditioning system with and without background air-supply were simulated; Velocity and temperature distributions of indoor air were described and analyzed according to the results. It is showed that both temperature and velocity in the working area have small nonuniformity coefficient and air distribution supplied by task air-conditioning in the working area is relatively uniform when desktop task air-conditioning system with background air-supply. While without background air-supply the velocity nonuniformity coefficient in the working area is small comparatively, but has relatively big nonuniformity coefficient of temperature; so temperature distribution in the working area is uneven and the temperature inhomogeneity is more obvious with increasing difference between the supplying air temperature and the indoor air design temperature.④Many operating modes of desktop task air-conditioning system with and without background air-supply were simulated, it is showed that the energy using coefficient changes along with the flow rate increases will increase firstly, when it achieves a maximum value and then decreases with the enhancement of the flow rate at any supply temperature when desktop task air-conditioning system with background air-supply. At the same design room temperature, the higher the supply air temperature the lower the energy using coefficient when desktop task air-conditioning system without background air-supply.Above these researches, the suggestions of the desktop task air conditioning system supply parameters: when the ambient temperature is 28℃, the air supply temperature is between 21℃and 23℃, the airflow is 90m3/h.The result of this research has provided the method and the basis for the task area air diffusion evaluation and TAC system design and has obvious practicality meaning.