The Study on Thermal Environment and Comfort for Desktop-based Task-ambient Air Conditioning
|School||Dalian University of Technology|
|Course||Thermal Power Engineering|
|Keywords||Task-ambient air conditioning Thermal comfort Thermal sensation|
People have cast off dependence on environment owing to the spreading of technology of air conditioning, and the quality of life has been improved a lot. The traditional style of air conditioning strives for a steady and uniform environment, but it fails to satisfy different demands for thermal comfort. It will also cause Building syndrome to stay in the air conditioning environment for a long time. It is always the goal of air conditioning technology to improve human thermal comfort and the indoor air quality. Task-ambient air conditioning system is the very way to achieve that purpose.At present task-ambient air conditioning system is being used somewhere at home and abroad, but people’s knowledge about it is only confined to concept. Study is developed on human thermal comfort and improvement on indoor air quality. This paper combines experiment and numerical simulation, and studies the distributing law created by task-ambient air conditioning system and it’s influence on human thermal comfort, then it brings forward exact model and parameters of task-ambient air conditioning.Basing on the analysis of human thermal comfort, by use of desktop task-ambient air conditioning and the experiment of human thermal comfort, the paper itself analyzes the influence of supply volume and temperature on human comfort in a certain background temperature. And it emphasizes on human local thermal comfort and its influence on overall thermal comfort under the neutral-hot environment. It indicates that in the background temperature of 28℃, and a certain supply temperature, human body will not have thermal discomfort. If the thermal sensation in the workaround approaches neutral, the thermal sensation will lag obviously when the occupants come to the background. It is suggested that the background temperature should be set under 28℃.The model of desktop task ventilation- background air conditioning system is built by numerical simulation, in order to improve the accuracy of simulating, a method of directly simulating the condition of exit boundary is selected as the inlet model of task-ambient air conditioning. It is analyzed characteristics of local environmental parameter ground, which is composed of different background temperatures, task ventilation parameters, supply volume and so on.It is discovered that desktop task ventilation creates a non-uniform environmental parameter ground around human body, there is difference of temperature between front and back of body, as well as upper and lower of body, hence different thermal sensation may be created. Study indicates that human will not have the sensation which is too cold or too hot, by combination of supply temperature and volume.Human comfort will be improved through the change of supply air current. According to the principle, impact jet supply air is advanced, and the pulsation quality is analyzed through experiments. The study indicates that the velocity of air current supply decreases, and the turbulence degree increases at a larger air supply volume. The quality can be used to improve human comfort.Method of manual regulation is brought forward on basis of those studies. It can reduce air supply towards the occupants to satisfy different needs of comfort, and total air supply of bottom installation can be reduced or fixed, so as to keep fresh air. Finally, taking the small office building of 2061 square meters (m2) in Dalian as an example, we compare the task-ambient air conditioning system and normal air conditioning system. Analysis indicates that the former reduces the peak value of cold load at 24% comparing with the latter, and the former saves energy consumption at 20% than the latter.