1 overview
most of ventilation and air conditioning system are required to give room or controlled by the regional and (or) exhaust air, different shaped rooms, different supply air and return air form and layout, depending on the size of the air flow will affect the distribution of velocity, temperature and humidity distribution and concentration distribution of indoor air pollutants. Indoor air velocity, temperature and humidity are the main factors of human thermal comfort, and the concentration of pollutants is an important indicator of air quality. Therefore, in order to make the activity of people in the room (called the work area) as a suitable temperature and humidity, the air quality of the environment, not only have the reasonable form and system of air handling, but also must have a reasonable air distribution. Air distribution is also called air flow organization, that is to say, the designer should organize the reasonable flow of air. Many scholars put forward the requirements and evaluation of air distribution from different angles. For example, the harmful pollutants hair cow workshop, with relevant pollutants indicators to evaluate the effect of air distribution, such as the maximum pollutant concentration area (should be less than the allowable concentration) equivalent diffusion radius (equivalent sphere radius), the average concentration of the uneven distribution of the actual work area and exhaust concentration ratio of [1]. And as the constant temperature and humidity air conditioning room to room air distribution is the requirement of temperature and humidity of each point in the work area is uniform, keep on temperature and humidity reference minimum difference. The air distribution requirements for "working area", the work area generally span below 2m, the process of the air conditioning room depends on the specific circumstances. The following are the main requirements of air flow distribution and the commonly used evaluation index.

2 of the temperature gradient in
air conditioning and ventilation in the room, and the room temperature into the different air, and the room has a heat source exists in the vertical direction is usually the temperature difference (temperature gradient). In a comfortable range, according to the IS07730 standard, the temperature difference between the work area of the ground above the 1.1m and 0.1M should not be greater than 3 degrees (which is essentially considered sitting work); the temperature difference between the American ASHRAE55-92 standard [2] and 0.1M 1.8m suggested that not more than 3 DEG C (this is considered standing work). From the reliability point of view, the vertical temperature gradient should be controlled by the latter. The wind speed in the working area of

3 is also an important factor affecting the thermal comfort of
. It is usually possible to improve the thermal comfort environment by increasing wind speed at higher temperatures. But the wind speed is usually boring. The results show that when the wind speed is less than 0.5m / s, people don't feel too much. The wind speed of the working area is defined in the specifications, standards and manuals of various countries. [3] our specification: comfort air conditioning indoor wind speed should be less than 0.2m / s, 0.3m / s should not be greater than the summer air conditioning technology; winter indoor wind speed should be less than 0.3m / s, the summer should adopt 0.2 ~ 0.5m / s.

4 air pressure and air distribution performance indicators
people in the air conditioning room is a common dissatisfaction with a sense of hair. Sense of hair is due to air temperature and wind speed (humidity and radiation room temperature assumed constant) cause the local area of the body is cold, causing discomfort. The United States ASHRAE with effective air temperature EDT (EffectiveDraftTemperature) to determine whether there is a sense of hair, it is defined as
EDT= (tx=tm) -7.8 (VX - 0.15) (10 - 1)
: TX, TM, temperature and average indoor temperature, indoor temperature at a certain location;
VX - in a wind chamber location M / S.
for the office, when EDT at -1.7 to 1 DEG C, VX