The task of the high-precision constant temperature and humidity air conditioning system is to control the indoor temperature, humidity and cleanliness within a certain fluctuation range to meet the requirements of the indoor environment in special occasions such as industrial production and scientific research. In recent years, with the development of China's productivity and the continuous improvement of scientific and technological level, the application occasions of constant temperature and humidity air conditioning systems have become more and more, and the requirements for temperature and humidity have also been continuously improved. First of all, a brief introduction is given to the determination of indoor environmental parameters in the design of high-precision constant temperature and humidity laboratory air conditioning.
    The determination of indoor environmental parameters of high-precision constant temperature and humidity rooms depends on the requirements of products, experimental objects or experimental equipment. Different requirements such as accuracy and reliability often make the complexity of constant temperature and humidity systems very different, and are also greatly related to the initial investment and operating costs of the system. Blindly improving the accuracy requirements often leads to an exponential increase in initial investment and operating costs; on the contrary, if the accuracy requirements are too low, it may directly lead to the failure of production and experimental activities. Therefore, before designing the system, HVAC professionals and users need to accurately put forward the requirements for the indoor environment according to the requirements of production and experimental objects.
Mainly including:
1) Control area. In some production and experimental processes, the temperature and humidity of the entire room need to be controlled. But in most cases, only specific production and experimental areas need to be strictly controlled.
2) Reference temperature and humidity. Many production and experiments require reference temperature and humidity to be fixed values. For example, many metrological experiments require a reference temperature of 22 °C, and some textile production and experiments require a reference relative humidity of 65%. There are also some special experimental processes and climate chambers that require the reference temperature and humidity in the room to be adjusted within a large range according to the experimental requirements. At this time, it is necessary to confirm its range and time of change.
3) Temperature and humidity accuracy. Temperature and humidity accuracy generally includes two requirements, namely, the time change rate and uniformity of a single control point. In the parameter confirmation stage, the meaning of the accuracy requirements must be clarified. The uniformity requirement is generally for temperature accuracy, which can be proposed in the form of vertical and horizontal temperature gradient requirements.
4) Fresh air requirements. Fresh air requirements are generally proposed based on the number of indoor staff. Fresh air has a great disturbance to the indoor environment, so the determination of fresh air volume should be as reasonable and accurate as possible. Since the number of ventilation times required in a constant temperature and humidity environment is generally large, the minimum fresh air ratio method cannot be used to determine it.
5) Reliability requirements. In some cases where the experiment cycle is long or important, there are clear requirements for the reliability of the constant temperature and humidity environment, such as requiring the system to run continuously for a certain period of time. At this time, it is necessary to consider the backup of the equipment.
6) Others. Some electronic and medical experimental environments have strict requirements on the purification level. Some experiments require strict control of noise and vibration. It may also be required to maintain a certain positive or negative pressure in the room.