The uses of high-precision constant temperature and humidity systems are mainly divided into two categories:
1. Constant temperature and humidity workshops, but no purification requirements;
2. There are both constant temperature and humidity requirements and purification level control is required;
the situation of the room: 1. The sensible heat in the room is large; 2. The sensible heat in the room is small.
Analyze the above two points:
1. Consider from the load aspect:
The air supply volume of the high-precision constant temperature and humidity system is determined by the sensible heat and supply air temperature difference in the room, rather than calculated based on the total cooling capacity of the system (sensible heat and latent heat of the room). The cooling capacity of the constant temperature and humidity unit generally accounts for 50% of the sensible heat and 50% of the latent heat, which is equivalent to fresh air accounting for about 20% of the total air supply volume. When the sensible heat in the room is large and the fresh air volume is not large, the calculated air supply volume is large, and the cooling capacity calibrated by the constant temperature and humidity system cannot be determined based on the total cooling capacity.
2. Consider the external residual pressure of the air-conditioning unit: the system with constant temperature and humidity but no purification requirements does not have high requirements for the external residual pressure of the air-conditioning unit. It mainly overcomes the supply and return air ducts, valves, diffusers, primary filters, etc. Conventional units can meet the requirements; the system with both constant temperature and humidity requirements and purification level control has higher requirements for the external residual pressure of the air-conditioning unit. Generally, the total system resistance is between 1100Pa and 1400Pa. It mainly overcomes the supply and return air ducts, valves, diffusers, primary filters (initial resistance 50Pa, final resistance 100Pa), medium efficiency filters (initial resistance 150Pa, final resistance 300Pa), high efficiency filters (initial resistance 250Pa, final resistance 500Pa), etc. Conventional units cannot meet the requirements. If the system needs to set up secondary return air, the crystalline constant temperature and humidity system cannot be used; in the case of single return air, the design form of constant temperature and humidity system + pressurization box is difficult to match with the fan in the constant temperature and humidity unit when selecting the model of the pressurization fan. The total air volume of fans of different models and powers is not a simple addition when connected in series or parallel, and the calculation is relatively complicated. It is recommended to design it as a single fan system as much as possible in the general design process.