In addition to adjusting the air temperature, the constant temperature and humidity machine also has the functions of humidity adjustment and dust removal. Compared with ordinary air-conditioners, the constant temperature and humidity precision air conditioning system can run all the year round without stopping, so its reliability is very high. There are many options for the air supply system of constant temperature and constant humidity machine. The common ones include the down delivery, the upper and the lower, and the upper side. The standard type constant temperature and humidity machine adopts medium efficiency filter to clean indoor air. According to customer needs, sub efficient air filters can be selected.
Characteristics of constant temperature and constant humidity unit:
1. the cooling capacity is generally between 10HP-200HP;
2. configuration of electric heating and electrode humidification, the heating amount is generally rich, air conditioner configuration humidification is small, need to be recalculated, the general need to increase a model or multi - configuration one;
3. the rated air volume requirements;
4. the rated cooling water requirements;
5. the resistance of the condenser is generally at 0.82-3.45mH2O;
6. the size of the air conditioning unit is small;
7. temperature control range: 18~25, sensitivity: + 1; humidity control range: 50~70, sensitivity: + 5;
8. machine is generally between 100~550.
9. design conditions: intake air dry bulb temperature 23 C, wet bulb temperature 17 centigrade, cooling water inlet temperature 30 C, effluent temperature 35 C;
Generally, it is suitable for temperature and humidity control or the whole design area is not large. If the area is large, the system is divided more, the position of the air conditioning machine room is relatively scattered, the management and system control will be inconvenient, and it is not conducive to the unified distribution of energy, and the waste of energy is more serious. In this case, the general area is greater than 2000m2, and the design of chiller + combined air handling unit is recommended.
The use of constant temperature and constant humidity unit is divided into two pieces.
1, constant temperature and constant humidity workshop, but no purification requirements;
2, both constant temperature and humidity requirements, and the need for purification level control;
The situation of the room:
1.) the heat in the room is larger.
2.) the sensible heat in the room is small;
A. consideration of the load:
The air volume of the system is determined by the sensible heat and air temperature difference in the room, not by the total refrigerating capacity of the system (the sensible heat and latent heat of the room). The cooling capacity of constant temperature and humidity unit is 50%, and latent heat is 50%, which is equivalent to 20% of the fresh air volume. When the heat is larger in the room, and when the new air volume is small, the amount of air supply is larger, and it can not be determined according to the refrigerating capacity of the constant temperature and constant humidity unit.
B. from external pressure consideration:
Constant temperature and humidity, but no purification requirements of the system for air conditioning units outside pressure requirements are not high, mainly to overcome the air supply and return pipes, valves, diffuser, initial filter, and other conventional units can meet the requirements;
The system not only has the requirement of constant temperature and humidity, but also needs the system of purifying grade control to have high external pressure requirement for air conditioning unit. The general system resistance is between 1100Pa and 1400Pa, which mainly overcomes the air supply and return pipe, valve, diffuser, initial effect filter (initial resistance 50Pa, final resistance 100Pa), middle effect filter (initial resistance 150Pa, final). Resistance 300Pa), high efficiency filter (initial resistance 250Pa, final resistance 500Pa) and so on, conventional units can not meet the requirements. If the system needs to set two return air, the clean type constant temperature and constant humidity unit can not be selected; the first return air condition, the design form of the constant temperature and constant humidity unit + pressurization box, because it is difficult to match the fan in the constant temperature and humidity unit when choosing the type of the pressure fan, the different type and different power fan are in series or parallel. When the total air volume is not simply added, the calculation is relatively complex. It is suggested that the single fan system should be designed as far as possible in the general design process.
The operating principle of the system
The operation of the constant humidity and humidity machine system is based on three interrelated systems: refrigerant circulation system, air circulation system, and electrical appliance automatic control system.
1, refrigerant circulation system
The liquid refrigerant in the evaporator absorbs the heat of the air (the air is cooled and dehumidified) and begins to evaporate, eventually forming a certain temperature difference between the refrigerant and the air, and the liquid refrigerant is completely vaporized into the gaseous state, then the compressor is inhaled and compressed (pressure and temperature increases), and the gaseous refrigerant passes the condenser (air cooling / water). Cold) absorbs heat and condenses into a liquid. Through the expansion valve (or capillary) throttling, the cryogenic low pressure refrigerant enters the evaporator to complete the refrigerant circulation process.
2, air loop system
The fan is responsible for inhaling the air from the air inlet. The air passes through the evaporator (cooling, dehumidification), humidifier and electric heater (Sheng Wen). The air is sent to the user's space after the air inlet. The air sent out and the air in the space will be mixed back to the air vent.
3, electrical automatic control system
It includes the power supply part and the automatic control part. Through the contactor, the power supply is divided into the temperature, humidity control and the fault protection parts of the compressor, the fan, the adder and the humidifier. The temperature and humidity control is through the temperature and humidity control, and the temperature and humidity of the return air is compared with the temperature and humidity set by the user, and the compressor is automatically run. Temperature, dehumidification, humidifier, electric heating (Sheng Wen) and other components to achieve automatic control of constant temperature and humidity.