A brief introduction to indirect evaporative cooling air conditioning (AHU) in HVAC engineering.
Indirect evaporative cooling and air conditioning technology, the output medium (air or water) and the working medium (air and water) are indirectly in contact with the heat and moisture exchange, and there is no qualitative exchange between the output medium and the working medium, only the exchange of sensible heat. As a special form of indirect evaporative cooling air conditioning technology, ** indirect evaporative cooling air conditioning technology uses the difference between the dry bulb temperature of the air and the decreasing wet bulb temperature to complete heat exchange, which is different from the general indirect evaporative cooling air conditioning technology (using the difference between the dry bulb temperature of the air and the fixed wet bulb temperature for heat exchange).
Indirect evaporative cooling, which is used to lower the temperature of an indoor room without the use of refrigerants. It uses the principle of evaporative heat absorption of water to pass outdoor air through a wet cooling medium, and then send the cooled air into the room to achieve a cooling effect. Unlike traditional direct evaporative cooling, indirect evaporative cooling separates the indoor air from the outside air to avoid increasing the humidity of the indoor air. It employs two air circulation systems: one for indoor air and the other for outdoor air.
The basic principle of indirect evaporative cooling is the use of wet cooling media, such as wet cardboard or wet filters. As outdoor air passes through a humid cooling medium, the air temperature decreases due to the evaporative endothermic effect of the water. The cooled outdoor air is then exchanged with the indoor air through a heat exchanger, reducing the temperature of the indoor air.
Between indoor air and outdoor air, heat transfer is carried out through a heat exchanger, but the two are isolated and the indoor air does not mix with the outdoor air. In this way, it is possible to achieve cooling while keeping the humidity of the indoor air relatively stable, so as to prevent the indoor air from becoming too humid.
The advantages of indirect evaporative cooling technology include reduced energy consumption, reduced reliance on refrigerants, reduced greenhouse gas emissions, and improved indoor air quality. It is often used in dry tropical or desert areas and can provide a comfortable indoor temperature in a hot environment.
Structural composition. Indirect evaporative cooling system: It is composed of a sprinkler device, a heat exchange core, an indoor fan, an outdoor fan, etc.
DX system: It is composed of DC inverter compressor, electronic expansion valve, evaporator, condenser, indoor fan, outdoor fan and other temperature and pressure sensors.
Sprinkler device: The sprinkler device is composed of circulating water pump, sprinkler head, water collection tank, water level switch, float valve and inlet and drainage solenoid valvesDuring operation, the circulating water pump pumps water from the lower sump to the top of the sprinkler device, and is dispersed by the sprinkler to spray downward, and finally falls into the sump to form a circulation.
Heat exchange core: The heat exchange core is composed of multiple high-efficiency heat exchange plastic sheets superimposed and forms a hot and cold air channel.
Indoor and outdoor fans: Both indoor and outdoor fans are high-efficiency EC centrifugal fans, which can realize stepless variable air volume adjustment of fans according to load changes.
Compressor: The compressor adopts DC inverter compressor, which can achieve variable cooling output according to different refrigeration needs, and ensure that the total cooling capacity of the refrigeration system meets the load demand.
Three cooling modes.
Dry mode: The temperature difference between indoor and outdoor is large, relying on indoor and outdoor air to exchange heat in the heat exchange core can provide sufficient cooling capacity, at this time, the external fan adjusts the speed according to the indoor cooling demand to control the cooling output.
Spray mode: The temperature difference between indoor and outdoor is small, and the spray system is turned on, and the water evaporates and absorbs heat on the surface of the heat exchange core, reducing the temperature of the outdoor side, and the external fan still adjusts the speed according to the refrigeration demand.
Spray + DX mode: When the heat exchange core and spray system cannot meet the indoor cooling demand, the mechanical refrigeration is turned on to supplement the cooling capacity, and the external fan adjusts the speed according to the condensation pressure.