The difference between dry coil and wet coil

The difference between dry coil and wet coil

Dry coil is a device use to provide cold or heat to indoor return air. In order to achieve the purpose of "drying", the temperature of the chilled water use in the dry coil is higher than that of the ordinary coil, and there is generally no condensation, so it is called "dry coil".

The inlet water temperature of the dry coil is generally about 2 degrees higher than the indoor air dew point (13°C in water and 18°C in the outlet water). The wind speed through the dry coil is preferably 2 m/s. The heat exchange effect is the best at this time. It is best to make a water collecting pipe to prevent condensate in the case of high humidity or when the water pipe is not well insulated.

Mainly used in the clean room constant temperature and humidity air conditioning system, the system is generally composed of MAU, FFU and DC three parts:

 　　 MAU (Make-up Air Unit) maintains the positive pressure and fresh air volume of the clean room, and at the same time achieves indoor humidity control requirements through dew point control;

 　　DC (Dry coil), mainly eliminates indoor sensible heat (heat generated by people, lighting, machinery, etc.) to control indoor temperature.

　　FFU (Fan Filter Unit) guarantees the indoor cleanliness level. To achieve the indoor cleanliness level, it must be combined with the treatment of MAU's primary, middle and high-efficiency filters. FFU alone cannot work;

Wet coils are divide into cooling coils and heating coils, which are equipment for cooling (or heating) and dehumidifying the fresh air or return air, and controlling the temperature and humidity of the supply air. Generally, condensate will be generated.

In clean room air conditioning system, the dry coil handles the sensible heat load in the clean room, while the MAU wet coil handles the fresh air load.

　　Coil tube selection should pay attention to the following points:

　　1. The enthalpy difference determines the number of copper tube rows of the coil;

　　2. The windward area of the coil is determined by the required air volume;

　　3. The wind speed on the coil is generally not more than 2.5m/s;

　　4. The coil fins are aluminum fins, and blue wave treatment is required to prevent corrosion.