Only need to firmly grasp one point, that is: the direct expansion air conditioning unit is the refrigerant directly with the air to be treated to complete heat exchange, without secondary heat exchange, that is: refrigerant air. However, the most common large-scale central air-conditioning system composed of water chillers and air-conditioning terminal units is different from the direct expansion air-conditioning unit, but: refrigerant water air, that is, the refrigerant absorbs heat from water and generates chilled water. The chilled water is then transported to the end unit such as fan coil unit in the room through the pipeline, and then circularly blows through the fan in the unit to make the room The inner air and the cooling water in the coil exchange heat to generate "cold air" to blow down.
In other words, the direct expansion air conditioning unit is a "primary refrigerant" system.
According to the above analysis, it can be seen that household air conditioners, including wall mounted units, cabinet machines, window machines and ceiling units, are all direct expansion air conditioning units. In shopping malls, office buildings and other occasions, the central air conditioning system with a refrigeration station (refrigeration main engine room) is obviously a water engine system, which is not an expansion type air conditioning unit.