How does dx cooling work

Another key feature of DX Packaged units is the advantage of having the entire cooling system self-contained in one unit. This allows for the installation on top of or alongside a building without too large of a footprint, and are generally less expensive to install. The refrigerant is continuously transformed from a liquid, to a vapor, and back again. This process cools down the refrigerant which is passed through an evaporator.

Warm water coming through a inch radius supply hose is passed over the evaporator and cooled off to the desired temperature. Typically the cooled water is used for existing air handler systems. The ducts are connected to the grills or diffusers that supply the chilled air to the room. The air absorbs the heat and gets heated and it passes through another set of the grill and into the return air duct that ends into the air handling unit room. This air is then re-circulated by the air handling unit.

Though the efficiency of the DX plants is higher, the air handling units and the refrigerant piping cannot be kept at very long distance since there will be lots of drop in pressure of the refrigerant along the way and there will also be cooling losses. Further, for the long piping, large amounts of refrigerant will be needed which makes the system very expensive and also prone to the ma instance problems like the leakage of the refrigerant.

Due to these reasons the DX type central air conditioning systems are used for small air conditioning systems of about 5 to 15 tons in small buildings or the number of rooms on a single floor. If there are large air conditioning loads, then multiple direct expansion systems can be installed. In such cases, when there is lesser heat load one of the plants can be shut down and the other can run at full load.

The DX expansion system runs more efficiently at higher loads. Even in case of the breakdown of the plants, the other plants can be used for the cooling purpose. The DX types of central air conditioning plants are less popular than the chilled water type of central conditioning plants. In this series of articles both these plants and air handling units have been described. Page content. It is the property of changing phase, i. The two components which facilitate the transfer of heat to or from the refrigerant are the evaporator located in the area to be cooled, and the condenser, located where heat may be dissipated, commonly outside of the building.

The majority of the heat energy is dissipated in the condenser, and in order for heat transfer to occur, the air surrounding the condenser coil must be at a lower temperature than the refrigerant.

This is why the compressor raises the temperature and pressure of the refrigerant, thus ensuring that there is sufficient heat gradient between the outside air and the refrigerant. Between the condenser and the evaporator is the expansion valve, which regulates the pressure of the refrigerant. By allowing the refrigerant to expand, we increase the volume of space the gas can occupy, and thus lower the number of collisions that the atoms will have.

This results in a lowering of kinetic thermal energy. Since the expansion valve lowers the pressure of the gas by allowing it to expand into the larger volume of the intake pipe feeding the evaporator, the refrigerant experiences a decrease in temperature. This is how we can actively make something colder than room temperature.

Refrigerants are designed to have a boiling point low enough to evaporate and turn into a gas at room temperature. For heat to transfer there has to be a temperature difference between the room and the refrigerant.

If the cold refrigerant now flows through the evaporator coils, and air blown across the evaporator coils is at a higher ambient temperature, the colder refrigerant will absorb the heat, or thermal energy from the air, which has the same effect as cooling that air.

By constantly cycling additional cold refrigerant through the room, heat can be steadily removed from the desired area, and dissipated outside the building. A mechanical cooling system that uses the evaporation and condensation of a refrigerant to remove heat from an area.