Condenser coil: in the outdoor unit, the gaseous refrigerant is compressed, which raises its temperature significantly, and passed through a condenser coil. The outdoor fan helps dissipate the heat from the refrigerant into the external environment.
Condensation: as the refrigerant releases heat to the outdoor air, it condenses back into a liquid state.
Expansion valve: after condensing, the high-pressure liquid refrigerant is passed through an expansion valve, which reduces its pressure and temperature.
Evaporator coil (again): the low-pressure, low-temperature liquid refrigerant is then sent back to the indoor evaporator coil to start the cycle again.
This continuous cycle of evaporation and condensation removes heat from the indoor space, effectively cooling it. The heat absorbed by the refrigerant indoors is released outside, maintaining a comfortable indoor temperature.
Types of Direct Expansion System
There are multiple types of DX cooling and refrigeration systems, each suited to specific applications and cooling requirements.
The choice of system depends on factors such as the size of the space, the desired level of control and energy efficiency considerations, but some common options include:
Split Air Conditioning Systems
Split systems consist of two main components: an indoor unit (evaporator coil and blower) and an outdoor unit (compressor and condenser coil).
They are commonly used in domestic and small commercial applications for cooling individual rooms or zones.
Packaged Air Conditioning Units
Packaged DX units are self-contained systems that contain all the components (evaporator, compressor, condenser and blower) in a single cabinet. They’re typically used for cooling larger commercial spaces or entire buildings.
There are different types of packaged units, including rooftop units (installed on the roof) and ground-mounted units.
Heat pumps are a type of DX system that can provide both heating and cooling. They work by reversing the refrigeration cycle, allowing them to extract heat from the outdoor air (even in cold weather) and transfer it indoors for heating.
Heat pumps are commonly used in domestic and commercial applications.
Variable Refrigerant Flow (VRF) Systems
VRF systems are a more advanced form of DX cooling and heating. They can provide simultaneous heating and cooling to different zones within a building, offering precise temperature control and high energy efficiency, and are often used in commercial and multi-zone residential applications.
Chilled Water Systems with DX Coils
In some commercial buildings, chilled water is used as the primary cooling medium, and DX coils are employed to cool the air.
Chilled water systems circulate cold water through a network of pipes to cooling coils in air handlers or fan coil units. DX coils in these units provide additional cooling by using refrigerant to cool the air further.
What is Direct Expansion Cooling Used For?
DX cooling is a versatile technology with a diverse range of applications - from ensuring human comfort to preserving products and critical equipment.
Some of the key areas where DX cooling is commonly employed include: