The operation of an industrial chiller system is driven by three interconnected subsystems: the refrigerant circulation system, the water circulation system, and the electrical automatic control system.
Refrigerant Cycle
Inside the evaporator, liquid refrigerant absorbs heat from the water and begins to evaporate. This process establishes a specific temperature differential between the refrigerant and the water; eventually, the liquid refrigerant completely evaporates and transforms into a gaseous state. Subsequently, this gaseous refrigerant is drawn into the compressor and compressed (resulting in increased pressure and temperature). The gaseous refrigerant then passes through the condenser (which may be air-cooled or water-cooled), where it releases its heat and condenses back into a liquid. After undergoing throttling via an expansion valve (or capillary tube), the refrigerant-now at a low temperature and low pressure-re-enters the evaporator, thereby completing the refrigerant circulation cycle.
Water Cycle
The water pump is responsible for drawing water from the water tank and pumping it to the equipment requiring cooling. As the chilled water absorbs heat from the equipment, its temperature rises before it flows back into the chilled water tank.
Electrical Automatic Control
This system comprises two main sections: the power supply section and the automatic control section.
The power supply section utilizes contactors to deliver electrical power to components such as the compressor, fans, and water pumps.
The automatic control section integrates various components-including thermostats, pressure protection switches, timers, relays, and overload protection devices-to achieve functions such as automatic start-up and shut-down based on water temperature, as well as system protection.
Generally, units with a capacity of 10 HP or greater utilize water-cooled heat dissipation, while units under 10 HP employ air-cooled heat dissipation.
Air-cooled industrial chillers are typically designed as integrated units, meaning the evaporator, compressor, and condenser are housed together within a single chassis. For higher-capacity air-cooled chillers, particular attention must be paid to the heat dissipation generated by the condenser's cooling fans during operation. When deployed within air-conditioned facilities, these integrated units require the installation of exhaust ducts to channel the heat expelled by the cooling fans to the outdoors.
Air-cooled industrial chillers can also be configured as split systems, wherein the condenser is positioned directly outdoors (referred to as the "outdoor unit"), while the evaporator and compressor are located indoors (referred to as the "indoor unit"). However, taking into account factors such as heat absorption during the refrigerant's circulation between the condenser and the evaporator, the distance between the indoor and outdoor units should ideally be kept within 6 meters. Additionally, the copper piping used to transport the refrigerant requires thermal insulation. The power and control cables for the fan can be routed alongside the copper piping; this allows for a simpler installation process, requiring the facility to create only a single opening for the entire bundle to pass through.
For industrial applications involving air-cooled chillers with low flow rates and low heat dissipation requirements, a self-contained (monobloc) unit is typically selected for direct use, in which case external heat dissipation issues do not need to be considered. Conversely, for air-cooled chillers with high flow rates and high heat dissipation requirements, a split-system configuration is the preferred choice.
The cooling efficiency of an air-cooled chiller's condenser is subject to slight fluctuations influenced by seasonal and climatic changes in the external environment. In contrast, water-cooled chillers-which utilize a cooling tower for heat dissipation-offer more stable cooling performance; however, their drawback is the requirement to install a cooling tower, resulting in limited mobility.
