Chiller fan coil system

Chiller-fan coil system - a centralized, multi-zone air conditioning system in which the coolant circulating under relatively low pressure - ordinary water (in a tropical climate) serves as a coolant between the central cooling machine (chiller) and local heat exchangers (air cooling units , fan coil units ) aqueous solution of ethylene glycol (in temperate and cold climates). In addition to the chiller (chillers) and fan coil units, the system includes piping between them, a pumping station (hydraulic module) and an automatic control subsystem.

Terminology

There is no translation for English “chiller” in GOST 22270-76 “Equipment for air conditioning, ventilation and heating” ^[2] . For the term “fan coil unit”, GOST translates “fan coil” (a fan using local built-in fan to recirculate and supply a mixture of indoor air with outdoor air that has previously been processed in a central air conditioner, as well as heating and / or cooling air).

Differences

Compared to VRV / VRF systems in which gas refrigerant circulates between the chiller and local units, chiller-fan coil systems have the following differences:

• Twice the maximum distance between the chiller and fan coil units. The length of the routes can reach hundreds of meters, since with a high heat capacity of the liquid coolant, the specific losses per linear meter of the route are lower than in systems with gas refrigerant.

• Wiring cost. To connect chillers and fan coils, ordinary water pipes, shutoff valves, etc. are used. Balancing water pipes, that is, balancing the pressure and flow rate of water between individual fan coils, is much simpler and cheaper than in gas-filled systems.

• Security. Potentially volatile gases (gas refrigerant) are concentrated in the chiller, which is usually installed outdoors (on the roof or directly on the ground). Pipe wiring accidents inside the building are limited by the risk of a flood, which can be reduced by automatic shut-off valves.

Weaknesses

Chiller-fan coil systems are more economical in energy consumption than roof systems, but they certainly lose in cost-effectiveness to systems with variable refrigerant flow ( VRF ). However, the ultimate performance of VRF systems is limited (volumes of refrigerated rooms up to several thousand cubic meters).

Faults

• Freon leak. Freon leakage can occur as a result of a leaking connection of the freon circuit.
• Failure of the compressor. In the compressor, as a rule, the stator winding is burned or the valves (piston group) are destroyed.
• Moisture in the refrigeration circuit. Moisture (water) can enter the refrigeration circuit as a result of leakage in the evaporator, resulting in the mixing of the two Freon-Water circuits.

Basic fluid cooling schemes

• Direct cooling .. The most common option. Liquid cooling takes place in a liquid / freon heat exchanger. The temperature difference between the inlet / outlet is not more than 7 ° C. Standard air conditioning + 7/12 ° C.
• Intermediate refrigerant cooling. This type of circuit is used when the difference in temperature of the liquid at the inlet and at the outlet of the chiller is more than 7 ° C.

Main Chiller Applications

• air conditioning and ventilation systems;
• cooling water, oil, and other liquids for production processes;
• cooling equipment, vacuum pumps, machine spindle;
• laser equipment and plasmatron;
• extruder cooling;
• lowering the temperature of the molds;
• cooling induction furnaces;
• injection molding machine cooling (TPA);
• decrease in the temperature of the circulating water;
• confectionery cooling;
• glycol in breweries and alcoholic beverages;
• hydraulic oil cooling;
• lowering the temperature of PET blowing equipment;
• cooling birds after slaughter;
• milk in the stream after milking;
• cooling of MRI devices.