Low pressure chillers - Chiller evaporator freezing


Chilled water

Privileged secondary refrigerant is water, if it cannot satisfy the needs of temperature, i.e. if the load temperature considerably exceeds 0C that water can be distributed without risk of freezing.

The greatest demand on chilled water - in air-conditioning systems. For this debt, water is needed for the temperature, as a rule, not less than 5C, and for this purpose, works with refrigerant evaporator temperatures close to freezing point. A very wide range of factory manufacturing of packaging are available water chillers or air-cooled condensers. Other types can have remote air-cooled or evaporative condensers and therefore require refrigerant pipe connections on the territory of these capacitors. Sizes range from 14 kW to 35 000kW, most installations within the 100-1500kW.

When water temperatures close to freezing, and evaporators, which are vulnerable to ice damage, it is important to have sufficient control to check the calibration of these and often, to avoid tampering by unauthorized persons.

Almost all the trouble, packaged water chillers arise due to the inability of security control. Several types of controls, often three or more on the same hardware, but there must never be less than two:

  1. Water flow switch to stop the machine if the thread stops chilled water chain
  2. Refrigerant low pressure cutout to protect against loss of charge
  3. Diversion of water from the low-temperature cut-out
  4. The evaporator pressure control valve
  5. Hot gas bypass valve to maintain the temperature of boiling above freezing and not for normal capacity management.
Most bottled drinking water chillers large enough to have the potential to manage devices in the compressor. Importantly, the thermostat will compressor unload when the water approaches the bottom of the safe limit, so as to keep the water as cold as you can without the risk of freeze damage.

In all but the smallest installations, two or more chillers are used, or one chiller with two separate circuits. This arrangement gives some continuity of service, if one machine is off-line for maintenance or other reasons, provides a more effective control and provides savings of running when the load is light.

If the water is below 5C, approach to freezing point brings significant possibility of ice formation and possible damage to the evaporator. Some other closed system, and either oversized heat exchange surfaces or high efficiency-a type of surface. In both of these facilities for improvement of heat exchange so that the surface in contact with water will never be cold enough to cause layers of ice to accumulate.....

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