Chiller

Chiller system: Compressors are the driving force in a vapor-compression chiller and act as a pump for the refrigerant. Compressed refrigerant gas is sent from the compressor to a condenser unit that rejects the heat energy from the refrigerant to cooling water or air outside of the system.

The liquid is drawn from the tank, pumped through the chiller and back to the tank. In industrial water chillers is the use of water cooling instead of air cooling. In this case the condenser does not cool the hot refrigerant with ambient air, but uses water that is cooled by a cooling tower.

Types


There are three different types of chillers:(1) air, (2) water, and (3) evaporative condensed chiller. There are four subcategories in each of the above categories for industrial chillers: (1) reciprocating, (2) centrifugal, (3) screw driven (4) and absorption chillers.

Brine chillers are a solution when cooling medium is water with glycol and this occures when low fruid temperature is demanded or glycol must be added to the cooling water in order to protect it from freezing.

Air-cooled chillers actively absorb heat from process water; they then transfer this heat into the air around the chiller unit. ... In the process, heat is absorbed from the chilled water circulating through the bundle. The compressor then pulls the refrigerant vapor from the evaporator.

The components of water cooled chillers and air cooled chillers are very similar. Each product contains an evaporator, condenser, compressor, and an expansion valve. The primary difference is whether air or water is used to provide the condenser cooling.

Chiller efficiency is generally expressed in terms of kW per ton (kW/ton.) A kW is a kilowatt of electrical input. A ton of cooling is equivalent to 12,000 BTU of cooling per hour. More efficient chillers will have lower kW/ton ratings indicating that they use less electricity to deliver the same amount of cooling.

Screw chiller vs Centrifugal chiller
The screw compressors have an ability to operate at 30 compression ratios that allows much efficient operation than the reciprocating compressor. Typically chiller efficiency is between 0.7 to 0.8 kW per ton, making rotary chillers more efficient than comparably sized reciprocating but less efficient than centrifugal.

The vapor to be condensed is circulated through a condensing coil, which is continually wetted on the outside by a recirculating water system. Air is pulled over the coil, causing a small portion of the recirculating water to evaporate. The evaporation removes heat from the vapor in the coil, causing it to condense.

Evaporative condenser Vs. cooling tower


A cooling tower is used to cool water by direct contact between that water and a stream of air. An evaporative condenser is used to cool water by passing that fluid through a heat exchanger which is itself cooled by contact with water passing through a stream of air.n
An evaporative condenser is used to remove excess heat from a cooling system when the heat cannot be utilised for other purposes. The excess heat is removed by evaporating water. In an evaporative condenser the primary coolant of the cooling system is cooled, which is the opposite of a cooling tower