Trane TRG-TRC012-EN notes

TRG-TRC012-EN 33

period five

Application Considerations

notes and temperatures that the air-cooled chiller. Generally, air-cooled chillers last 15

to 20 years, while water-cooled chillers last 20 to 25 years.

To summarize the comparison of air-cooled and water-cooled helical-rotary

chillers, air-cooled chiller advantages include lower maintenance cost, a pre-

packaged system for easier design and installation, and better low ambient

operation. Water-cooled chiller advantages include greater energy efficiency (at

least at design conditions) and longer equipment life.

All chillers require a minimum pressure difference between the evaporator and

condenser to ensure proper management of oil and refrigerant. This minimum

pressure difference depends on the chiller design and controls. The most

common method of maintaining this pressure difference at the various load

conditions is to control the condensing temperature by varying the temperature

or flow rate of water (or air) flowing through the condenser. By controlling the

condensing temperature, most helical-rotary water chillers can start and

operate over a wide range of conditions.

Controlling condensing temperature: 1) maintains chiller efficiency, 2)

maintains the required pressure differential between the evaporator and

condenser for controlled flow through the refrigerant metering system, and 3)

prevents the pressure imbalance that could cause oil loss problems.

Controlling the refrigerant pressure difference between the evaporator and

condenser of an air-cooled chiller is accomplished by varying the flow rate of

the air flowing through the condenser coils. This control is an integral part of

the chiller design.

cooling tower

condenser

water

pump

pump condenser

condenser

Figure 48