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Understanding the Basics of Chillers

Chillers are machines that absorb heat from water through a compression process. Chillers have varied mechanical structures, including rotary-screw, reciprocating and centrifugal systems, powered by steam, electric motors or gas turbines. The absorption chiller has no moving parts and is steam powered. There are various combinations of capacities, features and competencies that make up the different chiller types. The energy-saving capacity of a chiller depends on various factors like space constraints, operating conditions and energy saving features of the unit. Chillers use air, water and other mediums like propane to remove heat and generate cooling.

Chillers are machines that absorb heat from water through a compression process. Chillers have varied mechanical structures, including rotary-screw, reciprocating and centrifugal systems, powered by steam, electric motors or gas turbines. The absorption chiller has no moving parts and is steam powered. There are various combinations of capacities, features and competencies that make up the different chiller types. The energy-saving capacity of a chiller depends on various factors like space constraints, operating conditions and energy saving features of the unit. Chillers use air, water and other mediums like propane to remove heat and generate cooling.

Components

Mechanically structured chillers have four main components: an evaporator, condenser, compressor and expansion valve. The chiller’s evaporator operates at a lower temperature and pressure in comparison to the condenser where the temperature and pressure is higher. The absorption chiller makes use of heat to perform its cooling function. The chiller has a thermal compressor that consists of a generator, pump, throttle and absorber.

Process

The chiller’s cooling process starts in the evaporator; liquid refrigerant flowing over the evaporator absorbs heat generated by the circulation of chilled water in the evaporator tube bundle and evaporates. The compressor draws out refrigerant vapor and pumps it to the condenser. The refrigerant vapor raises the temperature of the condenser and condenses in the component’s tubes. From the condenser, the refrigerant passes through the expansion valve device and back into the evaporator to flow over the chilled coils; absorb more heat and complete the cycle.

Maintenance

Energy-efficient chillers function in an energy-saving manner when properly maintained. Recommended maintenance of the chiller unit once every quarter includes regular checks of compressor operating pressures and temperatures; motor voltages, electrical starters, relays and contactors; oil levels and pressures; refrigerant levels; refrigerant leaks; water flow rates, un-loader operation; cooling tower operation and water chemistry review for appropriate heat transfers.

New Technology

Innovative developments in chiller technology provide the tools needed to achieve improved chiller operating efficiencies. New technology is available with new model chillers, but in some units can be added to existing applications. Chiller efficiencies decline with time regardless of comprehensive maintenance routines, which include chemical water treatment and tube cleaning programs. New generation chillers offer maximum efficiency especially when combined with a variable-frequency drive. Highly efficient chillers have the capability to reduce energy requirements by approximately 30 to 50 percent in most unit applications.

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