Chiller removes heat from liquid coolants through vapor-compression, adsorption, or absorption cycles. Liquid circulates through heat exchanger for cooling equipment or process stream. Refrigeration generates waste heat, which must be exhausted or recovered.
Working Principle of Chiller?
Chiller cycle removes heat from fluid, transfers it to surroundings. The main components involved in the working of a chiller are the compressor, condenser, expansion device, and evaporator. Here’s a step-by-step explanation of the working principle:
- Compression: The process starts with the compressor. The compressor draws in low-pressure refrigerant vapor from the evaporator and compresses it, raising its pressure and temperature. This compression process increases the energy of the refrigerant.
- Condensation: The high-pressure and high-temperature refrigerant vapor from the compressor enters the condenser. In the condenser, the refrigerant releases heat to the surroundings, typically through air or water cooling. As the refrigerant loses heat, it undergoes a phase change from a vapor to a liquid state. This liquid refrigerant is still under high pressure.
- Expansion: The high-pressure liquid refrigerant then passes through an expansion device, often a metering valve or an expansion valve. The expansion device creates a restriction, causing a drop in pressure. As the refrigerant passes through the expansion device, its pressure and temperature decrease significantly. The refrigerant now exists as a mixture of liquid and vapor.
- Evaporation: Low-pressure refrigerant enters evaporator, contacting cooled fluid. As the refrigerant absorbs heat from the fluid, it evaporates and changes from a liquid to a vapor state. This evaporation process extracts heat from the fluid, cooling it down. The refrigerant vapor then returns to the compressor to repeat the cycle.
Refrigerant transfers heat from evaporator to condenser, releasing it to surroundings during refrigeration cycle. Chilled system controls temperature, pressure, flow using sensors and systems. This ensures efficient operation and precise control of the cooling process.
Types of Industrial Chillers
Air Cooled Chillers
Air-cooled chillers are refrigeration systems that use air as the cooling medium instead of water. Commercial and industrial cooling systems for buildings, processes. The working of an air-cooled chiller involves, circulation of a refrigerant, such as R-410A or R-134a, within a closed-loop system. The refrigerant absorbs heat from the process or building and carries it to the chiller unit. The chiller then transfers the heat from the refrigerant to the surrounding air using an air-cooled condenser.
Here are some key features and components of air-cooled chillers:
- Compressor: The compressor is the heart of the chiller system and is responsible for circulating the refrigerant. Common types of compressors used in air-cooled chillers include reciprocating, scroll, screw, or centrifugal compressors.
- Condenser: The condenser is where the refrigerant releases heat to the surrounding air. Air-cooled chillers use condensers with finned tubes for heat transfer.
- Fans: Air-cooled chillers use fans for heat transfer. The fans can be axial or centrifugal, and their speed can be variable or fixed, depending on the chiller design.
- Evaporator: Evaporator absorbs heat from cooling process fluid. It is a heat exchanger that allows the refrigerant to evaporate while extracting heat from the desired source.
- Expansion Valve: Expansion valve controls refrigerant flow, maintaining desired pressure and temperature for efficient cooling.
- Control System: Modern air-cooled chillers have advanced control systems for temperature, pressure, and operating conditions. These systems help optimize chiller performance and ensure efficient operation.
Water Cooled Chillers
Water-cooled chillers are refrigeration systems that use water as the primary method of heat transfer for cooling purposes. They are commonly used in large-scale commercial and industrial applications where high cooling capacities are required.
Here are some key features and components of water-cooled chillers:
- Compressor: Similar to air-cooled chillers, water-cooled chillers also incorporate compressors to circulate the refrigerant in the system. The compressor type can vary, including reciprocating, scroll, screw, or centrifugal compressors, depending on the cooling capacity and application requirements.
- Condenser: In water-cooled chillers, the condenser is responsible for transferring heat from the refrigerant to water. Shell-and-tube heat exchanger condenses refrigerant, releasing heat to cooling water.
- Cooling Tower: Water-cooled chillers require a cooling tower as an integral part of the system. The cooling tower cools the heated water coming from the condenser by utilizing evaporation and natural convection. Cooled water is recirculated for heat exchange.
- Evaporator: The evaporator in a water-cooled chiller is similar to that of an air-cooled chiller. Heat exchanger absorbs heat from cooled process fluid. Evaporator transfers chilled water for heat transfer, cooling it back to application.
- Expansion Valve: Expansion valve controls refrigerant flow, maintaining desired pressure and temperature for efficient cooling.
- Pumps and Water Circulation System: Expansion valve controls refrigerant flow, maintaining desired pressure and temperature for efficient cooling. These pumps ensure the proper flow rate and pressure to optimize heat transfer efficiency.
- Control System: Advanced control systems monitor and manage water-cooled chillers’ parameters. These control systems help optimize chiller operation, energy efficiency, and reliability.