Introduction
This article provides an in-depth exploration of air cooled chillers.
It covers detailed information on various aspects including:
- Working Principles of Air Cooled Chillers
- Operational Mechanisms of Air Cooled Chillers
- Different Varieties of Air Cooled Chillers
- Practical Uses and Advantages of Air Cooled Chillers
- And more...
Chapter 1: Understanding Air-Cooled Chiller Functionality
This chapter introduces the basic principles of air-cooled chillers, explaining their key components and operational mechanisms.
What Are Air-Cooled Chillers?
Air-cooled chillers are refrigeration systems designed to lower fluid temperatures in conjunction with a building's air handling system. Unlike traditional industrial chillers requiring cooling towers, these units expel heat using fans. By utilizing air to cool water and other fluids, they effectively reduce temperatures in equipment, processes, and spaces through heat absorption and dissipation.
Comprising a compressor, evaporator, condenser, and expansion valve, air-cooled industrial chillers serve diverse environments including industrial facilities, shopping centers, hotels, and medical institutions. They're particularly suitable for multi-building locations like amusement parks and outdoor shopping centers, providing reliable cooling for both large and small operations.
Their compact design makes them portable, cost-effective to maintain, and easy to install. Versatile portable units are practical for large events or emergencies, featuring simpler structures similar to water-cooled chillers. Most models use either screw or scroll compressors.
Often called modular chillers, these units can be horizontally stacked to increase capacity, ranging from about 10 to 550 refrigeration tons (RT). Scroll compressor models reach approximately 200 RT, while screw compressor versions can achieve up to 550 RT.
Typically equipped with at least two compressors for redundancy, these systems continue operating at reduced capacity if one compressor fails. While less efficient than water-cooled alternatives, with energy efficiency ratios around 1.00 kW/ton, they remain practical solutions for many applications.
Key Components of Air-Cooled Industrial Chillers
The main elements include:
Compressor in Air-Cooled Chillers
The compressor drives refrigerant circulation through the system. Common types include screw, reciprocating, scroll, rotary, and centrifugal models. Centrifugal compressors operate differently, using impellers to accelerate and decelerate gas for compression, unlike positive displacement compressors that use screws, pistons, or rotors to increase vapor pressure.
Available in hermetic, semi-hermetic, and open configurations, compressors suit various capacity needs. Hermetic models house both motor and compressor in sealed units for low-capacity applications, while semi-hermetic versions allow mid-range capacity. Open configurations separate but connect motor and compressor components for high-capacity use.
Condenser in Air-Cooled Chillers
This heat exchanger transfers heat from refrigerant to air, typically using copper tubes with liquid refrigerant and aluminum fins to enhance heat transfer. While most employ air-cooled condensers, some models use evaporative or water-cooled alternatives.
Water-cooled versions use water for refrigerant cooling, whereas evaporative models combine air and water to increase air temperature through evaporation, with air facilitating vapor removal.
Condenser Fans
These distinctive components circulate air across the condenser, removing heat and enabling the system to restart the cooling cycle effectively.
Expansion Valves
These valves precisely regulate refrigerant flow according to cooling demand. By receiving and depressurizing liquid refrigerant before it enters the evaporator, they create backflow and transform refrigerant into a low-pressure liquid-vapor mixture, which becomes hot then cold gas as pressure increases.
Seven valve types—including thermal, electronic, and automatic—manage refrigerant flow while maintaining pressure differentials between condenser and evaporator, facilitating refrigerant transformation.
Evaporator/Heat Exchanger
This component removes heat from refrigerant before it returns to the condenser. As a heat exchanger, it transfers heat from refrigerant to water or coolant. Available in coil, shell and tube, and plate configurations, each type offers distinct heat transfer efficiencies.
By cooling refrigerant to gas, the evaporator enables heat absorption from water or air handlers. Different designs—including shell and tube, finned, and plate—enhance cooling efficiency through increased contact area.
Notable evaporator variations:
- Shell and Tube: Typically copper or steel tubes, ideal for liquid cooling.
- Finned Evaporators: Feature secondary fins that enhance heat exchange by increasing surface exposure.
- Plate Evaporators: Use grooved metal plates for refrigerant distribution, including welded designs with eutectic solutions for improved contact.
Filter Drier
This component protects the system by removing contaminants and moisture. Regular replacement is necessary due to clogging from prolonged use, ensuring system longevity and efficiency.
Chapter 2: Air Cooled Industrial Chiller Operation
Air-cooled industrial chillers operate by extracting heat from processed water in closed-loop systems. Essential for manufacturing, plastics, food and beverage, and HVAC applications, these units circulate chilled water through facility air handlers or process equipment. After absorbing heat, water returns to the chiller where the evaporator's liquid refrigerant absorbs thermal energy, evaporating into low-pressure vapor.
This vapor travels to the compressor, becoming high-pressure, high-temperature gas before entering air-cooled condenser coils. Here, fans force ambient air across coils, dissipating heat and condensing refrigerant back to liquid. Outdoor or well-ventilated indoor installation helps manage heat buildup, making these units ideal for water-limited environments
