How Does a Chiller System Work?
Introduction
Chiller systems are the backbone of many industrial and commercial cooling applications, working quietly behind the scenes to remove heat and maintain the right climate for comfort, safety and operational efficiency.
In simple terms, a chiller is a machine that uses a refrigeration cycle to extract heat from a liquid and distribute chilled liquid to air handlers, fan coil units or process equipment. From air conditioning in large buildings to precision cooling in production lines, chillers play a vital role across industries.
In this guide, we’ll explain how a chiller system works, explore how a chiller works in various applications and why it’s important for efficient cooling.
What is a Chiller System?
A chiller system is a specialised cooling unit designed to remove heat from a liquid – usually water or a water/glycol solution – using a refrigeration cycle. That chilled liquid is then circulated to equipment or air systems to provide cooling. In essence, a chiller works by transferring unwanted heat from one place to another, ensuring a controlled temperature for comfort or process efficiency.
Main Types of Chiller Systems
There are two primary types of chillers, each suited to different needs and environments:
- Air-cooled chillers: use ambient air to dissipate heat through condenser fans and coils. These are simpler to install, require less infrastructure and are often found in smaller commercial buildings or facilities where water availability is limited.
- Water-cooled chillers: use water from a cooling tower to remove heat from the condenser. These are typically more energy efficient for large-scale applications and are commonly used in big commercial complexes, industrial plants and data centres.
Common Sectors Using Chillers
Chillers are used across a wide range of sectors:
- Commercial buildings: provide comfort cooling for offices, shopping centres, hotels and hospitals.
- Manufacturing: maintain optimal temperatures for machinery, chemical processes, plastics manufacturing, and more.
- Data centres: keep server rooms at safe operating temperatures to ensure uptime and prevent costly downtime or for large scale liquid cooling systems
- Pharmaceutical production: maintain precise climate conditions for drug formulation, storage and packaging.
- Food processing: provide temperature control during processing, packaging and cold storage.
- Medical facilities and laboratories: support MRI machines, medical imaging equipment and lab processes that require temperature stability.
- Beverage and brewing: control fermentation temperatures and cool finished products before packaging.
- Aerospace and automotive: cool manufacturing equipment and support climate control in assembly areas.
- Power generation: support turbine cooling and auxiliary systems in energy plants.
- Event venues and stadiums: large-scale comfort cooling for arenas, exhibition halls and entertainment spaces.
How a Chiller System Works
Understanding how a chiller system works starts with following the refrigeration cycle through its four key stages. Regardless of the setup or setting, the principles are the same – the system moves heat from where it’s not wanted and rejects it elsewhere.
The high-pressure liquid refrigerant then passes through the expansion valve, which reduces its pressure and temperature before it re-enters the evaporator. This rapid pressure drop prepares the refrigerant to absorb heat again, and the cycle repeats.
How Chiller Systems Work in HVAC Applications
In commercial and large-scale residential buildings, chillers work to provide a constant source of chilled water to meet varying cooling demands throughout the year. The chiller operates as the heart of the HVAC system, delivering cool water to air handling units (AHUs) and fan coil units (FCUs), which then condition and circulate the air within the building.
Integration with AHUs and FCUs
- Air handling units: large central units that use the chilled water from the chiller to cool air before distributing it through ductwork. Ideal for open-plan spaces and multiple zones.
- Fan coil units: smaller, localised units that also use chilled water but serve specific rooms or areas, offering more individual temperature control.
In both cases, the chiller cools the water in its evaporator before it’s pumped to these terminal units, ensuring the building remains comfortable even on the hottest days.
Seasonal Efficiency and Load Variation
Cooling requirements change with the seasons and even throughout the day. In summer, chillers often operate near full capacity, while in spring and autumn, partial-load operation is common.
Modern chillers are designed to modulate their output for optimal seasonal efficiency, reducing energy consumption without compromising comfort.
Variable-speed drives, staged compressors and smart controls all contribute to better performance under fluctuating loads.
How Industrial and Commercial Chillers Work
While the basic refrigeration cycle is the same, the difference lies in the purpose of the cooling and the operating conditions.
Commercial Comfort Cooling
Commercial chillers are designed primarily to maintain comfortable indoor temperatures. The system focuses on:
- Consistent comfort: regulating air temperature and humidity.
- Energy efficiency: operating under seasonal load variations to reduce running costs.
- Quiet, unobtrusive operation: minimising disruption in public environments.
Industrial Process Cooling
Industrial chillers are built for reliability under demanding, often continuous, operating conditions. They remove heat from manufacturing processes, machinery or chemical reactions to ensure product quality and protect equipment. They are typically engineered to handle:
- Higher heat loads: large amounts of heat generated by industrial processes.
- Precise temperature control: critical for sensitive processes.
- Harsh environments: dust, vibration or extreme temperatures.
Factors Affecting Chiller Performance
The efficiency and reliability of a chiller depend on several operating and maintenance factors. Optimising these elements can improve performance and reduce energy costs.
1. Ambient Temperature
The temperature of the surrounding environment plays a major role in chiller efficiency. For air-cooled chillers, higher outdoor temperatures make it difficult for the condenser to reject heat, reducing overall capacity. Water-cooled chillers are less sensitive to air temperature but still depend on cooling tower water conditions for optimal performance.
2. Chilled Water Setpoint
The chilled water setpoint – the temperature to which the system cools the water – directly affects energy consumption. Lowering the setpoint increases the cooling load and energy use, while raising it (within acceptable limits), can reduce running costs without compromising comfort or process requirements.
3. Maintenance and System Cleanliness
Dirt, scale and biological growth in the condenser, evaporator or water lines can restrict heat transfer, forcing the chiller to work harder. Regular maintenance, including tube cleaning, filter replacement and system inspections, is essential to maintain peak efficiency and extend equipment life.
4. Refrigerant Type and Charge
The type of refrigerant used impacts efficiency, environmental compliance and operating costs. Equally important is maintaining the correct refrigerant charge – too much or too little can reduce capacity, increase energy consumption and risk component damage.
By keeping these factors in check, building operators and plant managers can ensure their chiller operates efficiently, reliably and with minimal downtime.
The Importance of Regular Maintenance
Routine maintenance keeps a chiller operating at peak performance, with benefits including:
- Efficiency: clean heat exchange surfaces, correct refrigerant charge and well-calibrated controls help the system run with less energy.
- Reliability: early detection of issues such as worn components, refrigerant leaks or control faults reduces the risk of unexpected breakdowns.
- Extended lifespan: proper care can add years to a chiller’s service life, protecting your investment and reducing capital replacement costs.
What a Chiller Maintenance Plan Should Include
A comprehensive chiller maintenance plan typically covers:
- Inspection and cleaning of evaporator and condenser tubes
- Checking and adjusting refrigerant levels to manufacturer specifications
- Testing safety and control systems to ensure correct operation
- Lubricating moving parts such as compressor bearings and motor components
- Water treatment to prevent scale, corrosion and biological growth in chilled and condenser water circuits
- Reviewing operational logs to spot performance trends before they become issues
Chillers play a key role in industrial, commercial and HVAC cooling, offering reliable and energy-efficient temperature control. At Aggreko, we specialise in providing high-performance, flexible cooling solutions for unique industry needs.
Whether you need temporary cooling for peak demand periods or a long-term, scalable chiller system, our expertise ensures your operations run smoothly and efficiently. We help businesses make informed decisions, ensuring they invest in the right solution to meet their cooling challenges today and in the future.