5 Must-Have Features in a Chiller Principle

How Air Cooled Chillers Work

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In this article, we will explore how air cooled chillers work. These chillers are commonly found in small to medium-sized commercial and office buildings. They are usually placed externally, either on the roof or at ground level. This is because air cooled chillers do not utilize cooling towers. Instead, they release their heat into the surrounding air, requiring access to a large volume of fresh air to remove the unwanted heat from the building. Scroll to the bottom to watch the tutorial video on this topic.

How Air Cooled Chillers Work

Air cooled chillers produce "chilled water" which is pumped throughout the building to Air Handling Units (AHUs) and Fan Coil Units (FCUs). These units remove unwanted heat from the building and transfer it into the chilled water loop. The chilled water enters the AHUs/FCUs at around 6°C (42.8°F) and exits the heat exchanger at around 12°C (53.6°F). The water then returns to the air cooled chiller to release this heat into the atmosphere before repeating the cycle.

The warm return "chilled water" enters the evaporator where it passes along the outside surface of the inner tubes containing the refrigerant. After transferring its thermal energy to the refrigerant, the water exits at the opposite end. The refrigerant then moves through the components of the chiller, changing its pressure, temperature, enthalpy, and entropy to transport the unwanted heat away from the evaporator.

Main Components of an Air Cooled Chiller

1. The compressor – typically screw, scroll, or reciprocating
2. The condenser – a bundle of horizontal pipes containing hot refrigerant, surrounded by thin metal sheets that help distribute heat into the air blown across them
3. Condenser fans – These fans draw air across the condenser coils, entering from the sides and forcing the air upward into the ambient atmosphere
4. Expansion valve – This valve expands the refrigerant before it enters the evaporator
5. Evaporator – This is where chilled water is produced and heat from the warm return "chilled water" is extracted to be sent to the condenser

Refrigerant Movement in the Chiller

The compressor drives the refrigerant. The refrigerant initially leaves the compressor as a high-pressure, high-temperature, superheated vapor, then enters the condenser.

As the refrigerant moves through the condenser, it transfers its thermal energy to the ambient air stream forced by the fans. During this process, the refrigerant condenses into a liquid. By the time it exits the condenser, it is a high-pressure, medium-temperature, saturated liquid.

The refrigerant then enters the expansion valve, which meters its flow around the system. The simplest type, the thermal expansion valve, controls refrigerant flow by measuring the pipe temperature at the evaporator outlet and adjusting the flow rate to maintain the desired temperature setpoint.

Inside the expansion valve, a small orifice restricts the refrigerant flow, creating a sudden pressure drop that allows the refrigerant to expand into a liquid/vapor mixture. This expansion lowers the refrigerant's pressure and temperature.

The refrigerant then enters the evaporator and flows through a series of horizontal tubes surrounded by chilled water flowing in opposing directions. By the time the refrigerant exits the evaporator, it has picked up the unwanted heat from the return chilled water and leaves as a low-pressure, low-temperature saturated vapor. The chilled water exits at approximately 6°C (42.8°F), having transferred its thermal energy to the refrigerant.

Chiller: What is it? How Does It Work? Types & Uses

Introduction

This article contains information on chillers, their various types, and their functions.

You will learn:

• What is a Chiller?
• Uses of Chillers
• How Chillers Work
• Types of Chillers
• Laser Chillers and How They Work
• And much more ...

Chapter One – What is a Chiller?

A chiller is a cooling system that removes heat by circulating a heat-absorbing refrigerant through a series of mechanisms where the heat is released. The essential components of an industrial chiller include a compressor, condenser, expansion valve, and evaporator. They work together to circulate the refrigerant and remove heat from a process, operation, or space.

There are several types of industrial chillers, each with a unique process for removing heat. Generally, industrial chillers use air or water as a cooling method. For instance, air-cooled chillers use fans to cool the system, whereas water-cooled chillers use circulating water in conjunction with a cooling tower.

Industrial chillers may also differ based on the type of compressor they use. Compressors in all industrial chillers function to compress the refrigerant, increasing its temperature and pressure before it moves to the condenser. The method by which compressors complete this function can vary.

Industrial chillers operate on the principle of vapor compression or absorption. They are designed to provide a continuous flow of coolant to maintain a preset temperature. Industrial chillers form a continually circulating fluid system that lowers temperatures by removing heat.

Chapter Two - How Are Industrial Chillers Used?

For many years, industries have searched for effective cooling solutions for manufacturing processes. Early air conditioners could not provide adequate cooling for large buildings, production processes, high-capacity machinery, and assembly operations. Technological advancements since the 1950s have introduced cooling equipment capable of producing low temperatures for operations like laser cutting and die casting. Modern manufacturing facilities now rely on sophisticated cooling systems, which have evolved from simple water baths used in the mid-twentieth century.

Uses for Industrial Chillers

Industrial

Industrial operations generate heat through friction, high-powered equipment, and furnaces or ovens. To increase the lifespan of heavy-duty equipment, industrial chillers circulate cooled liquid to maintain efficiency and productivity.

Work Environment

On manufacturing floors, temperatures can quickly rise during full operation, creating an unsafe working environment. To protect employee safety, industrial chillers are used to maintain proper temperature conditions. Combined with air handling units, they can cool work areas with chilled air, much like an air conditioner. Depending on the building, air-cooled chillers can be placed on top of or inside the building.

Plastic Manufacturing

Plastic, a temperature-sensitive material, requires proper cooling to avoid damage. The cooling temperature of a mold determines the quality of the final product. Industrial chillers maintain the quality of plastic products by providing a cooling bath. In the extrusion process, a heat exchanger separates the water from the extrusion process.

Metal Plating

The metal plating industry uses high-temperature electroplating or electroless plating processes. The high temperatures generated require industrial chillers to remove heat from the plated metal.

Food Production

The food industry adheres to strict regulations regarding ingredient and product storage temperatures. Industrial chillers in the food industry function similarly to traditional food cooling systems.

Power Generation

Power plants generate significant heat while producing electrical power. Chillers cool components and processes by absorbing the heat they produce.

Medical Industry

Medical equipment such as MRI scanners and CT scanners require precise temperature control. Industrial chillers provide constant cooling to ensure the efficient operation of critical medical equipment.

Pharmaceutical

Pharmaceutical manufacturing requires chilled water for precise temperature control. Industrial chillers offer the accuracy needed for pharmaceutical processes. They can be central process chillers or compact units. The four basic types used in the pharmaceutical industry include reciprocating, screw-driven, centrifugal, and absorption chillers.

Laser

Laser industrial chillers are designed to cool laser equipment or processes to maintain optimal performance. CO2, high-power exciters, and ion lasers require precise and accurate cooling, often achieved through water-cooled industrial chillers.

Temporary Chiller Systems

Temporary HVAC systems are often rented and installed for major construction projects. Builders and contractors use them to ensure proper heating, ventilation, and cooling during construction. Three common reasons for utilizing temporary HVAC systems include:

• Heating and Dehumidification: New construction during cold weather, replacing equipment, or critical humidity control applications like data centers.
• Ventilation: Maintaining negative pressure or circulating air in smoke-filled areas, positively pressuring areas like large vessels, or cooling submarine sections.
• Air Conditioning: Maintaining cool conditions during summer projects, replacing existing systems, or when the chiller plant has failed.

The portable industrial chiller shown below is an example of a temporary chiller for project sites, available in air-cooled and water-cooled versions, offering excellent performance features.

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Chapter Three - How Industrial Chillers Work?

Although there are many types of industrial chillers, most operate on the same heat removal principle. An essential part of the process is the coolant or refrigerant, which can hold more heat than air and helps maintain stable temperatures. The concept of chilling is based on removing heat from a process and releasing it into the air.

All industrial chillers include a condenser, compressor, expansion valve, and evaporator that circulate a fluid or refrigerant. The process is designed to transform the refrigerant from a liquid to a vapor and back to a liquid. In its vapor form, the refrigerant removes heat from a process; once returned to its liquid form, it circulates back to capture more heat.

Refrigeration Circuit

Compressor

The compressor takes low-pressure, low-temperature refrigerant and compresses it into a high-pressure, high-temperature gas. Three types of compressors are centrifugal, turbocor, and screw.

Condenser

The compressed gas flows through coils in the condenser, where air or water moves over the coils to remove heat. The refrigerant loses heat and condenses into a liquid.

Evaporator

In the evaporator, the refrigerant turns back into a gas, becoming cold and absorbing heat. Here, the refrigerant and fluid interact, and heat is removed from the fluid and transferred to the refrigerant. Common evaporator types include copper coil, shell and tube, and plate.

Expansion Valve

The expansion valve, which may be a thermostatic or electronic type, controls refrigerant flow between the condenser and evaporator, adjusting according to the cooling load.

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Fluid Circuit

The fluid circuit carries the processed fluid to the item to be cooled, directly lowering its temperature.

Pump

The pump circulates cool water or a water/glycol solution from the industrial chiller to the cooling system.

Filter

The filter captures contaminants, dirt, and particles from the chiller fluid and is part of the air intake system.

External Heat Exchanger

An external heat exchanger is used with materials that cannot come into contact with the industrial chiller. Examples include submersible cooling coils, plates, shells, and tubes, and jacketed tanks. While the condenser acts as a heat exchanger, some systems use an additional heat exchanger in the fluid cycle, depending on the design.

Industrial Chiller Energy Efficiency and IPLV

Chillers consume substantial electrical power during operation, with efficiency measured by energy consumption relative to refrigeration delivered. The Coefficient of Performance (COP) and Energy Efficiency Ratio (EER) are two methods for this measurement. A high COP or EER indicates peak efficiency.

The Integrated Part Load Value (IPLV), established by the Air Conditioning, Heating, and Refrigeration Institute (AHRI), provides a more accurate efficiency measure. Chillers often operate below capacity, and the IPLV accounts for this by evaluating performance at different design loads.

Understanding chiller efficiency is crucial for purchasers, as an efficiently operating chiller reduces operating costs and increases savings.

Chapter Four – Types of Industrial Chillers

Industrial chillers are categorized based on how the refrigerant releases absorbed heat and their compressor type. There are also specially-designed chillers for unique functions. Given technological advancements and changes in chiller designs, creating a complete list of all types is challenging.

Types of Chillers

Water Cooled Industrial Chillers

Water-cooled chillers are typically combined with a cooling tower and use a condenser water treatment system to remove mineral deposits. The tower sends water to the chiller to be cooled.

Air Cooled Industrial Chillers

Air-cooled chillers are used where discharge is not problematic. They absorb heat from water and transfer it to the air.

Screw Industrial Chillers

Screw chillers, which can be air or water cooled, use a helical rotor to move and compress refrigerant vapors.

Scroll Industrial Chillers

Scroll chillers use a set of scrolls to compress refrigerant, operating quietly and efficiently. Their environmental friendliness has increased their popularity.

Centrifugal Industrial Chillers

Centrifugal chillers use compression to convert kinetic energy into static energy, increasing refrigerant temperature and pressure. Impeller blades pull in and compress the refrigerant.

Absorption Industrial Chillers

Absorption chillers use steam or hot water to change the refrigerant into vapor, which then moves to the condenser and back to the absorber. The refrigerant vapor is absorbed by a solution, condensing to release heat.

Reciprocating Industrial Chillers

Reciprocating chillers use pistons to create pressure in the refrigerant. They can have sealed or open construction, requiring regular maintenance.

Explosion-Proof Industrial Chillers

Designed for heavy-duty use, explosion-proof chillers follow National Fire Protection Agency guidelines and feature reinforced structures for safety. They operate like regular chillers but with extra protection.

Low Temperature Industrial Chillers

Designed for industries requiring temperatures below -40°F (-40°C), these chillers are used in ice rinks, petrochemical cooling, chemical extraction, medical, pharmaceutical, and food processing, and product testing labs.

Evaporative Industrial Chillers

Evaporative chillers use evaporation to cool the air efficiently. They use a reservoir, fan, and thick pads. Hot air drawn through the pads evaporates water and drops the air temperature significantly.

Thermoelectric Industrial Chillers (TEC)

TECs use the Peltier effect to generate heat flux at the connection of two dissimilar materials. A TEC assembly can directly cool a cold plate or a refrigerant liquid and is typically used for applications requiring less than 400 watts of cooling.

Chapter Five - Laser Industrial Chillers

The term laser stands for Light Amplification by Stimulated Emission of Radiation. Lasers are created when electrons in optical materials absorb electrical energy, become excited, and emit electromagnetic radiation. Unlike normal light, laser light is coherent and moves in the same direction.

When directed at a surface, laser light turns into heat, cutting or melting the material. To maintain laser efficiency and prevent damage, industrial chillers are used for cooling. Laser chillers remove heat to maintain optimal wavelengths and laser beam quality. High-powered lasers often require powerful water-cooled chillers, while low-powered lasers can use fans.

Types of Laser Chillers:

• UV Lasers
• CO2 Laser Glass Tube
• Semiconductor
• CO2 Rf Tube Laser
• Fiber Laser for Cutting, Marking, and Engraving

Cold Plates

Cold plates, key components in cooling lasers, are used with recirculating chiller systems. They can be tubed or aluminum vacuum brazed, providing efficient cooling by optimizing heat transfer.

Types of Cold Plates:

• Tubed: Metal plates with channels holding tubes where coolant flows to the laser. The tubing ensures good surface-to-surface contact for heat transfer.
• Aluminum Vacuum Brazed: Fins create turbulence under the cold plate to reduce thermal resistance.

Cold plates can be mounted on lasers, receiving cooling liquids from a chiller. The hot liquid from the process is then transferred back.

Vapor Compression Industrial Chillers

These chillers use a refrigerant cycle through an evaporator, compressor, condenser, and expansion valve. They efficiently cool high watt loads. In laser systems, they can be varied to suit evaporator cycles or directly cool the cold plate.

Compressor vapor style chillers are commonly used for high-powered lasers, capable of cooling up to 10kW.

Miniature Rotary Compressor

Widely used