• SkillCat Team

Basics & Components of Chiller Systems

Updated: Aug 20


Basics of Chiller System


In this module, we will learn about a chiller system. We will also discuss the basic working of a chiller system. kip to quiz!


Introduction


A chiller system is a machine that is used to produce cold water. It takes in room temperature water and decreases its temperature. This cold water is used in industrial processes and to cool buildings or any industrial equipment.


A chiller system is similar to a hot water geyser in our homes. The geyser takes in water and heats it. This gives us hot water. Similarly, a chiller takes in water and cools it.


A chiller produces cold water by using the basic refrigeration cycle. Recall that the main components of the basic refrigeration cycle are:

  • Condenser,

  • Metering device,

  • Evaporator, and

  • Compressor.

Let us look at a short video to recall the basic refrigeration cycle!


The basic function of removing heat is carried out by all the components of the basic refrigeration cycle in a chiller system. The size and type of these components in a chiller system are different from the residential HVAC systems.


Let us now briefly look at the history of chiller systems. The concept of chilled water systems has been around since ancient Roman times. The Romans would run water through tubes in the walls of the house to keep the space inside the house cool.


Willis Carrier invented the first modern centrifugal chiller in 1926. Since then, chillers have undergone much innovation and different types of chillers are available today.


Advantages of Chiller Systems


Chillers are used to provide cooling for medium to large-sized buildings. For smaller buildings, we provide cooling by using smaller, individual HVAC systems. When the building reaches a certain size, it becomes cost-effective to use a chiller.


A chiller system can even provide cooling to multiple buildings. This makes them a cost-effective and economical choice for large commercial buildings.


Chiller systems are an expensive initial investment. However, they are efficient systems and save money on energy consumption. So, they allow a good return on investment in relatively less time.


For example, if a hotel has 150 rooms, instead of installing 150 air conditioners for each room, we can install only one chiller. The chiller can provide cooling to all 150 rooms. It would cost less, take up less space, and be more efficient.


In a chiller system, we provide cooling by supplying cold water to different rooms in the building. We cool this water by using a refrigerant, and then the cold water cools the building. So, unlike air conditioners, we do not require a large amount of refrigerant.


In chiller systems, the refrigerant required for cooling the water is all in one place in the building.We do not run refrigerant lines inside the building.


Recall that some refrigerants are toxic and flammable. It can be hazardous if they leak. So we can cool a large space without having to supply the hazardous refrigerant to this space.


Comfort Cooling


Cold water from chiller systems is mainly used for

  • Comfort cooling, or

  • Process cooling.

We will learn about these cooling processes in more detail.


Comfort cooling is to create comfortable temperatures for humans. It is the same as air conditioning in residential applications. However, chillers do it on a larger scale than air conditioners.


Process Cooling


Process cooling is when chilled water is used to cool any equipment or for industrial purposes. Chillers circulate cold water through machinery to remove heat.


Heat is generated in all industrial machines and equipment. If this heat is not removed, it will create problems such as a reduction in productivity and frequent machine failures. So, chillers are used in industries to remove heat to avoid these problems.


Chiller systems are often used in industrial applications such as:

  • injection molding,

  • textiles production,

  • food processing, and

  • pharmaceutical.

The chillers in these industries are called process chillers.


A chiller is a machine that is used to generate cold water.

The cold water is used for

  • Comfort cooling, or

  • Process cooling.

Comfort cooling is the process of cooling spaces for humans. It is the same as air conditioning in residential applications.


Process cooling is providing cold for industrial purposes and cooling industrial machines. Chiller systems are often used in industrial applications such as:

  • injection molding,

  • textiles production,

  • food processing, and

  • pharmaceutical.


Components of Chiller - Part 1


In this module, we will go over the components of a chiller system. We will also look at how they work in chiller systems. Skip to quiz!


Introduction

Recall that the main components of any HVAC system are:

  • Compressor,

  • Condenser,

  • Metering device, and

  • Evaporator.

We will go over each of these components in a chiller system in detail.


Compressor


Recall that the compressor’s main job is to increase the pressure of the refrigerant. We see the following types of compressors in chillers.

  • Reciprocating compressors,

  • Scroll compressors,

  • Screw compressors, and

  • Centrifugal compressors.

Recall that these are categorized based on how they work.


Recall that reciprocating compressors are driven by a motor. They work similar to an automobile engine. They are not popular nowadays because of the noise, efficiency, and maintenance issues. They are used in smaller chiller systems up to 100 tons capacity.


Recall that the scroll compressor consists of two matching scrolls, one stationary and the other rotating around the first. One scroll rotates around the other in a circular motion to compress the refrigerant. They are used in very small chiller systems up to the capacity of 60 tons.


Recall that the screw compressor has two shafts that are shaped like wood screws. In these, we can have one or two screws that rotate to compress the refrigerant. Screw compressors are normally used in 200 to 800 tons capacity chillers.


Recall that the centrifugal compressor compresses the gas using centrifugal force. Centrifugal force acts in a direction pointing away from the center of the rotation. These are used in larger capacity chiller systems up to 2000 tons.



Condenser


Recall that the condenser’s main job is to cool down the refrigerant. The main types of condensers in chiller systems are:

  • Fin and tube condenser,

  • Microchannel condenser, and

  • Shell and tube condenser.

These condensers are classified based on their structure.


Fin and tube condenser is similar to residential air conditioner’s condenser. Recall that fins are made of aluminum, and tubes are made of copper.


The hot refrigerant flows through the tubes, and fins help to cool it by distributing the heat to the outside air. Fins increase the surface area for heat transfer. This cools down the refrigerant inside the condenser.


Recall that microchannel condensers are made of thin zig-zag aluminum fins. These condensers work similar to fin and tube condensers but are more efficient than them.


Shell and tube condenser consists of a series of copper tubes inside a large shell. Water flows in the tubes, and hot refrigerant flows in the shell. Running water in the tube cools down the refrigerant inside the shell.



Metering Device


Recall that the metering device’s job is to decrease the pressure of the refrigerant. Chiller systems mainly use the two main types of metering devices:

  • Thermal expansion valve, and

  • Electronic expansion valve.

We will discuss how these metering devices work in chillers in detail.


Recall that the thermostatic expansion valve is also called TEV or TXV. This is used in residential HVAC systems as well as chiller systems. This controls the amount of refrigerant that flows into the evaporator based on the evaporator outlet temperature.


The thermal expansion valve is used smaller capacity chillers. The sensing bulb of TEV is attached to the outlet of the evaporator. TXV increases or decreases the flow of refrigerant into the evaporator based on the temperature measured by the sensing bulb.


Recall that electronic expansion valves are also called EEVs or EXVs. These are the evolution of the TEVs. These give the best performance because these are electrically operated metering devices.


EEVs have a motor inside their body. The motor controls the positioning of these valves. So These allow a very accurate amount of refrigerant into the evaporator. Let us look at a video to recall the working of EEV.



Evaporator


Recall that the evaporator in residential HVAC systems has refrigerant flowing through them. As the room air is blown over the evaporator coils, it gets heated or cooled.

Chiller systems usually contain a shell and tube type of evaporator. Recall that shell and tube evaporator consists of a bundle of copper tubes inside a large metal shell.


In the chiller systems, the evaporator coils filled with refrigerant have water flowing over them instead of air. So the refrigerant cools the water. A shell and tube evaporator has two parts:

  • An outer shell, and

  • Inner tubes.

The outer shell is a large metallic cylinder. The shell does two main functions of

  • protecting the inner tubes, and

  • not allowing the fluid in the shell to leak outside.

It has two openings, an inlet and an outlet for the fluid to flow into and out of the shell.


The inner copper tubes enter the outer shell from one side and leave through the other side. Recall that copper is an excellent conductor of heat. So the copper tubes allow the transfer of heat from the fluid inside to the fluid outside the tube.


Water flows inside of these tubes, and the outer shell is filled with refrigerant. The two fluids do not mix with each other, and only heat transfer takes place between the fluids. In some chillers, the refrigerant may flow through the inner tubes, and water may be filled in the outer shell.


So, either water or refrigerant flows in the shell, and the other flows in the tube. They do not come in contact with each other. The outer shell is sealed off and leakproof to prevent refrigerant from leaking outside.


In the evaporator, the water transfers the heat to the liquid refrigerant and boils it into vapor. As the water transfers the heat to the refrigerant, it cools down. This is how we get cold water.


We see the following types of compressors in chillers.

  • Scroll compressors,

  • Screw compressors, and

  • Centrifugal compressors.

We mainly use two types of condensers in chiller systems:

  • Fin and tube condenser, and

  • Shell and tube condenser.

The two types of metering devices used in chillers:

  • Thermal expansion valve, and

  • Electronic expansion valve.

Chiller systems usually contain shell and tube type of evaporators. A shell and tube evaporator is the most efficient type of evaporator to transfer heat between two liquids.

Components of Chiller - Part 2


In this module, we will go over the secondary components of a chiller system. We will also look at how they work in chiller systems. Skip to quiz!


Introduction


Recall that the main components of any HVAC system are:

  • Compressor,

  • Condenser,

  • Metering device, and

  • Evaporator.

Beyond the main components of the chiller system, there are many secondary components present in the commercial system, including:

  • Receiver,

  • Oil Separator,

  • Filter drier, and

  • Sight glass.

Recall that compressed refrigerant vapor is condensed to a liquid refrigerant in the condenser at high pressure. The receiver is mounted at the exit of a condenser. After leaving the condenser, the liquid refrigerant passes through the receiver.


When the expansion valve opens or closes, the liquid level in the condenser will change. This could lead to the whole system becoming unstable. The receiver compensates for the liquid level changes in the condenser due to variation in load.


The refrigerant discharging from the compressor will carry oil from the compressor. In some cases, the amount is excessive, and the oil does not return. To avoid this, we use an oil separator to separate the oil from the refrigerant and return it to the compressor.


Inside the refrigeration system, there can be other foreign materials such as water, metal oxides, and dirt. This may cause the system to work inefficiently or to stop working. We use a filter drier to remove these foreign materials from the refrigerant to make the system work more efficiently.


Sight glass is a small glass window installed in the liquid line. It allows us to see through it. If there are any bubbles in the glass, it means that there low refrigerant charge.


Beyond the main components of the chiller system, there are many secondary components present in the commercial system, including:

  • Receiver,

  • Oil Separator,

  • Filter drier, and

  • Sight glass.


Types of Chillers



In this module, we will learn about types of chillers. We will also look at the pros and cons of each type. Skip to quiz!


Introduction


In any commercial or industrial applications, the types of chiller systems found are:

  • Air-cooled chillers, and

  • Water-cooled chillers.

We will look into these chiller systems in detail.


Air-cooled and water-cooled chillers differ by how the refrigerant in the condenser is cooled. Recall that the condenser's job in any system is to take the heat out of the refrigerant and cool it.


For example, when we come home on a hot summer day, we either sit in front of a fan or take a shower to cool down our bodies. Similarly, to cool the condenser of chiller systems, we use either air or water.


If the condenser in the chiller is cooled by air, it is an air-cooled chiller. If it is cooled by water, it is a water-cooled chiller. Let us look at a video to understand the types of chiller systems.


Air-cooled Chiller

The condensers usually found in the air-cooled chiller systems are

  • Fin and tube condenser, and

  • Microchannel condenser.

These condensers look similar but vary in fins shape attached to copper tubing.


Recall that fin and tube condensers are made of aluminum plate fins. These fins are attached to the refrigerant tubing. Recall that microchannel condensers are made of thin zig-zag aluminum fins.


Fans blow outside air over the condenser to cool it. Air-cooled chillers are usually placed externally, on the roof, or at ground level because they need access to a lot of outdoor air.


Air-cooled chillers have many advantages over water-cooled chillers. Some of them are:

  • Low initial cost

  • They require less maintenance

  • They require less space

  • They can be installed on the roof of the building

  • No need for a separate mechanical room

Recall that the water-cooled chiller’s condenser is cooled with water. So, water-cooled chillers require extra components like cooling towers and condensing water pumps. Air-cooled chillers do not require these extra components. These are simpler in design.


Air-cooled chillers also have some disadvantages over water-cooled chillers. Some of them are:

  • They are installed outside the building.

  • As they are placed outside the building, the compressors and fans noise that can disturb us.

Air-cooled chillers do not have a long lifespan. This is because they are placed outside the building and exposed to sun, rain, frost, snow, and wind throughout the year. This can damage their components.


Water-cooled Chiller


Water-cooled chillers usually have shell and tube type of condensers. Their condenser is connected with a cooling tower. Cooling towers are large boxes that allow water and air to come in contact with each other to lower the temperature of the hot water.


Water from the cooling tower is used to cool the condenser of the water-cooled chiller. Water-cooled chillers work more efficiently because they use water to cool the condenser. Water can cool things much better than air.


Water-cooled chillers have many advantages over air-cooled chillers. Some of them are:

  • They can handle a large amount of loads.

  • They are more efficient because their condenser is cooled by water.

Water-cooled chillers have a long lifespan. This is because they are placed inside a mechanical room, so they are not exposed to sun, rain, frost, snow, and wind


Water-cooled chillers also have some disadvantages over air-cooled chillers. Some of them are:

  • installation cost is more

  • require more maintenance

  • consume more energy

Water-cooled chillers require a constant supply of water to the cooling tower. So they are not suitable for areas having a water shortage. They consume more energy because of the cooling tower and condensing pumps.


In any commercial or industrial applications, the types of chiller systems found are:

  • Air-cooled chillers, and

  • Water-cooled chillers.

If the condenser in the chiller is cooled by air, it is the air-cooled chiller. If it is cooled by water, it is the water-cooled chiller.


Air-cooled chillers cost less. But they do not have a long lifespan because they are exposed to the atmosphere. Water-cooled chillers are more efficient because of lower condenser temperatures created by water. But they cost more to install and maintain.




Question #1: What does a chiller system produce?

  1. Hot water

  2. Cold water

  3. Hot air

  4. Cool air

Scroll down for the answer...