This article contains information on chillers, their different types, and their work.
A chiller is a cooling system that removes heat by circulating heat-absorbing a refrigerant through a series of mechanisms through which the heat is released. The essential components of a chiller are a compressor, condenser, expansion valve, and evaporator. They work in unison to circulate a refrigerant that removes heat from a process, operation, or space.
There are several different types of chillers, each of which has a different process for removing heat. All chillers use air or water as a cooling method. For example, air cools a chiller system using fans, while a water-cooled chiller circulates water with a cooling tower.
Aside from the two cooling processes, chillers are further differentiated by the type of compressor they have. Compressors in all chillers have the same function: to compress the refrigerant and increase its temperature and pressure before it moves on to the condenser. There are several variations as to how the compressor completes its function.
There are several variations as to how the compressor completes its function.
Chillers operate on the principle of compression or absorption of a vapor. They are designed to provide a continuous flow of coolant to maintain a preset temperature. As the diagram shows, they are a continually circulating system of fluid that lowers the temperature by reducing heat.
For many years, industries have searched for ways to provide cooling for manufacturing processes. The basic air conditioner, introduced at the beginning of the twentieth century, could not provide sufficient cooling for large buildings, production processes, high-capacity machinery, and assembly operations.
Technological advances, beginning in the 1950s and continuing into the twenty-first century, have introduced cooling and heat removal equipment capable of producing temperatures that can cool laser cutting and die casting operations. The water baths from the middle of the twentieth century have grown into an essential part of modern manufacturing.
Industrial operations create heat through the use of friction, high-powered equipment, and furnaces or ovens. To increase the lifespan of heavy-duty equipment, a chiller unit circulates cooled liquid through equipment in order to maintain efficiency and productivity.
On the manufacturing floor, temperatures can rise rapidly when equipment is in full operation, creating an unsuitable working environment. To protect employee safety, industrial operations use chillers to keep working conditions at the proper temperature. With the addition of an air handling unit, chillers can cool work areas with chilled air, much like an air conditioner. Depending on the building, air cooling chillers can be on top or inside of the building.
Plastic is a very temperature-sensitive material that can be damaged by being too hot and needs to be properly cooled. The correct cooling temperature of a mold determines the quality of the final product. Chillers are used to provide a cooling bath that maintains the quality of plastic products. In the extrusion process, a heat exchanger separates the water from the extrusion process from the cooling water.
The metal plating industry uses high-temperature electroplating or electroless in the plating process. The bonding of a coating on metal produces extreme temperatures requiring heavy-duty chillers to remove the heat from the plated metal.
The food industry has strict regulations regarding the storage temperatures of ingredients and products. Chillers for the food industry operate much like a traditional cooling system for food.
Power plants generate a great deal of heat to produce electrical power. Chillers cool components and processes by absorbing the heat they generate.
Medical equipment requires precise temperature control. MRI scanners, CT scanners, and LINAC machines produce heat that has to be removed and controlled. Chillers provide a constant source of cool temperatures to ensure the efficient operation of critical equipment.
Medicines require the use of chilled water in the manufacturing process and need precise temperature control. Chiller units have the accuracy and precision for the chilling process and can be central process chillers or compact process chillers. The four basic types of pharmaceutical chillers are reciprocating, screw-driven, centrifugal, and absorption.
Laser chillers are designed to cool laser equipment or laser processes. For a laser to perform at peak efficiency, it has to maintain an optimal wavelength. CO2, high-power exciters, and ion lasers have to be precise and accurate. They depend on a chiller water cooling system.
Nearly half of all major construction projects have temporary HVAC systems, rented, installed, operated, and maintained to remove temporary heating, ventilation, and cooling systems. Builders and contractors use the flexibility of temporary systems to win contracts for their projects.
There are three common reasons for the use of a temporary HVAC system, which include:
The portable chiller below is an example of a temporary chiller that could be used at a project site. This particular model comes air and water cooled and has other features that provide excellent and exceptional performance.
Though there are a wide variety of chillers, the majority of them use the same principle for removing heat. An essential part of the process is the coolant or refrigerant, which holds more heat than water and aids in maintaining an efficient cooling process. Heat is removed from the coolant and released into the air. The concept of a chiller is based on the principle that cooling involves the removal of heat from a process and releasing it into the air.
All chillers have a condenser, compressor, expansion valve, and evaporator that circulate a fluid or refrigerant. The process of a chiller is designed to transform the refrigerant from a liquid to a vapor and back to a liquid. In its vapor form, the refrigerant removes the heat from a process. When it is returned to its liquid form by the compressor and condenser, it circulates back through the system to capture the heat from a process or operation.
The compressor takes low-pressure and low-temperature refrigerant and compresses it until it becomes a high-pressure and high-temperature gas. Three types of compressors are centrifugal, turbocor, and screw.
The compressed gas flows through coils in the condenser, where air or water moves over the coils to remove heat from the refrigerant. Once the refrigerant loses its heat, it condenses into a liquid.
In the evaporator, the refrigerant returns to being a gas, becomes very cold, and absorbs heat. It is in the evaporator where the refrigerant and fluid interact and where heat is removed from the fluid to be transferred to the refrigerant. Three common types of evaporators are copper coil, shell and tube, and plate.
The expansion valve, which may also be known as a thermostatic or electronic expansion valve, controls the amount of refrigerant that passes between the condenser and evaporator and changes the flow based on the cooling load.
The fluid circuit, or cycle, carries the processed fluid to the item to be cooled and directly lowers its temperature.
The pumping system circulates cool water, or a water/glycol solution, from the chiller to the cooling process.
The filter is designed to capture contaminants, dirt, and particles that may enter the chiller fluid. They are also part of the air intake system.
The purpose of an external heat exchanger for chillers is for use with materials that cannot come in contact with the chiller. They include submersible cooling coils, plate, shell and tube, and jacketed tank.
Though the condenser acts as a heat exchanger, some systems have a heat exchanger as part of the fluid cycle system, depending on the design of the system.
Chillers consume a great deal of electrical power during the chilling process, the efficiency of which is measured by the energy it consumes compared to the refrigeration it delivers. The Coefficient of Performance (COP) and the Energy Efficiency Ration (EER) are the two methods for measuring energy efficiency. If a system has a high COP, it is operating at peak efficiency. This also applies to the EER. Most companies inaccurately indicate that their units operate at 100% EER or COP, which is not possible since the number does not include a chiller’s load.
The Integrated Part Load Value (IPLV) is a better indicator of the efficiency of a chiller unit, which is a standard established by the Air Conditioning, Heating, and Refrigeration Institute (AHRI). Most of the time, a chiller operates below capacity, a calculation determined by the IPLV.
The IPLV rating includes an understanding that most chillers operate below their design rating most of the time. By breaking down the performance of a chiller at four different design loads, the final rating is a better representation of a chiller’s performance.
Since a chiller is one of the single largest users of electricity that commercial enterprises can purchase, it is critically important that purchasers have an understanding of how to measure a chiller’s efficiency. An efficiently operating chiller has a lower operating cost, leading to significant company savings.
There are several divisions of chillers based on how the refrigerant dispels the heat it absorbs, and the type of compressor. There are also specially designed chillers that perform unique and unusual functions. Due to the amount of technological developments, improvements, and changes to chiller designs over the years, it is impossible to form a complete list of all types of chillers.
Water cooled chillers are normally combined with a cooling tower and use a condenser water treatment system to remove mineral deposits. The cooling tower sends water to the chiller to be cooled.
An air cooled chiller is used where discharge is not a problem. It absorbs heat from water and transfers it into the air: first, heat from circulating chilled water is absorbed in the evaporator, and then, the refrigerant condenses, in the condenser, and releases the heat into the air.
Screw chillers can be water or air cooled and use a helical rotor to move and compress the refrigerant vapors.
Scroll chillers have a set of scrolls that are used to compress the refrigerant and operate quieter and more efficiently. Since they are environmentally friendly, they are increasing in popularity.
Centrifugal chillers use compression to convert kinetic energy into static energy to increase the temperature and pressure of the refrigerant. Impeller blades pull in the refrigerant and compress it.
In an absorption chiller, a generator uses steam or hot water to change the refrigerant into a vapor, which moves to the condenser and is then sent back to the absorber. The refrigerant vapor is absorbed by a solution, which condenses into a vapor to release heat.
Reciprocating chillers use pistons and a chamber to create pressure in the refrigerant. They can have sealed or open construction, with sealed units having all of the components sealed in a single unit. Since reciprocating units function like an automobile engine, they require regular maintenance.
Explosion-proof chillers are designed for heavy-duty use and must follow specific National Fire Protection Agency (NFPA) guidelines in their construction. They have a specially reinforced structure to protect against flammable materials and must be specially ordered. The main purpose of explosion-proof chillers is for the protection and safety of workers. Explosion-proof chillers operate on the same principles as a regular chiller but with added reinforced protection.
Low-temperature chillers are for industries that operate below freezing and require chillers that can produce temperatures at – 40° F (-40° C). They are used for ice rinks, petrochemical cooling, chemical extraction, and medical, pharmaceutical, and food processing industries, as well as product testing labs.
An evaporative chiller uses the power of evaporation to cool air. When water evaporates, it becomes a gas. High energy particles leave, causing the surrounding air's temperature to drop radically. This process can be felt when air is misted into a room. An evaporative chiller takes the natural process of evaporation and enhances it through the use of technology.
An evaporative chiller's process requires using a reservoir of water, a fan, and thick pads. The fan draws in hot air, which crosses through the thick pads that absorb water from the reservoir. As the hot air passes through the pads, the water on the surface evaporates and causes the air temperature to drop by nearly 20 degrees Fahrenheit.
The term laser is an acronym for Light Amplification by Stimulated Emission of Radiation. A laser is created when the electrons in the atoms of optical materials such as glass, crystal, or gas absorb the energy of an electrical current. The added energy excites the electrons and moves their orbit from low energy to high energy to create electromagnetic radiation.
In normal light, lightwaves move in different wavelengths and directions, with each wavelength having a different color with peaks and valleys. Viewed by the naked eye, the light looks white. In a laser beam, light is coherent and moves in the same direction, with all the peaks and valleys moving together. The amplified light energy generates a significant amount of heat energy.
When the light from a laser is directed at a surface, its light energy turns from light energy to heat that cuts, melts, or burns a material. The result of the process is the creation of heat that has to be removed to ensure the efficiency of the laser and avoid damaging it. Industrial lasers use various chillers and cooling methods to maintain a constant temperature.
Laser chillers are designed to remove heat from the laser process to maintain the laser’s wavelengths and ensure the quality of the laser beam. Powerful water cooled chillers are used with high-powered lasers, while low-powered lasers can be cooled using other means such as various types of fans.
When making the selection of a laser chiller, it is important to choose a chiller that matches the type of laser being used. Laser chillers are used with:
Cold plates are key components for the cooling of lasers and are used with recirculating chiller systems. There are several forms of cold plates, including tubed and aluminum vacuum brazed.
Cold plates can be mounted on the laser and receive cooling liquids from a chiller. The hot liquid from the process is then transferred back to the chiller. In some cases, the cold plate can be designed as the electrodes of a laser system.
TECs use the Peltier effect, where a heat flux is generated at the connection of two dissimilar materials across which a DC current is passed. The positive and negative semiconductors are arranged parallel in the thermal path and in a series along the electrical path. As voltage is applied, electrons carry heat to one side, making the other side cold. The collected heat is removed by fans into the ambient air.
A TEC assembly can be mounted directly onto the cold plate or be used to cool a refrigerant liquid. TECs are normally used with applications where cooling is less than 400 watts.
Vapor compression chillers use a refrigerant that cycles through an evaporator, compressor, condenser, and expansion valve. The process of a vapor compression chiller system is efficient for cooling high watt loads using less energy. In a laser system, a vapor compression system can be used by varying the evaporator cycle. Other cooling methods run the refrigerant directly through the cold plate.
The compressor vapor style of liquid chiller is the most-used cooling technique for high-powered lasers. They are capable of cooling up to 10kW and can be used with any type of laser.
The miniature rotary compression system has become a widely used method for cooling lasers. The development of the rotary compressor has made it possible to miniaturize compression systems for heat loads of 100 Watts. The smaller compact design has found extensive use with lasers.
Miniature rotary compressor chillers are portable with precision temperature control. Cooling ranges between 3 kW up to 140 kW, with operating temperatures of 20 °F to 80 °F (-6.6 to 26.6 °C).
In a direct expansion chiller system, the refrigerant flows directly through the cold plate and is driven by the compressor, a process that eliminates the need for a water cooling loop and simplifies the system. The need for a secondary coolant loop is eliminated in the design of a direct expansion cooling system. In the process, the refrigerant undergoes an isothermal phase change that offers exceptional temperature control across the cold plate.
Direct expansion systems have the typical components of a compressor, condenser, expansion valve, and evaporator that absorb the heat directly. They are a compact cooling solution with a miniature rotary compressor. The advantage of the system is the precision at which it controls the temperature. Direct expansion cooling systems are designed for high heat flux applications such as laser cutting and burning.
Though the basic mechanism of a chiller is the same for all types, as with any type of industrial equipment, regular maintenance guarantees that it will perform according to its specifications. Manufacturers strongly encourage scheduled monitoring and checking of chiller components and provide guidelines for how it should be performed.
Heat transfer is a major part of a chiller's operation. Condenser coils can become clogged or have free air passage.
A chiller's ability to perform properly is highly dependent on the refrigerant. Improperly charged refrigerant can severely impact the chiller's performance.
Water used with cooling towers has to meet the parameters for proper water flow. Debris, dirt, solids, and contaminants can interfere with water flow and be detrimental to the chiller.
For the best performance from a chiller, all of its reservoirs should be checked to make sure they have an adequate supply of fluids.
Chillers operate at their optimum at 50° F (10° C). Unmonitored temperature changes can harm the chiller's operation. For best results, a regular examination of the glycol inlet and outlet temperatures helps in catching possible problems.
All equipment collects dirt and dust in the manufacturing process. For peak efficiency, the exposed parts of a chiller should be regularly cleaned. Filters should be changed to avoid clogging.
Air cooled chillers are refrigeration systems that cool fluids and work in tandem with the air handler system of a facility. Air cooled chillers are types of chillers that rely on the use of fans to reject heat outside the...
A glycol chiller is a chilling system that uses a percentage of glycol mixed with water to create extremely low temperatures far beyond the freezing point of water. The two types of glycol are ethylene glycol based or propylene glycol based...
Laser cooling is a multi-process that includes a number of techniques in which atomic and molecular samples are cooled down to a temperature near absolute zero. These techniques depend on...
A water chiller, or chilled water system, is a type of refrigeration system which uses water as a secondary refrigerant. They are used for larger, more complex, heating, ventilating, air conditioning, and refrigeration (HVACR) applications...
Cooling towers are specialized heat exchangers that remove heat from water mainly by means of latent heat loss from evaporation while coming into contact with an airstream. Aside from evaporative cooling, water is also cooled by sensible heat transfer due to the temperature difference between air and water...
Heat exchangers are pieces of equipment used to transfer heat between two or more fluids. This process usually involves abundant working or utility media such as water or air that rejects or absorbs heat from a more valuable fluid such as crude oil, petrochemical feedstocks, and fluidized products...
Open loop cooling tower makes use of direct contact with the air in order to cool down the water. It is essentially a heat exchanger. In these types of cooling towers, there is the partial heat transfer due to heat exchange between...
A plate heat exchanger (PHE) is a compact type of heat exchanger that utilizes a series of thin metal plates to transfer heat from one fluid to the other. These fluids are typically at different temperatures...
A shell and tube heat exchanger (STHE) is a type of heat exchanging device constructed using a large cylindrical enclosure, or shell, that has bundles of perfectly spaced tubing compacted in its interior. Heat exchanging is the transfer of heat from one substance or medium to a similar substance or medium...