Water Chiller System

What Is A water Chiller System

In large HVACR (Heating, Ventilation, and Air Conditioning) systems, you will encounter chiller systems, which some people also call chilled water systems. It operates by secondary refrigeration and uses water as the heat transfer medium.

This type of system does not have an independent terminal and is specifically designed to provide cooling for complex building complexes. In large Spaces such as industries, shopping malls, and hospitals, chiller systems can deliver cooling capacity to each area.

The Basic Refrigeration Cycle System of The Water Chiller

Water Chiller Refrigeration System

Compressor

The compressor compresses the low-temperature and low-pressure gaseous refrigerant into a high-temperature and high-pressure state through the reciprocating motion of the piston or screw, providing the driving force for subsequent heat exchange.

Condenser

When the high-temperature and high-pressure refrigerant enters, the heat is transferred to the outside through water cooling or air cooling. Water-cooled condensers often adopt shell and tube structures, using circulating water to carry away heat. The air-cooled type accelerates air convection through fins and fans.

Evaporator

The liquid refrigerant absorbs the heat of the medium to be cooled in the evaporator and exchanges heat with water or air through the tube wall. The evaporation temperature needs to be precisely controlled to prevent freezing or overheating.

Throttling Device

The thermal expansion valve monitors the outlet status of the evaporator in real time through the temperature sensing bulb and automatically adjusts the refrigerant flow rate. Capillary tubes achieve simple throttling through a fixed aperture. This stage directly affects the evaporation pressure and superheat, and it is necessary to regularly check for any blockages or leaks.

The coordinated operation of these four components ensures the circulation and conversion of the refrigerant between the gaseous and liquid states. The compressor provides power, the condenser releases heat, the evaporator absorbs heat, and the throttling device balances pressure. Together, they form a complete refrigeration closed loop.

Chilled Water Circulation System of The Water Chiller

Chilled Water Circulation

The chilled water circulation in your chiller system is divided into a primary chilled water system and a secondary chilled water system.

• Primary Chilled Water Circulation System:

The primary chilled water circulation system is the cooling capacity directly produced by the main unit. The evaporator of the chiller cools the water, which is directly pumped to the end of your equipment to cool the workshop or room.

• Secondary Chilled Water Circulation System:

If the quality of the primary chilled water is poor and prone to scaling. The cooling capacity of the primary water will be transferred to the secondary cooling water through the heat exchanger. This way, it not only protects the main unit but also flexibly ADAPTS to the cooling requirements of different regions.

Cooling Water Circulation

The condenser transfers heat to the cooling water of the chiller, and the water pump then sends this hot water to the cooling tower, dissipating the heat into the atmosphere.

In simple terms, chilled water is responsible for delivering cold, while cooling water is responsible for discharging heat.

Water-cooling Machine Auxiliary System

Frozen Filtration Water System

The chilled water filtration module in your chiller system is a component specifically responsible for the cleanliness of chilled water. The chilled filtration water system is embedded in the inlet pipe. It relies on the filter screen and activated carbon to block rust, sand, and impurities, keeping the chilled water flowing through the evaporator clean.

Gas-Liquid Separation in The Chilled Water System

Water Chiller Air Separator System

The air separation system is usually hidden inside the unit and operates by means of a gas-liquid separation tank. When the chilled water circulates, the gases dissolved in the water will gradually escape and accumulate into small bubbles.

The air separation system slows down the water flow rate, allowing the bubbles to float towards the top of the tank, and then the air is discharged through an independent exhaust pipe.

Chilled Water Automatic Exhaust Valve System

The automatic air release valve for chilled water is installed at the high points of the pipeline, such as elbows or the end of long-distance pipelines. These places are most prone to air accumulation, which affects the efficiency of water flow.

When the float ball in the valve senses the water level dropping, it will automatically open the small hole to release air. After the air float ball was discharged and dropped, the valve was closed again to prevent water leakage.

Parameter Control of The Chilled Water System

Water Chiller Main  Variable System

The core parameters of the main variable water chiller you installed (such as the temperature or flow rate of the chilled water) are directly locked by the main unit. This system is suitable for precision workshops. The reaction vessels and lasers in precision workshops are sensitive to temperature. A difference of 0.5℃ can affect the process. This system can stably support the process.

Water Chiller Variable System

Variable water chillers are more flexible. It can change along with the end demand. When the production line is busy, it automatically increases the flow rate and lowers the temperature. Production is less at night, and the flow rate is reduced to save electricity. If the load of your factory fluctuates greatly, this system can save electricity and reduce costs.

Types of Water Chiller Systems

According to The Condenser

Air-Cooled Water Chiller System

The air-cooled water chiller system you often see is a refrigeration device that dissipates heat by air. It does not use water as the cooling medium and directly dissipates the heat of the refrigerant into the surrounding air, making it suitable for scenarios where water is scarce or where a complex water system is not desired.

Advantages:

• Simple structure, no additional facilities such as cooling towers or circulating water pipes, and low initial installation cost.
• Daily maintenance is worry-free. There is no need to clean the tower, change water, check the filter screen, or wipe the condenser.
• It is particularly suitable for medium and small loads, such as office buildings, community hospitals, and small injection molding factories. It provides stable cooling and saves water.

Disadvantages:

• The fan makes noise when rotating. Sound insulation should be considered when placed in hospitals or office buildings.
• Long-term exposure to wind and sun causes the components to age quickly, and their lifespan may be two to three years shorter than that of water-cooled ones.

Scope of application:

If you are building in a water-scarce area or opening a small manufacturing plant, clinic, or data center, choosing an Air-cooled water chiller is just right. No need to dig Wells or connect water pipes. It can be installed quickly and is economical to use. It does not hold back the cooling of medium and small loads.

Water-Cooled Water Chiller System

The water-cooled water chiller system dissipates heat through the combination of water and refrigerant. The core is to transfer the heat of the refrigerant to the chilled water, and then use another set of water circulation to discharge the heat into the atmosphere.

Advantages:

 The water-cooled system has precise temperature control, with a temperature difference that can be reduced to ±0.5℃. It is suitable for workshops in the pharmaceutical and food industries that require a constant temperature.

It is highly efficient and more energy-efficient than air cooling when the ambient temperature is high or a large number of devices need to be cooled.

The structure is stable, and the core components wear out slowly.

Disadvantages:

It requires the installation of cooling towers and the connection of water pipes, with a large initial investment.

It’s not cost-effective to use in water-scarce areas.

Condensate water needs to be treated regularly; otherwise, scale will form in the pipes, affecting heat exchange.

Application fields:

Water-cooled chiller systems are suitable for large-scale projects, such as cooling reaction vessels in chemical plants, temperature control in pharmaceutical workshops, or places with stable cooling water, like shopping malls and hospitals. They can withstand long-term high-load cooling.

According to The Operation Mode

Steam Compression Water Chiller

A vapor compression chiller relies on the compressor to drive the refrigerant for circulation. The evaporator absorbs the excess heat from the process. The compressor heats up the refrigerant. The condenser discharges heat to the outside. The expansion valve allows the refrigerant to return to the evaporator. It has an evaporator, a condenser, and an expansion unit, but no absorbing medium. It relies entirely on mechanical compression to do work.

Steam Absorption Water Chiller

Absorption chillers are different. They do not use compressors and are driven by heat sources (such as steam or gas). There is no compressor in the system.

According to The Compressor

Centrifugal Compressor

Advantages:

Centrifugal water chillers have a large cooling capacity and high cooling efficiency even under high loads. The new type of centrifugal chiller is also equipped with intelligent control and a variable frequency drive.

Applicable fields:

High-load cooling applications, district cooling systems, data centers, airports, and large commercial buildings.

Screw Compressor

Advantages:

Screw-type chillers can adapt to different loads. The design is relatively durable and operates with very low noise. It also has a special advantage, which is its small floor space.

Application scenarios:

Suitable for small and medium-sized applications, such as plastic processing, food and beverage factories.

Scroll Compressor

Advantages: 

The scroll water chiller can adapt to the constantly changing refrigeration demands. It also runs relatively quietly. And the maintenance is relatively simple. Choosing a scroll water chiller can save a lot of trouble for subsequent maintenance.

Application scenarios:

Precise cooling or green cooling requirements in the laboratory.

Reciprocating Compressor

Advantage:

The only advantage of reciprocating water chillers is that they are cheap. It is cheaper than the other types of chillers. If your budget is a bit tight, reciprocating chillers are not out of your question

Disadvantages:

Reciprocating chillers have relatively more defects. It makes a lot of noise when running and is not suitable for scenarios where quietness is required. The internal small components of reciprocating chillers are also prone to damage and require frequent repairs. Its service life is also relatively short. It has almost been eliminated from the market now and is not easy to find.

Suitable scenarios:

For household use or small factories that want to make do, reciprocating water chillers are recommended.

Application Fields of Chilled Water Systems

Manufacturing Industry

Metal Processing

During metal processing, such as turning, milling, drilling, and grinding, heat is generated due to friction. Chillers are very common in mechanical processing workshops. Water chillers can reduce the heat generated during metal processing.

Mold Injection Molding

In chemical plants, mold manufacturing is often used to produce plastic products. The water chiller can quickly cool down the mold.

Food Processing

For food refrigeration in food processing plants, small water-cooled machines can be used instead of refrigerators.

Data Centers And Communications

Data Center

When the server is full, IT forwards heat. The chiller supplies chilled water to IT equipment to control the temperature in the computer room.

Telecommunication Hub

The communication base stations and switches operate for a long time. The regional cooling system uses pipes to supply chilled water to dissipate heat throughout the entire computer room.

Special Scenarios

Chemical engineering and petroleum

The high-temperature corrosion of the reaction vessel, the corrosion-resistant chiller can withstand it, and the chemical process conditions are stable.

Hydroponic Cultivation

Plant roots require a constant temperature. Hydroponic coolers cool down the nutrient solution, making the growth more uniform.

Explosion-Proof Workshop

The explosion-proof chiller does not ignite gas and is safe.

Alternative Energy 

The biogas biofuel equipment generates heat, and the dedicated chiller cools it down, but the gas production efficiency does not decrease.

There are also HVAC chillers to cool the building, metal surface treatment coolers to ensure no defects in electroplating, and printing machine cooling to prevent paper deformation. The application of industrial chillers lies in every corner that requires precise cooling.

Design Considerations for The Water Chiller System

Calculate The Quasi-Cooling Load And Capacity

It is necessary to first figure out how much heat needs to be removed. This is the basis for choosing a chiller. Refrigeration load is usually calculated in cooling tons or BTU per hour. One cooling ton equals 12,000 BTU per hour, approximately 3.5 kilowatts. For instance, the total heat generated by the equipment in the workshop must be matched with the corresponding cooling capacity. If it’s too small, the cooling won’t be sufficient; if it’s too large, it wastes electricity.

Set The Temperature And Flow Rate of The Chilled Water

The key is to calculate the temperature and flow rate of chilled water through heat exchangers to ensure that the coils can effectively remove heat.

Select The Right Mode for Controlling The Refrigeration Capacity

The methods for controlling the capacity of chillers with different types of compressors vary. For the scroll type, the motor speed can be adjusted by VFD, or the displacement of the compression chamber can be changed by switching the solenoid valve. For centrifugal and screw types, the refrigerant flow at the inlet is adjusted and controlled by an inlet guide valve or VFD.

Consider The Configuration of Multiple Chillers

When applied on a large scale, it is better to use multiple small cold water machines than a single large one. Chillers often operate at partial load. If there are multiple units, one can be shut down to reduce capacity while the others are fully loaded, which will be more efficient. Moreover, if one unit breaks down, the entire system won’t shut down. Backup redundancy is more secure.