Air vs. Water Cooled Chillers: Which is Best for Data Centers? - Trane

Which chiller type is best for data centers: air cooled, or water cooled? There’s no single answer. HVAC system designers need to ask a lot of questions before advocating one type of chiller over another. The obvious equipment choice is sometimes over-ruled by unique project factors including the available square footage, backup power strategies, local regulations limiting power and water use, or the owner’s sustainability priorities.

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Ideally, data centers will consult with the HVAC company on the front end of the design process to make sure the solution meets short- and long-term objectives. If you’re the one making the decision on behalf of a data center, it helps to understand the pros and cons that are inherent to each type of chiller.

Capacity: Packaged air-cooled chillers are typically available in sizes ranging from 7.5 to 500 tons [25 to 1,580 kW]. Packaged water-cooled chillers are typically available from 10 to 4,000 tons [35 to 14,000 kW]. In other words, water-cooled chillers can deliver higher cooling capacity with fewer units and a smaller footprint.

Maintenance: Air-cooled chillers eliminate the need for cooling towers. Water-cooled chillers require cooling towers, which have critical maintenance demands: water treatment, chiller condenser-tube cleaning, tower mechanical maintenance, and freeze protection. Systems that use open cooling towers must have a water treatment program to prevent contaminants such as bacteria and algae. Cooling towers also evaporate water so you will need access to a large supply of make-up water to replace the evaporated volume.

Location: The pursuit of cheap power and lower taxes is changing the face of the data center industry, placing huge facilities in remote locations far removed from the users. If placed in location where temperature drop below freezing, air-cooled chillers can be easier to operate , because they eliminate the problems associated with operating a cooling tower in severe winter conditions. Cooling towers may require special control sequences, basin heaters, or even an indoor sump for safe operation in freezing weather.

Energy efficiency: Water-cooled chillers are typically more energy efficient than air-cooled chillers. The refrigerant condensing temperature in an air-cooled chiller is dependent on the ambient dry-bulb temperature. The condensing temperature in a water-cooled chiller is dependent on the condenser-water temperature, which is dependent on the ambient wet-bulb temperature. Since the wet-bulb temperature is often significantly lower than the dry-bulb temperature, the refrigerant condensing temperature (and pressure) in a water-cooled chiller can be lower than in an air-cooled chiller. The lower condensing temperature, and therefore lower condensing pressure, means that the compressor needs to do less work and, subsequently, consumes less energy. This efficiency advantage may lessen during nighttime operation because the dry-bulb temperature tends to drop faster than the wet-bulb temperature when the sun goes down.

Delivery & Installation: Most air-cooled chillers are “packed systems.” The system, including the condenser, compressor, and evaporator, is designed and configured at the factory for optimal performance and reliability, which reduces design and delivery time and simplifies installation. Water-cooled chillers have the added complexities of condenser-water piping, pumps, cooling towers, and controls.

Longevity: With the continued technology advances and growth in more data processing, the data center infrastructure needs to be able to support these advancements while delivering consistent performance. In general, air-cooled chillers last 15 to 20 years while water-cooled chillers last 20 to 30 years.

Partially, it’s because water-cooled chillers are typically installed indoors and operate at lower condenser fluid pressure, while air-cooled chillers operate outdoors, at higher condenser pressure.

Water conservation: Water availability, cost, treatment requirements as well as potential additional construction complexity all play a role in system selection. Since air-cooled chiller do not require water, they are often a preferred choice especially in locations where there is a water shortage, or the water is very expensive.

Water is one of two major resources data centers consume [1] . Combined, US data centers were responsible for consumption of 626 billion liters of water in , which includes both water consumed directly at data center sites and water used to generate the electricity that powered them that year. However, as the report points out, far more water is used to generate electricity that powers data centers than to cool them so chiller efficiency again comes back into consideration.

In summary, air-cooled chiller advantages include lower maintenance costs, a prepackaged system for easier design and installation, and better performance in freezing temperature. Water-cooled chiller advantages include greater energy efficiency, larger capacities, and longer equipment life. Yet, the best choice for the project may also depend on an entirely different set of decisions criterial. It’s important for data centers and system designers to take all factors into consideration to make sure the chiller that ultimately gets specified balances all the objectives over the long term.

Water Cooled Chiller: What Is It and How Does It Work?

If you're in the market for a cooling solution for your commercial or industrial building, you may have heard the term "water-cooled chiller" thrown around. But what exactly is it, and how does it work? In this article, we'll break down the basics of water-cooled chillers, their components, and how they function.

What is a Water-Cooled Chiller?

A water-cooled chiller is a type of chiller that uses water as a cooling agent instead of air. It is an efficient and effective cooling solution that is commonly used in commercial and industrial buildings.

Unlike air-cooled chillers, which use air as the cooling agent, water-cooled chillers are more efficient because they can transfer heat more effectively.

Components of a Water-Cooled Chiller

A water-cooled chiller has four primary components: the evaporator, compressor, condenser, and expansion valve.

1. Evaporator

The evaporator is the component that cools the water or other fluid. It is a heat exchanger that transfers heat from the fluid to the refrigerant. The refrigerant absorbs the heat, evaporates, and turns into a gas. The cooled fluid then circulates through the building to provide cooling.

2. Compressor

The compressor is the heart of the water-cooled chiller. It compresses the refrigerant gas, which increases its temperature and pressure. The high-pressure gas then flows to the condenser.

3. Condenser

The condenser is a heat exchanger that removes heat from the refrigerant gas. It releases the heat to the surrounding environment, typically through a water-cooled tower or a cooling tower. As the refrigerant cools, it turns back into a liquid and flows to the expansion valve.

4. Expansion Valve

The expansion valve is a metering device that regulates the flow of refrigerant to the evaporator. It reduces the pressure and temperature of the refrigerant, which allows it to absorb heat from the fluid in the evaporator.

How Does a Water-Cooled Chiller Work?

The water-cooled chiller operates by circulating water or other fluids through the evaporator. The evaporator cools the fluid by transferring heat to the refrigerant. The refrigerant then flows to the compressor, where it is compressed and heated.

The hot, high-pressure gas flows to the condenser, where it releases heat into the environment. The refrigerant then flows to the expansion valve, where it is expanded and cooled before returning to the evaporator to repeat the cycle.

Advantages of Water-Cooled Chillers

Water-cooled chillers have several advantages over air-cooled chillers, including:

More efficient cooling due to the use of water as the cooling agent

Lower energy consumption

Quieter operation

Longer lifespan

Disadvantages of Water-Cooled Chillers

While water-cooled chillers offer several advantages, they also have some drawbacks. These include:

Higher upfront cost compared to air-cooled chillers

More complex installation and maintenance

Requires a cooling tower or other water source, which can increase water usage

May be less effective in hot and humid environments

Applications of Water-Cooled Chillers

Water-cooled chillers are commonly used in commercial and industrial buildings, including:

Hospitals and medical facilities

Data centers

Manufacturing plants

Hotels and resorts

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Office buildings

Maintenance and Care

Proper maintenance and care are crucial to the efficient and effective operation of a water-cooled chiller.

Regular inspections, cleaning, and repairs can help extend the lifespan of the system and prevent costly breakdowns. It is also important to monitor the water quality and temperature to ensure optimal performance.

Cost Considerations

Water-cooled chillers typically have a higher upfront cost than air-cooled chillers. However, they are more energy-efficient, which can lead to long-term cost savings. It is important to consider both the initial cost and the long-term operating costs when choosing a cooling system.

Energy Efficiency

Water-cooled chillers are generally more energy-efficient than air-cooled chillers. They can provide up to 50% energy savings, which can result in significant cost savings over time.

In addition, water-cooled chillers may be eligible for rebates or incentives from utility companies for their energy efficiency.

Environmental Considerations

Water-cooled chillers can have an impact on the environment due to their water usage. However, there are ways to reduce the environmental impact, such as by using a closed-loop system that recirculates water, implementing water conservation measures, and using environmentally friendly refrigerants.

Conclusion

Water-cooled chillers are an efficient and effective cooling solution for commercial and industrial buildings. They use water as the cooling agent and have several components that work together to provide cooling.

While they have some disadvantages, including a higher upfront cost and more complex installation, they offer several advantages, including energy efficiency and quieter operation.

Proper maintenance and care are crucial to the effective operation and long lifespan of a water-cooled chiller.

Frequently Asked Questions

How long do water-cooled chillers typically last?

With proper maintenance and care, water-cooled chillers can last up to 25 years or more.

Can water-cooled chillers be used in hot and humid environments?

Yes, but they may be less effective in these conditions and require additional maintenance.

What is the difference between a water-cooled chiller and an air-cooled chiller?

Water-cooled chillers use water as the cooling agent, while air-cooled chillers use air.

What is a cooling tower?

A cooling tower is a device that removes heat from the water used in a water-cooled chiller.

Are water-cooled chillers more energy-efficient than air-cooled chillers?

Yes, water-cooled chillers are generally more energy-efficient than air-cooled chillers.

Water Chiller: What Is It and How Does It Work?

What is a Water Chiller?

A water chiller is a type of refrigeration system that uses water as a secondary refrigerant to control the cooling of products. It is important to note that a chiller does NOT create cold. A chiller removes heat.

In large, multi-story buildings it simply isn’t practical to pump coolants around the building to multiple air handlers. Long runs of refrigerant pipes would increase the probability of leaks. Coolant leaks would create a potentially hazardous environment for employees; pollute the environment, and waste money. Instead, a chiller provides a centralized location for the coolant to be put to work to remove heat from water. 

How Chillers Work

Chillers circulate chilled water to air-handlers in order to remove heat from the air by transferring the heat to water, i.e. condition the air.

A chiller has two separate systems (or sides):

The chilled water / air handler side where coolant removes heat from water.

The condenser / cooling tower side where water removes heat from the coolant.

Warm water from the air handler returns to the chiller where heat is passed from the water to a liquid refrigerant. The heat from the air handler water turns the liquid coolant into a gas. The spent refrigerant enters the compressor where it is turned into a hot vapor. Upon leaving the compressor, the refrigerant vapor enters the condenser side of the chiller where heat is transferred from the hot vapor refrigerant to water that is on its way to the cooling tow

er. This heat removal condenses the refrigerant back into a liquid. The now liquid coolant is reused to chill more water for the air handler.

The coolant remains contained in the chiller. It is the heat exchange between the coolant and water that both cools the water to condition the air in the handler and removes heat from the refrigerant for reuse.

There are a wide variety of types of chillers that utilize varying pressures, different numbers of tanks and chambers, etc., however the fundamental application is the same as the closed-looped cooling system in your home. Coolant expands to a gas as it removes heat from the water. The now chilled water is pumped to air handlers. The heated gaseous refrigerant is condensed into a liquid for reuse.

In the United States, chiller capacity is measured in terms of tons or ‘tons of refrigeration.’ One ton of refrigeration is roughly equal to the cooling power of one ton (2,000 pounds or 907 kilograms) of ice melting in a twenty-four hour period. Chillers can also be measured in British Thermal Units per hour (BTU/h) and Watts (W). For perspective, an average residential air conditioning unit can be 1 to 5 tons (3 to 20 kW) in capacity. However, a commercial chiller can be from 15 to 150 tons (53 to 5,275 kW) in cooling capacity.

A facility manager and / or building owner may decide to monitor temperature, pressure, liquid

 flow rate, and electrical power to help maintain an efficient chiller.

Chiller Diagram

How Water Cooled Chillers Work with Veris Products

Product Family

Why it is used on a Chiller

Power Meters Monitors the power used by the chiller. May assist with load shedding agreements. Excessive power usage may indicate a mechanical problem in the chiller pump motor(s). Pressure

Wet DP used to monitor the differential pressure between chilled water supply and return, as well as condenser water supply and return. Controls bypass valve to regulate flow based on demand. Provides a secondary proof of flow by monitoring the differential between supply and return air.

Gauge pressure is used to monitor pressure in the condenser and evaporator units to determine the ultimate pressure on the line. Using a gauge pressure product on both the supply and return will provide the data needed for the BMS to calculate the differential pressure.

High or low pressure readings may be an indicator of a mechanical failure in the system like a leak, pump failure, locked rotor, a clog, etc.

Current Sensors Monitors run status on all pump motors. Can be used to detect on / off status, locked rotor, and overall pump status for proof of function / water flow. Proof of functionality. No need to manually check each pump. (If current is flowing, the pump is working.) Temperature Used to monitor temp for chilled water loop and condenser water loop, helps to control the valve that determines water recirculation speed. Helps to determine pump speed, how much water needs to be returned, and is a main control point for the system. Flow Meters

Flow Meter monitors water flow in the supply and return lines of the chilled water loop and condenser water loop. Provides both proof of flow and measures usage.

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