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Liquid Cooling Introduction

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Last updated May 20, 2024 | Published on Dec 15, 2020

Liquid cooling is an effective way to remove high heat loads from components. Excessive heat can compromise the reliability of a system and engineers are now turning to liquid cooling when air cooling no longer provides enough heat removal. Two types of liquid cooling are contact cooling and cabinet cooling.

What is Liquid Cooling and Why You Should Use It

A liquid cooling loop for contact cooling typically consists of a cold plate, pump, heat exchanger, and pipes or hoses. Heat generated by a component is transferred from the component to the thermally conductive cold plate, and then to the liquid coolant that flows through the cold plate. The heated coolant is then pumped through the heat exchanger, where heat is moved from the coolant to either the ambient air or, in the case of a liquid-to-liquid heat exchanger, to another liquid. The cooled liquid then flows through the pipes or hoses back to the cold plate, completing the liquid cooling loop. Instead of a heat exchanger, a recirculating chiller, a liquid cooling system, or facility water may be used to provide cool liquid to the process.

With cabinet cooling the air within the cabinet is cooled by flowing cold liquid through the heat exchanger and distributing the air within the cabinet via the heat exchanger fan. As with contact cooling, cabinet cooling may receive the cold liquid from facility water, a recirculating chiller, or another heat exchanger.

Benefits of Liquid Cooling

Liquid cooling has two primary benefits over air cooling. One benefit is higher performance, since the fluids most commonly used for it have much higher thermal conductivity than air. A second benefit is that it is often much quieter and requires less space than air cooling. Since less air flow is needed, electronics can be packed in more tightly.

Liquid Cooling Technologies

Boyd designs and manufactures all the thermal components in a liquid cooling loop, providing Total Thermal Solutions. Boyd's liquid cooling products include both standard and custom cold plates, chassis, chillers, cooling systems, and heat exchangers. Various fluids can be used with the liquid cooling products, including water, deionized water, ethylene glycol, oil, polyalphaolefin, and dielectric fluids. Please contact Boyd to discuss using other fluids.

Liquid Cooling Industry Applications

Liquid cooling is used to cool high power electronic devices within many industries, including medical, military and defense, laser, data centers, semiconductor, transportation, printing, and more.

For low heat loads, recirculating chillers are usually the simplest solution as installation is so easy. At high heat loads, liquid-to-liquid cooling systems are more cost effective. However, their use is restricted to situations where chilled facility water is available. The necessity to plumb them into facility water may affect the locations they can be used in and the portability of the equipment.

If you have high heat loads and need to reject the heat to facility water, the choice between an LCS and a recirculating chiller with a water-cooled condenser depends on your set-point temperature. If your set-point temperature is higher than your maximum facility water temperature, an LCS is more cost-effective. However, if you need to cool close to or below the facility water temperature, you will need a refrigerant based chiller with a water-cooled condenser.

Liquid Cooling Links

Boyd offers a variety of resources to help you find the right liquid cooling technology for your application. Learn more about our href=”https://www.boydcorp.com/thermal/liquid-cooling.html”>Liquid Cooling Solutions and how you can help cool your system

Custom Liquid Cooling System Economics

Impact of Customization Options on the Overall Cost of a Liquid Cooling System

Cooling systems, including compressor-based chillers, liquid-to-liquid cooling systems, and ambient cooling systems, can be purchased as standard products "off-the-shelf", modified from existing standard systems, or completely custom designed to meet your unique needs. By working with a manufacturer that has a large number of standard technologies available, as well as significant experience designing custom systems, you'll be able to modify a standard cooling system or design an entirely custom cooling system with a better value proposition. If a standard cooling system or a slightly modified standard cooling system will meet your needs, you'll generally save over designing an entirely custom system. However, if a modified or custom cooling system is what you need, involving your manufacturer early in the design process and reviewing the cost drivers is important since the costs can vary quite a bit.

With custom cooling systems, the non-recurring engineering required to meet design specifications can be a significant up-front cost. Some of the specifications that can contribute to engineering materials and assembly costs include the type of cooling system, custom versus standard internal components, the locations and spacing of the internal components, controllers for numerous sensors and instrumentation, special power requirements, compatibility with specific coolants, and agency approvals.

Ambient Cooling System, Liquid-to-Liquid Cooling System, or Recirculating Chiller

An ambient cooling system, such as a modular liquid cooling system, will provide reliable cooling for applications where precise temperature control and cooling below ambient temperature are not required. An MCS consists of a high performance heat exchanger integrated with a fan, pump, and tank in a durable metal chassis (See Figure 1). A standard MCS can handle up to 3,5 kW. A liquid-to-liquid cooling system also has a heat exchanger, pump, and tank within a chassis. However, a liquid cooling system can offer precise temperature control of process water and transfers waste heat to facility water via a liquid-to-liquid heat exchanger (See Figure 2). If facility water is not available and precise temperature control or cooling below ambient temperature is needed, a good solution is a recirculating chiller.

A standard LCS and a recirculating chiller are similar in costs, depending on the sizes and options selected. However, a standard LCS offers up to 20 kW of cooling, whereas a standard recirculating chiller offers cooling capacities from 825 W - 95 kW. Regardless of the type of cooling system, if you determine that a modified standard or custom cooling system is what you'll need, it is important to note that there will probably be a minimum order quantity required by the manufacturer.

Custom Internal Components

Even in custom cooling systems, virtually all of the internal components are standard products. With a wide variety of heat exchangers, pumps, tanks, and fans on the market, it is rare that there is not a component already designed and built that will work for the cooling system. If a custom internal component is needed, there are additional engineering design and manufacturing steps involved in the process and hence additional costs (See “Heat Exchanger Manufacturing Cost Drivers” for more information on custom heat exchangers).

Locations and Spacing of the Internal Components

Unlike the rare requirement of a custom internal component, a common requirement for custom cooling systems is finding a way to pack more and more cooling into smaller and smaller spaces. This can be accomplished by packing the components more tightly and/or by selecting smaller components that are more efficient. The tighter or more densely packed the components are within the chassis or cooling system package though, the more challenging it is to design and manufacture. Sometimes the more compact it is, the more difficult it is to service too. With more tightly packed components, there is less airflow and therefore less performance. In turn, a more powerful fan or better performing heat exchanger may be required. Also, as component locations or spacing are changed, pressure drop needs to be looked at along with connections and other design elements to ensure a reliable product that meets or exceeds expectations.

Controllers for Sensors and Instrumentation

Controllers provide numerous ways to monitor the cooling system by a display or data output to a remote computer. The standard recirculating chiller controllers offer digital temperature display, calibration offset, low flow shut-off, auto-restart, °C/°F toggle, audible alarm, alarm mute, digital pressure sensing, low level, low/high temperature, pressure display, fault shut-off (toggle on/off), and relay contacts. The LCS cooling system controllers offer digital temperature display, °C/°F toggle, over-temperature indicator, calibration offset, low level indicator, low flow indicator, and analog output. If additional sensors and instrumentation are needed, the cost of the controller can rise significantly. In a custom cooling system, a non-standard controller can be one of the most expensive parts. Weighing the costs and benefits of every sensor and instrumentation requirement is highly recommended. For example, in deionization sensing, do you need to know the exact value or do you just need to be alarmed if it reaches a certain point? An alarm is less expensive than output of a precise digital reading. The same goes for flow, pressure, and temperature. For some applications, the additional sensing and instrumentation is well worth the additional cost. It can provide extra protection to the cooling system and to the equipment being cooled, which may be worth thousands or even millions of dollars.

Special Power Requirements

As with the controller, it's important to determine if special power requirements for your application are worth the additional cost. The electrical configurations available with standard cooling systems meet the needs of most applications. Configuration options that provide a more universal power configuration, such as being able to operate on both frequencies, will cost more. It may be more cost effective to manufacture two or more types of custom cooling systems that will work for use in separate locations versus manufacturing one that is universal.

Compatibility with Specific Coolants

A standard modular cooling system is compatible with a wide range of coolants, including water, deionized water, oil, and ethylene glycol solutions. The standard LCS is compatible with water, deionized water, and ethylene glycol solutions. Standard recirculating chillers are compatible with water, deionized water, ethylene glycol solutions, and polyalphaolefin (PAO), the standard XT chillers are compatible with a variety of fluids depending on operating temperatures, including HFE-7100, HFE-7500, Baysilone® Fluid M 20, and clean water/EGW/PGW, and the standard XL and RM recirculating chillers are compatible with clean water, EGW and PGW. If other coolants are required, all wetted materials within the system must be evaluated to minimize corrosion and ensure system performance is optimized. Designing a cooling system to be compatible with other coolants could require additional engineering and non-standard components, such as special tubing or pumps. Compatibility with ethylene glycol solutions or water is generally the easiest compatibility to design in, with PAO and Fluorinert™ compatibility providing more of a challenge and a higher cost.

Agency Approvals

Another somewhat costly specification is designing a custom cooling system for agency approvals. Most of the standard cooling systems are CE Certified and ITSNA tested to UL 61010-1 or MET tested to UL 1995. However, ensuring a new design has met agency approvals adds another layer of engineering design and quality control steps, including retesting of custom systems.

The more complex or unusual the cooling system requirements are, the more engineering it will require and therefore the more costly it is likely to be. With custom systems, the engineering time involved to meet specifications is usually a significant initial cost, with non-standard controllers being the biggest recurring cost. The costs of a modified or custom cooling system can vary by thousands of dollars, so knowing the design specifications that impact cost is key. Understanding the types of cooling system available, how standard parts will expedite design and production, when real estate savings may not be worth the money, and which sensors and instrumentation are must-haves vs. nice-to-haves will make a difference. In addition, it's important not to forget that coolant selection, power requirements, and agency approvals come into play as well.

Visit our Ambient Liquid Cooling Section or our Chiller Section to learn more about our Liquid Cooling System Solutions.

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