Beyond Performance: Addressing Reliability Concerns in Liquid Cooling

The Boyd Difference

Understanding the Roots of Coolant Leakage in Liquid Cooling Systems

In liquid cooling systems, coolant leakage poses a significant risk and can compromise performance and reliability. Understanding why coolant leaks is crucial for effective prevention. Corrosion and fluid interconnect issues are the primary factors that cause coolant leakage.

Fluid Interconnect Issues:

Ensuring Leak-Free Reliability in Liquid Cooling System Fluid Interconnect Joints, Fittings, and Seals

Our liquid cooling systems feature diverse joint technologies to meet varying customer needs while preventing leaks. We solder or braze joints to create strong, durable metal components and assemblies, perfected over decades of manufacturing experience. For barb fittings, we enhance security by pairing them with tube clamps, ensuring a tight and leak-free connection. To protect O-ring seals, we incorporate filters during testing and within our Coolant Distribution Units (CDUs) to remove larger particles that could damage the seals’ integrity. Boyd meticulously manufactures, handles, tests, and packages liquid cooling loop joints, fittings, and seals to ensure secure fluid interconnections before they reach the customer. This rigorous process maintains joint integrity and minimizes leak risks.

Erosion corrosion occurs when increased coolant velocity erodes metal surfaces, often caused by turbulent flow or sharp turns in the coolant path. This erosion weakens materials, heightening the risk of leaks and eventual system failure. Effective design solutions minimize flow velocity changes and ensure smooth coolant pathways to prevent erosion corrosion.

Boyd addresses these corrosion risks by implementing advanced seals, corrosion-resistant materials, precise manufacturing techniques, and rigorous testing in liquid cooling systems. These proactive measures not only mitigate fluid interconnect issues but also ensure reliable and efficient operation. They safeguard the integrity of high-value electronics, reduce downtime, and lower maintenance costs over the system’s lifespan.

Optimizing Leak Containment: Beyond System Shutdown

Optimizing Performance, Eliminating Leaks: The Boyd Advantage in Liquid Cooling

Boyd pioneers’ innovation through the design of leak-free solutions, advanced sealing techniques, and corrosion-resistant materials. Our engineering and material science expertise enables us to develop robust solutions that ensure the integrity and reliability of liquid cooling systems. Boyd tackles challenges such as fluid interconnect issues and corrosion risks through rigorous testing and precision manufacturing capabilities. Schedule a consultation with our experts to explore our comprehensive range of leak-free solutions tailored to meet your specific project needs and optimize system performance.

Embedded systems are becoming more complex, processing and analyzing a growing number of sensors and signals. The result of this increased computing is often higher and more concentrated electronic heat loads.

How to Design a Liquid Cooling System for High-Performance System Thermal Management

Because excessive heat compromises the reliability of a system, air cooling is no longer adequate for some applications. Many engineers are turning to liquid cooling to remove the heat.

The complexities of designing a liquid cooling system can be intimidating for those unfamiliar with this set of technologies. Although selecting thermal components for a liquid cooling loop is relatively straightforward, there are other considerations or nuances that can be overlooked. These include materials compatibility, corrosion prevention, condensation control, the position of the liquid cooling loop, use of standard versus custom parts, joints, fittings, connectors, and maintenance and service.

A liquid cooling loop typically consists of a liquid cold plate, pump, heat exchanger, and pipes or hoses (Figure 1). The board generates waste heat, which is transferred from the board to the thermally conductive plate, and then to the liquid coolant that flows through the cold plate. Typically, the fluid path matches hot spots on the board. The heated coolant is then pumped through the heat exchanger, where heat is moved from the coolant to either ambient air, or, in the case of a liquid-to-liquid heat exchanger, to another liquid coolant. The cooled coolant then flows through pipes or hoses back to the cold plate, completing the cooling loop. Under normal operation, liquid coolant continuously flows through the liquid cooling loop to keep the board cool.

Material Compatibility

Since all materials and the fluid in the liquid cooling loop need to work together as a system, they need to be compatible with one another and should be selected together. Copper works well for most applications, since it has excellent thermal conductivity and is compatible with most non-corrosive fluids. Aluminum is compatible with fluids such as polyalphaolefin (PAO), oil, ethylene glycol and water solutions (EGW), as well as Fluorinert™, an electrically insulating inert perfluorocarbon fluid manufactured by 3M and used in many electronics cooling applications. Stainless steel is compatible with most fluids, including corrosive fluids such as deionized water. Several different fluids are compatible with various standard cold plate and heat exchanger materials (Figure 2).

Figure 2: Various fluids are compatible with a variety of standard cold plate and heat exchanger materials

Most liquid coolants also need a small percent of additives to inhibit corrosion and to lubricate the pump. However, it is important to note that corrosion inhibitors can be rendered ineffective by incompatible materials elsewhere in the system, so this must be evaluated as well. Biocides, algaecides, and pH adjustments may also be helpful in maintaining your system, depending on which liquid coolant is selected.

Corrosion Prevention

Corrosion can cause problems two different ways. Not only can material corrode away, which leads to leaks, but the corroded material can be deposited elsewhere in the system and block fluid passages or filters. This can produce a pressure drop that causes reduced coolant flow. In addition, if the deposition occurs on active heat transfer surfaces, the extra thermal resistance caused by fouling can make temperatures rise.

Both galvanic corrosion and erosion-corrosion should be minimized in the liquid cooling loop. Galvanic corrosion occurs when dissimilar metals are in electrical contact with each other in the presence of an electrolyte such as a conductive liquid. Most water-based coolants are electrolytic to some degree. To prevent galvanic corrosion, either the loop should be designed with similar materials throughout the system, ideally with just one metal, or a non-conductive fluid should be used. The galvanic potentials of all materials in the system should be considered. This includes not only the primary thermal components, but also all connectors, fittings, valves, and junctions in the fluid path.

Erosion-corrosion is the acceleration in the rate of corrosion in metal due to the relative motion of a fluid and a metal surface. It is most often found in pipe bends & elbows, tube constrictions, and other structures that alter flow direction or velocity. Erosion-corrosion is most prevalent in soft alloys, such as copper and aluminum.

Some methods for minimizing erosion-corrosion include allowing bends to have larger angles, changing pipe diameters gradually rather than abruptly, and improving flow lines within the pipe by deburring, i.e., smoothing out irregularities. Other methods include reducing the amount of dissolved oxygen, changing the pH, and switching the pipe material to a different metal or alloy. See our application notes “Erosion-Corrosion in Cooling Systems” and “Avoiding Galvanic Corrosion” for more information on corrosion.

Condensation and Liquid Cooling Loop Design

In addition to minimizing corrosion, it’s important to minimize or prevent condensation. One of the risks of using coolants below ambient temperatures is that condensation may form on cool surfaces. This condensation can drip onto electronics or collect in the bottom of the system and cause corrosion. To avoid condensation, surface temperature can be maintained above the ambient dew point by either insulating these surfaces or using higher fluid temperatures. Boyd offers a variety of insulating materials like SOLIMIDE® Foam to maintain line temperatures and prevent condensation and potential damage.

In a properly designed and maintained liquid cooling loop, leaks are very unlikely. However, to minimize the effect of any potential leaks, the reservoir and liquid loop can be located below electronics that would short out if coolant or condensate dripped or sprayed on them. Other options include installing a liquid shield or barrier over the high-voltage portions of the electrical system.

When designing the liquid cooling loop, there is also the option of using standard or custom parts. There are advantages and disadvantages to each. Standards are readily available if replacements are needed. Custom parts, on the other hand, are optimized for the application’s size, performance, and device requirements. However, they will have longer lead times and may have a higher cost.

Joints, Fittings, and Connectors

The number of joints in the cold plate or heat exchanger is important. When there are more joints that must be brazed, there is a higher risk of leaks. It is important to ensure that the manufacturer is highly skilled at brazing, has proper test procedures in place, and eliminates any unnecessary braze points within a custom component.

To prevent leaks, the right fittings must be selected and properly used. For a leak-free joint, a beaded tube fitting mates with a hose that is secured with a clamp. Hard plumbing is generally preferable to hoses, but hoses may be used in environments where systems are exposed to shock or vibration. A unit with a straight tube fitting can be welded into the system or used with a self-locking, torque-free fitting. With a quick-disconnect coupler that isn’t drip-free, you’ll need to expect the occasional drop of fluid when connecting or disconnecting the fittings. For more information, please review our application note on “Choosing a Quick Disconnect Coupler”.

Another option is to use O-rings fittings that are manufactured to Society of Automotive Engineers (SAE) material specifications or those manufactured to military specifications. These fittings are available in various materials and sizes and provide a reliable leak-free seal. Boyd’s O-Ring portfolio and expertise can help ensure you select the right material, certifications, and size quickly to help prevent leaks within your system.

Maintenance and Service

Although maintenance and service may be the last thing engineers consider when designing a liquid cooling loop, including this consideration in the design process will help to reduce problems over the long term. Several different types of questions must be answered.

For example:

• Will the pump need lubrication over its life or is the coolant going to perform that function?
• Will the fluid reservoir need topping off?
• Which components are field-replaceable?
• What is the maintenance schedule?
• What is the required pump life?
• If pump replacement is needed, how does one charge the system and start the system up?

Other questions concern what the user must do to get the system working again.

• Does this require removing the electronics and cold plate, or just the electronics, and can both be easily removed and replaced merely by snapping in a new one?
• If the cold plate is replaced, will it be shipped with cooling fluid?
• Does the OEM ship the system or field-replaceable unit filled with fluid?
• If so, freezing of the fluid may be a concern, such as in aircraft cargo holds that get very cold.

These questions must be considered by members of both design, operations and maintenance teams. Involving all affected individuals in the decision will help to ensure smooth operations in the future.

Materials compatibility, corrosion prevention, condensation control, the position of the liquid cooling loop, standard versus custom parts, joints, fittings, connectors, hoses, and maintenance and service requirements all must be considered when designing either a modified standard or custom liquid cooling loop. When properly integrated into a system, liquid cooling can provide highly effective heat removal with low risk. Today, tens of thousands of cold plates and heat exchangers are liquid cooling electronics in some of the most demanding and high-performance applications.

Written by Richard Goldman and Tracey Barber
Original Published in RTC magazine, July 2006

Visit our Liquid Heat Exchanger Section or Liquid Cooling System Section to learn more about Boyd’s full liquid loop solutions.

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

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

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.

This simple step-by-step guide explains the different types of cooling systems available and highlights how to select the right product for your application.

Considerations to Picking a System for Your Application

The first consideration is whether you need precise temperature control or need to cool below ambient (air) temperature. If you can answer ‘no’ to both of these, you are looking for a cooling system that will simply remove bulk heat. The most cost effective solution is an ambient cooling system.

The biggest cost drivers for aluminum cold plates, after those mentioned above, are machining time and additional processing steps. Cold plate manufacturers typically have a cost associated with machining time which covers depreciation costs of the machine, power, supplies, and maintenance. Therefore, the longer the cold plate sits in the machine the more costly it is. Each additional processing step continues to drive the cost up.

Ambient Cooling Systems

There is no temperature control circuit, so an ambient cooling system does not maintain a pre-set temperature. Since the ambient air provides the cooling, the ambient temperature is the lower limit for the fluid exit temperature.

Although they appear simple, ambient cooling systems are engineered for maximum capacity. The cooling system manufacturer’s thorough understanding of heat exchanger performance allows the liquid flow rate and air flow rate to be performance-matched to extract the most cooling capacity from the system. The plumbing is designed for high reliability and components are carefully selected to avoid any galvanic corrosion issues. An off-the-shelf ambient cooling system is extremely easy to use – simply connect the fluid inlet / outlet fittings to your equipment, fill the tank and turn it on!

But what if you need to control the temperature or cool below room temperature? Recirculating chillers and liquid-to-liquid cooling systems are both good alternatives.

Recirculating Chillers

Recirculating chillers offer precise temperature control (within 0.1°C) and cooling below ambient temperature. They are quiet, cover a wide range of cooling capacities, and are available with many different options and additional features. Recirculating chillers are compact, quiet and easy to install.

Recirculating chillers use refrigerant for cooling. They operate in a similar way to your refrigerator at home, except that they cool water instead of air. The process water circuit includes an evaporator, tank, and pump. The water is cooled by the refrigerant as it passes through the evaporator. On the other side of the evaporator the refrigerant evaporates to cool the water, then passes through a compressor and condenser, rejecting the heat to the ambient air.

When heat loads get high, chillers can cause the room’s air conditioning system to become overloaded as they reject the waste heat into the ambient environment. One option is to use a chiller with a liquid-cooled condenser. In this case, the refrigerant is cooled by facility-chilled water instead of air, making the chiller quieter and avoiding room-warming problems.

Another alternative for high heat loads is a liquid-to-liquid cooling system.

Liquid-to-liquid Cooling Systems (LCS)

The process side circuit is completely isolated from the facility water, protecting your equipment from fluctuations in temperature, flow rate of the facility water and any contaminants that may be present. Since the facility water provides the cooling, the facility water temperature is the lower limit for fluid exit temperature.

Liquid-to-liquid cooling systems are popular for high heat load applications as they are compact – approximately 1/3 the size of a refrigerant-based chiller of similar capacity. Without a compressor, they are also very quiet and energy efficient.

Recirculating chiller or liquid-to-liquid cooling system?

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.

Selecting a Modular Cooling System

Calculate Which System You Need

MCS performance is shown as Q/ITD versus flow rate. Q is heat load, and ITD is the initial temperature difference, or the difference between MCS liquid inlet temperature and ambient air temperature.

To select the correct MCS system, you first need to determine Q/ITD. Then, using the MCS performance graph, draw a horizontal line at the calculated Q/ITD value. Finally, check that the pump will provide sufficient flow rate.

Example:

A laser produces 700 W of waste heat. The water temperature exiting the laser should be less than 35°C. Ambient room temperature is 20°C. The laser equipment requires a flow rate of at least 1 gpm. Which MCS system should be selected?

First, determine Q/ITD Q/ITD = 700 W/(35°C-20°C) = 46.7 W/°C

Using the thermal performance graph, you can see that at flow rates above 0.5 gpm, MCS20 will provide adequate performance. The standard BB pump offers a flow rate of 1.3 gpm so it will work well. If you are considering an alternative pump, use the pump flow rate calculation to verify that with the given pressure drop, flow rate will be sufficient.

Selecting a Liquid-to-Liquid Cooling System

How to Calculate which Liquid-to-Liquid Cooling System is Right for Your Application

In most Liquid-to-Liquid Cooling applications, we know the temperature of facility water (TF), the desired process set-point temperature (TP), the flow rate through the process ( P) and the heat load of the process, Q.

To determine the required capacity, Q/ITD, we first need to calculate the change in temperature, ΔT, through the process. We can do this either by solving the heat capacity equation:

or by using the heat capacity graphs found in our Thermal Reference Guide.

Next, we calculate Q/ITD to find the required cooling capacity. Q is the process heat load. ITD, the initial temperature difference, is the difference in temperature between warm return water, (TP+ ΔT) and cold facility water (TF).

Finally, refer to the Liquid Cooling System (LCS) performance curves to determine the facility process flow rate required to achieve calculated Q/ITD.

Example Liquid-to-Liquid Cooling System Calculation

Referencing the LCS performance graph, we can see that a facility flow rate above 2 gpm will meet required performance.

Conclusions for Selecting a Liquid System

Ultimately, the required cooling capacity, temperature stability, set-point temperature, and availability of facility cooling water will dictate which system to use. For further assistance in choosing a cooling system, contact our thermal design engineers to discuss your specific application requirements. Based on inputs such as your heat load and required flow rate, it will even recommend an appropriate product.

Cooling Solution for the Critical SuperCam Assembly of the Perseverance Mars Rover

The SuperCam Module of the Perseverance Mars Rover

NASA’s Perseverance Rover mission is to search for signs of previously or currently habitable conditions on Mars and for signs of past microbial life. The SuperCam utilizes remote-sensing techniques to conduct minerology analysis of both the environment and samples within the robotic-arm workspace. The SuperCam is a technological improvement over Curiosity’s ChemCam, as it adds two new techniques for determining mineralogy a color imager, and an acoustic system to remotely determine physical properties of targets.long tradition The SuperCam includes a broad range of spectroscopy instruments, some of which utilize Thermal Electric Coolers (TECs) that use the Peltier effect to pump heat away from electronics and maintain tight temperature control. The TECs need to reject heat to help protect the electronics vital to minerology observations.

Custom Cryogenic Heat Pipes to Withstand Martian Environments

Heat pipes are a common component in many electronic assemblies used to either spread or transport heat. Many applications use heat pipes to prevent heat build-up and potential damage to sensitive and expensive equipment by quickly moving heat away to cooler regions. While most heat pipes are robust and straightforward; customizations and material selections enable these straightforward solutions to solve more complex challenges, applications and operating environments.

For the Perseverance Rover, maintaining a safe operating temperature of data collection equipment is paramount to the success of the rover. There is no way to do maintenance and repair to the Rover once it’s launched, so thermal management solutions must reliably perform in extreme temperatures common on Mars over the entire lifetime of the rover. Failure is not an option. Boyd’s heat pipes are an ideal solution for space applications like these as they’ve been proven to operate consistently over decades of operation with no active moving parts.

Mars is much colder than Earth but there is less atmosphere, so natural convection air cooling is much slower making electronics at risk of overheating despite the colder environment. This colder environment makes common copper-water heat pipes unsuitable for the Mars Rovers. To solve the performance and environment challenge, Boyd uses our Material Engineering expertise to feature methanol as an alternative working fluid for passive two-phase cooling, which doesn’t freeze at Rover temperatures.

Boyd has previous experience fabricating solutions for Mars missions, making us a solid partner in developing reliable thermal management solutions that meet the demands of reliably performing on Mars. We leveraged our understanding of Martian environment design challenges to create a new heat pipe solution in partnership with Los Alamos National Labs for the SuperCam module. The SuperCam module enables critical imaging, mineral, and chemical analysis, a central portion of the Perseverance Rover mission.

Los Alamos National Labs approached Boyd to help transport a total 6W of heat away from the charge-coupled devices (CCDs, optical detectors) within the SuperCam Module to be transferred to thermoelectric coolers (TECs). As a team, LANL and Boyd developed three heat pipe assembliesto cool 2W each, constructed with two 5mm diameter plated copper-methanol heat pipes. This enables a stable ~20°C of cooling below the temperature of the Rover Accessory Mounting Plate (RAMP).*

One Company, Many Solutions for Space Exploration

Thermal Management is only one of Boyd’s strengths when it comes to supporting space exploration and aerospace applications. From our flame-resistant SOLIMIDE® Insulating Foams to EMI/RFI Management, Boyd can help protect your equipment and cargo in the demanding environments of space with thin atmospheric conditions. Other Engineered Material solutions like Optically Clear Adhesives and High Performance Gaskets protect camera and sensor lenses, sealing and protecting against harsh external environments.

Boyd strives to provide quality, reliable solutions to all industries, but it is a privilege to support the Perseverance Rover and be a part of NASA’s mission to explore Mars. Our long tradition of providing highly engineered thermal management solutions for space exploration will enable the Perseverance Rover to endure for years to come.

Preparing for Launch

As NASA is making final preparations for the launch, Boyd Corporation continues to develop and fabricate solutions for upcoming Martian projects. We’re looking forward to a successful launch on July 22nd (or August 11th at the latest) and the eventual deployment of the Perseverance Rover on Mars in February 2021. Good Luck NASA and thank you Los Alamos National Laboratory for the opportunity to be a part of history!

Are you working on a project that has demanding thermal management requirements or must survive harsh environments? for your challenging applications!

Improving Heat Transfer Between Surfaces and Overall Thermal Performance

This thermal resistance can be expressed as Rja, where:

• Rja – Thermal resistance from the device junction to ambient air or water
• Rjc – Thermal resistance from the device junction to the package case, determined by the electronic device manufacturer (designer has no direct influence)
• Rcs – Thermal resistance from the package case to the heat sink or cold plate, determined by the size and quality of the contact areas between the electronic device and the heat sink or cold plate, the materials used, and contact pressure
• Rsa – Thermal resistance from the heat sink or cold plate to ambient air or water, determined by the heat sink or cold plate design (material and geometry)

Therefore, one way to reduce Rja is to reduce Rcs, the contact resistance between the electronic device case and ambient-cooled, finned heat sinks or liquid-cooled cold plates. There are several factors that impact Rcs, including surface flatness, surface roughness, contact force or clamping pressure, surface cleanliness, and interface materials.

Surface Flatness and Surface Roughness

Table 1:

A mounting surface flatness of 0.001 in/in is generally required for satisfactory contact between the electronic device and the heat sink or cold plate. The surface roughness should be equivalent to that of the electronic device, where 32-64 µin is usually adequate. Finer finishes add unnecessary cost with little or no improvement in thermal performance. Surface flatness is typically much more critical than surface finish in achieving a good thermal interface.

Contact Force

Surface Cleanliness

Thermal Interface Material

Contact Thermal Resistance Factors Review

Contact conditions encompass a number of areas including surface flatness, surface roughness, surface cleanliness, contact pressure, and interface materials. There are many technologies and techniques available for optimizing the thermal path from the electronic device junction to the heat sink. It’s important to minimize the thermal resistance in order to maintain the electronic device temperature below its maximum rated value and increase the end product reliability.

As the COVID-19 pandemic continues to accelerate, the world is faced with new challenges each to combat and overcome the virus. With each rising challenge, companies are coming together to rapidly manufacture the necessary medical supplies and equipment to treat patients properly.

Boyd is prepared and experienced to design and manufacture the thermal systems to support around the clock use of these ventilators. Our Heat Sinks and Heat Pipe Assemblies are built to withstand long term use without fail. These technologies are an efficient, long lasting cooling solutions which incorporates the fast, high-capacity, two-phase heat transfer of heat pipes to remove local hot spots and improve air cooled heat sink efficiency. Heat Spreading Heat Pipe Assemblies reduce heat buildup around electronic components and enable more even heat spreading to maximize airside fin efficiency.

Microplate PCR Seals & PCR Thermal Cyclers

The most common form of testing for COVID-19, is collecting sputum from a throat or nasal swab and conducting a polymerase chain reaction, also known as PCR. From there, the samples are sent to a lab to detect traces of viral RNA.

These test kits are also among the shortage of medical supplies and are the first step to identifying if Coronavirus is present. The kits are composed of PCR plates, tubes & caps, seals, and accessories.

Long term exposure to the elements and various environmental impacts expose medical supplies and devices to a multitude of contaminants that can impact the safety, efficiency, reliability, purity, and life cycle of the device or its components. Boyd has decades of expertise in engineering die-cut, PCR plate seals designed to minimize the impact of unwanted contaminants specific to PCR trays.

PCR Thermal Cyclers amplify DNA by regulating temperature in cyclical programs. It is essential that these PCR devices analyze the data quickly and reliably. Boyd provides technologies specific to these devices include High Capacity Chillers & Heat Pipe Assemblies, Heat Sinks, Noise Vibration/Thermal Insulation and more. To learn more, check out this case study on DNA Cyclers/Thermal Cyclers.

The X-ray generating element in a CT scanner produces vast amounts of X-rays, but in order to protect and maintain safe levels of X-ray exposure, the majority of the X-rays are converted into heat which can be safely dissipated. Liquid cooling is the most compact and efficient method for cooling high density heat loads for applications similar to X-ray machines. Liquids can absorb and transport more heat than air, enabling high performance cooling solutions.

Face Shields

Companies around the world have stepped up to the plate by putting their usual products on hold to manufacture millions of face shields, masks and other medical protective equipment per day. Some health care personnel are making masks from home with store bought fabrics.

For a first line of defense while wearing a N95 face mask, full face shield protectors are used to block fluid, liquid splash, dust, and more. The fluid-resistant full face shield also helps prevent face touching with its wide-angle design. Boyd is currently working with customers around the world to convert the plastic shield protector, the elastic band for the shield, and the adhesive foam pad that helps keep the shield away from the face, allowing room for safety glasses and an N95 mask.

Stay Safe

Boyd is working hard to help provide solutions that battle the COVID-19 pandemic in the best way we know how: quickly creating reliable and cost-effective solutions for our medical customers.

Thermal interface material (TIM) is a crucial part of any thermal management solution. Since it’s physically a small portion of most applications, it’s an easy component to overlook. But thermal interface material can make or break a device and its associated product.

An Introduction on Liquid Pressure Drop and How to Select a Pump

Advancements in technology continue to drive the complexity and functionality of new products. As these products increase in complexity, OEMs are adding more components to meet increasing functionality demands of their customers, which comes at additional cost in materials, manufacturing, logistical complexity, and assembly.

Boyd designs thermal systems for maximum performance at a specific flow rate. Less flow will cause the system to underperform. Flow rate is dependent upon the system’s pressure drop and the pump’s head pressure. This application note reviews how to determine your pressure drop and how to select a pump for your system. It also provides tips on how to minimize pressure drop.

For example; if a system has a CP10 tubed cold plate attached to a 6105 copper heat exchanger with 10 feet of 3/8″ tubing, add the CP10, 6105 and hosing liquid pressure drop curves together. 1-2 psi is a good assumption for standard pressure drop of 10 feet of tubing at 1-2 GPM. When the results are plotted, the graph should look similar to Figure 1.

Selecting a System Pump

In general, the flow rate provided by a pump is inversely proportional to pressure, which means that the flow rate will increase as pressure decreases (see Figure 2). In order to select a pump with appropriate head pressure, the pump curve provided by the pump manufacturer should be plotted over the system pressure drop curve. The system will operate at the intersection of the two curves. In our example, the pump will operate at 1.6 GPM and 13.5 psi (see Figure 3) because the two plotted lines intersect at this point.

If the pressure drop of the system is known for one point, the curve can be estimated by drawing a straight line from no flow and no pressure drop to the known pressure drop point. The line’s intersection with the pump curve provides a good estimate of the expected flow rate. In our example, assume a system pressure drop number of 2 GPM and 18 psi is known (see Figure 4). Using this method, the estimated system flow rate is 1.5 GPM, close to the 1.6 GPM determined using the more precise method.

Minimizing Pressure Drop

In most cases minimal pressure drop through a system is desirable. Some tips on how to reduce pressure drop are:

• When feasible, keep the number of 90° bends to a minimum. Like a kink in a garden hose, a sharp bend causes pressure drop.
• Keep hose lengths as short as possible. Longer hose or tube lengths create greater surface area that is in contact with the fluid and causes additional fluid friction and pressure drop.
• Work with large diameter hoses. Ever try to drink through a narrow coffee stirrer? The small diameter makes you work much harder than you would with a regular straw.
• Where possible, use a fluid that has low viscosity. Fluid viscosity is a liquid’s ability to flow (think about water as opposed to molasses). Using a liquid that has high viscosity will adversely affect the pressure drop of your system.
• Quick disconnect fittings should be avoided, as they often cause unnecessary loss of pressure.

Remember the importance of pressure drop and match the pump curve to your system pressure drop curve. The pressure drop can be minimized by removing the kinks; avoiding long and thin hoses; and keeping the system on the same level. Follow these simple steps and your thermal solution will deliver the promised performance.

What is Thermal Interface Material?

Many engineers focus more on heat sink design but often forget to spend time considering how heat gets from the heat source to the heat sink. Even the smoothest surface has some level of surface roughness. The roughness of two surfaces in contact with each other creates air pockets. Since air is a good thermal insulator, air pockets from mating surface roughness impedes heat transfer from one surface to another.

In the image below, heat coming from the black surface can only conduct through to the grey heat sink at the points highlighted in red. Orange arrows help visualize that heat is coming from the entire black surface but is restricted through these contact points. Air pockets are represented in light blue. Heat can transfer through the blue air pockets, albeit highly inefficient and very little compared to the level of conduction through the red contact points.

This is applicable for any electrical device, commonly enclosed in a case, that transfers heat to a metal heat sink without a thermal interface material.

What does Thermal Interface Material do?

This is where using thermal interface material comes in. TIM replaces most of these air pockets with a material optimized for better thermal conductivity. By using thermal interface material, we increase how much heat is transferred away from the heat source and into the heat sink.

In the diagram below, dark blue represents thermal interface material. Most of the light blue air pockets have been eliminated and replaced with a more conductive material. Heat is now efficiently conducting across the entire surface. This improves heat transfer away from the heat source significantly. It’s nearly impossible to remove 100% of air in most cases so there are still small air pockets in little nooks and crannies. But the thermal performance in this instance is greatly improved to the scenario with no TIM present.

Thermal interface material comes in many different formats and options: electrically isolating or electrically conductive, silicone base or silicone free, compliant or hard, solid or liquid or both, etc. TIM selection is a very application specific decision.

Learn More about Thermal Interface Materials

Learn more about the different types of Thermal Interface Materials, typical options available for each, and common uses for them. Or estimate the impact of adding different thermal interface materials in Boyd Genie in your air cooled heat sink application.

Key Factors that Determine the Cost of Fabricating Heat Exchangers

Manufacturing costs can be greatly impacted by demand, but this is not necessarily within the thermal or design engineers’ control. However, you can reduce costs by understanding how core and frame materials, interface tolerances, coatings, and other requirements can affect the cost of a heat exchanger. By involving your heat exchanger manufacturer early in the design process, you’ll be able to identify the manufacturing cost drivers and select the most cost effective design.

Core and Frame Materials

Core and frame material specifications can add significantly to the cost of a heat exchanger. The core, which may consist of tubes, fin, and/or sheet metal, can be manufactured using a variety of metals. The metals most commonly used in heat exchangers are copper, aluminum, and stainless steel. The cost of these metals has risen significantly over the past several years, making their percent of the total heat exchanger cost even greater. Since stainless steel is more expensive than copper or aluminum, it makes sense to opt for copper or aluminum unless your application requires stainless steel. Heat exchangers may also be manufactured using nickel, cupronickel, hastelloy®, inconel®, titanium, or other metals. However, these metals are not used as frequently due to their higher costs.

Usually the core’s materials are specified to ensure that fluid path metals are compatible with the coolant selected for the application. For example, stainless steel might be specified for use with deionized water, whereas cupronickel might be specified for use with saltwater. Heat exchanger core material may also be selected based on weight. Aluminum and titanium are preferential for military and aerospace applications since these metals are less dense.

Core costs can also vary based on the type of heat exchanger selected. Cost variations are due to the different amounts of materials required to make the specific heat exchanger as well as the amount of factory time required to manufacture the part. The least expensive type of heat exchanger to manufacture is a copper tube-fin heat exchanger. Stainless steel tube-fin heat exchangers are more expensive than copper because stainless steel is more expensive by weight, it requires more time to punch, and it must be welded. Like tube-fin heat exchangers, vacuum-brazed flat tube oil cooler heat exchangers are relatively easy to produce. Conversely, the most expensive type of heat exchanger to produce is a vacuum-brazed plate-fin heat exchanger.

Other heat exchanger specifications that can add cost are the materials and processes used to attach the heat exchanger’s frame to the core. Pop rivets are the least expensive option, followed by screws and then welding. Screws will provide a bit more strength than pop rivets. Flat tube heat exchanger frames are generally attached with rivets or welding. With welding, the result is an even stronger and more reliable part that is better able to handle shock and vibration. Welding is also preferable when space and weight are concerns, such as with plate-fin heat exchangers that are used in weight sensitive applications (e.g. airborne applications). Welding eliminates the need to use rivets, which can add weight. In addition, rivets may require a larger heat exchanger frame than welding does since the rivets need a wide section of metal to pass through and effectively hold the heat exchanger frame and core together. Due to additional factory time involved in the welding process, however, welding is more expensive than the other two methods.

Interface Tolerances for Installing Heat Exchangers

After core and frame materials, interface tolerance specifications for mounting and plumbing features are the next biggest cost drivers. For mounting features, the most cost effective approach is to design mounting features into individual sheet metal components. This will yield tolerances ranging from ± 0.03″ to ± 0.06″ ( ±0.076cm to ± 0.1.52 cm). If tighter tolerances are needed, the product will have to be machined during the final production stages, which will require additional machine time. The heat exchanger is also at risk of contamination from metal chips or coolant from machining, so extra care must be taken. This additional machining step can therefore add significantly to the cost.

Normal plumbing tolerances are ± 1/8″- ± 3/16″ (± 0.318 cm to ± 0.476 cm) for copper tube fin heat exchangers and ± 1/8″ (± 0.318 cm) for stainless steel and aluminum products. If tighter tolerances are required for plumbing, more expensive tooling and an increase in labor and inspection time will also be required. Off-the-shelf plumbing fittings are the least costly, however, they have looser tolerances. A beaded tube fitting that mates with a 3/8″ (0.953 cm) ID hose and is secured with a clamp does not require tight tolerances, so opting for this type of fitting may help to keep costs low. The most expensive fitting options are custom machined fittings.

Coatings for Heat Exchangers and Cold Plates

Finishes to Protect Thermal Management Solutions

Electrodeposition or E-Coat

A third coating method that provides corrosion protection is called an e-coat, also known as electrodeposition or electrocoating. A DC charge is applied to a metal part immersed in a bath of oppositely charged paint particles. The paint particles are drawn to the metal part and paint is deposited on the part, forming an even, continuous film over the entire surface. Of the four types of coatings described here, it is the most expensive type of corrosion protection.

Heat Exchanger Coatings

Another significant cost driver is heat exchanger coatings for corrosion protection or for cosmetic purposes. Coating for corrosion protection is most common on aluminum heat exchangers, since aluminum corrodes more easily than other metals. There are several types of heat exchanger coatings to minimize corrosion: chemical conversion coating, anodization, e-coating, and painting.

One of the most widely used coating options is chemical conversion coating or chromate conversion coating, also known as “Chem Film”, that minimizes surface oxidation. Most government and commercial heat exchanger engineering specifications require that aluminum be chemical conversion coated (per military standard MIL-DTL-5541F, previously MIL-C-5541E).

In addition to Chem Film, another option that can be used to protect aluminum is anodization. Anodizing minimizes corrosion and abrasion by modifying the crystal structure close to the metal surface. It produces a harder part with even greater corrosion protection. However, it is not a common coating and it’s more expensive than chemical conversion coating.

A third coating method that provides corrosion protection is called an e-coat, also known as electrodeposition or electrocoating. A DC charge is applied to a metal part immersed in a bath of oppositely charged paint particles. The paint particles are drawn to the metal part and paint is deposited on the part, forming an even, continuous film over the entire surface. It is the most expensive type of heat exchanger corrosion protection.

Heat exchangers may also be coated with paint for corrosion protection or cosmetic purposes. For example, copper heat exchangers are sometimes painted for aesthetics since uncoated copper may change color over time. For epoxy paint applications, the cost per heat exchanger can range from $10-$200 per heat exchanger. The cost of the paint application will depend not only on the coating itself, but also on the amount of surface area to be coated. Weigh the value of the added corrosion resistance or improved appearance against cost to determine to opt for coating or painting. How long do you want your heat exchanger to last? Will your heat exchanger be visible and how important to your end users is heat exchanger appearance? The appearance of a heat exchanger on equipment in a hospital is likely to be more important than the appearance of a heat exchanger on equipment in a factory.

Heat Exchanger Design and Manufacturing Partnerships

Working with a heat exchanger manufacturer early in the design stage or being flexible on a build to print design will allow for the greatest amount of cost savings. Although the biggest cost driver in heat exchanger manufacturing is annual demand, there are many other factors over which thermal and/or component engineers have some control. Ensure that there is a reason for every specification, as every specification may drive up cost. When core and frame materials, tolerances, and coating specification are outlined, it’s important to determine whether they are necessary for the application or not. In addition, it’s important to realize that there are many alternatives in heat exchanger design as well as the manufacturing processes used, both of which impact cost.