Industry Developments for Cooling Overclocked CPUs

By Norman Quesnel, Senior Member of Marketing Staff
Advanced Thermal Solutions, Inc.

(This article will be featured in an upcoming issue of Qpedia Thermal e-Magazine, an online publication dedicated to the thermal management of electronics. To get the current issue or to look through the archives, visit http://www.qats.com/Qpedia-Thermal-eMagazine. To read other stories from Norman Quesnel, visit https://www.qats.com/cms/?s=norman+quesnel.)

Almost as long as personal computers have been around, users have been making modifications “under the hood” to make them run faster. A large segment of these users are overclockers, who make adjustments to increase the clock speeds (the speed at which processors execute instructions) of their CPUs and GPUs.

Many PC gamers get into overclocking (OC) to make their programs run faster. Gamecrate.com, a gamer site, defines overclocking as the practice of forcing a specific piece of hardware to operate at a speed above and beyond the default manufactured rating. [1]

To overclock a CPU is to set its clock multiplier higher so that the processor speeds up. For example, overclocking an Intel Core i7 CPU means to push its rated clock speed higher than the 2.80 GHz that it runs at “out of the box.” When performed correctly, overclocking can safely boost a CPU’s performance by 20 percent or more. This will let other processes on a computer run faster, too.

Cooling Overclocked CPUs

Fig. 1. An Intel Core i5-469k Processor Can Be Overclocked to Run 0.5-0.9 GHz over Its Base Frequency. Air Cooling is Provided by a Hyper D92 from Cooler Master.[2]

To serve the global overclockers market, some chip makers keep the door open to overclocking by allowing access to their multipliers. They do this with a variety of “unlocked” processors. Intel provides many unlocked versions of their processors, as denoted with a ‘k’ at the end of their model number.

For example, the Skylake Core i7-6700k and Haswell-E Core i7-5820k are made with unlocked clock multipliers. In fact, Intel targets overclockers with marketing campaigns and support services.

Fig. 2. Intel Actively Targets Overclockers with Its Unlocked Processors.[3]

Besides gaming, overclocking can improve performance for applications such as 3-D imaging or high-end video editing. For GPUs, faster speeds will achieve higher frames per second for a smoother, faster video experience. Overclocking can even save money, if a lower cost processor can be overclocked to perform like a higher end CPU.[4]

For many gamers, overclocking enhances their enjoyment by giving more control over their system and breaking the rules set by CPU manufacturers. One overclocker on Gamecrate.com said, “Primarily, I like to do it because it’s fun. On a more practical note it’s a great way to breathe some life into an old build, or to take a new build and supercharge it to the next level.”[1]

Heat Issues from Overclocking

Overclocking a processor typically means increasing voltage as well. Thus, the performance boost from overclocking usually comes with added component heat that needs to be controlled. Basically, the more voltage added to components, the more heat they are going to produce. There are many tutorials on overclocking and most of these resources stress that it’s essential to manage a component’s increased heat.[5]

Programs are available that monitor the temperature of a processor before and after overclocking it. These programs work with the DTS, digital thermal sensors that most processor manufacturers include inside their component packages. One such program is Core Temp, which can be used with both Intel and AMD cores. Some component OEMs also offer their own software to monitor temperatures in their processors.[6]

Fig. 3. The Core Temp Program Can Display Temperatures of Individual Cores in a System.[6]

Typically, an overclocker will benchmark a CPU or other component to measure how hot it runs at 100 percent. Advanced users can manually do the overclocking by changing the CPU ratio, or multiplier, for all cores to the target number. The multiplier works with the core’s BCLK frequency (usually 100) to create the final GHz number.

Tools like the freeware program Prime95 provide stability testing features, like the “Torture Test,” to see how the sped up chip performs at a higher load. These programs work with the system’s BIOS and typically use the motherboard to automatically test a range of overclocked profiles, e.g. from 4.0-4.8 GHz. From here, an overclocker may test increasing voltages, e.g. incrementally adding 0.01 – 0.1 V while monitoring chip stability.

An overclocked component’s final test is whether it remains stable over time. This ongoing stability will mainly be influenced by its excess heat. For many overclocked processors, a robust fan-cooled heat sink in place of the stock fan is essential. For others, only liquid cooling will resolve excess heat issues.

Fan Cooling

The advantage of using air coolers is no worry about leaking, which may lead to component or system damage. With the air cooled heat sinks, the bigger and faster the fan (CFM), the better, and there are a multitude of fan-sink cooling solutions that gaming PCs can accommodate.

In reality, higher performance fan-cooled sinks typically also employ liquid. It is used inside heat pipes that more efficiently convey heat from the processor into the sink’s fan cooled fin field.

Fig. 4. The Top-Rated Hyper 212 EVO CPU Air Cooler from Cooler Master Has Four Heat Pipes Transferring Heat to Aluminum Fins.[7]

Air cooled heat sinks for overclockers cost well under $50 and are available from many sources. They’re often bundled with overclock-ready processors at discounted prices.

A greater issue with air cooling can be the fan noise. A high performance fan must spin very quickly to deal with heavy system workloads. This can create an unpleasant mixture of whirs, purrs and growls. Many of the gaming desktops generate 50-80 decibels of noise at load. Though most fans are quieter, pushing out 25-80 CFM, they are louder than most standard PC processor fans.[8]

Liquid Cooling

Liquid cooling has become more common because of its enhanced thermal performance, which allows higher levels of overclocking. Prices are definitely higher than air-cooled heat sinks, but liquid systems offer enthusiasts a more intricate, quieter, and elegant thermal solution with definite eye-appeal.

From the performance standpoint, liquids (mainly water in these systems) provide better thermal conductivity than air. They can move more thermal energy from a heat source on a volume-to-volume basis.

Fig. 5. The Top-Rated Nepton 280 Liquid CPU Cooler Has a Fast Pump Flow and a Large Radiator Cooled with Dual Fans that Reach 122 CFM Airflow.[9]

A typical liquid cooling system features a water block that fits over the overclocked CPU, a large surface area, a fan-cooled heat exchanger (radiator), a pump, and a series of tubes connecting all elements. One tube carries hot fluid out from the water block, the other returns it once it is cooled by the radiator. Some liquid cooling systems can also be used on multiple processors, e.g. a CPU and a gaming chipset.

While there are more components to a liquid cooling system, there are also major advantages. For one, the water block is usually much smaller and lower-profile than an attached, high-performance air cooler. Also, the tubing set up allows the heat exchanger and pump to be installed in different locations, including outside the PC enclosure. An example is the Sub-Zero Liquid Chilled System from Digital Storm. It unlocks overclocks of Intel’s i7-980X CPU up to 4.6 GHz while idling the processor below 0°C.[10]

Fig. 6. Digital Storm’s Cryo-TEC System Places an Overclocked CPU in Direct Contact with Thermo-electric Cold Plates Dropping Core Temperatures to Below 0°C.[11]

Prices for liquid cooling systems can easily surpass $200, though newer systems can be bought for under $100.

A fan still must be attached to the radiator to help cool it, but it doesn’t have to spin as quickly as it would if it were attached to a heat sink. As a result, most liquid-cooled systems emit no more than 30 decibels.

Conclusion

Overclocking can be considered a subset of modding. This is a casual expression for modifying hardware, software or anything else to get a device to perform beyond its original intention. If you own an unlocked CPU you can get significant added performance, for free, by overclocking the processor. When modifying processor speeds, i.e. increasing them, high temperatures will occur. Higher performance cooling solutions are needed.

Fig. 7. YouTube Video of Overclocked CPU Melting Solder Before It Stops Working at 234°C.[12]

To serve the world of overclockers, a steady stream of air and liquid cooling systems are being developed. Many of them are high precision, effective, stylish and surprisingly affordable. Often they share the same technology as mass market quantity, lower performing cooling systems (basic heat sinks, heat pipes, for example), but provide much higher cooling capabilities for ever-increasing processor speeds.

References
1. Gamecrate.com, https://www.gamecrate.com/basics-overclocking/10239
2. Techreport.com, http://techreport.com/review/27543/cooler-master-hyper-d92-cpu-cooler-reviewed/3
3. Legitreviews.com, http://www.legitreviews.com/intel-devils-canyon-coming-this-month-intel-core-i7-4790k-core-i5-4690k_143234
4. Digitaltrends.com, http://www.digitaltrends.com/computing/should-you-overclock-your-pcs-processor/
5. Techradar.com, http://www.techradar.com/how-to/computing/how-to-overclock-your-cpu-1306573
6. Alcpu.com, http://www.alcpu.com/CoreTemp/
7. Coolermaster.com, http://www.coolermaster.com/cooling/cpu-air-cooler/hyper-212-evo/
8. Digitaltrends.com, http://www.digitaltrends.com/computing/heres-why-you-should-liquid-cool-your-cpu/
9. Coolermaster.com, http://www.coolermaster.com/cooling/cpu-liquid-cooler/nepton-280l/
10. Gizmodo.com, http://gizmodo.com/5696553/digital-storms-new-gaming-pcs-use-sub-zero-liquid-cooling-system-for-insane-overclocks
11. Digitalstorm.com, http://www.digitalstorm.com/cryo-tec.asp
12. Youtube.com, https://www.youtube.com/watch?v=9NEn9DHmjk0

For more information about Advanced Thermal Solutions, Inc., its products, or its thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

#WeOwnTheBoard: ATS Has Thermal Solutions to Cover the Whole Board

We Own The Board

Advanced Thermal Solutions, Inc. (ATS) has an extensive line of heat sinks and board level thermal solutions that allow ATS engineers to work with industry-leading components and solve the industry’s toughest thermal challenges. (Advanced Thermal Solutions, Inc.)

Advanced Thermal Solutions, Inc. (ATS) has an extensive product line of innovative, off-the-shelf and custom heat sinks and attachments that provides the broadest range of designs to meet the demanding thermal challenges presented by today’s high-powered electronics. Led by its patented maxiFLOW™, which provides the highest thermal performance for physical volume it occupies compared to other heat sinks on the market, ATS has a solution to meet any thermal problem.

In addition, ATS engineers have world-renowned expertise in thermal management and are capable of designing liquid and air cooling solutions using heat sinks, heat pipes, heat exchangers, fans, and cold plates. ATS has more than two decades of solving the industry’s toughest thermal challenges and have a proven record of success in handling the industry’s leading components.

From the latest generation of Intel processors to Altera’s high-powered Stratix FPGA to Qualcomm’s ARM processors to Texas Instruments, Nvidia, NXP, Cavium, and many more, ATS has the experience, the analytical capability, and the products to provide you with the necessary thermal management.

Board Level Solutions

maxiFLOW™ – maxiFLOW™ heat sink design provides the highest thermal performance for the physical volume that it occupies as compared to other heat sink designs. maxiFLOW™ heat sinks are ideally suited to meet the thermal requirements of a broad range of electronics packages, including: BGA, QFP, LCC, LGA, CLCC, TSOP, DIPs and LQFP.

Straight Fin – ATS offers a large variety of high performance Straight fin heat sinks that can be used in many applications where the direction of the airflow is clearly defined. The straight fin heat sink can be utilized in areas where the maxiFLOW™ flair-fanned cannot be used, providing an excellent alternative for cooling thermally sensitive devices.

Cross-Cut – Electronics packages are numerous and range from BGA, QFP, LCC, LGA, CLCC, TSOP, DIPs, LQFP and many others. ATS offers a large variety of cross cut heat sinks that can be used in a variety of applications where the direction of the airflow is ambiguous. The cross cut allow for the heat sink to receive air from any direction.

Pin Fin – Electronics packages are numerous and range from BGA, QFP, LCC, LGA, CLCC, TSOP, DIPs, LQFP and many others. ATS offers a large variety of cross cut heat sinks that can be used in a variety of applications where the direction of the airflow is ambiguous. The cross cut tape on allow for the heat sink to receive air from any direction and can be easily attached to the device by a thermally conductive tape.

fanSINK™ – In many electronic systems, such as telecomm and datacom chassis, or 1U, 2U servers and blades, the system air flow rate is not adequate for cooling of high power devices. Therefore, additional air flow introduced at the device level is required. ATS offers a large family of fanSINK™ products for applications where FPGA or ASICs in BGA packages are deployed. ThefanSINK™ can be either clipped on to the device by maxiGRIP™ or superGRIP™ heat sink attachment technologies or taped on.

Power Brick – DC/DC power converters are an essential part of PCB design and their performance requires a stable temperature for optimum performance. ATS has produced a broad array of high performance power brick heat sinks, based off of the patented maxiFLOW™ design, to effectively cool DC/DC power converters and power modules deployed in a host of electronics applications. ATS’ power brick heat sinks are available in full, half, quarter and eighth packaging.

pushPIN™ – With over 108K different push pin heat sink assembly configurations, ATS offers the largest push pin heat sink offering in the market. Select from fine and ultra-fine pitch heat sinks designed for high velocity air flows and coarse pitch heat sinks for low velocity air flow conditions. Offered in straight fin, cross-cut and the ultra performance maxiFLOW™ fin geometries, ATS pushPIN™ heat sink line is suited to meet a wide variety of applications for components ranging in size from 25mm-70mm. Push pins are offered in brass and plastic and are packaged with different compression springs to achieve precise force required for secure attachment.

blueICE™ (Ultra Low Profile) – In many electronics systems, such as Telecomm, Datacomm, Biomedical equipment and others, card-to-card spacing is small, yet stringent thermal requirements remain the same. Electronics packages such as BGA, QFP, LCC, LGA, CLCC, TSOP, DIP, LQFP are commonly used with stringent thermal requirements in a tight space with limited airflow. Ultra low profile heat sinks offered by ATS range from 2 to 7mm in height and are ideally suited for tight-space application electronics since they offer the best thermal performance. Their thermal resistance is as low as 1.23° C/W within an air velocity of 600 ft/min.

Standard Board Level – ATS’ high quality, low cost, aluminum stamped heat sinks are ideal for low power thermal management solutions. The simple design and manufacturing of these heat sinks allows high volume manufacturing and reducing assembly costs. Stamped heat sinks are ideally used for TO packages and other power devices.

Extrusions – Aluminum extrusions are the most cost-effective solutions for the majority of electronic cooling applications. ATS offers a wide variety of aluminum profiles used for heat sink fabrication and other aluminum applications. Whether you are seeking a standard extrusion profile or the expertise from our design team to create a new and innovative profile, ATS has the capabilities and expertise to meet your requirements.

Heat Sink Attachments

superGRIP™ – superGRIP™ is a two component attachment system which quickly and securely mounts heat sinks to a wide range of components, without needing to drill holes in the PCB. superGRIP™ provides a strong, even attachment force with minimal space required around the components perimeter, making it ideal for densely populated PCBs. superGRIP™ is available with ATS maxiFLOW™ heat sink and straight fin heat sinks.

maxiGRIP™ – maxiGRIP™ is a unique, two component attachment system which quickly and securely mounts heat sinks to a wide range of components, without needing to drill holes in the PCB. The steady, even attachment force provided by maxiGRIP™ allows the heat sink and thermal interface material to achieve maximum thermal performance. maxiGRIP™ is available with ATS maxiFLOW™, straight fin, fanSINK™ and device specific heat sinks.

Thermal Tape
– The interface material plays a pivotal role in transporting the heat from the component to the heat sink. The tape is applied to the base of the heat sink and then the heat sink is attached to the component. For tape to work well, proper cleaning of the component surface and the base of heat sink is required. Also, it is usually necessary to apply the tape with a certain amount of pressure.

How Did Thermal Performance of Aluminum Heat Sink Compare to Copper?

Advanced Thermal Solutions, Inc. (ATS) was recently tasked with creating a more cost-effective and lighter solution for a customer that was looking to replace a relatively large heat sink, which was dissipating the heat from four components on a printed circuit board (PCB). The customer did not want a skived heat sink, so ATS engineers created a custom aluminum heat sink embedded with copper heat pipes to draw the heat away from the components.

Aluminum Heat Sinks

ATS engineers worked on a comparison of a copper heat sink with an aluminum heat sink that had embedded heat pipes running above the components. Analysis showed that the aluminum heat sink nearly matched the thermal performance of the copper and was within the margin required by the client. (Advanced Thermal Solutions, Inc.)

ATS engineers used analytical modeling and CFD simulations to examine the thermal performance of two aluminum heat sink designs: one with heat pipes that stopped at the edge of the components and the other with heat pipes that ran above the components. Analysis demonstrated that the design with heat pipes running above the components kept junction temperatures within 2°C of the original copper heat sink and an average difference of less than 1°C.

Peter Konstatilakis, a Field Application Engineer at ATS who worked with the client on this analysis, sat down with Marketing Communications Specialist Josh Perry to discuss the technical details behind the thermal analysis and the results that were presented to the customer.

JP: Thanks for taking the time to talk about this project Peter. What was it that they approached you with? What was the problem or the challenge?
PK: There was a long lead time with sourcing this copper; it’s a relatively large and heavy part.  This size bar of copper isn’t typically stocked. So, we were having sourcing issues with this non-standard copper stock and they were having weight and cost issues. They had to cut this heat sink in half for testing because they were overweight on the board. Through shock and vibe testing, if the heat sink is too heavy then it can actually rip out of the board.

An alternative was to make the heat sink through a manufacturing process called skiving. Skived heat sinks have a fin count tolerance, so you may have more fins than are specified or you might have less fins, and some of the fins may be curved, which poses cosmetic issues with skived heat sinks; the fins aren’t perfectly straight. It’s not really an issue thermally, especially if companies don’t see the heat sinks too often, but this client’s customers see the boards, see the heat sinks, and they wanted them to look perfect.

Instead of having to get this copper, we thought, why don’t we make an aluminum heat sink with heat pipes? That’s sort of where this came from.

JP: So the problem with skiving a heat sink was mostly an issue with aesthetics?
PK: Yeah, exactly. The tolerance on the fin spacing was +/- three fins, due to the high number of fins. I did a quick analytical analysis with our heat sink calculation tool and the difference in thermal resistance was maybe 1%. That was because the heat sink has such a large surface area and losing a fin or two only changes the performance by a percent or less. On a smaller heat sink, you will see a greater difference. I told the customer but they said that they still didn’t want to go with skived for aesthetic reasons. Instead, we extruded aluminum and then we put heat pipes in the base.

JP: Why was it necessary to add heat pipes to the heat sink?
PK: The big thing, in this case, is the spreading. You can see the locations of the components and then how large the heat sink is. There’s definitely a lot of spreading resistance in the base because there’s so much distance between the heat sink and all the components, so that’s the main issue that we were trying to take care of with the heat pipes. An aluminum heat sink with heat pipes is definitely a lot lighter than a copper heat sink, about three times lighter. Overall it’s much easier to source and also much cheaper. I think it’s again about three times as much for copper.

JP: When this challenge came across your desk, what was the first thing that you looked at? How did you approach the challenge?
PK: What I did was look at our analytical tool again and I modeled this heat sink in all copper. Since there are four components it’s a little complicated, but I modeled them as one component in the middle of the heat sink with gap pad and everything and got the performance of that heat sink. Once I did that, I ran CFD simulations on the copper heat sink with the components placed as they are in the application and the performance values were within 15%. So, doing that, we knew that we had a good CFD model.

After running the baseline simulations on the copper, I moved onto the aluminum heat sink knowing that we had a good CFD model and that we could trust the results. I used the aluminum heat sink and put heat pipes in the base. I started with heat pipes out in front of the components and then the next simulation was with heat pipes above the components. Obviously, if the heat pipes are above the component then you’ll get a little better spreading resistance and the heat will flow better.

Aluminum Heat Sinks

The first of two aluminum heat sink designs had heat pipes that stopped at the components. This design was not as effective as when the heat pipes ran above the components. (Advanced Thermal Solutions, Inc.)

JP: How significant of a difference was it?
PK: From the base line of the copper heat sink, it was around a 1-2°C difference, on average.

After looking at these two simulations, I met with Dr. Kaveh Azar (founder, CEO and President of ATS) to discuss the results. With the heat pipes above the components, we were seeing an average difference of less than 1%. It performs worse by less than 1% and I’m currently doing a couple of other simulations to see if we can improve that by adding more heat pipes, making the heat pipes wider, or even running less conservative heat pipes since the conductivity I’m running with is 2000 W/m-K axially and 400 W/m-K through the cross section. Really, the axial conductivity should be around 20,000-50,000 W/m-K, and the copper wall and wick effective conductivity is around 100-200 W/m-K due to the low conductivity of the porous copper sintered wick. The conservative values I used were to get the simulation up and running, while I’ll end up analytically determining the respective heat pipe conductivity.

I’m also doing an all-aluminum simulation just so we can see what that looks like and so we can see how much better the copper heat sink is in general.

This turned into just looking at the heat sink and trying to put heat pipes in them to seeing if we could also vary the length and see if we could get better performance. Your pressure drop increases as the length increases, so the higher the pressure drop then the lower the air flow is going to be in the system, the lower the airflow then the lower the performance. There is sweet spot for the length. I’m looking at that with our analytical calculator. And then the base thickness as well, we’re looking at that too.

Aluminum Heat Sinks

The results of the CFD analysis showed that the average temperature difference between the copper and the second aluminum heat sink design was less than one degree. (Advanced Thermal Solutions, Inc.)

JP: With the aluminum heat sink within 1% of the copper, did that make switching from copper worth it for the customer?
PK: It definitely did. If you’re within 1% and the customer has a little margin already, then it’s worth it because it’s three times lower cost, lower weight, and it will look better because it’s extruded rather than skived.

JP: Just to clarify, what is the difference between skiving and extruding?
PK: Extruding, basically, is pushing a hot piece of metal through a die that is in the shape of a heat sink, so it’s like putting play-doh through a die. You get a heat sink with the fin pitch and everything, where skiving uses a copper block and they come in with a blade and peel the fin out. The blade comes in and pushes a layer up. You can skive aluminum as well and they’re about the same cost, but you can’t extrude copper for a heat sink.

This showed our thermal capability to the customer. It showed that we can design custom heat sinks. We can make them more cost-effective, better performing, whatever they need.

JP: When you’re working through these types of challenges, how much of it becomes a foundation of knowledge that you can then take to another customer’s project?
PK: The more experience that you have, the better. Like any field, the more experience you have then you can look at something and know right off the bat if it’s going to work or not. It also helps in terms of understanding how to model certain applications and where to start with the design.

JP: Did we run these simulations here or did we have (ATS engineer) Sridevi Iyengar run the simulations in India?
PK: We did it here. Sri does a lot, but she uses FloTHERM and I’m quicker with Autodesk CFDesign. FloTHERM can be used for bigger systems because it takes less of a mesh. Generally, FloTHERM only works in rectangular coordinates, where CFDesign works with tetrahedrons, allowing the simulation of angled objects. Since it works with tetrahedrons though, it takes longer to mesh and run than FloTHERM. You can’t really have anything angled in FloTHERM and obtain accurate results. We ended up having to angle the heat pipes in order to contact the components, which are in a different plane than the rest of the heat sink.

JP: I know it is a priority at ATS, but why was it important to have an analytical component, not just CFD, in finding a solution?
PK: Analytical modeling is used to ensure that the CFD results make sense. When you see the graphs from CFD, it looks appealing to the eye and you get drawn to it. It’s science and engineering that is made visible, whereas heat transfer and fluid dynamics (for air) are invisible to the naked eye. Another method of ‘seeing’ heat transfer is using an infrared thermal camera or liquid crystal thermography, while a water tunnel or inducing smoke into the flow can be used to see fluid flow. The analytical also gives us a good first judgement and solid design direction.

Optimization for the length of the heat sink and the base thickness, I did with our analytical tool. CFD simulations take a lot of time, so I can narrow down the number of designs and determine what we want to simulate. Rather than doing 10 different simulations, when each takes on average three or four hours, I can get instant results and say, okay, a 5 mm base is the sweet spot, so let me try in CFD 4 mm thickness, 5 mm, and 6 mm; narrowing it down to three simulations.

Analytical modeling gives us quick what-if scenarios, which we say a lot, and it definitely helps give you an understanding of what to expect. If the numbers are way off then I know something is wrong in the CFD model and I check to see if my mesh and other parameters are correct. It humbles you almost and it helps you understand the application and what you’re simulating. The last thing you want to do is give a customer incorrect data.

It gives you two independent solutions. We say analytically this solution is validated, so we have faith in the model. Now, here is the model and it shows better what we want to do.

To learn more about Advanced Thermal Solutions, Inc., visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

#JustChilling: ATS Recirculating and Immersion Chillers for Liquid Cooling Systems

ATS Chillers

Advanced Thermal Solutions, Inc. has a line of recirculating and immersion chillers for conditioning the coolant in liquid cooling systems. (Advanced Thermal Solutions, Inc.)


ATS offers a variety of chillers, including the CHILL V and CHILL iM series, for conditioning the coolant in liquid cooling systems. The ATS-CHILL V series, including the ATS-Chill150V, ATS-Chill300V, and ATS-Chill600V, are re-circulating, vapor compression chillers that offers precise coolant temperature control using a PID controller. The ATS-CHILL iM is an immersion chiller for precise control of the bath temperature by immersing the evaporator in a fluid bath.

Learn more about ATS recirculating and immersion chillers in this recent blog post or in the video below:

ATS Liquid Cooling Products

In addition to chillers, ATS has a complete product offering for Liquid Cooling Closed Loop Systems, including flow meters, leak detectors, heat exhangers, and cold plates. ATS can also design off-the-shelf or custom liquid cooling systems to meet the thermal needs of a project.

ATS 3-Core design approach identifies the type of cooling required at the analysis level and informs the client of its options, saving cost and time on design iteration and simulation verification. Once it is determined that liquid cooling is the option to pursue, the ATS design team identifies all the required components of the liquid loop, as well its packaging requirements and integration in the system.

ATS offers a complete array of off-the-shelf liquid loop components that can be readily deployed or custom-designed to meet the thermal requirements of the system. Subsequent integration of the liquid loop into the system provides the customer with a turn-key option for thermal management of their system.

Don’t get burned! Take advantage of ATS expertise in liquid and air cooling to ensure proper thermal management for your project.

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

Cold Plates and Recirculating Chillers for Liquid Cooling Systems

Recirculating Chillers

ATS cold plates and recirculating chillers can be used in closed loop liquid cooling systems for high-powered electronics. (Advanced Thermal Solutions, Inc.)


The miniaturization of high-powered electronics and the requisite component density that entails have led engineers to explore new cooling methods of increasing complexity. As a result, there is a growing trend in thermal management of electronics to explore more liquid cooling systems and the reintroduction, and re-imagining, of cold plate technology, which has a long history that includes its use on the Apollo 11 space shuttle.i

Thermal management of high-powered electronics is a critical component of a design process. Ensuring the proper cooling of a device optimizes its performance and extends MTBF. In order for a system to work properly, engineers need to establish its thermal parameters from the system down to the junction temperature of the hottest devices. The use of cold plates in closed loop liquid cooling systems has become a common and successful means to insure those temperatures are managed.

Cold plate technology has come a long way since the 1960s. At their most basic level, they are metal blocks (generally aluminum or copper) that have inlets and outlets and internal tubing to allow liquid coolant to flow through. Cold plates are placed on top of a component that requires cooling, absorbing and dissipating the heat from the component to the liquid that is then cycled through the system.

In recent years, there have been many developments in cold plate technology, including the use of microchannels to lower thermal resistanceii or the inclusion of nanofluids in the liquid cooling loop to improve its heat transfer capabilities.iii

An article from the October 2007 issue of Qpedia Thermal eMagazine detailed the basic components of a closed loop liquid cooling system, including:

• A cold plate or liquid block to absorb and transfer the heat from the source
• A pump to circulate the fluid in the system
• A heat exchanger to transfer heat from the liquid to the air
• A radiator fan to remove the heat in then liquid-to-air heat exchanger

The article continued, “Because of the large surface involved, coldplate applications at the board level have been straight forward…Design efforts for external coldplates to be used at the component level have greatly exceeded those for PCB level coldplates.”

Exploring liquid cooling loops at the board or the component level, according to the author, requires an examination of the heat load and junction temperature requirements and ensuring that air cooling will not suffice to meet those thermal needs.iv

To read the full article on “Closed Loop Liquid Cooling for High-Powered Electronics,” click http://coolingzone.com/blog/wp-content/uploads/2017/01/Qpedia_Oct07_Closed_Loop_liquid_cooling_
for_high_power_electronics.pdf
.

Chillers provide additional support for liquid cooling loops

In order to increase the effectiveness of the cold plate and of the liquid cooling loop, recirculating chillers can be added to condition the coolant before it heads back into the cold plate. The standard refrigeration cycle of recirculating chillers is displayed below in Fig. 1.

Chiller,s Cold Plates

Fig. 1. The standard refrigeration cycle for recirculating chillers. (Adavanced Thermal Solutions, Inc.)

Several companies have introduced recirculating chillers to the market in recent years, including ThermoFisher, PolyScience, Laird, Lytron, and Advanced Thermal Solutions, Inc. (ATS). Each of the chiller lines has similarities but also unique features that fit different applications.

In order to select the right chiller, Process-Cooling.com warns that it is important to avoid “sticker shock” because of testing conditions that are ideal rather than based on real-world applications. The site suggests a safety factor of as much as 25 percent on temperature ranges to account for environmental losses and to ensure adequate cooling capacity.v

The site also noted the importance of speaking with manufacturers about the cooling capacity that is needed, the required temperature range, the heat load of the application, the length and size of the pipe/tubing, and any elevation changes.

“Look for a chiller with an internal pump-pressure adjustment,” the article stated. “This feature enables the operator to dial down the external supply pressure to a level that is acceptable for the application. Because the remaining flow diverts internally into the chiller bath tank, no damage will result to the chiller pump or the external application.”

When trying to decide on the right size chiller for your particular application, there are several formulas that can help make the process easier. Bob Casto of Cold Shot Chillers, writing for CoolingBestPractices.com, gave one calculation for industrial operations. First, determine the change in temperature (ΔT), then the BTU/hour (Gallons per hour X 8.33 X ΔT), then calculate the tons of cooling ([BTU/hr]/12,000), and finally oversize by 20 percent (Tons X 1.20).vi

Not every application will require industrial capacity, so for smaller, more portable chillers, Julabo.com had a secondary calculation for required capacity (Q).

Q=[(rV cp)material+(rV cp)bath fluid]ΔT/t

In the above equation, r equals density, V equals volume, cp equals constant-pressure specific heat, ΔT equals the change in temperature, and t equals time. “Typically, a safety factor of 20-30% extra cooling capacity is specified for the chilling system,” the article continued. “This extra cooling capacity should be calculated for the lowest temperature required in the process or application.”vii

Comparison of Industry Standard Recirculating Chillers

Recirculating Chillers

Applications for liquid cooling systems with chillers

Recirculating chillers offer liquid cooling loops precise temperature control and coupled with cold plates can dissipate a large amount of heat from a component or system. This makes chillers (and liquid cooling loops in general) useful to a wide range of applications, including applications with demanding requirements for temperature range, reliability, and consistency.

Chillers have been part of liquid cooling systems for high-powered lasers for a number of years to ensure proper output wavelength and optimal power.viiiix To ensure optimal performance, it is important to consider safety features, such as the automatic shut-off on the ATS-Chill 150V that protects against over-pressure and compressor overload. Other laser-related applications include but are not limited to Deep draw presses, EDM, Grinding, Induction heating and ovens, Metallurgy, Polishing, Spindles, Thermal spray, and Welding.x

Machine hydraulics cooling and semiconductors also benefit from the inclusion of chillers in liquid cooling loops. Applications include CVD/PVD, Etch/Ashing, Wet Etch, Implant, Inductively Coupled Plasma and Atomic Absorption Spectrometry (ICP/AA), Lithography, Mass Spectroscopy (MS), Crystal Growing, Cutting/Dicing, Die Packaging and Die Testing, and Polishing/Grinding.xi

One of the most prominent applications for liquid cooling, heat exchangers, cold plates, and chillers is in medical equipment. As outlined in an ATS case study,xii medical diagnostic and laboratory equipment requires cyclic temperature demands and precise repeatability, as well as providing comfort for patients. For Harvard Medical School, ATS engineers needed to design a system that could maintain a temperature of -70°C for more than six hours. Using a cold plate with a liquid cooling loop that included a heat exchanger, the engineers were able to successfully meet the system requirements.

Liquid cooling with chillers are also being used for medical imaging equipment and biotechnology testing in order to provide accurate results. ATS CEO and President Dr. Kaveh Azar will discuss the “Thermal Management of Medical Electronics” in a free webinar on Jan. 26 at 2 p.m. For more information or to register for the webinar, click https://www.qats.com/Training/Webinars.

Conclusion

Closed loop liquid cooling systems are not new but are gaining in popularity as heat dissipation demands continue to rise. Using cold plate technology with recirculating chillers, such as the ATS-Chill150V, ATS-Chill300V, and the ATS-Chill600V, to condition the coolant in the system can offer enhanced heat transfer capability.

Portable and easy to use, ATS vapor compression chillers are air-cooled to eliminate costly water-cooling circuits and feature a front LED display panel that allows users to keep track of pressure drop between inlet and outlet and the coolant level. They each use a PID controller.

Recirculating Chillers

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

References
i http://history.nasa.gov/SP-287/ch1.htm
ii https://heatsinks.files.wordpress.com/2010/03/qpedia_0309_web.pdf#page=12
iii http://www.sciencedirect.com/science/article/pii/S0142727X99000673
iv https://www.qats.com/cpanel/UploadedPdf/Qpedia_Thermal_eMagazine_0610_V2_lorez1.pdf#page=16
v http://www.process-cooling.com/articles/87261-chillers-evaluation-and-analysis-keys-to-selecting-a-winning-chiller?v=preview
vi http://www.coolingbestpractices.com/industries/plastics-and-rubber/5-sizing-steps-chillers-plastic-process-cooling
vii http://www.julabo.com/us/blog/2016/sizing-a-cooling-system-control-temperature-process-heating-operations
viii http://www.laserfocusworld.com/articles/print/volume-37/issue-6/features/instruments-accessories/keeping-your-laser-cool0151selecting-a-chiller.html
ix https://www.electrooptics.com/feature/keeping-it-cool
x http://www.lytron.com/Industries/Laser-Cooling
xi http://www.lytron.com/Industries/Semiconductor-Cooling
xii https://www.qats.com/cms/2016/10/04/case-study-thermal-management-harvard-medical-school-tissue-analysis-instrumentation/