Author Archives: Josh Perry

Recent Research Into Next-Generation Heat Exchangers for Electronics Thermal Management

Posted on January 24, 2019 | 1 comment

Since it was published around one year ago, the “What is a Heat Exchanger” video (watch it below) has been one of the most watched on the ATS YouTube page. With the obvious interest in heat exchangers in particular (and liquid cooling in general), we are curating recent research into the technology and its applications in the thermal management of electronics.

The following are three examples of papers written about heat exchangers including applications in the automotive space to developing microchannels to enhance thermal performance to optimizing heat exchangers for use with high-powered electronics.

We have posted several pieces of content on this blog about heat exchangers in the past. Examples include:

Since heat exchangers remain a popular topic for engineers, we will continue to add new pieces about the technology in the coming months.

Novel Power Electronics Three-Dimensional Heat Exchanger

Read the full paper at https://www.nrel.gov/docs/fy14osti/61041.pdf.

Abstract: Electric-drive systems, which include electric machines and power electronics, are a key enabling technology to meet increasing automotive fuel economy standards, improve energy security, address environmental concerns, and support economic development. Enabling cost-effective electric-drive systems requires reductions in inverter power semiconductor area, which increases challenges associated with heat removal. In this paper, we demonstrate an integrated approach to the design of thermal management systems for power semiconductors that matches the passive thermal resistance of the packaging with the active convective cooling performance of the heat exchanger. The heat exchanger concept builds on existing semiconductor thermal management improvements described in literature and patents, which include improved bonded interface materials, direct cooling of the semiconductor packages, and double-sided cooling. The key difference in the described concept is the achievement of high heat transfer performance with less aggressive cooling techniques by optimizing the passive and active heat transfer paths. An extruded aluminum design was selected because of its lower tooling cost, higher performance, and scalability in comparison to cast aluminum. Results demonstrated a 102% heat flux improvement and a package heat density improvement over 30%, which achieved the thermal performance targets.

Microchannel Heat Exchanger for Electronics Cooling Applications

Read the full paper at http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1636343.

Abstract: The power consumption of electronic devices, such as semiconductor diode laser bars, has continually increased in recent years while the heat transfer area for rejecting the associated thermal energy has decreased. As a result, the generated heat fluxes have become more intense making the thermal management of these systems more complicated. Air cooling methods are not adequate for many applications, while liquid cooled heat rejection methods can be sufficient. Significantly higher convection heat transfer coefficients and heat capacities associated with liquids, compared to gases, are largely accountable for higher heat rejection capabilities through the micro-scale systems. Forced convection in micro-scale systems, where heat transfer surface area to fluid volume ratio is much higher than similar macro-scale systems, is also a major contributor to the enhanced cooling capabilities of microchannels. There is a balance, however, in that more power is required by microchannels due to the large amount of pressure drop that are developed through such small channels. The objective of this study is to improve and enhance heat transfer through a microchannel heat exchanger using the computational fluid dynamics (CFD) method. A commercial software package was used to simulate fluid flow and heat transfer through the existing microchannels, as well as to improve its designs. Three alternate microchannel designs were explored, all with hydraulic diameters on the order of 300 microns. The resulting temperature profiles were analyzed for the three designs, and both the heat transfer and pressure drop performances were compared. The optimal microchannel cooler was found to have a thermal resistance of about 0.07 °C-cm2 /W and a pressure drop of less than half of a bar.

Thermal Analysis of the Heat Exchanger for Power Electronic Device with Higher Power Density

Read the full paper at http://pe.org.pl/articles/2012/12a/70.pdf. Abstract: Liquid cooling system has been used in high power electronic device systems to cool down the temperature of power electronic device. Heat exchanger is an important part of liquid cooling system to transfer the heat generated by power electronic device into air. In this paper, a Streamline-upwind/Petrov-Galerkin (SUPG) stabilized finite element analysis method was proposed to solve the water and air governing formulas including the mass conservation equation, the momentum conservation and the energy conservation equation. Furthermore, the thermal characteristic of a heat exchanger is simulated, and the result was compared with an experiment. The comparison shows that this method is effective.

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

1 Comment

Posted in Heat Exchangers

Tagged heat exchangers, liquid cooling

Low-profile thermal solutions required for cooling high-density boards

Posted on January 4, 2019 | 3 comments

Advancements in the telecommunications, Internet of Things (IoT), broadcast, biomedical, and other industries demand more power, more data processing, and more capabilities. Engineers have been required to fill boards to the brim in order to meet the ever-increasing call for more and this high-density board design requires creative thermal management solutions.

With today’s high-density boards, low-profile solutions are required to ensure proper thermal management even in tight spaces. (Advanced Thermal Solutions, Inc.)

Standard heat sink sizes are too large for many telecom systems, module and blade servers, or IoT gateways, where card-to-card and internal spacing is limited, and may not be designed to handle the lower airflow that is the result of numerous components packed into tight spaces. With space and airflow at a premium, engineers need low-profile solutions that are lightweight, compact, and will not sacrifice thermal performance.

Advanced Thermal Solutions, Inc. (ATS) has several low-profile heat sink options that will give engineers greater flexibility in designing boards and systems while still managing heat.

Ultra-Low-Profile blueICE™ Heat Sinks

ATS blueICE™ heat sinks are specially designed for low airflow systems where space is limited. The heat sinks range in height from 2-7 mm and the spread-fin array maximizes surface area to enhance thermal performance even in low airflow systems. Their thermal resistance is as low as 1.23 °C/W within an air velocity of 600 ft/min.

The heat sinks are lightweight, ranging from 4-30 grams, and no mechanical attachment is required. Thermal tape is all that is needed to attach blueICE™ heat sinks to a component, which further reduces weight and assembly time and saves valuable space on the board.

In systems where boards are packed tightly together, low-profile heat sinks can provide the necessary thermal performance without significantly adding to the height of the components on the board. Also, the design of blueICE™ heat sinks removes heat from devices even with lower airflow.

Low-Profile maxiFLOW™ Heat Sinks

ATS has also made low-profile versions of its ultra-high-performance maxiFLOW™ heat sinks, available with either maxiGRIP™ or superGRIP™ mechanical attachments. The low-profile, spread-fin array maximizes surface area and enhances convection cooling, while attachment technology offers secure hold without a significant increase in footprint or the need to drill holes in the board.

Low-profile maxiFLOW™ heat sinks are designed for component heights ranging from 1.5-2.99 mm and the specially-designed fin array increases the surface area to provide the highest thermal performance per volume occupied when compared to other heat sinks on the market.

Using maxiGRIP™ or superGRIP™ heat sink attachment technology also gives design engineers more flexibility because of their easy assembly and removal. There is no damage to the board, which is important because of dense PCB routing and the potential need for rework.

Heat Pipes and Vapor Chambers

In situations where low-profile heat sinks will not fit, ATS has heat pipes and vapor chambers that will transport heat away from a component and can be attached to a heat sink or the system chassis/enclosure to dissipate the heat to the ambient. These innovative cooling solutions will meet even the toughest thermal challenges.

Heat pipes can be used to move heat from devices to heat sinks, the chassis, or system enclosure to remove the heat to the ambient. (Advanced Thermal Solutions, Inc.)

ATS has expanded its line of high-performance, off-the-shelf round and flat heat pipes to provide the broadest offering on the market. Engineers can avoid the extra cost of custom lengths by selecting from the more than 350 product numbers that ATS has created. Flat heat pipes are available in lengths of 70-500 mm, with widths of 4.83-11.41 mm, and heights of 2-6.5 mm.

Vapor chambers are essentially flat heat pipes and provide another low-profile option for spreading heat. (Advanced Thermal Solutions, Inc.)

Vapor chambers are essentially flat heat pipes that can be used in the base of heat sinks to spread heat. ATS has expertise designing vapor chambers and heat pipes into electronics systems to improve thermal management, especially with limited space and airflow. Their high thermal conductivity can move a lot of heat from devices and they can be easily attached to heat sinks to form cooling assemblies.

See how low-profile solutions are needed in IoT sensor-level infrastructure in the following video:

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Posted in Uncategorized

Webinar on Fan Characterization

Posted on January 3, 2019 | Leave a comment

Advanced Thermal Solutions, Inc. (ATS) is hosting a series of monthly, online webinars covering different aspects of the thermal management of electronics. This month’s webinar will be held on Thursday, Jan. 24 from 2-3 p.m. ET and will cover fan characterization and deployment in an electronics system. Learn more and register at https://qats.com/Training/Webinars.

Technology Review: Data Center Cooling

Posted on December 20, 2018 | 1 comment

(This article was featured in an 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.)

Qpedia continues its review of technologies developed for electronics cooling applications. We are presenting selected patents that were awarded to developers around the world to address cooling challenges. After reading the series, you will be more aware of both the historic developments and the latest breakthroughs in both product design and applications.

This article explores recent patents and technical advancements from the data center cooling industry. (Wikimedia Commons)

We are specifically focusing on patented technologies to show the breadth of development in thermal management product sectors. Please note that there are many patents within these areas. Limited by article space, we are presenting a small number to offer a representation of the entire field. You are encouraged to do your own patent investigation.

Further, if you have been awarded a patent and would like to have it included in these reviews, please send us your patent number or patent application.

In this issue our spotlight is on data center cooling solutions.

There are many U.S. patents in this area of technology, and those presented here are among the more recent. These patents show some of the salient features that are the focus of different inventors.

Hybrid Immersion Cooled Server with Integral Spot and Bath Cooling

US 7724524 B1, Campbell, L., Chu, R., Ellsworth, M., Iyengar, M. and Simons, R.

An immersion cooling apparatus and method is provided for cooling of electronic components housed in a computing environment. The components are divided into primary and secondary heat generating components and are housed in a liquid sealed enclosure. The primary heat generating components are cooled by indirect liquid cooling provided by at least one cold plate having fins. The cold plate is coupled to a first coolant conduit that circulates a first coolant in the enclosure and supplies the cold plate. Immersion cooling is provided for secondary heat generating components through a second coolant that will be disposed inside the enclosure such as to partially submerge the cold plate and the first coolant conduit as swell as the heat generating components.

The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a method and associated hybrid immersion cooling apparatus for cooling of electronic components housed in a computing environment. The components are categorized as primary and secondary heat generating components and are housed in a liquid tight enclosure. The primary heat generating components are cooled by indirect liquid cooling provided by at least one cold plate having fins.

The cold plate is coupled to a first coolant conduit that circulates a first coolant in the enclosure and supplies the cold plate. Immersion or direct liquid cooling is provided for secondary heat generating components through a second coolant that will be disposed inside the enclosure such as to partially submerge the cold plate and the first coolant conduit as Well as the heat generating components.

In one embodiment, the cold plate and the coolant conduit each comprise extended external surfaces used to transfer heat from the second coolant to the first coolant. In one embodiment the second coolant cools the electronics via free convection or a combination of free convection and boiling while an alternate embodiment provides a sub merged pump to aid circulation. In yet another embodiment, the electronics are housed on an electronics board that is tilted at an angle to also aid circulation of the second coolant.

Thermal Caching For Liquid Cooled Computer Systems

US 7436666 B1, Konshak, M.

The present invention involves supplementing the liquid cooling path within a given rack of electronic components in order to reduce the temperature rise of critical components before damage or data loss can occur in the event of a primary cooling system failure. Liquid cooled racks generally have piping and heat exchangers that contain a certain volume of liquid or vapor that is being constantly replaced by a data center pump system. Upon a data center power or pump failure, the How stops or is diminished. The coolant, however, is still present within the rack components. Upon detection of a lack of H_ow, an unexpected rise in the coolant temperature, or a significant reduction in H_ow pressure, and before any liquid can be drained away from the racks, an electrically or hydraulically operated valve bypasses the supply and return of the data center cooling path, creating an independent closed loop supplemental cooling system within the rack itself.

One embodiment of a system for mitigating a failure of a data center’s liquid cooling system is shown. A high level block diagram of one embodiment of a system for thermal caching in a liquid cooled computer system is presented. Under normal circumstances, coolant is delivered to a rack housing a plurality of liquid cooled components by a data center liquid cooling system supply and return lines. The supply and return lines are coupled to the rack by quick disconnecting and the coolant is pumped through the conduits by one or more data center pumps. Within the rack a secondary cooling loop is established that is in fluid communication with the data center cooling loop.

Upon entering the rack the data center supply line enters a monitoring device. In one embodiment of the present invention the device monitors fluid flow, pressure, and/or temperature. Other characteristics of the fluid that can also be used to identify a failure of the data center cooling system as imposed on the supply line. Thereafter, and before allowing the coolant to access any of the electronic components housed within the rack, a one way valve is placed on the supply lid entering the rock. The valve allows fluid to pass from the data center cooling supply line into the rack but prevents flow from regressing toward the supply line should the flow stop and/or an adverse pressure gradient is experienced.

Similarly, a two-way valve is placed on the coolant return line that returns heated coolant from the electronic components to the data center coolant return line. The two way valve is in communication with the monitoring device and capable of receiving a signal that indicates a failure in the primary or data center liquid cooling system.

Upon receiving such a signal from the monitoring device, the two-way valve closes either electrically or hydraulically and diverts the return coolant from the electronic devices to the supplemental or secondary liquid cooling loop. The supplemental liquid cooling loop, which is housed entirely within the rack, thereafter operates independent of the data center liquid cooling system.

Modular High-Density Computer System

US 7688578 B2, Mann, R., Landrum, G. and Hintz, R.

A modular high-density computer system has an infrastructure that includes a framework component forming a plurality of bays and has one or more cooling components. The computer system also has one or more computational components that include a rack assembly and a plurality of servers installed in the rack assembly. Each of the one or more computational components is assembled and shipped to an installation site separately from the infrastructure and then installed within one of the plurality of bays after the infrastructure is installed at the site.

Historically, a room oriented cooling infrastructure was sufficient to handle this cooling problem. Such an infrastructure was typically made up of one or more bulk air conditioning units designed to cool the room to some average temperature. This type of cooling infrastructure evolved based on the assumption that the computer equipment is relatively homogeneous and that the power density is on the order 1 -2 Kilowatts per rack. The high density racks mentioned above, however, can be on the order of 20 Kilowatts per rack and above. This increase in power density, and the fact that the equipment can be quite heterogeneous leads to the creation of hot spots that can no longer be sufficiently cooled with simple room-oriented cooling systems.

By separating the computational components of a high density computer system from the requisite cooling, power distribution, data l/O distribution, and housing infrastructure components, significant advantages can be achieved by embodiments of the invention over current configurations of such computer systems. The computational components can be assembled and tested for proper operation while the infrastructure components are shipped separately in advance of the computational components. Thus, the infrastructure cooling components, data and power distribution components, and framework components can be delivered and their time-intensive installation completed more easily and prior to receiving the tested computational components.

Moreover, the shipping of the computational components separately from the infrastructure components achieves less laborious and less costly delivery and handling of the components. Finally, it makes it easier for the data center to upgrade or add additional infrastructure and infrastructure components to a current installation.

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Posted in datacenter

Tagged data center cooling

Cooling News: New Thermal Products Showcase

Posted on December 18, 2018 | Leave a comment

In this article, Qpedia will explore some innovative thermal management products that have recently hit the market. These new thermal products encompass a variety of thermal management applications from CPU coolers to thermal interface materials (TIM) to sensors and test instruments to advanced materials and concepts.

EC fans provide low-power cooling

A new family of EC (electronically commutated) fans provide cooling in AC applications that prioritize low power and energy savings. Provided by Orion Fans, the fans offer up to 50% lower overall power consumption, with brushless DC motors and voltage transformation inside their motors. This allows applications to meet energy-consumption requirements for programs like Energy Star.

The EC fans are available in 60 mm, 120 mm, 172 mm, and 250 mm sizes. Most of the models are available with a universal voltage range. The 250 mm fans can be purchased with dual-speed functions in 115 V and 230 V models. The series also includes 60 mm, 120 mm, and 172 mm models with IP68-ATEX ratings, enabling them to be used in applications that might involve flammable gas or explosive atmospheres.

3D-Printed Cooler for High Performance Chips

Imec has developed a new impingement chip cooler that uses polymers to achieve a cost-effective fabrication. The cooler features nozzles of only 300 µm, made by high-resolution stereolithography 3D printing. This method allows customization of the nozzle pattern design to match the heat map and the fabrication of complex internal structures. The 3D printing allows production of the whole structure in one part, reducing production cost and time.

Imec’s impingement cooler achieves a high cooling efficiency, with a chip temperature increase of less than 15°C per 100W/cm2 for a coolant flow rate of 1 l/min. It outperforms benchmark conventional cooling solutions in which the thermal interface materials alone already cause a 20-50°C temperature increase.

Thermally Optimized Wedgelocks

Advanced Cooling Technologies, Inc. (ACT) has introduced Isothermal Card Edge, ICE-Lok wedgelocks. Wedgelocks are used when electronics cards must be easily replaceable. The wedgelock is a mechanical clamp that allows a card to be swapped quickly, but has the drawback of being a relatively poor thermal conductor. The new ICE-Lok is designed to enhance the card-to-chassis, through-the-wedgelock heat conduction by adding more contact surfaces between the card and the chassis.

The new wedgelock design offers a 30% reduction in thermal resistance compared to similarly sized COTS wedgelocks. This has enabled reduction of component temperatures of up to 10°C in some 100W card applications. ICE-Lok wedgelocks have been thoroughly tested for thermal and mechanical stability with repeated insertion/removal testing. They are designed to meet the dimensional requirements of the VITA specification; and the new friction lock feature ensures that card deformation is avoided.

Boron Arsenide Crystals for Chip Cooling

Three teams from around the US are now saying that crystals of the semiconductor boron arsenide (BAs) show promise in this context and they have measured a high thermal conductivity of more than 1000 W/m/K at room temperature for this material. This value is three times higher than that of copper or silicon carbide, two materials that are routinely employed for spreading heat in electronics.

Researchers predicted that BAs should have a theoretical thermal conductivity as high as that of diamond (2,200 W/m/K), which is the best heat conductor known, back in 2013. However, to reach this high value, high quality crystals are needed since defects and impurities dramatically degrade thermal properties.

Updated Thermal Management Software

Enclosure manufacturer Eldon has updated its thermal management software tool. The software tool has been designed to assist engineering firms, panel builders, and users in dimensioning cooling or heating equipment for electrical enclosures. The tool is used to define a solution that ensures the temperature inside the enclosure does not fall below or exceed the limits required. The tool calculates climate control requirements including heat dissipation within the enclosure, component by component, and generates solutions for both indoor and outdoor applications.

It recommends an array of temperature or humidity modulating and measuring devices, such as air conditioners, heat exchangers, filter fans, vortex coolers, heaters, thermostats and hygrostats. It takes the size of the enclosure as well as the environmental conditions under which it will operate into account. Included in the new version are: ‘Save’ and ‘Load’ functionality; improved power data layout presentation; and a voltage selector for vortex coolers.

Cold Plates Cool IGBTs

New IGBT cold plates from Advanced Thermal Solutions feature a mini-channel fin design for unmatched thermal performance. This ATS series offers a 30% or more improvement in thermal performance compared to commercially available cold plates.

These IGBT cold plates offer a maximum pressure of 60 psi. ATS-CP-1000 cold plate, at a flow rate of 4L/min, transfers 1kW of heat at 5.5°C temperature difference between the cold plate base and inlet fluid temperature. If the coolant has particles, a #60 filter or finer is recommended to remove possible particles in the liquid.

Author Archives: Josh Perry

Recent Research Into Next-Generation Heat Exchangers for Electronics Thermal Management

Low-profile thermal solutions required for cooling high-density boards

Webinar on Fan Characterization

Technology Review: Data Center Cooling

Hybrid Immersion Cooled Server with Integral Spot and Bath Cooling