Category Archives: Liquid Cooling

Technology Review: Liquid Cooling Solutions

Posted on September 14, 2018 by | Leave a 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.

Liquid Cooling Solutions

The focus of this article is to highlight recent patents for liquid cooling devices. (Advanced Thermal Solutions, Inc.)

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 liquid-based 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.

Liquid Cooling Devices

Embedded Microchannel Cooling Package for a Central Processing Unit

US 7515415 B2, Monfarad, A. and Yang, J.

An indirect cooling liquid embedded package design for use with a computer central processor unit is suitable for thermal management of high heat dissipation electronic components such as server processors. The indirect contact cooling liquid embedded packaged CPU has mechanical coupling and embedded plumbing that attaches to the board pumped liquid supply and indirect cooling of the heat-generating portion of the CPU with an embedded microchannel heat exchanger. The coolant package system for the CPU removes higher levels of heat indirectly from the core of the processors by convective cooling.

Cooling liquid flows into the microchannel piping in the CPU substrate. Cooling liquid continues to flow out of the microchannel piping into a silicon or metallic microchannel heat exchanger that is directly bonded to a silicon die for cooling of the heat-generating portion of the CPU. As a result, an embedded microchannel indirect contact cooling liquid package for a CPU can be utilized to remove substantially higher levels of heat from the core of the processors by forced convective liquid flow through the microchannel heat exchanger attached to the core of the CPU. Cooling liquid is introduced into the package of the server CPU by mechanically attaching the CPU to the board through a socket interconnect. Pins of the socket serve to provide electrical connection between the board and the CPU, while a few pins are designed for the purpose of providing an inlet and an outlet for cooling liquid into and out of the CPU package.

The cooling system of the present invention also uses the existing package-to-board practice of using sockets and therefore the entire cooling system is embedded into the processor-to-board assembly. From the end user’s point of view, there is a tremendous amount of simplification of board design as the bulky fan and heat sink assemblies are removed. The replacement, according to the present invention, is a central liquid cooling system that can be made redundant to substantially prevent any reliability issues in the field.

Planar Heat Pipe for Cooling

US 8305762 B2, Wits, W., Mannak, J. and Legtenberg, R.

The invention claimed is a circuit board for cooling of heat-dissipating components assembled thereon, including at least two panels at least one of which is populated With heat-dissipating components, both panels being metal clad on a side, at least one of the panels being formed from a printed circuit board laminate and comprising a plurality of grooves on its metal clad side, the panels being bonded together by an adhesive layer With their metal clad sides oriented face to face so as to form a circuit board containing a sealed cavity having a height defined by a thickness of the adhesive layer and the separation of the metal clad sides, the cavity being partly filled with a fluid, the fluid circulating by capillary action along the grooves towards zones exposed to heat where the fluid vaporizes.

Vapor may circulate back by pressure gradient effect through the cavity towards zones not exposed to heat where it condenses. In a mode of implementation, the heat pipe may be embedded in a circuit board formed by the panels for inherent cooling of heat-dissipating components.

Thus, key advantage provided by the present invention in any of its aspects is that it is based on most standard processes of multilayer PCB fabrication such as laminating, selective metal plating and etching. Therefore, it is a highly cost-effective solution. Furthermore, the invention provides a very flexible design solution enabling to adapt the cooling paths to the PCB layout, especially to the higher heat dissipation locations. Not requiring any supplementary materials, it is even considerably lighter than a tubular heat pipe-based solution.

Implemented as enhancement of a computer aided engineering tool, heat pipe cooling cavities could be designed concurrently with the layout of components placement and printing of circuits, ensuring optimized thermal management. This enables multilayer PCB assemblies, which are high density electronic devices, to benefit the most from the integrated heat pipe cooling function.

Cooling System for Electronic Equipment

US 7508666 B1, Henneberg, M. and Johnson, L.

A cooling solution includes a system providing thermal energy dissipation for electronic equipment located in support racks or cabinets of a facility. According to one embodiment, the system is integrated with a facility where the support cabinets are located. The system providing thermal energy dissipation includes a cooling loop, a fan unit for moving air across the cooling loop and one or more ducts forming a confined flow pathway for the moving air between the fan unit and cabinets for delivery to the electronic equipment.

More specifically, the cooling loop contains a supply of circulating heat absorbing fluid such that the heat absorbing fluid removes thermal energy from the air moved by the fan unit. Each cabinet is formed with an exhaust pathway such that the moving air enters the cabinet from the duct, flows across the electronic equipment to remove thermal energy therefrom, and exits the cabinet.

Claims include a cooling system for a facility housing electronic equipment, the facility having a support surface on which a cabinet holding the electronic equipment is located, the system comprising: a cooling loop located beneath the support surface and containing a supply of circulating heat absorbing fluid; a fan unit located beneath the support surface and configured to move air across the cooling loop such that the heat adsorbing fluid removes thermal energy from the moving air; at least one duct forming a confined flow pathway for the moving air between the fan unit and the cabinet, wherein the cabinet is formed with a substantially lateral exhaust pathway such that the moving air enters via a back region of the cabinet, flows across the electronic equipment, housed by the cabinets, to remove thermal energy therefrom, and exits a front region of the cabinet; and a chilling plate positioned downstream of the flow of moving air exiting the cabinet such that the chilling plate is located outside of the front region of the cabinet, the chilling plate is coupled to a secondary cooling loop containing a supply of heat absorbing fluid.

Claims also include a method for providing thermal energy dissipation for network-based electronic equipment housed within a plurality of cabinets located on a support surface of a facility, each of the plurality of cabinets having an interior formed with a through passageway extending from an entrance at a first side of each of the plurality of cabinets to an exit at a second side of each of the plurality of cabinets, the method comprising: providing a cooling loop containing a supply of circulating heat adsorbing fluid; providing a fan unit configured to move air across the cooling loop such that the heat adsorbing fluid removes thermal energy from the moving air; directing the moving air from the fan unit to the through passageway of each of the plurality of cabinets such that the moving air flows across the electronic equipment to remove thermal energy therefrom, and exits the plurality of cabinets; and providing a plurality of chilling plates positioned downstream of the flow of moving air exiting the plurality of cabinets such that one of the plurality of chilling plates is located outside of each of the plurality of cabinets, respectively, each of the plurality of chilling plates is coupled to a secondary cooling loop containing a supply of heat absorbing fluid.

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.

Leave a comment

Posted in Liquid Cooling

Tagged ,

ATS Releases New Liquid Cooling eBook

Posted on June 8, 2018 by | Leave a comment

Advanced Thermal Solutions, Inc. (ATS) has created an new Engineering eBook on Liquid Cooling and its applications in the thermal management of electronics. Click here to download this free, 16-page eBook loaded with technical content.

Leave a comment

Posted in Liquid Cooling

Tagged ,

How to Achieve Localized Cooling with Cold Plates

Posted on January 16, 2018 by | 6 comments

Many applications in electronics cooling require a cold plate to remove heat from discrete components laid out on a board. In these circumstances, it is more efficient that the liquid does not completely fill the cold plate, but is only transferred to areas that need to be cooled.

With this kind of design, the required volumetric flow rate of the coolant will be significantly lower than if the entire cold plate was filled with liquid. The schematic for a typical example of this scenario is given in Figure 1. [1]

Localized Cooling With Cold Plates

Figure 1. Schematic of a Board with a Localized Area of Heat Dissipation . [1]

In Figure 1, areas A, B, C and D must be cooled for the components dissipating from 5 to 15 W/cm2. The other areas, designated as open, have components that interfere with the cold plate and must be avoided in the design. Two designs were considered for this case: a drilled hole and a press-fit tube. Figure 2 shows the drilled hole concept.

As can be seen, there are multiple small holes around the heat dissipating components under the cold plate surface. Large holes are machined to interconnect the smaller holes. A technique called gun drilling was used for machining the long holes. The entire cold plate was made from a copper block.

Cold Plates

Figure 2. Schematic of the Drilled Hole Cold Plate Design. [1]

Figure 3 shows the press-fit tube design. In this approach, a copper tube with high thermal conductivity is routed through the areas of heat transfer and either brazed or epoxied to the aluminum cold plate base. This design is considerably lighter and cheaper than the drilled hole design.

Cold Plates

Figure 3. Schematic of the Press-Fit Tube Cold Plate Design. [1]

To analyze the performance of this cold plate configuration, simple analytical tools can be used for a standard cold plate design. A brief summary of the equations is described here. To analyze the problem, we first have to calculate how much flow is going through the cold plate, and evaluate the pressure drop of the flowing fluid.

Pressure drop is calculated from:

Where
Um = bulk mean fluid velocity (m/s)
f = fanning friction factor
Awet = wetted surface area of the tube
Ac = cross section of the tube
K = loss coefficients related to turns, sudden expansion and contraction, etc.

The friction factor was obtained from the following equation which is in satisfactory agreements for the laminar, turbulent and transition regimes [2]

Where

Where ν is the kinematic viscosity of the fluid (m2/s) and P is the wetted perimeter of the tube.

For the heat transfer calculation, the Nusselt number can be calculated from standard correlations in the literature for fully developed flow. The Nusselt number is related to the heat transfer coefficient as:

Where
Kf = fluid conductivity

For thermally developing flow the following correlation can be used: [3]

Where
Num = mean Nusselt number
Nu∞ = fully developed Nusselt number
L = duct length

Then the convective resistance can be calculated as:

Where
hm = mean heat transfer coefficient

For the tube fitted design the overall thermal resistance is made of four components: convection, tube conduction resistance, epoxy conduction resistance and the cold plate. It is stated as:

Where
Rh = convection resistance
Rtube = conduction resistance of tube walls
Repoxy = conduction resistance of the epoxy
Rcoldplate = conduction resistance of the cold plate

For the drilled design the overall thermal resistance can be written as:

If the heat transfer coefficient is based on the local fluid temperature, then a caloric resistance must be added based on the fluid mass flow rate. The effective heat transfer coefficient is then:

Where
ṁ = mass flow rate (kg/s)
Cp = fluid heat capacitance (kJ/kg·K)

Figure 3 shows the pressure drop of the two designs as a function of water flow rate. It can be seen that with a water flow rate up to 1.89 l/min (0.5 GPM) the pressure drop between the two designs is almost the same, but at higher flow rates the drilled design’s pressure drop exceeds the tube design. The sharp 90-degree turn of the drilled holes, which lead to a higher loss coefficient, is the major contributor to the higher pressure drop.

Figure 4. Total Pressure Drop of the Drilled Design and the Tube Design as a Function of the Volumetric Flow Rate. [1]

Figures 5 and 6 show the effective heat transfer coefficient of the two designs as a function of flow rate. The bend and sharp increase of the curves around 0.95 l/min (0.25 GPM) is due to the flow transitioning from laminar to turbulent. The drilled hole design shows effective convection heat transfer between 7,000 and 27,000 W/m2K for the range of flow between 0 and 7.56 l/m (2.6 GPM). The press-fit tube design on the other hand shows a lower effective heat transfer coefficient of between 6,000 and 17,000 W/m2K.

This is mostly due to the interfacial resistance and tube wall conduction. In the drilled design example, these two resistances do not exist. In a real application, the pumping of fluid is constrained by the pump and its characteristic curve. Even though the drilled hole shows a higher heat transfer coefficient for the same flow rate, the extra pressure drop caused by the drilled design may have a lower flow rate hence lowering the heat transfer coefficient.

Figure 5. Effective Heat Transfer Coefficient of the Tube Design as a Function of Flow Rate for Different Regions on the Plate. [1]

Figure 6. Effective Heat Transfer Coefficient of the Drilled Hole Design as a Function of Flow Rate for Different Regions on the Plate. [1]

Figure 7 shows another cold plate design, this one by Lytron. [4] In this design, the extended-surface cold plate material and micro-channel aluminum extrusion are sandwiched between aluminum sheets. The entire assembly is welded using vacuum brazing. It is all aluminum, which makes it very light weight. The flexibility of this design allows the placement of cooling channels in different positions to enable localized cooling.

Figure 7. Lytron Vacuum Brazing of a Cold Plate for Localized Cooling. [4]

The above analytics show that the performance of a cold plate for localized cooling can be calculated using a simple analytical tool. The designer then has to consider such factors as weight, manufacturing, cost and thermal performance to decide the best option for his or her design. The characteristic of the pump has a paramount effect on the design and cannot be neglected.

References:

1. Seaho, S., Moran, K. and Rearick, D. (IBM Corporation) and Lee, S. (Aavid Engineering), Thermal Performance Modeling and Measurements of Localized Water Cooled Cold Plate, http://www.aavidthermalloy.com/technical/papers/pdfs/water.pdf
2. Churchill, S., Comprehensive Correlating Equations for Heat, Mass and Momentum Transfer in Fully Developed Flow in Smooth Tubes, Ind. Eng. Chem. Fundam., Vol.16, 1977.
3. Al-Arabi, M., Turbulent Heat Transfer in the Entrance Region of a Tube, Heat Transfer Eng., Vol. 3, 1982.
4. http://www.lytron.com

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

6 Comments

Posted in Cold Plates, Liquid Cooling, Thermal Analysis

Tagged , , ,

Thermal Performance of Macro and Microchannel Cold Plates in Electronics Cooling

Posted on January 8, 2018 by | 2 comments

In recent years, intense activity has been gone into improving the capabilities of cold plates. Specifically, the use of microchannels has provided great improvements in cold plate thermal performance. Regardless of a cold plate’s channel size, the following equations can be used for heat transfer coefficients when determining thermal performance. [1]

Where,

= Nussselt number

Dh = hydraulic diameter

= Reynolds number

 

ν = kinematic viscosity
Pr = Prandtle number

The pressure drop can also be calculated as:

Where,
P = density
f = friction factor

In recent years, microchannel cold plates have gained popularity due to their high performance. Webb shows that the best results can be achieved when the channel aspect ratio is about 7.4, and with a fin aspect ratio of 8. [2] Figure 1 shows a Fin-H copper microchannel with a channel hydraulic diameter of 0.49 mm. Due to the small size of the channels, the flow is generally considered to be laminar. The optimization resulted in a 25-mm wide and 20-mm long microchannel cold plate. [2]

Webb considered both single-pass and two-pass designs on the water side. The two-pass version was made to determine if there was any mal-distribution of the water from the single-pass case.

Microchannel Cold Plates

Figure 1. Copper Microchannel Fin-H Used in a Cold Plate. [2]

Figure 2 shows the thermal resistance of the Fin-H for the 1-pass and 2-pass designs as a function of flow rate.

Figure 2. Thermal Resistance of a Fin-H Cold Plate as a Function of the Water Flow Rate. [2]

This figure shows that the 1-pass version has a much better thermal resistance than the two-pass model for the same flow rate. It also shows that the flow has been distributed relatively uniformly. Figure 3 shows the pressure drop of the cold plate as a function of flow rate for the Fin-H and the Thermaltake Bigwater 735 cooler. [3] The figure shows the pressure drop of the 1-pass design is only 38% of the 2-pass design.

Figure 3. Pressure Drop of a Fin-H Cold Plate and a Thermaltake Cooler as a Function of the Water Flow Rate. [2]

Figure 4 shows the thermal resistance of the Fin-H cooler in the 1-pass design compared to the Thermaltake cooler [3]. At 2.28 l/min the Thermaltake’s thermal resistance is 0.106 K/W. The balance point of the Fin-H for 1-pass is with a thermal resistance of 0.07 K/W at a flow rate of 0.361 l/min. This is only 16% of the flow rate for the Thermaltake cooler.

Referring to Figure 3, the pressure drop is almost the same for both coolers. The major implication is that the microchannel cold plate requires a smaller pump compared to macrochannel cold plates, and provides a 50% increase in thermal performance.

Figure 4. Thermal Resistance of a Fin-H Cold Plate and a Thermaltake Cooler as a Function of the Water Flow Rate. [2]

Another innovative approach is the concept of forced-fed boiling (FFB). [4] Figure 5 shows a schematic of this process. It consists of a micro-grooved, thin copper surface with alternating fins and channels. The microgrooves have a hydraulic diameter of 28 microns, an aspect ratio of 15, and a fin density of 236 fins per cm.

There are feed channels on top of the micro-grooved surface. The fluid is forced through these channels into the microgrooves, which are located on top of the heated surface. The fluid vaporizes in the microgrooves and moves upward, while the liquid flows beneath the escaping vapor. This keeps the surface wet, resulting in an increase of the critical heat flux (CHF).

Figure 5. A Force-Fed Boiling Cold Plate. [4]

Figure 6 shows the heat transfer as a function of the temperature difference between the inlet fluid and the surface for various values of the flow rate for R245fa, a non-aqueous fluid for low pressure refrigeration applications. The figure shows that for heat fluxes of about 200 W/cm2 or less, heat transfer is independent of the flow rate, but this is not the case at higher heat fluxes. It also shows that the slope of the heat flux decreases with increasing temperature difference.

Figure 6. Heat Flux as a Function of the Temperature Difference for the FFB Cold Plate. [4]

Figure 7 shows an interesting trend for the heat transfer coefficient as a function of heat flux for the same fluid. At first, the heat transfer coefficient increases with the increase in heat flux. This indicates that by increasing the heat flux, a phase change process takes place which changes the single-phase flow to two-phase heat transfer. After reaching an impressive peak at 300 KW/m2K, the heat transfer coefficient starts to decrease. This is attributed to local dryouts from bubble generation, which also blocks the microchannels.

Figure 7. Heat Transfer Coefficient as a Function of Heat Flux for the FFB Cold Plate. [4]

While advances in cold plate performance have been incremental, their technology is still evolving. Improvements in microchannel manufacturing will open more opportunities in this field. Microchannel cold plates provide tremendous heat transfer coefficient capacities, but limitations prevent their broad deployment.

Fouling, dryout, and fabrication issues have been major negating factors for microchannel deployment in the broader market. Microchannel cold plates may have particular value in such applications as military, space, and high capacity computing, where service and maintenance are part of the deployment.

However, from the design and problem-solution standpoint, microchannel cold plates can be an effective part of a closed loop liquid cooling system.

References
1. Dittus, F. and Boelter, L., Publications on Engineering, University of California at Berkley, 1930.
2. Webb, R., High-Performance, Low-Cost Liquid Micro-Channel Cooler, Thermal Challenges in Next Generation Electronic Systems II, Millpress Science Publishers, Rotterdam, The Netherlands, 2007.
3. Thermaltake Company, 2006.
4. Cetegen, E., Dessiatoun, S., and Ohadi, M., Force Fed Boiling and Condensation for High Heat Flux Applications, VII Minsk International Seminar: Heat Pipes, Heat Pumps, Refrigerators, Power Sources, Minsk, Belarus, 2008.

Learn more about Advanced Thermal Solutions, Inc. (ATS) standard and customized, high-performance liquid cold plates by visiting https://www.qats.com/Products/Liquid-Cooling/Cold-Plates.

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

2 Comments

Posted in Cold Plates, Liquid Cooling, Microchannels, Thermal Analysis

Tagged , ,

What Fluids Can Be Used With Liquid Cold Plates in Electronics Cooling Systems

Posted on November 13, 2017 by | 15 comments

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

Liquid cooling systems transfer heat up to four times better than an equal mass of air. This allows higher performance cooling to be provided with a smaller system. A liquid cooled cold plate can replace space-consuming heat sinks and fans and, while a liquid cold plate requires a pump, heat exchanger, tubing and plates, there are more placement choices for cold plates because they can be outside the airflow. [1]

One-time concerns over costs and leaking cold plates have greatly subsided with improved manufacturing capabilities. Today’s question isn’t “Should we use liquid cooling?” The question is “What kind of liquid should we use to help optimize performance?”

Liquid Cold Plates

Figure 1. A Liquid Cooling System for a Desktop PC with Two Cold Plates. [2]

For liquid cold plates, the choice of working fluid is as important as choosing the hardware pieces. The wrong liquid can lead to poor heat transfer, clogging, and even system failure. A proper heat transfer fluid should provide compatibility with system’s metals, high thermal conductivity and specific heat, low viscosity, low freezing point, high flash point, low corrosivity, low toxicity, and thermal stability. [3]

Today, despite many refinements in liquid cold plate designs, coolant options have stayed relatively limited. In many cases, regular water will do, but water-with-additives and other types of fluids are available and more appropriate for certain applications. Here is a look at these coolant choices and where they are best suited.

Basic Cooling Choices

While water provides superior cooling performance in a cold plate, it is not always practical to use because of its low freezing temperature. Additives such as glycol are often needed to change a coolant’s characteristics to better suit a cold plate’s operating environment.

In fact, temperature range requirements are the main consideration for a cold plate fluid. Some fluids freeze at lower temperatures than water, but have lower heat transfer capability. The selected fluid also must be compatible with the cold plate’s internal metals to limit any potential for corrosion.

Table 1 below shows how the most common cold plate fluids match up to the metals in different cold plate designs.

Table 1. Compatibility Match-ups of Common Cold Plate Metals and Cooling Fluids [1]

The choices of cold plate coolants will obviously have varied properties. Some of the differences between fluids are less relevant to optimizing cold plate performance, but many properties should be compared. Tables 2 and 3 show the properties of some common coolants.

Tables 2 and 3. Comparisons of Properties of Typical Electronic Coolants. [4]

An excellent review of common cold plate fluids is provided by Lytron, an OEM of cold plates and other cooling devices. The following condenses fluid descriptions taken from Lytron’s literature. [5]

The most commonly used coolants for liquid cooling applications today are:

  • Water
  • Deionized Water
  • Inhibited Glycol and Water Solutions
  • Dielectric Fluids

Water – Water has high heat capacity and thermal conductivity. It is compatible with copper, which is one of the best heat transfer materials to use for your fluid path. Facility water or tap water is likely to contain impurities that can cause corrosion in the liquid cooling loop and/or clog fluid channels. Therefore, using good quality water is recommended in order to minimize corrosion and optimize thermal performance.

If you determine that your facility water or tap water contains a large percent of minerals, salts, or other impurities, you can either filter the water or can opt to purchase filtered or deionized water. [5, 6]

Deionized Water – The deionization process removes harmful minerals, salts, and other impurities that can cause corrosion or scale formation. Compared to tap water and most fluids, deionized water has a high resistivity. Deionized water is an excellent insulator, and is used in the manufacturing of electrical components where parts must be electrically isolated. However, as water’s resistivity increases, its corrosivity increases as well. When using deionized water in cold plates or heat exchangers, stainless steel tubing is recommended. [5, 7]

Inhibited Glycol and Water Solutions – The two types of glycol most commonly used for liquid cooling applications are ethylene glycol and water (EGW) and propylene glycol and water (PGW) solutions. Ethylene glycol has desirable thermal properties, including a high boiling point, low freezing point, stability over a wide range of temperatures, and high specific heat and thermal conductivity. It also has a low viscosity and, therefore, reduced pumping requirements. Although EGW has more desirable physical properties than PGW, PGW is used in applications where toxicity might be a concern. PGW is generally recognized as safe for use in food or food processing applications, and can also be used in enclosed spaces. [5, 8]

Dielectric Fluid – A dielectric fluid is non-conductive and therefore preferred over water when working with sensitive electronics. Perfluorinated carbons, such as 3M’s dielectric fluid Fluorinert™, are non-flammable, non-explosive, and thermally stable over a wide range of operating temperatures. Although deionized water is also non-conductive, Fluorinert™ is less corrosive than deionized water. However, it has a much lower thermal conductivity and much higher price. PAO is a synthetic hydrocarbon used for its dielectric properties and wide range of operating temperatures. For example, the fire control radars on today’s jet fighters are liquid-cooled using PAO. For testing cold plates and heat exchangers that will use PAO as the heat transfer fluid, PAO-compatible recirculating chillers are available. Like perfluorinated carbons, PAO has much lower thermal conductivity than water. [5, 9]

Conclusion

Water, deionized water, glycol/water solutions, and dielectric fluids such as fluorocarbons and PAO are the heat transfer fluids most commonly used in high performance liquid cooling applications.

It is important to select a heat transfer fluid that is compatible with your fluid path, offers corrosion protection or minimal risk of corrosion, and meets your application’s specific requirements. With the right chemistry, your heat transfer fluid can provide very effective cooling for your liquid cooling loop.

References
1. https://www.aavid.com/product-group/liquidcoldplates/fluid
2. http://semi-therm.org/wp-content/uploads/2017/04/How-to-design-liquid-cooled-system.pdf
3. Mohapatra, Satish C., “An Overview of Liquid Coolants for Electronics Cooling,” ElectronicsCooling, May 2006.
4. http://www.calce.umd.edu/whats_new/2012/Presentations/David
%20Saums%20PPt.pdf
5. http://www.lytron.com/Tools-and-Technical-Reference/Application-Notes/The-Best-Heat-Transfer-Fluids-for-Liquid-Cooling
6. https://www.thereadystore.com/5-gallon-collapsible-water-container
7. https://www.amazon.co.uk/IONISED-WATER-Mineralised-Deionised-Distilled/dp/B00X30JKGY/ref=pd_lpo_vtph_263_tr_t_2?_encoding=UTF8&psc=1&refRID=QNAM8H7J8R1AEDP8W5FF
8. http://www.rhomarwater.com/products/catalog/envirogard-heat-transfer-fluid-antifreeze
9. http://www.skygeek.com/anderol-royco-602-cooling-fluid.html

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

Cold Plates for IGBT and Power Electronics from Advanced Thermal Solutions   For information on ATS Cold Plates, visit our Cold Plate page at https://www.qats.com/Products/Liquid-Cooling/Cold-Plates

15 Comments

Posted in Cold Plates, Liquid Cooling

Tagged , ,