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Cold Plate Design For Thermal Management

Notes on customised Cold Plate！

The advantages of liquid cooling methods are their high cooling efficiency and the technology is divided into two types, contact and non-contact, depending on whether direct contact is made with the heat generating device. Contact liquid cooling solutions include immersion and spray liquid cooling, while non-contact liquid cooling solutions are typically cold plate liquid cooling.

Of the three types of liquid cooling, liquid cooling plate liquid cooling technology is the earliest and most popular type of liquid cooling, and therefore has the highest market maturity and operability.

The cold plate liquid cooling is mainly used to indirectly transfer the heat from the components to the cooling liquid enclosed in the circulation pipe through the cold plate (a closed cavity made up of highly thermally conductive metals such as copper and aluminium), which then uses the cooling liquid to carry the heat away, and its transfer characteristics through the working fluid to transport the intermediate heat to the back end for cooling.

Cold Plate Design For Thermal Management -Trumonytechs

There are four advantages in terms of application

  1. Good material compatibility.
  2. Lower requirements for heat generating devices and simpler installation.
  3.  Lower cost, fast development of applications, no need for expensive water-cooled units.
  4.  High density, high efficiency and high reliability.

Common cold plate types

2.1. Profile + Stir Friction Welding

This type of cold plate uses an extrusion process to shape the cold plate runners directly, using machining to open up the circulation and finally using a stir friction welding process to seal the runners and receiver.

Profile + Stir Friction Welding-Cold Plate Design For Thermal Management

Advantages

  1. Good reliability
  2. Good load-bearing capacity
  3. Good surface flatness
  4. Good heat transfer effect
  5. High production efficiency

Disadvantages

  1. More complex processing, high cost
  2. Thicker and heavier
  3. High space occupation
  4. Low heat dissipation density, surface not suitable for designing too many screw holes

2.2. Harmonica tube liquid cooling plates

The principle of this process is to extrude aluminium to create the runners and then weld them together with the two end collectors.

Cold Plate Design For Thermal Management

Advantages

  1. Low cost and light weight
  2. Simple structure and high production efficiency

Disadvantages

  1. Single runner, small contact area
  2. Thin wall, average heat exchange effect, poor load bearing

2.3.Blow-up liquid cooling plates

Blow-up liquid cooling plates is the most important liquid-cooled plate at present, the process plate printed out graphite composition of the pipeline, by hot rolling the two plates combined, blowing gas to blow up the pipeline.

Blow-up liquid cooling plates-Cold Plate Design

Advantages

  1. Low cost and high production efficiency
  2. High heat transfer efficiency and fast cooling speed
  3. The thinnest position can be achieved 0.5mm, light weight

Disadvantages

  1. Soft material, shortcomings in pressure resistance and strength
  2. Low performance, prone to leakage

2.4. Stamped liquid cooling plates

The principle of this process is to rely on presses and dies to stamp the aluminium to create plastic deformation and form flow channels, with the upper and lower shells being welded together by brazing.

Stamped liquid cooling plates-Cold Plate Design

Advantages

  1. The runners can be of any design
  2. Large contact area, good heat exchange effect
  3. High production efficiency
  4. High pressure and strength resistance

Disadvantages

  1. Need to open mould, high cost
  2. High leveling requirements, difficult to install

2.5.Plate and Fin liquid cooling plates

The principle of this liquid cooling plates is to fill the upper and lower heat-conducting panels with serrated heat-transfer fins, which are then sealed by vacuum brazing technology without brazing flux.

Advantages

  1. High surface cleanliness, good fluidity and corrosion resistance
  2. Heat transfer performance, better uniformity of flow paths

Disadvantages

  1. High cost
  2. High flatness requirement, difficult to install

Cooling plate design thermal factors

The design steps and factors to consider for liquid-cooled panels are similar to those for heat sinks in air-cooled or natural heat dissipation equipment. The fluid medium to which the cold plate is exposed is a liquid; for air-cooled or natural heat dissipation the fluid medium is a gas.

The basic factors to be considered when designing a cold plate radiator are:

  1. increasing the contact area between the solid and the fluid within a given volume of space thereby enhancing heat transfer.
  2. contact with the heat generating source through the thermally conductive interface material.
  3. the contact surface of the fluid with the solid.
  4. Heat transfer from the heat generating source to the cold plate and then to the liquid medium flowing in the cold plate and carried out of the system.

Cold Plate Thermal Specifications

The factors of the heat generating source have a major role in determining the cost and complexity of the cold plate design. The heat dissipation factors can be subdivided into four categories of variables: uniform heat flux, fixed flow rate, maximum pressure drop and maximum surface temperature. The variables are also adjusted according to the customer’s actual situation and can be further divided into four main application scenarios.

  • Scenario 1: uniform input heat flux, fixed flow rate, specified maximum pressure drop limited at a fixed flow rate, and specified maximum surface temperature where uniform surface temperature is not required
  • Scenario 2: Uniform input heat flux, fixed flow rate, specified maximum pressure drop limited at a fixed flow rate, and specified maximum surface temperature where uniform surface temperature is not required, with unevenly varying heat loads, generally concentrated in multiple locations under the component or under a specific area.
  • Scenario 3: Uniform input heat flux, fixed flow rate, specified maximum pressure drop limited at a fixed flow rate, and non-uniform variation in temperature at the surface of the cold plate, all with varying temperatures across the component.
  • Scenario 4: Same as scenarios 1, 2 and 3, but the maximum surface temperature must be uniform over the entire cold plate or under a specific component.

Based on Trumonytechs’s experience in designing cold panels, scenarios two and three are common scenarios encountered with fixed-cooled panels, but in the case of scenarios one and four, the complexity and cost of the design increases.
When designing a customer-specified fixed cooling panel, the steps taken by Trumonytechs thermal experts are to define the thermal map, generate a liquid circuit concept, calculate the temperature rise and pressure drop, and change the liquid circuit route if necessary.

We prototype the design based on the parameters entered by the customer and design the cold plate with the most reliable process. After the design is completed, the cold plate is simulated and tested (cold plate pressure drop, inlet temperature, outlet temperature, temperature difference between the inlet and outlet of the cold plate, maximum temperature difference between the surface of the cold plate and the maximum temperature difference of the battery pack) to see the feasibility of the design before proceeding to the next step of mass production.

liquid cooling plates runner design

Our design step-by-step process:

1. First form the liquid circuit concept then calculate the temperature and pressure drop

2. Determine cold plate material

1) Cost, availability, processability and other general design factors
2. Thermal conductivity, chemical compatibility with the liquid, material density, freezing point and boiling point

3. Flow path design

The direction of the fluid in a liquid cooling system will directly affect the direction of heat transfer and transfer efficiency, our engineers consider factors such as:

  1. Heat source distribution: the fluid is as close as possible to the heat source to reduce the diffusion heat resistance
  2. Structural avoidance: the flow path should be at a safe distance from the fixed holes in the cold plate
  3. Uniform layout: the fluid should sweep evenly across the cold plate to make effective use of the heat sink area
  4. Control the flow rate: the greater the flow rate, the higher the convective heat transfer coefficient
  5. Reduce flow resistance: design series and parallel flow channels to reduce flow resistance and reduce the risk of leakage
  6. Feasibility and processability

How to reduce complexity and production costs

The creation of a liquid-cooled plate goes through a series of processes before it becomes a standard product in production. The first step is to discuss the theoretical drawings (for the production of liquid-cooled panels in case of customisation), Tronytechs will respond to their needs within 24 hours and hold a technical seminar to shorten the development cycle and to push the project forward; if no liquid-cooled drawings are available, we will arrange for the appropriate technical engineer to meet your liquid-cooled needs. processors.

“When faced with complex liquid cooling requirements, the Trumonytechs team will take into account a number of factors, in addition to the heat dissipation power required by the product itself (ultra-high/ultra-low), the operating environment (rapid changes in high and low temperatures), the thermal parameters of the core and potential safety hazards, etc. Trumonytechs will focus on reducing the complexity of the cooling plate, from the discussion of design dimensions, the choice of liquid cooling plate style (plate, fin, microchannel tube, etc.), the adjustment of the runner arrangement and circuit optimisation, the distribution of the heat dissipation area, the determination of the production process (CNC, FSW, CMT, FDS, MIG, TIG and more), the spare parts The whole range of components (liquid-cooled cases, heat-conducting silicone mats, quick-plug connectors, piping, through-box connectors, battery coolers, etc.) is supported by Yangchi Technology.

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