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Cold Plate Design For Thermal Management

Liquid cooling methods are great because they cool well. The technology has two types. They are contact and non-contact. This division depends on whether they make direct contact with the heat-generating device. Contact liquid cooling solutions include immersion and spray cooling. Non-contact liquid cooling solutions are typically cold plate cooling.

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

The cold plate liquid cooling mainly transfers heat from the components to the cooling liquid. This liquid is in a pipe that surrounds the cold plate. The plate is a closed cavity made of thermally conductive metals like copper and aluminum. The cooling liquid carries the heat away. It uses the working fluid to take the heat to the back end for cooling.

Cold Plate Design For Thermal Management -Trumonytechs

Table of Contents

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 for liquid-cooled plates are similar to those for heat sinks. They are for air-cooled or naturally-cooled 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

  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. Heat dissipation factors can be divided into four variable types. These are uniform heat flux, fixed flow rate, maximum pressure drop, and maximum surface temperature. The variables are also adjusted to fit the customer’s needs. They can be divided into four main uses.

Scenario 1: The input is a uniform heat flux. The flow rate is fixed. The pressure drop is limited at a fixed flow rate. The surface temperature has a specified maximum. A uniform surface temperature is not required.

Scenario 2: The inputs are: a constant heat flux, fixed flow rate, and set maximum pressure drop. The system also has a set maximum surface temperature. The surface does not need to have a uniform temperature. Instead, the heat loads vary unevenly. They are generally concentrated in multiple locations under the component or a specific area.

Scenario 3: The input has uniform heat flux. The flow rate is fixed. The pressure drop is limited. The drop is limited at a fixed flow rate. There is non-uniform temperature variation on the surface of the cold plate. The temperatures vary across the components.

Scenario 4: It is the same as scenarios 1, 2, and 3. But, the maximum temperature must be uniform. It must be uniform over the whole cold plate or under a specific component.

Trumonytech has experience in designing cold panels. Scenarios two and three are common with fixed-cooled panels. But, for scenarios one and four, the design becomes more complex and costly. When designing a customer-specified fixed cooling panel, Trumonytechs thermal experts take these steps. They define the thermal map, make a liquid circuit concept, calculate the temperature rise and pressure drop, and adjust the circuit route if needed.

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 done, we simulate and test the cold plate. We check its pressure drop, inlet temperature, outlet temperature, and temperature differences. We also check the maximum temperature difference between the cold plate’s surface and the battery pack’s maximum temperature difference. These tests check if the design is feasible before 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 customization), Trumonytechs 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 several 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 optimization, 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 Trumonytechs.