What is the Optimum Design of a Cooling Plate for Uniform Cooling?

A question the battery thermal team often face is: What is the Optimum Design of a Cooling Plate for Uniform Cooling? To achieve optimum uniform cooling, a cold plate must be designed to minimize temperature gradients across its surface and prevent localized hotspots.

Cell to Cell Temperature Gradient

The cell to cell temperature gradient in a battery pack will limit the performance and lifetime. However, there will always be a cell temperature gradient and a cell to cell temperature gradient. It is very difficult not to have if we are rejecting or absorbing heat.

However, we can reduce the variations with good cooling plate designs

The optimum design for uniform cooling incorporates the following strategies:

1. Advanced Flow Routing and Topologies

• Counter-Flow and Series-Parallel Channels: Simple straight channels are ill-suited for uniform cooling because the coolant temperature increases linearly from inlet to outlet, creating a massive temperature gradient.
  • Counter-flow arrangements—where fluid is routed in opposite directions in adjacent channels—effectively cancel out this temperature gradient.
  • Similarly, parallel-serpentine (or series-parallel) configurations combine the low pressure drop of parallel branches with the comprehensive surface coverage of serpentine routing, effectively eliminating flow “dead zones” and balancing the temperature field.

Counter flow, a top view where instead of a single flow front across the cell groups, you can provide a flow channel with a return loop under each cell. This gives you a better cell to cell balance since the coldest inlet temperature gets paired with the warmest outlet temperature.

The trade-off is that you now have a temperature gradient across the individual cells. This is helped somewhat by the rest of the conductive cooling element that helps heat flow across that individual cell gradient. Ian Stines

Porsche Cayenne EV: Liquid cooling plates are arranged on the top and bottom of each module.

The cells appear to interface directly via Thermal Interface Material (TIM) with each plate (see module image below).

Cooling on both long edges of each cell will halve the top to bottom temperature delta in a cell.

• Bionic and Fractal Branching: Mimicking biological networks like leaf veins, blood vessels, and spider webs allows for hierarchical branching that distributes fluid smoothly over a large area. These bionic structures maintain high fluid velocities near heat-intensive areas (like battery electrode tabs) and use fine branches to penetrate stagnant corner zones, reducing surface temperature variance by over 60% compared to traditional designs.
• Topology Optimization (TO): Using computer algorithms to mathematically dictate material distribution results in organic, tree-root-like channel structures. Because TO inherently sizes flow branches according to local pressure requirements, it perfectly balances velocity, eliminates stagnant regions, and creates near-isothermal conditions across the plate.

2. Multi-Inlet and Multi-Outlet (MIMO) Manifolds

A single-inlet, single-outlet system forces coolant to travel a long path, absorbing heat the entire way.

• Transitioning to Single-In, Multiple-Out (SIMO) or MIMO layouts (such as three inlets and three outlets) divides the effective path length, frequently “resetting” the coolant temperature and significantly improving the uniformity coefficient.

• Strategic placement, such as a single-inlet, dual-outlet configuration or a side-inlet, middle-outlet (CM-type) design, has been proven to optimize flow symmetry, producing the smallest possible high-temperature regions.

3. Internal Channel Perturbations

• Dimples and Turbulators: Instead of relying strictly on serpentine channels, incorporating “dimples” into the cooling plate breaks up the fluid flow and locally increases velocity. This improves the heat transfer coefficient and temperature uniformity without the massive pressure drop penalties typical of serpentine designs.

Ford Mach-E: The water enters at the centre on one side of the plate and then flows around the “race track” and back via each side to the central outlet. The dimples manage the structural offset of the two halves of the plates and break up the liquid flow.

• The pressure drop offered by this type of a design is less compared to a standard S bend for the same channel height.
• The density of these dimples are adjusted to spread the flow towards the edges of the plate from the centre and also to locally increase the fluid velocity by decreasing the sectional area.
• The person in the video was talking about turbulent flow. When a flow exits into a large cross sectional area such as this, the flow is mainly laminar.
• Not much information is available on the distance between the top plate and the bottom plate. This is an important factor that decides the pressure drop and the heat transfer coefficient. However, this design heavily relies on the large surface area for convective heat transfer rather having a high heat transfer coefficient.
• The top plate is used to reduce the temperature difference between the inlet and outlet of the coolant due to its higher conductivity.

• Gradually Varied Fins: Instead of using uniform internal fins, using Gradually Varied Circular Notched Fins (GV-CNF) minimizes localized heat accumulation. By varying fin sizes and shapes along the flow path, the design continuously disrupts the fluid boundary layer without creating massive pressure drops, leading to a highly uniform wall temperature.
• Cavities and Tesla Valves: Incorporating hemi-circular cavities or Tesla-valve bifurcations into the channel walls induces vortex formation and fluid mixing. This fluid-on-fluid interaction improves thermal uniformity by up to 70% while actually reducing pressure drop compared to solid pin-fin obstructions.

4. Hybrid Cooling Enhancements

• Jet-Impingement/Micro-Channel (JIMC): In standard microchannels, heat transfer efficiency decays along the flow direction as the liquid warms. JIMC systems solve this by forcing coolant through an array of micro-holes, creating jets that impinge directly and evenly across the entire heated surface before the fluid routes into microchannels. This supplies cool fluid everywhere simultaneously, providing exceptional temperature uniformity.
• Vapor Chambers and Phase Change Materials (PCMs): For systems with transient heat spikes, coupling the liquid cold plate with vapor chambers drastically reduces the maximum temperature difference. Alternatively, embedding PCMs within the cold plate structure allows the system to absorb heat spikes uniformly through the latent heat of fusion, maintaining a steady, isothermal surface during fluctuating thermal loads.

Cooling Plate Design

There are many key aspects that we need to consider in the design of a cooling plate, including:

1. Thermal Load and System Requirements
2. Internal Flow Channel Architecture
3. Material Selection and Galvanic Corrosion
4. Coolant Chemistry
5. Manufacturing and Structural Integrity
6. Thermal Interface and Mechanical Mounting

References

1. Yang, Z.; Yao, Q.; Wang, Y.; Gu, J.; Yu, Z.; Li, Q.; Sun, X.; Yang, X. Optimization of Heat Transfer and Flow Performance of Microchannel Liquid-Cooled Plate Based on Orthogonal Test. Buildings 2025, 15, 905.
2. Zhu H, Shi P, Dong X, Hai B. Numerical Analysis of Temperature Rise Characteristics of Parallel Serpentine Channel Lithium Battery Modules. ACS Omega. 2025 Jul 16;10(29)
3. Tang, Z., Xiang, Y., Li, M., and Cheng, J. (November 30, 2023). “A Novel Liquid Cooling Battery Thermal Management System With a Cooling Plate Based on Biomimetic Fractal Channels.” ASME. J. Electrochem. En. Conv. Stor. November 2024; 21(4)
4. Gao, H.; Hou, X.; Ma, W.; Ma, Y. Design and Thermal Performance Analysis of a Liquid Cooling Plate Based on Gradually Varied Circular Notched Fins for Lithium-Ion Batteries. Processes 2025, 13, 924.