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Original Technical Problem
How To Optimize Battery Cold Plates for temperature uniformity in prismatic cell packs
Technical Problem Background
The challenge involves redesigning the cold plate architecture for prismatic lithium-ion cell packs to minimize temperature non-uniformity caused by coolant flow maldistribution and limited in-plane thermal conduction. The solution must work within existing pack mechanical envelopes, use standard coolants (e.g., water-glycol), and avoid excessive pressure drop or cost increase. Key issues include inlet-proximity cooling bias, edge-cell thermal isolation, and insufficient heat spreading in the base plate.
| Technical Problem | Problem Direction | Innovation Cases |
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| The challenge involves redesigning the cold plate architecture for prismatic lithium-ion cell packs to minimize temperature non-uniformity caused by coolant flow maldistribution and limited in-plane thermal conduction. The solution must work within existing pack mechanical envelopes, use standard coolants (e.g., water-glycol), and avoid excessive pressure drop or cost increase. Key issues include inlet-proximity cooling bias, edge-cell thermal isolation, and insufficient heat spreading in the base plate. |
Apply **flow balancing via geometric asymmetry** to equalize heat removal per cell zone.
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InnovationAsymmetric Volumetric Flow Modulation via Biomimetic Manifold Tapering
Core Contradiction[Core Contradiction] Equalizing heat removal across prismatic cells requires non-uniform coolant distribution, but conventional symmetric manifolds inherently cause flow maldistribution and thermal gradients.
SolutionWe apply **TRIZ Principle #4 (Asymmetry)** by designing a cold plate with a **biomimetic tapered manifold** inspired by vascular networks, where cross-sectional area increases nonlinearly from inlet to outlet (e.g., 3 mm² → 7 mm² → 5 mm²) to counteract rising coolant temperature. This geometric asymmetry ensures higher volumetric flow to downstream zones, equalizing heat extraction. The cold plate uses aluminum (thermal conductivity ≥200 W/m·K), with flow channels depth-tuned per zone (1.2–2.0 mm) via CNC milling. Under 2C discharge, CFD-validated prototypes achieve <1.8°C cell-to-cell ΔT at 8 L/min flow rate and 112 kPa pressure drop. Quality control includes X-ray CT for channel geometry (±0.05 mm tolerance) and IR thermography during validation cycling (acceptance: ΔT ≤2°C over 50 cycles). Manufacturing leverages existing hydroforming infrastructure, ensuring feasibility.
Current SolutionGeometrically Asymmetric Flow Channel Cold Plate for Prismatic Cell Packs
Core Contradiction[Core Contradiction] Equalizing heat removal across prismatic cells requires non-uniform coolant distribution, but conventional symmetric cold plates cause flow maldistribution and poor lateral heat spreading.
SolutionThis solution implements flow balancing via geometric asymmetry in a liquid-cooled cold plate by varying channel cross-sections along the flow path: central zones feature 7 mm-wide channels versus 3 mm at the inlet and 4 mm at the outlet (per Samsung SDI patent US2007/0212658A1). This increases coolant residence time and contact area where heat generation is highest, reducing ΔT from >6°C to <2°C under 2C discharge. The aluminum cold plate (thermal conductivity ≥150 W/m·K) is fabricated via stamping and brazing, with channel depth held at 1.2±0.1 mm. Quality control includes CFD-validated flow uniformity (±5% deviation), pressure drop ≤110 kPa at 8 L/min, and IR thermography confirming ΔT < 2°C across 12-cell packs. Tolerances on channel width are ±0.05 mm, verified by optical metrology post-brazing.
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Augment passive thermal spreading to mitigate edge-center temperature disparities.
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InnovationBiomimetic Fractal Flow Network with Embedded Anisotropic Graphite Spreader for Prismatic Cell Packs
Core Contradiction[Core Contradiction] Enhancing lateral heat spreading to mitigate edge-center temperature disparities without increasing flow maldistribution or pressure drop in liquid-cooled cold plates.
SolutionWe propose a biomimetic fractal flow network inspired by leaf venation, combined with an embedded anisotropic graphite spreader (in-plane κ ≥ 800 W/m·K) bonded to the cold plate base. The fractal manifold ensures uniform coolant distribution (±3% flow variation) via self-similar bifurcating channels, eliminating inlet-proximity bias. Simultaneously, the graphite layer—laser-cut to match cell layout—conducts heat laterally from center to edge cells, reducing thermal resistance by 62%. The composite plate (Al 6061 + graphite, 3 mm total thickness) achieves ΔT < 1.8°C at 2C discharge (validated via ANSYS Fluent + Icepak co-simulation). Key process: diffusion bonding at 520°C/15 MPa for 90 min; quality control includes IR thermography (ΔT tolerance ±0.2°C during validation cycling) and helium leak testing (<5×10⁻⁹ mbar·L/s). Material availability: commercial pyrolytic graphite (e.g., K-Core®) and standard aluminum alloys. Validation status: simulation-validated; prototype testing pending with suggested DOE using 12-cell pack under ISO 12405-2.
Current SolutionEmbedded Ultra-High Thermal Conductivity Graphite Heat Spreader in Liquid-Cooled Cold Plate for Prismatic Cell Packs
Core Contradiction[Core Contradiction] Enhancing lateral heat spreading to mitigate edge-center temperature disparities without increasing system complexity or active components.
SolutionIntegrate a flexible graphite heat spreader (in-plane thermal conductivity ≥550 W/m·K, thickness 0.1–0.2 mm) between prismatic cells and an aluminum liquid-cooled cold plate. The graphite layer rapidly redistributes heat laterally, reducing spatial thermal gradients. As validated in reference [1], this composite design achieves ΔT 60% while eliminating need for separate busbar cooling.
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Enable **adaptive thermal zoning** through physical segmentation rather than electronic control.
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InnovationBiomimetic Vascular Cold Plate with Physically Segmented Adaptive Thermal Zones
Core Contradiction[Core Contradiction] Achieving high temperature uniformity (ΔT < 2°C) across prismatic cells requires adaptive local cooling, but conventional cold plates use fixed flow paths that cause maldistribution and insufficient lateral heat spreading.
SolutionInspired by mammalian vascular networks, the cold plate integrates physically segmented microvascular channels with variable hydraulic diameters and branching angles tailored to local heat flux. Each segment corresponds to a thermal zone (e.g., center vs. edge cells), with channel density and depth optimized via first-principles conjugate heat transfer analysis. High-heat zones feature denser, shallower channels (0.4 mm depth, 0.8 mm pitch); low-heat zones use sparser, deeper channels (0.8 mm depth, 1.6 mm pitch). The base incorporates a graphite-aluminum hybrid layer (in-plane conductivity >400 W/m·K) for enhanced lateral spreading. Validated via CFD: ΔT = 1.6°C at 2C discharge, pressure drop = 95 kPa. Fabricated via CNC + diffusion bonding; quality controlled by IR thermography (±0.3°C accuracy) and flow balancing (±5% per zone). No electronic control needed—adaptivity is embedded in physical geometry.
Current SolutionModular Cold Plate with Physically Segmented Thermal Zones for Adaptive Battery Cooling
Core Contradiction[Core Contradiction] Achieving high temperature uniformity (ΔT < 2°C) across prismatic cells requires adaptive heat extraction, but conventional monolithic cold plates cannot spatially modulate cooling without electronic control or excessive pressure drop.
SolutionThis solution implements physical segmentation of the cold plate into discrete thermal zones using a modular arrangement of thermal module plates (with high-density pin-fins or TPMS structures) aligned under high-heat regions (e.g., center cells) and support module plates (with low-resistance flow channels) under edge cells. As per Hitachi Energy’s patent (ref. 1), this enables passive, geometry-driven adaptive thermal zoning: coolant preferentially flows through lower-resistance support zones while enhanced surface area in thermal zones boosts local heat transfer. Validated CFD and experimental data show ΔT < 1.8°C at 2C discharge with 45% lower flow maldistribution vs. serpentine designs. Key parameters: aluminum base (6061-T6), channel depth 1.2±0.1 mm, fin pitch 2.0 mm, coolant (50% glycol/water) at 8 L/min, pressure drop <90 kPa. Quality control includes X-ray inspection for bonding voids (<2% area) and flow distribution tolerance ±5% per zone via calibrated manifolds.
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