Liquid Cold Plate Channel Design for a Battery Module

The problem

Liquid cold plates are the main thermal solution in car and many commercial-vehicle packs. The channel layout sets how evenly cells are cooled and how much pump power is needed. A serpentine channel is simple but builds up a temperature gradient and a large pressure drop; parallel channels flow unevenly unless the manifold is designed well. Quantifying these trade-offs is core work for a battery thermal engineer.

Objectives

• Define module heat load, coolant, flow rate and thermal targets from example cell data.
• Model a parametric cold plate with interchangeable channel layouts and a thermal interface layer.
• Run conjugate heat transfer studies for at least three layouts across a flow-rate sweep.
• Rank layouts by maximum temperature, temperature spread and pumping power, and validate with hand calculations.

What you need

Key concepts

Conjugate heat transfer

Conduction in cells, interface and plate is solved together with forced convection in the coolant, giving cell temperatures directly.

Flow maldistribution

In parallel channels, coolant takes the path of least resistance, so channels near the inlet often carry more flow. Manifold shape and channel resistance control this.

Pumping power

Hydraulic power equals pressure drop times volume flow. It rises steeply with flow rate, so higher flow buys lower temperatures at an increasing energy cost.

Hydraulic diameter and Reynolds number

Dh = 4A/P for a rectangular channel; Re = ρ·v·Dh/μ tells whether flow is laminar, which affects heat transfer and pressure-drop correlations.

Step-by-step guide

1. 1

   Set requirements and heat load

   Choose an example module of 12 prismatic cells in series, each with a datasheet internal resistance, and a design current giving a stated heat per cell. Add a margin for busbar heating. Set the coolant as a 50/50 ethylene glycol-water mix at an example inlet temperature of 25 °C, with a flow range of 1 to 6 litres per minute. Set example targets: maximum cell temperature under 40 °C, spread under 3 °C and pressure drop under a stated limit for an example pump.

   Checkpoint: A requirements sheet with heat per cell, coolant properties, flow range and three numeric targets.

2. 2

   Model cells, interface and plate

   Model each cell as a block with datasheet dimensions and pattern them on the plate. Model the thermal interface as a thin solid or, preferably, apply it later as a Flow Simulation contact resistance so it does not drive mesh size. Build the cold plate as a base with machined channels and a brazed cover, with plate thickness and channel width, depth and rib width as global variables. Choose a 3xxx-series or 6xxx-series aluminium from the material library and note the joining method assumed.

   Checkpoint: A rebuildable assembly where changing channel width updates every channel cut.

3. 3

   Create channel layouts

   Sketch each channel path on the plate top face and cut with Extruded Cut or a Sweep: a single serpentine, parallel straight channels in U-flow and Z-flow, and a parallel layout with tapered inlet and outlet manifolds to even out flow. Keep the cooled footprint and total wetted area similar so the comparison is fair. Hold each layout as a configuration and add inlet and outlet fittings. Close fittings with Create Lids.

   Checkpoint: Check Geometry reports one fluid volume for each configuration, and wetted areas are tabulated for comparison.

4. 4

   Define the coolant and materials

   In the Engineering Database, create a user-defined liquid for the glycol-water mix using property data from a reliable source at the operating temperature range, or temperature-dependent tables if available. Create a user-defined solid for the cells with effective conductivity, which is usually anisotropic for prismatic cells, and set it with orthotropic values where your data supports it. Assign aluminium to the plate. Record every property and its source.

   Checkpoint: Materials and fluid listed in the project with values and sources recorded in an appendix.

5. 5

   Set boundary conditions and goals

   Run the Wizard as Internal with Heat Conduction in Solids. Apply an Inlet Volume Flow on the inlet lid at the chosen flow and an Environment Pressure on the outlet lid. Apply Volume Sources to each cell and a Contact Resistance between cells and plate from the interface datasheet. Make outer surfaces adiabatic for a conservative case. Add Volume Goals for maximum and minimum cell temperature, Surface Goals for inlet and outlet pressure and an Equation Goal for pressure drop.

   Checkpoint: A trial run converges with all goals reported and outlet temperature above inlet temperature.

6. 6

   Mesh refinement and hand checks

   Add a Local Mesh in the channels so that at least four to five cells span channel depth, and use refinement at fluid-solid interfaces. Run three mesh levels for the serpentine case and confirm maximum cell temperature changes under 0.5 °C and pressure drop under 5 per cent. Hand-calculate Reynolds number and a Darcy-Weisbach pressure drop including bend losses, and compare. Check the coolant temperature rise against Q = ṁ·cp·ΔT.

   Checkpoint: Converged mesh, hand pressure drop within about 20 per cent and an energy balance within 3 per cent.

7. 7

   Run the flow-rate sweep

   Set up a Flow Simulation Parametric Study with inlet volume flow as the variable from 1 to 6 litres per minute in steps, for each layout configuration. Collect maximum cell temperature, cell temperature spread, pressure drop and pumping power. Plot maximum temperature against pumping power for each layout; this Pareto-style plot shows which layout gives the coolest cells for the least energy.

   Checkpoint: One plot per metric with every layout, and a temperature-versus-pumping-power plot that separates the layouts clearly.

8. 8

   Diagnose maldistribution

   For the parallel layouts, add Surface Goals for mass flow in each channel and plot flow per channel. Use Cut Plots of velocity in the manifold to show where flow concentrates. Adjust the manifold taper or channel inlet widths in the tuned configuration until channel flows are within an example ±10 per cent of the mean. Re-run and show the effect on cell temperature spread.

   Checkpoint: A bar chart of flow per channel before and after manifold tuning, with spread within the target band.

9. 9

   Check plate structure

   Take the highest operating pressure plus a safety margin and apply it as a uniform pressure inside the channels in a SOLIDWORKS Simulation static study of the cover plate, with the brazed ribs bonded and fittings fixed. Check stress against the yield strength of the alloy in the brazed or annealed condition and keep deflection small enough not to open gaps at the interface. Note that braze joints need their own test.

   Checkpoint: Factor of safety above an example 2 and cover deflection below an example 0.1 mm.

10. 10

    Drawings and report

    Make drawings of the chosen plate with channel geometry, flatness tolerance on the cell face, fitting threads and ISO 2768 general tolerances. Write up heat load, properties, set-up, mesh and hand checks, sweep results, maldistribution tuning and structure check. State limits: steady state, uniform heat generation and assumed properties. Recommend a test rig with a heater block in place of cells and thermocouples at predicted hot and cold spots.

    Checkpoint: A drawing and a report with a recommended layout and flow rate, and a validation test plan.

Testing & validation

• Mesh convergence on maximum cell temperature within 0.5 °C and pressure drop within 5 per cent.
• Coolant temperature rise agrees with Q = ṁ·cp·ΔT within 3 per cent.
• Pressure drop agrees with a Darcy-Weisbach hand calculation within about 20 per cent.
• Cover plate structural check shows safety factor above the stated target.

Expected results

A parametric cold plate with four layouts, temperature and pressure results across a flow sweep, a tuned manifold with even channel flow and a recommended layout and operating flow backed by hand checks and a structural check.

Take it further

• Run a transient fast-charge heat profile and check peak temperature.
• Compare a stamped and brazed plate with a machined plate using SOLIDWORKS Costing.
• Add a heater-block test rig to validate the CFD.
• Study bottom versus side cooling for the same module.

Viva and review questions

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