Multi Axial Creep Fatigue Damage Accumulation in Vacuum Brazed Battery Pack Cooling Structures
Vacuum brazed aluminum cooling plates fail under coupled multi-axial creep-fatigue when pressure pulses interact with static cell swelling constraints.
Aluminum Cooling Plates
Meaning
Thermal management devices extract heat from lithium-ion battery cells by circulating fluid through internal channels or bonded tubes pressed against module housings. Aluminum cooling plates transfer thermal energy away from active chemistry during high-current charging and discharging cycles. Extruded aluminum alloys possess high thermal conductivity and low mass density, making them suitable for housing fluid pathways without adding excessive dead weight to the battery pack.
Coolant fluid flows through micro-channels inside the plate, absorbing heat through conduction and carrying it to an external heat exchanger. Material selection prioritizes corrosion resistance and mechanical yield strength to withstand internal fluid pressure and vibration loads experienced during vehicle operation.
Thermal Resistance
Engineers measure the efficiency of aluminum cooling plates by evaluating the thermal boundary resistance between the cell surface and the cooling fluid. Interfacial gaps reduce heat transfer rates, so manufacturers apply thermal interface materials or pressure pads to eliminate air voids. Thermal grease or gap filler pads conform to microscopic surface irregularities, lowering the total thermal resistance across the assembly.
Lower thermal resistance values allow higher continuous discharge currents without exceeding the maximum operating temperature limits specified by the cell manufacturer.
Fluid Dynamics
Internal channel geometry dictates the pressure drop and pumping power required to circulate the coolant through the cooling circuit. Narrow channels increase fluid velocity and turbulence, which improves convective heat transfer coefficients at the expense of higher hydraulic resistance. Coolant flow distribution must remain uniform across all parallel channels to prevent localized hot spots within large format battery modules.
Pressure sensors and flow meters verify that the fluid delivery system operates within the designed parameters for mass flow rate and allowable pressure drop.
Structural Integrity
Mechanical durability requirements dictate that aluminum cooling plates withstand cyclic pressure pulses and vibrational stress over the service life of the energy storage system. Burst pressure testing determines the maximum internal pressure the plate can tolerate before structural failure occurs. Brazing quality and weld integrity prevent coolant leakage into the electrical enclosure, avoiding short circuits and catastrophic thermal runaway events.
Corrosion inhibitors mixed with water-glycol coolants protect the internal aluminum surfaces from pitting and galvanic degradation caused by dissimilar metals in the hydraulic loop.