| Tube Material | Aluminum alloys, such as 3003 or 6063 | Low density, good thermal conductivity, and good formability. Aluminum is widely used where low mass and efficient heat transfer are priorities. | Tube dimensional control, surface cleanliness, alloy verification, and leak testing should be established for each production lot. | Suitable for lightweight battery packs. Internal corrosion protection and coolant compatibility must be evaluated when the coolant contains water or glycol. |
| Tube Material | Austenitic stainless steel, such as 304L or 316L | High corrosion resistance, good mechanical strength, and good resistance to elevated temperature. Stainless steel generally has lower thermal conductivity than aluminum or copper. | Tube welding, annealing where required, weld-bead inspection, dimensional inspection, and pressure or helium leak testing are commonly used. | Appropriate for demanding corrosion environments or applications requiring higher mechanical robustness. The additional mass and lower thermal conductivity should be considered. |
| Tube Material | Copper, such as C11000 or C12200 | Very high thermal conductivity and good formability. Copper is heavier and can require careful galvanic-corrosion control when joined to aluminum components. | Material certification, tube-wall inspection, brazed-joint quality control, cleanliness testing, and leak testing are important. | Useful where heat transfer is the primary requirement. Isolation coatings or compatible joining methods may be needed in mixed-metal assemblies. |
| Tube Material | Engineering polymers or multilayer polymer tubes | Low weight, electrical insulation, and good chemical resistance can be achieved with suitable polymer systems. Thermal conductivity is usually lower than that of metals. | Material batch control, dimensional stability, burst testing, permeation testing, coolant compatibility testing, and connector retention testing are required. | Suitable for electrically isolated routing and flexible connections. Temperature, pressure, permeation, aging, and flame-performance requirements must be defined. |
| Tube Geometry | Round, flattened, serpentine, or formed tube | Geometry influences coolant velocity, pressure drop, contact area, packaging efficiency, and local heat-transfer performance. | CNC bending, roll forming, hydroforming, or dedicated forming tools may be used. Final parts require checks for bend radius, flattening, twist, and deformation. | A flattened or serpentine tube can improve module contact and packaging efficiency, while a round tube may simplify joining and pressure management. |
| Manufacturing Process | Extrusion and drawing | Extrusion creates the basic aluminum or copper tube profile; drawing can improve dimensional accuracy, wall uniformity, and surface finish. | Process controls normally include die condition, drawing reduction, wall-thickness measurement, straightness, and surface-defect inspection. | Appropriate for repeatable tube profiles and higher-volume production. Tooling design should account for the required cross-section and bendability. |
| Manufacturing Process | Bending and three-dimensional forming | Produces routing paths that match battery-pack geometry and can reduce the number of joints and fittings. | Typical checks include bend angle, centerline radius, end position, ovality, wrinkling, cracking, and blockage of the coolant passage. | Proper tooling and bend-radius selection help prevent wall thinning and flow restriction, especially with thin-wall tubing. |
| Manufacturing Process | Laser welding, TIG welding, brazing, or controlled soldering | The joining method affects joint strength, heat-affected zones, cleanliness, corrosion resistance, and leak performance. | Weld parameters, joint preparation, shielding gas, filler material, and inspection criteria should be documented. Cross-section analysis may be used for process validation. | Laser welding supports precise, automated joints; brazing can join compatible dissimilar components but requires careful flux and residue control. |
| Connection Design | Quick connectors, bead-lock fittings, flared joints, or welded ports | Connections must maintain sealing performance under vibration, thermal cycling, pressure variation, and coolant exposure. | Recommended checks include insertion force, pull-out force, seal compression, dimensional fit, pressure cycling, and leak testing. | Connector material, elastomer selection, and electrical isolation should be compatible with the coolant, operating temperature, and service life. |
| Sealing System | EPDM, FKM, HNBR, or other coolant-compatible elastomers | Seal performance depends on temperature range, glycol concentration, additives, compression set, and exposure time. | Seal validation commonly includes immersion aging, compression-set testing, thermal cycling, pressure cycling, and post-aging leakage inspection. | The elastomer should be selected from coolant compatibility data rather than from temperature rating alone. |
| Surface Treatment | Cleaning, anodizing, conversion coating, or protective coating | Surface treatment can improve corrosion resistance, bonding performance, electrical isolation, or resistance to handling damage. | Cleanliness, coating thickness, adhesion, appearance, chemical resistance, and electrical insulation should be verified where applicable. | Internal surfaces must remain free from loose particles, oil, flux, and coating debris that could contaminate the coolant circuit. |
| Thermal Performance | Coolant flow rate, channel layout, and contact area | Cooling performance is governed by coolant properties, flow distribution, tube-wall resistance, contact resistance, and heat-source temperature. | Thermal testing should measure inlet and outlet temperatures, flow rate, pressure drop, and temperature uniformity under representative heat loads. | A design with high nominal heat-transfer capability may still perform poorly if flow is uneven or contact with the battery module is inconsistent. |
| Hydraulic Performance | Pressure drop and flow distribution | Pressure drop increases with tube length, bends, fittings, roughness, and flow rate. Parallel channels require balanced hydraulic resistance. | Flow-versus-pressure-drop curves should be established using the intended coolant and temperature range. Blockage and partial-flow conditions should also be assessed. | Lower pressure drop reduces pump power, while adequate flow velocity helps maintain heat-transfer performance and temperature uniformity. |
| Leak and Pressure Testing | Air-under-water, pressure decay, or helium leak testing | Leak testing verifies the integrity of tubes, welds, brazed joints, fittings, and seals. Test sensitivity depends on the selected method and equipment. | Test pressure, hold time, allowable leakage, test medium, and acceptance criteria must be defined in the product specification and production control plan. | The test method should represent the actual service risk and should not damage seals or deform thin-wall tubing. |
| Cleanliness Control | Flushing, filtered drying, and sealed packaging | Residual particles, oil, moisture, flux, and metal debris can restrict flow, contaminate coolant, or damage pumps and valves. | Controls may include particulate inspection, gravimetric residue testing, filtered flushing, moisture control, capped ports, and controlled packaging. | Cleanliness requirements should be defined by particle size, particle count, ionic residue, moisture level, and packaging duration where relevant. |
| Durability Validation | Thermal cycling, vibration, pressure cycling, and corrosion testing | Battery cooling pipes experience temperature changes, vibration, assembly loads, coolant exposure, and pressure fluctuations throughout their service life. | Validation plans commonly combine thermal cycling, vibration, pressure cycling, coolant aging, salt or environmental exposure, and post-test leak inspection. | Test limits should be based on the actual vehicle or energy-storage-system environment rather than on material properties alone. |
| Supplier Selection Criteria | Material traceability, process capability, and quality documentation | A capable supplier should demonstrate repeatable dimensions, stable joining processes, documented inspection, and controlled change management. | Important records include material certificates, process-control plans, inspection reports, leak-test records, capability studies, and corrective-action procedures. | The best supplier is not determined by material choice alone; design support, validation capacity, production consistency, and long-term serviceability are equally important. |
