Flat vs Spiral Baffles: Material Selection & Performance Comparison
Design Comparison: Flat vs. Spiral Flow Path
Internal cooling channels inside core pins require divider plates to guide the water up and down. The divider design significantly alters fluid behavior:
Flat Baffles (Straight Divider)
A flat metal or plastic sheet divides the channel into two equal semi-circular paths. The water flows straight up, turns $180^\circ$ at the top, and flows straight down.
Fluid Mechanics: To achieve turbulent heat transfer, flat baffles require high velocity, corresponding to a Reynolds number **$Re > 10,000$**. The primary issue is the stagnant zone at the top corners, where boundary layers separate, leading to local heat buildup.
Spiral Baffles (Rotational Guide)
A spiral structure wraps around a central stem, forcing the coolant to follow a helical path up and down the channel.
Fluid Mechanics: The helical path generates centripetal forces, creating secondary swirl flows. These vortices break down the boundary layer and generate turbulent mixing at a lower Reynolds number **$Re > 4,000$**. This allows high heat transfer coefficients even with lower-volume cooling pumps.
Material Comparison Matrix
Baffle material choice impacts corrosion resistance, thermal conductivity, and mechanical durability under thermal cycling:
| Baffle Material | Thermal Conductivity ($k$) | Max Temperature | Chemical Resistance | Tensile Strength |
|---|---|---|---|---|
| Brass (C3604) | $109\text{ W/m·K}$ | $200^\circ\text{C}$ | Moderate (susceptible to dezincification) | High |
| Stainless Steel (SUS304) | $16\text{ W/m·K}$ | $250^\circ\text{C}$ | Excellent (resists soft water corrosion) | Very High |
| Nylon-GF30 (Polyamide) | $0.3\text{ W/m·K}$ | $120^\circ\text{C}$ | Excellent (inert to water treatment chemicals) | Moderate |
For chemical safety and material standard reference, consult ISO material specifications.
Pressure Drop vs. Heat Transfer Efficiency
The spiral baffle's longer helical path length increases wall friction, which raises the overall pressure drop ($\Delta P$) in the circuit. Molds with numerous deep cores must balance the thermal benefits of spiral baffles against the risk of reducing total flow below the turbulent threshold. In circuits where pressure is limited, standardizing on high-flow brass flat baffles is often preferred.