Does Your Headlamp Design Delay Condensation Clearing?
Case Studies, United States
Our study showed enclosure design greatly affects clearing times.
For automotive headlamps, a venting solution must provide three critical functions: responsive pressure equalization, reliable protection against ingress of water/fluids and particulates, and condensation management. While lamp design has little effect on the first two functions, design factors can significantly impact a vent’s ability to quickly clear condensation.
A recent Gore laboratory study compared the condensation clearing times achieved by two identical GORE® Automotive Vents (AVS 9) in two very different headlamp enclosure designs (each from a leading OEM).
The headlamps, identified in this paper as “Lamp A” and “Lamp B,” were chosen based upon OEM request. Lamp B was from a vehicle identified as having no warranty claims related to condensation. “Lamp A” was from a vehicle for which no warranty data was provided.
To confirm why one lamp had more warranty complaints than the other, Gore engineers conducted a two-step analysis.
Step 1: Condensation Clearing Test
Gore developed a proprietary test protocol to evaluate the condensation performance of headlamps.
The Gore test includes preconditioning to ensure lamp conditions at the start of the test are identical. Temperature and relative humidity are controlled during the testing, to isolate the effect of lamp design on condensation clearing performance.
Under identical test conditions, using the identical vent, Lamp A took more than six times longer to clear than Lamp B.
Further, this result was congruent with the warranty data, where no condensation-related warranty claims were reported for Lamp B.
Step 2: Visual analysis / disassembly of each lamp
Fick’s Law
Visual analysis provides clear evidence of Lamp B’s much faster condensation clearing time compared to Lamp A.
Lamp B’s faster clearing time is attributed to the fact that its internal lamp design is more favorable to diffusion. The process of diffusion is governed by Fick’s Law.
Diffusive Paths from Lens to Vent
To facilitate diffusion, maximize the A/dx ratio between areas of high and low moisture concentration. We can more clearly illustrate this principle by examining each lamp’s diffusive path.
In comparing these headlamp designs, we see that:
- Diffusive Path Length dxB < dxA
- Exchange Surface AA < Exchange Surface AB
Therefore AB/dxB >> AA/dxA and under equal concentration gradients, we would expect Lamp B to have faster clearing performance. This expectation is consistent with OEM warranty data.
Additionally, we would also expect lamp A to have greater potential for localized “cold spots” due to the close clearances, which can lead to condensation.
Summary
Consistent with previous data Gore has generated, this laboratory testing and visual analysis reinforce the conclusion that a lamp’s internal design can significantly impact how rapidly a diffusive vent can clear condensation.
Find out more about this experiment, and ask your local Gore representative about more condensation-management solutions for your automotive lighting.