AUTOMOTIVE HEADLAMP HIGH POWER LED COOLING SYSTEM AND ITS EFFECT ON JUNCTION TEMPERATURE AND LIGHT INTENSITY

1. Overview:

  • Title: AUTOMOTIVE HEADLAMP HIGH POWER LED COOLING SYSTEM AND ITS EFFECT ON JUNCTION TEMPERATURE AND LIGHT INTENSITY
  • Authors: Ramesh Kumar Chidambaram¹, Rammohan Arunachalam¹
  • Year of Publication: 2020
  • Journal/Conference: Journal of Thermal Engineering
  • Keywords: HPLED Cooling System, HPLED Junction Temperature, Headlamp Reflector Temperature, Halogen, Light Intensity

2. Background:

Automotive headlamps are crucial for nighttime safety and vehicle aesthetics. Historically, halogen and xenon bulbs were prevalent, but halogen bulbs are inefficient, generating significant heat, while xenon bulbs have slower ignition times. High-Power Light Emitting Diodes (HPLEDs) offer higher efficiency and longer lifespans, but their compact size leads to high junction temperatures when integrated into conventional headlamp assemblies, potentially reducing their lifespan. This necessitates the development of effective cooling systems for HPLEDs in automotive applications.

3. Research Objectives and Questions:

  • Research Objective: To design and test a compact cooling system for HPLEDs within a conventional headlamp assembly, evaluating its impact on junction temperature and light intensity.
  • Key Research Questions: How does a compact cooling system affect the junction temperature and light intensity of HPLEDs?
  • Research Hypothesis: A compact cooling system will decrease HPLED junction temperature and increase light intensity.

4. Methodology:

  • Research Design: A combined experimental and simulation approach was employed. ANSYS software was used to model and simulate various heatsink designs to optimize dimensions for the headlamp assembly.
  • Data Collection: Experiments were conducted on a popular SUV's headlamp assembly using a 16W CREE CXB1816 HPLED. Light intensity (in lux) was measured at various test points (up to 28 meters) on a flat black surface in the absence of external light sources. Temperature data was collected using thermocouples at multiple locations (heatsink and reflector).
  • Analytical Methods: ANSYS simulation results guided heatsink selection. Experimental data were analyzed statistically to determine the effects of the cooling system on junction temperature and light intensity. Airflow characteristics were analyzed using Reynolds number calculations.
  • Subjects and Scope: The study compared a 55W halogen bulb with a 16.2W HPLED within a modified headlamp assembly, investigating the impact of varying cooling fan speeds.

5. Main Findings:

  • Key Findings: The proposed cooling system reduced HPLED junction temperature by approximately 25% under laminar flow conditions. Light intensity increased by about 30.9% due to the temperature reduction. The HPLED headlamp reflector inner wall temperature was 49% lower than the halogen bulb's. For equivalent light intensity, HPLED consumed only one-third of the energy used by the halogen bulb.
  • Statistical/Qualitative Analysis: ANSYS simulations determined optimal heatsink dimensions. Experimental data demonstrated a direct correlation between cooling fan speed (airflow rate), junction temperature, and light intensity. Reynolds number calculations characterized the airflow regime.
  • Data Interpretation: Increased airflow resulted in lower junction temperatures and higher light intensities. A 1°C decrease in junction temperature corresponded to a 2.7 lux increase in light intensity at a specific test point.
  • Figure List and Description: Figures (1-12) detailed experimental setup, test point locations, temperature distributions (heatsink and reflector), light intensity profiles at various distances and angles, and the impact of cooling fan speed on junction temperature and light intensity.
Figure 3. Thermocouple mounting positions in the heatsink and headlamp reflector
Figure 3. Thermocouple mounting positions in the heatsink and headlamp reflector

6. Conclusions and Discussion:

The study demonstrated that the compact cooling system significantly improved HPLED performance, reducing junction temperature and increasing light intensity. The system offered substantial energy savings compared to halogen bulbs. While the experimental setup did not fully replicate real-world driving conditions, the findings provide valuable insights for HPLED headlamp design and thermal management. The simulation results provided a reasonable correlation with experimental findings.

7. Future Research:

Future work should involve testing under real-world driving conditions to validate the findings in a more representative environment. Further investigation into different HPLED types and cooling system designs is recommended. More sophisticated thermal modeling and simulation techniques could enhance the accuracy of the predictions.

8. References:

The paper cited numerous studies on LED thermal management and automotive lighting, supporting the methodology and contextualizing the findings. Specific details are omitted for brevity but are extensively present in the original paper.

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Copyright:

This summary is based on the paper "AUTOMOTIVE HEADLAMP HIGH POWER LED COOLING SYSTEM AND ITS EFFECT ON JUNCTION TEMPERATURE AND LIGHT INTENSITY" by Ramesh Kumar Chidambaram and Rammohan Arunachalam. (DOI information not provided).

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