High heat flux brings about severe thermal problems for light-emitting diode (LED) automotive headlamps in narrow heat removal spaces, which will degrade their performance and lifespan. This study proposes an easily fabricated and feasible 1.3 mm thick 2D T-shaped in-plane ultra-thin vapor chamber (UTVC) for cooling the high heat flux of LED automotive headlamps. The effects of heating modes, unequal input heat load, and orientations on the thermal performance of the T-shaped UTVC are investigated. The results show that double-sided heating can improve the temperature uniformity of the T-shaped UTVC and reduce the thermal resistance compared to the single-sided heating. The lowest thermal resistances under single-sided and double-sided heating are 1.127 K/W at 12 W and 0.898 K/W at 16 W, respectively. When the total power is identical, the proposed 2D T-shaped UTVC can work effectively at unequal input power. The orientations have a significant impact on the thermal performance of the 2D T-shaped UTVC, and the thermal performance under different orientations changes with anti-gravity state < horizontal state < gravity-assisted state. The proposed T-shaped UTVC can work effectively under diverse operating ranges.

This paper presents a circular ultra-thin vapor chamber (UTVC) with a thickness of 1.3 mm for LED lamp thermal management. Superhydrophilic patterned microstructure (SPMS) arrays are fabricated on the upper and bottom covers to replace the traditional wick structure. The heat transfer performance of the ultra-thin vapor chamber was experimentally investigated under different cooling water temperatures in the horizontal orientation. The cooling water temperatures range from 25 to 40 °C, and the input-heat loads range from 5 to 25 W. The results show that for the proposed UTVC with SPMS arrays, the temperatures rise rapidly with increasing input-heat load and then level off after a certain period, with the temperature rise being considerably smaller than that of the ceramic heater. The condenser temperature difference increases with both the input-heat load and the cooling water temperature, and it ranges from 1.2 to 7.3 °C. Both the heater-to-vapor-chamber thermal resistance and the system thermal resistance increase with a higher input-heat load and a lower cooling water temperature. The heater-to-vapor-chamber thermal resistance ranges from 0.80 to 1.34 K/W, and the system thermal resistance ranges from 3.10 to 4.13 K/W.