Thermal performance of a central-jetting microchannel heat sink designed for a high-power laser crystal

Thermal management has become one of the critical problems in high-power laser systems. The laser crystal, which dissipates a heat flux over 150 W/cm(2), is the most challenging component when solving the thermal problem. In this work, a specialized central-jetting microchannel heat sink (MCHS) is proposed purposely for a small-size laser crystal with high heat fluxes. Considering the space constraint and installation restriction, the MCHS has a narrow width to fit with the laser crystal, while its length is extended to enhance the heat dissipation capability. The MCHS is integrated by welding the two layers completely through a vacuum brazing method. Central-jetting impingement is introduced to enhance the cooling efficiency. Coolant is flushed vertically into the microchannel layer toward the central heating region where the heating source is attached at the central bottom of the MCHS. We conduct a parametric study on the thermal performance of the MCHS by experiments. The overall heat transfer coefficient of the MCHS achieves 50 x 10 3 W/(m(2)center dot K), and the average heat transfer coefficient of the microchannel reaches 21.5 x 10 3 W/(m(2)center dot K). The surface temperature of the heating head is controlled below 65 degrees C, and the temperature variation is less than 5 degrees C. In the solid bottom of the MCHS, thermal resistance in vertical direction is over 1.8 times of that in the horizontal direction, ensuring an efficient heat dissipation in the extended volume. The local heat transfer characteristics are further examined through additional numerical simulations. The wall temperature of the microchannel and the local heat transfer coefficient have a high plateau in the heating region, and then drop significantly along the flow direction. Due to heat transfer enhancement by jet impingement, the heat transfer coefficient in the central region is generally 15% higher than that averaged on the full microchannel. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Thermal management is a critical problem in high-power laser systems, especially for the laser crystal component. This study proposes a specialized central-jetting microchannel heat sink (MCHS) for small-size laser crystals with high heat fluxes. Experimental results show that the MCHS has a high heat transfer coefficient and effective cooling performance.