Forced convective cooling of a high-power solid-state laser slab

A cooling system utilizing the concept of forced convection has been devised to cool the slab of a high-power solid-state laser. Numerical studies were conducted to investigate the thermal effect of the slab cooled by water flowing in a narrow channel. Numerical simulations were performed for Reynolds numbers between 500 and 8000. The calculation results show that for fixed Reynolds number, when the channel height is reduced, the local Nusselt number decreases while the local heat transfer coefficient increases. The maximum thermal stress occurs at the pumped surface in contact with the water coolant, and its location moves from the upstream end to the center of the pumped surface with increasing the Reynolds number and/or reducing the channel height. For fixed Reynolds number with fixed channel height, both the highest temperature and the maximum thermal stress increase with increasing the thermal load, but they increase in a different manner—the former increases linearly while the latter increases more quickly for greater thermal load. The maximum permissible thermal load increases with increasing the Reynolds number and/or reducing the channel height. Such thermal load is decided by the limit temperature for small Reynolds number and/or small channel height case but by the limit thermal stress for large Reynolds number and large channel height case.