Thermal Shock Resistance of Chemical Vapor Deposited Zinc Sulfide under Active Cooling

The thermal shock resistance of chemical vapor deposited zinc sulfide (CVD ZnS) infrared side window of high-speed vehicles with convective cooling is studied using finite volume method. The involved factors are the surface heat flux, coolant temperature, convective heat transfer coefficient, and thermal shock initial temperature. All the material properties are temperature-dependent. The study shows that convective cooling can improve the thermal up shock resistance of CVD ZnS caused by aerodynamic heating at the upper surface. On the other hand, it can also lead to thermal down shock failure at the lower surface. The critical failure time corresponding to thermal down shock failure is much less than that corresponding to thermal up shock failure. Thus, thermal down shock failure should be avoided in application. The critical thermal shock initial temperatures, below which convective cooling will not cause thermal down shock failure, for different coolants are calculated.