Thermal assessment of sublimation cooling with dry-ice sprays

Spray cooling systems usually use liquids to extract large amounts of heat through phase-change vaporization processes. However, in several applications, cooling requirements are transient and an efficient thermal management implies a proper control of the liquid film deposited on the surface. This represents a challenge to the optimization of thermal management systems and raises the question if there are other approaches able to perform cooling without a liquid film. This is why the present work explores sublimation as the phase-change cooling process using dry ice (CO2) particle sprays. By the Joule-Thomson effect through a sudden expansion, liquid carbon dioxide can be converted into dry ice particles. The experimental results obtained with dry ice sprays for transient cooling show how shorter injection durations (<0.5 s) produce more uniform decays in temperature distribution, while longer pulses (>0.5 s) lead to higher heterogeneities on the impact area with potential use for hotspot cooling. The cooling heat flux generated by spray impact produces a maximum around the aforementioned temporal threshold of 0.5 s, although the maximum performance is close to the 1 s injection duration. Finally, the order of magnitude of the measured spatial average energy removed from the surface is compatible with cooling requirements found, for example, in mold cooling processes. Therefore, this evidences its potential application as an additional thermal management strategy to reduce cycle times and improve the industrial production of molding parts.