Eulerian multiphase analysis for heat transfer enhancement by CO2 sublimation in slot jet impingement

Abstract

A new numerical method for carbon-dioxide (CO2) slot jet impingement cooling with dry ice is proposed and its analysis predicts an improvement in heat transfer performance by sublimation. When the CO2 passes through the tiny orifice gap or jet nozzle, it experiences the rapid temperature drop as well as pressure decrease by the Joule-Thomson effect. This temperature drop causes the formation of small CO2 dry-ice particles in the jet flow. Besides the enhanced cooling performance by lowered bulk-jet temperature, the significantly improved heat transfer can be expected by the additional sublimation effect between the dry-ice particles and cooling target.

Computational analysis for solid-gas two-phase jet impingement flow was performed using a commercial CFD two-phase solver as a framework. Additional in-house code accounting for the sublimation effects is embedded into the solver. The effect of sublimation on heat transfer performance was investigated by the variance of flow rate or Reynolds number.

As a result, analysis of gas-solid jet considering sublimation predicts higher heat transfer coefficients than those without sublimation analysis, and sublimation maintains the temperature of the jet bulk flow for a longer time through the absorption of additional thermal energy. As the Reynolds number increases, the amount of sublimation increases and thus heat transfer enhancement is also accompanied. It can be confirmed that the heat transfer performance at the jet target surface edge weakened by the diffusion of the wall jet flow can be compensated by the dry ice sublimation. The sublimation model presented in the current study shows that the characteristics of the impinging jet cooling containing dry ice are effectively analyzed.