Investigation of the mechanism of nucleate boiling through numerical modeling
The fundamental mechanisms accounting for the enhanced heat transfer in nucleate boiling caused by individual bubbles are difficult to quantify analytically or experimentally. A comprehensive, self-consistent numerical model has been developed to quantify these fundamental mechanisms and provide a clearer picture of the processes that occur at this microscopic level. A numerical grid generation technique was employed to transform the complicated and time-dependent geometry of a nucleate boiling bubble during growth and departure, and the axisymmetric Navier-Stokes and energy equations applied to the bulk fluid field were solved using a finite-difference formulation. The specific boiling situation chosen for simulation was saturated water at one atmosphere pressure and 8.5 K wall superheat. The results clearly indicate that microlayer evaporation is the dominant heat-transfer mechanism for this situation both in terms of energy for bubble growth and enhanced wall heat transfer. For the conditions considered, microlayer evaporation provided 90% of the energy for bubble growth and 87% of the enhanced wall heat transfer. In contrast, enhanced wall convective effects were essentially non-existent during growth and minimal following departure.
- Research Organization:
- Wyoming Univ., Laramie (USA)
- OSTI ID:
- 7255281
- Country of Publication:
- United States
- Language:
- English
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