Numerical study of bubble behaviors and heat transfer in pool boiling of water/NaCl solutions using the lattice Boltzmann method

Abstract

Through modification of the equation of state applicable to the non-volatile salt solution and characterization of the effect of solute concentration on the physical properties of the solution, a lattice Boltzmann pseudopotential model was developed and used to study the pool boiling processes of pure water and NaCl solutions. The model quantitatively verified the equilibrium vapor pressure reduction and boiling point rise of the NaCl solution with solute concentration. The complete pool boiling curves of pure water and the NaCl solution were simulated, and the differences in bubble behaviors and heat flux evolutions in pure water and the NaCl solution at different superheats were analyzed. The results revealed that the difference of heat flux between water and NaCl solution in the nucleate boiling regime is dominated by the nucleation site density and bubble departure frequency at lower superheats, while dominated by the bubble interactions at larger superheats. As a result, the NaCl solution presents a lower nucleate boiling heat flux than that of water when the imposed superheat is smaller than a critical superheat, while it exhibits a larger heat flux even a higher critical heat flux than water when the superheat is higher than the critical superheat. Furthermore, the lower bubble departure frequency in NaCl solution film boiling was captured by simulation. The simulated film boiling heat flux of the NaCl solution was smaller than that of water, and both the simulated results fitted the Berenson correlation well.