析出物を伴う懸濁液プール核沸騰熱伝達に関する研究

Seawater, NaCl solution and nanofluid pool nucleate boiling experiments were conducted to examine the effects of deposit on a heat transfer surface. At lower heat flux from free convection heat transfer to onset of nucleate boiling, the tendency of these boiling curves for the seawater, the NaCl solution and the nanofluid was almost the same with distilled water, considering the physical properties of each fluid. At higher heat flux from onset of nucleate boiling to critical heat flux, the tendency of these boiling curves was different from each other. The superheat for the seawater, the NaCl solution and the nanofluid was higher than the superheat for the distilled water. The heat transfer surface was burned out at the higher heat flux in the nanofluid experiments than in the distilled water experiments. This might be caused by micro-scale-channels of the deposited nanoparticles layer on the heat transfer surface. In seawater experiments, CaSO4 which is one of the sea salts deposited on the heat transfer surface at lower heat flux than the critical heat flux of the distilled water. The thickness of the layer grew with time. The low thermal conductivity of CaSO4 resulted in large heat conduction resistance from the heat transfer surface to the deposit layer surface. The CaSO4 deposition layer caused temperature excursion of the heat transfer surface. The result means that the critical heat flux in the seawater is lower than that of the distilled water.