Study of Pool Boiling Heat Transfer on Various Surfaces with Variation of Flow Velocity

In this study, a smooth flat surface, low fin, Turbo-B, and Thermo excel-E surfaces are used to examine the effect of the flow velocity on the pool boiling heat transfer coefficients (HTSC) and critical heat fluxes (Chefs). HTSC and Chefs are measured on a smooth square heater of 9.53 Χ 9.53 m2 at 60 .deg. C in a pool of pure water at various fluid velocities of 0, 0.1, 0.15, and 0.2 m/s. Test results show that for all surfaces, Chefs obtained with flow are higher than those obtained without flow. Chefs of the low fin surface are higher than those of the Turbo-B and Thermo excel-E surfaces due largely to the increase in surface area and sufficient fin spaces for the easy removal of bubbles. Chefs of the low fin surface show even 5 times higher Chefs as compared to the plain surface. On the other hand, both Turbo-B and Thermo excel-E surfaces do not show satisfactory results because their pore sizes are too small and water bubbles easily cover them. At low heat fluxes of less than 50 k W/m2, HTSC increase as the flow velocity increases for all surfaces. In conclusion, a low fin geometry is good for application to steam generators in nuclear power plants