In a pool boiling experiment with water boiling on a large horizontal surface at atmospheric pressure, a heat flux of 4 x 10⁵ W/m² was measured at an excess temperature of 14.5 K. What was the boiling surface material?

GIVEN

• Water at atmospheric pressure boiling on an unknown surface
• Heat flux and excess temperature

PROPERTIES AND CONSTANTS

From Appendix 2, Table 13, the properties of water at 100°C are

Density (ρ_l) = 958.4 kg/m³

Specific heat (c_l) = 4211 J/(kg K)

Absolute viscosity (μ_l) = 277.5 x 10^–6 kg/ms

Prandtl number (P_rl) = 1.75

Heat of vaporization (hfg) = 2.257 x 10⁶ J/kg

Vapor density (ρ_v) = 0.598 kg/m³

Table 10.2 gives

Surface tension (σ) = 58.9 x 10^–3 N/m