Project ForgeHeat Transfer
Convection
GATE 2018
Medium
Vapor bubbles form in nucleate boiling at 10 bubbles/s per site, 100 sites/m², bubble diameter 10⁻³m. Latent heat=1000 kJ/kg, vapor density=1 kg/m³. The heat flux (W/m²) is (rounded off to third decimal place)
0.524 W/m^2(± 0.02 accepted)
Explanation
Bubble volume=(4/3)π(5×10⁻⁴)³=5.236×10⁻¹⁰m³. Mass/bubble=5.236×10⁻¹⁰kg. Heat/bubble=5.236×10⁻¹⁰×10⁶J=5.236×10⁻⁴J. Flux=1000 bubbles/(s·m²)×5.236×10⁻⁴=0.524 W/m².
Source: GATE CH 2018 (2018)
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