Thermodynamics HW Solutions 762

# Thermodynamics HW Solutions 762 - Chapter 9 Natural...

This preview shows page 1. Sign up to view the full content.

Chapter 9 Natural Convection 9-95 An ice chest filled with ice at 0 ° C is exposed to ambient air. The time it will take for the ice in the chest to melt completely is to be determined for natural and forced convection cases. Assumptions 1 Steady operating conditions exist. 2 Air is an ideal gas with constant properties. 3 Heat transfer from the base of the ice chest is disregarded. 4 Radiation effects are negligible. 5 Heat transfer coefficient is the same for all surfaces considered. 6 The local atmospheric pressure is 1 atm. Properties The properties of air at 1 atm and the anticipated film temperature of ( T s + T )/2 = (15+20)/2 = 17.5 ° C are (Table A-15) Ice chest, 0 ° C 3 cm Q Air T = 20 ° C 30 cm 1 - 2 5 K 003442 . 0 K ) 273 5 . 17 ( 1 1 7316 . 0 Pr /s m 10 493 . 1 C W/m. 02495 . 0 = + = = = × = ° = f T k β υ Analysis The solution of this problem requires a trial-and-error approach since the determination of the Rayleigh number and thus the Nusselt number depends on the surface temperature which is unknown. We
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Ask a homework question - tutors are online