$1\mathrm{.}5-$m$-$diameter, $5-$m$-$long cylindrical propane tank is initially filled with liquid propane,

whose density is $581$ kg$/$m$3.$ The tank is exposed to the ambient air at $25\backslash$deg C in calm weather.

The outer surface of the tank is polished so that the radiation heat transfer is negligible. Now

a crack develops at the top of the tank, and the pressure inside drops to $1$ atm while the

temperature drops to $42\backslash$deg C$,$ which is

the boiling temperature of propane

at $1$ atm. The heat of vaporization of

propane at $1$ atm is $425$ kJ$/$kg$.$ The

propane is slowly vaporized as a

result of the heat transfer from the

ambient air into the tank, and the

propane vapor escapes the tank at

$42\backslash$deg C through the crack. Assuming the propane tank to be at about the same temperature as

the propane inside at all times, determine how long it will take for the tank to empty if it is

not insulated.