$9\mathrm{.}48$ Common practice in chemical processing plants is to clad pipe insulation with a durable, thick aluminum foil. The functions of the foil are to confine the batt insulation and to reduce heat transfer by radiation to the surroundings. Because of the presence of chlorine $($at chlorine or seaside plants$),$ the aluminum foil surface, which is initially bright, becomes etched with inservice time. Typically, the emissivity might change from $0\mathrm{.}12$ at installation to $0\mathrm{.}36$ with extended service. For a $300-$mm$-$diameter foil$-$covered pipe whose surface temperature is $\backslash (90^\{\backslash$circ$\}\backslash$mathrm$\{$C$\}\backslash ),$ will this increase in emissivity due to degradation of the foil finish have a significant effect on heat loss from the pipe? Consider two cases with surroundings and ambient air at $\backslash (25^\{\backslash$circ$\}\backslash$mathrm$\{$C$\}\backslash )$ : $($a$)$ quiescent air and $($b$)$ a cross$-$wind velocity of $\backslash (10\backslash$mathrm$\{$~m$\}/\backslash$mathrm$\{$s$\}\backslash ).$