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$2-$shell passes and $4-$ube passes HX is used to heat glycerin from $20\backslash$deg C to $40\backslash$deg C by hot water which enters the thin$-$walled $2-$cm diameter tubes at $90\backslash$deg C and leaves at $50\backslash$deg C$.$ The total length of the tubes in HX is $50$ m$.$ The convection heat transfer coefficient is $25$ W$/$m$2$K on the shell side and $150$ W$/$m$2$K on tube side. Determine the heat transfer rate after fouling with a fouling factor of $0\mathrm{.}0008$ m$2$K$/$W occurs on the outer surface of the tubes? $(50$ points$)$