Saturated vapour at $323K$ condenses on outside of a bank of $16$ horizontal tubes in $44$ square array. Calculate the rate of condensation per metre length of array if the tube surface is at $313$K$.$

$Do=12mm$

Properties of fluid at mean film temperature are

${}_f=2\mathrm{.}5{10}^{-4}k\frac{g}{m}s$

$k_f=0\mathrm{.}069\frac{W}{m}k$

${}_f=1174k\frac{g}{m}3$

$=132k\frac{J}{k}g$