Q. 153 Cow milk is pasteurized at a flow rate of $1 \mathrm{~kg} . \mathrm{s}^{-1}$ in a counter-current heat exchanger using hot water as the heating medium. The milk enters the heat exchanger at $15^{\circ} \mathrm{C}$ and exits at $50^{\circ} \mathrm{C}$. The specific heat of cow milk is $3.5 \mathrm{~kJ} . \mathrm{kg}^{-}$ ${ }^{1} .{ }^{\circ} \mathrm{C}^{-1}$ and remains constant at the inlet and exit of the heat exchanger. The inlet and exit temperatures of the hot water are $75^{\circ} \mathrm{C}$ and $60^{\circ} \mathrm{C}$ respectively. If the overall heat transfer coefficient is $1800 \mathrm{~W} \cdot \mathrm{m}^{-2} .{ }^{\circ} \mathrm{C}^{-1}$, the heat transfer surface area in $\mathrm{m}^{2}$ is (rounded off to 2 decimal places). Assume steady state conditions.
