(Solved): B2. A single-effect evaporator operates at \( 13 \mathrm{kPa} \). Calculate the heating surface ar ...

B2. A single-effect evaporator operates at \( 13 \mathrm{kPa} \). Calculate the heating surface area required to concentrate \( 4500 \mathrm{~kg} / \mathrm{hr} \) of \( 10 \% \) caustic soda solution to \( 41 \% \) using steam at \( 390 \mathrm{~K} \). The overall heat transfer coefficient is \( 1.25 \mathrm{~kW} / \mathrm{m}^{2} \mathrm{~K} \) and the heating surface is \( 1.2 \) meters below the liquid level. The boiling-point rise of the solution is \( 30 \mathrm{~K} \) and the feed temperature is 291 \( \mathrm{K} \). DATA: \( \quad \) Specific heat capacity of \( 10 \% \) caustic soda feed solution \( =4.0 \mathrm{~kJ} / \mathrm{kg} \mathrm{K} \) Specific heat capacity of \( 41 \% \) caustic soda product solution \( =3.26 \mathrm{~kJ} / \mathrm{kg} \mathrm{K} \) Density of the boiling liquid \( =1390 \mathrm{~kg} / \mathrm{m}^{3} \)