Sodium hydroxide solution is to be concentrated from 10% to 30% by weight using a single effect evaporator operating at atmospheric pressure, The liquid circulates through a calandria consisting of 1 m long tubes 32 mm OD and 28 mm ID. Dry saturated steam is circulated through a calandria at 394 K. If the overall heat transfer coefficient is 1.75 kW m-2 how many tubes will the calandria require to concentrate 0.075 kg s-1 of dilute solution?
The specific heat of the solution can be assumed to be constant at 4.18 kJ kg-1 K. The latent heat of evaporation is 2270 kJ kg-1 for the feed and steam, the boiling point rise is 15 K. The feed temperature is 303 K.