Question

Q1. A double-effect evaporator is being used (in forward mode) to concentrate a sodium chloride solution from 4 to 20 weight %. The solution enters the first effect at 298K at a rate of 3000 kg/h, and saturated steam at a pressure of 1.5 bars is fed into a tube bundle in the Ist effect. The steam condenses at 1.5 bars and the condensate is withdrawn at the saturation temperature corresponding to this pressure. The pressure at the second effect is adjusted as 0.4 bar. The overall heat-transfer coefficients of the first and second effects can be taken as 1000 and 700 W/m²K, respectively a) Draw and label a flow chart of the process, Calculate b) the rate of product, and total evaporation rate in two effects. c) The temperature differences of the two effects d) Give the temperature of the vapor leaving first Effect and second effect, and BPR’s of each effect, e) Find the enthalpies of the all streams. f) Determine the heat transfer area needed to accomplish the desired exit concentration (only one estimate is enough.) g) Calculate the steam economy based upon the results of the first estimate. h) If you need to continue to the calculation, how will you estimate the new trial? Write only the procedure to find the area.