A triple effect standard vertical tube evaporator each effect of which has 140 m² of heating surface is to be used to concentrate from 5 % solids to 40% solids a solution possessing a negligible boiling point elevation. Forward feed is to be used. Steam is available at 120°C, and the vacuum in the last effect corresponds to a boiling temperature of 40°C. The overall coefficients in W/m2-°C are 2950 in I, 2670 in IIl and 1360 in III, all specific heats may be taken as 4.2J/g°C, and radiation is negligible. Condensates leave at condensing temperature. The feed enters at 90°C. Calculate a) the kilograms of 5% liquor that can be concentrated per hour and b) the steam consumption in kilograms per hour

A stream of ammonia is cooled from 100oC to 20oC at a rate of 180 kg/hr in the tube side of a double-pipe counter-flow heat exchanger. Water enters the heat exchanger at 10oC at a rate of 250 kg/hr. The outside diameter of the inner tube is 3 cm and the length of the pipe is 7m. Using the log-mean temperature difference, calculate the overall heat transfer coefficient (U) for the heat exchanger. Determine the log-mean temperature difference. Determine the heat transfer coefficient for the heat exchanger.   Cp for ammonia is 5234J/kgK and cp for water is 4180J/kgK.

3 A continuous countercurrent adiabatic rotary drier is being designed for the production of 500 lb/h of a product containing 2% moisture from wet crystal containing 30% moisture, wet basis. The air entering the drier will have a dry-bulb temperature of 230°F and a wet-bulb temperature of 102°F. The air leaving the drier will be at a temperature of 115°F. Because of the small size of the crystals, the highest allowable air velocity is 10 lb dry air/ft2-min of drier cross section. Find: a. Dry air required (lb/min) b. Cross-sectional area of the drier c. Length of drier required if the volumetric coefficient of heat transfer is 25 BTU/ft3-h-°F

1. A plastic (k = 0.5 W/m K) pipe carries a coolant at -35 °C with a heat-transfer coefficient of 300 W/m².K. The pipe ID is 3 cm and the OD is 4 cm. The exterior pipe surface is exposed to air at 25°C with a heat-transfer coefficient of 20 W/m²K. Radiative heat transfer may be neglected in this problem. (a) Calculate the rate of heat transfer to the coolant per meter of pipe length. (b) Calculate the temperature of the exterior pipe surface.