Fifty thousand lb/h of a 20 wt% aqueous solution of NaOH at 120oF is to be fed to an evaporator operating at 3.7 psia, where the solution is concentrated to 40 wt% NaOH. The heating medium is saturated steam at a temperature 40oF higher than the exiting temperature of the caustic solution. Determine the: (a) boiling-point elevation of the solution; (b) saturated-heating-steam temperature and pressure; (c) evaporation rate; (d) heat-transfer rate; (e) heatingsteam flow rate; (f) economy; and (g) heat-transfer area if U=300 Btu/h-ft2-oF.

Condensation of Steam on Vertical Tubes. Steam at 1 atm pressure abs and 100°C is condensing on a bank of five vertical tubes each 0.305 m high and having an OD of 25.4 mm. The tubes are arranged in a bundle spaced far enough apart so that they do not interfere with each other. The surface temper- ature of the tubes is 97.78°C. Calculate the average heat-transfer coefficient and the total kg condensate per hour. Ans. h = 15 240 W/m².K

2. A piston-cylinder device initially contains 0.8 kg of nitrogen gas at 160 kPa and 240 °C. The nitrogen gas is now expanded to a pressure of 100 kPa isothermally. Determine the work boundary during this process. 3. A frictionless piston-cylinder device contains 6 kg vapor at 600 kPa and 400 °C. When heat is transferred to the system, the vapor temperature is increasing up to 500 °C. Calculate the work net during this heat transfer process.

Heat Transfer Question

9. SOC high crude oil is to be heated from 15° C to 55° C at the rate of 1,50 ton/h using a stream from the plant. The crude oil is pumped in to the tube and the heating stream is pumped into the shell side of an available heat exchanger. The heating stream enters in to the tube at 150° C and leaves the tube at 110° C. The average properties of both the fluids are given below. The available heat exchanger (1-2 pass) has shell diameter of 23% in. The shell has 324 tubes, ¾ in. OD, BWG 14 (wall thickness), 12 feet long arranged on 1 in. Square pitch and supported by baffles with a 25% cut, spaced at 9 in interval. You need to find the suitability of this exchanger for the purpose. What will be the allowable fouling factor? Heating stream Crude oil cp, J/g. ° C 2.2 2 H, CP 5.2 2.9 P, kg/m3 k, W/m. C 866 822 0.12 0.138