Problem 1 (15 points) A gas mixture of 0.21 g mol NH3, 1.7 g mol O...

 

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Problem 1 (15 points) A gas mixture of 0.21 g mol NH3, 1.7 g mol O and 0.05 g mol HO is contained at a total pressure of 880 mmHg and 353 K. Calculate the following (a) mass fraction of each component (b) partial pressure of each component in mm Hg (c) total volume of mixture in m Info: latm = 760mm Hg and R = 82.057 x 10-3(m.atm)/(kgmol.K). Use molecular weights from any source (for example: https://webbook.nist.gov/chemistry/form-ser/). Problem 2 (15 points) An evaporator is used to concentrate salt solution. A feed of 300 kg/d of a salt solution containing 20 wt% salt is evaporated, producing 68 wt% salt solution. Calculate the amount of salt solution produced, amount of water removed, and required heat to evaporate the water removed. Problem 3 (15 points) Whole milk at 25C having a density of 1036 kg/m and viscosity of 2.0 cp is flowing at the rate of 3.0 kg/s in a glass pipe with a diameter of 105.2 mm. (a) Determine the flow regime (b) Calculate the flow rates in m/h for a Reynolds Number of 2100 and 4000 Problem 4 (20 points) Water stored in a large, well insulated storage tank at 20C and atmospheric pressure is being pumped at steady state from this tank by a pump at a rate of 100m /h. Motor driving the pump supplies energy at a rate of 25 kW. The water is used as cooling medium and passes through a heat-exchanger where 600 kW of heat is added to water. The water from the heat-exchanger flows to a second, large vented tank which is 50 m above the first tank. Determine the final temperature of water delivered to the second tank. Hint: Use steam tables Problem 5 (20 puan) A pipe having thickness of h has inner surface at T, and outer surface at To. If the thermal conductivity of the pipe material varies such that k(T) = ko + aT+ aT3 where ko, ao, a1 are constants, derive an expression for the one-dimensional heat flux at the inner surface of the pipe, q/A. Problem 6 (15 puan) A gas at 350K is flowing inside a 2-in schedule 40 commercial steel pipe. The convective heat transfer coefficient on the inner surface of the pipe is 30 W/mK and the convective heat transfer coefficient on the outside surface is 10.8 W/mK. The air outside the pipe is at 300 K. (a) Calculate the heat loss per meter of bare steel pipe. (b) If the pipe were insulated with lagging having a mean thermal conductivity of k = 0.07 W/mK, what would be the thickness of lagging in order to reduce the heat loss by 25%. Assume that, inside and outside heat transfer coefficients and thermal conductivity of the steel are the same (Hint: See Appendix A5 for the dimensions of the steel pipe, and Appendix A3-16 for thermal conductivity of steel). Problem 1 (15 points) A gas mixture of 0.21 g mol NH3, 1.7 g mol O and 0.05 g mol HO is contained at a total pressure of 880 mmHg and 353 K. Calculate the following (a) mass fraction of each component (b) partial pressure of each component in mm Hg (c) total volume of mixture in m Info: latm = 760mm Hg and R = 82.057 x 10-3(m.atm)/(kgmol.K). Use molecular weights from any source (for example: https://webbook.nist.gov/chemistry/form-ser/). Problem 2 (15 points) An evaporator is used to concentrate salt solution. A feed of 300 kg/d of a salt solution containing 20 wt% salt is evaporated, producing 68 wt% salt solution. Calculate the amount of salt solution produced, amount of water removed, and required heat to evaporate the water removed. Problem 3 (15 points) Whole milk at 25C having a density of 1036 kg/m and viscosity of 2.0 cp is flowing at the rate of 3.0 kg/s in a glass pipe with a diameter of 105.2 mm. (a) Determine the flow regime (b) Calculate the flow rates in m/h for a Reynolds Number of 2100 and 4000 Problem 4 (20 points) Water stored in a large, well insulated storage tank at 20C and atmospheric pressure is being pumped at steady state from this tank by a pump at a rate of 100m /h. Motor driving the pump supplies energy at a rate of 25 kW. The water is used as cooling medium and passes through a heat-exchanger where 600 kW of heat is added to water. The water from the heat-exchanger flows to a second, large vented tank which is 50 m above the first tank. Determine the final temperature of water delivered to the second tank. Hint: Use steam tables Problem 5 (20 puan) A pipe having thickness of h has inner surface at T, and outer surface at To. If the thermal conductivity of the pipe material varies such that k(T) = ko + aT+ aT3 where ko, ao, a1 are constants, derive an expression for the one-dimensional heat flux at the inner surface of the pipe, q/A. Problem 6 (15 puan) A gas at 350K is flowing inside a 2-in schedule 40 commercial steel pipe. The convective heat transfer coefficient on the inner surface of the pipe is 30 W/mK and the convective heat transfer coefficient on the outside surface is 10.8 W/mK. The air outside the pipe is at 300 K. (a) Calculate the heat loss per meter of bare steel pipe. (b) If the pipe were insulated with lagging having a mean thermal conductivity of k = 0.07 W/mK, what would be the thickness of lagging in order to reduce the heat loss by 25%. Assume that, inside and outside heat transfer coefficients and thermal conductivity of the steel are the same (Hint: See Appendix A5 for the dimensions of the steel pipe, and Appendix A3-16 for thermal conductivity of steel).