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Chapter 18

Chapter 18. counting. Accounting for Mass. RAT (Individual).

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Chapter 18

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  1. Chapter 18 counting Accounting for Mass

  2. RAT (Individual) • The 1980 and 1990 census of the Hometown, USA found that the population was 8,926 and 10,112, respectively. During that 10 year period the Chamber of Commerce reported that 945 people had moved in, 108 people had moved out and that there were 516 births. • As an INDIVIDUAL take 10 minutes to determine: a) accumulation b)net input, and c)net generation from 1980 to 1990.

  3. Conservation of Mass “Mass can neither be created nor destroyed.” Is there an exception to this rule? Answer: Yes! During nuclear fusion and fission, matter is transformed into energy. E=mc2

  4. UAE We will first consider cases that do not have generation of consumption of mass. i.e. no fission or fusion Final Amount - Initial Amount = Input - Output Accumulation = Net Input

  5. Aerospace EngineeringClosed Book • A cargo plane has a mass of 50,000 lbm when empty. It takes on 10,000 lbm of fuel and 7000 lbm of freight. When it arrives at its destination it has a mass of 59,000 lbm. How much fuel was burned during the flight? • Output = ? • Initial Amount = 50,000 lbm • Final Amount = 59,000 lbm • Input = 17,000 lbm • UAE: Output = Initial Amount - Final Amount + Input • Output = 8000 lbm

  6. Chemical EngineeringClosed Book • Water is added to a heated kettle at a rate of 10kg/h. A scale shows that the weight of the kettle increases by 4 kg/h. At what rate does water evaporate from the kettle? • Is enough information given? • Final Amount - Initial Amount = Input - Output Accumulation

  7. Chapter 18 counting Accounting for Mass

  8. Chemical EngineeringClosed Book • 100 kg of fresh maple tree sap contains 5% sugar and 95% water. • Water is boiled to produced maple syrup containing 80% sugar and 20% water. • What is the final mass T of the syrup? • How much water S evaporated? • How much water W is in the maple syrup? • Final Amount - Initial Amount = Input - Output

  9. Chemical Engineering • Final Amount - Initial Amount = Input - Output • T - 100kg = 0 - S • There are two unknowns. • Initially there is 5 kg of sugar (5% of 100kg). • There is also 5 kg of sugar after boiling. • Therefore… • (5kg)/T = 80% • Now there are two equations and unknowns.

  10. Chemical Engineering • Balance the following chemical reactions: H2O2 H2O + O2 C2H5OH + O2 CO2 + H2O CO + H2 CH4 + H2O

  11. Nuclear Engineering • What is nuclear fusion? • the process whereby lighter elements are combine to form heavier elements • What is nuclear fission? • the process whereby heavier elements are combine to form lighter elements

  12. +  + Nuclear Engineering • Balance the following nuclear fusion reaction: H + H + H + H  He + positron + neutrinos + Light E=mc2 + + + + + +

  13. Mass loss? 4  1 hydrogen = 6.693  10-27 kg - 1 helium = 6.645  10-27 kg ---------------------------------------------- Mass lost = 0.048  10-27 kg The extra mass is converted to pure energy. i.e. light.

  14. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +  + + Nuclear Engineering • Consider the following Uranium fission reaction: 235U + n  junk + Light • The energy of the light created is… • E = 3.2 × 10-11 J/atom

  15. Nuclear Engineering • Example 18.4 • How much mass is consumed when each atom in 1.000000 kg of Uranium undergoes fusion? • How much mass remains? Use the UAE.

  16. Homework Question

  17. Chapter 19

  18. Team Exercise (10 minutes) • Final Amount - Initial Amount = Input - Output • A grain drier is fed 10,000 lbm/hr of wet corn (25% water) which is dried to 14% water by the drier. • How much water (lbm/hr) is removed by the drier, and how much (lbm/hr) dried corn (at 14% water) exits the drier?

  19. Homework

  20. Ping Pong Ball Launcher 5’ x 5’ x 5’ 15’ 25’

  21. Ping Pong Ball Launcher • You may initiate each launch but cannot load or touch the ping pong balls after the first launch. • There is a 2 minute time limit. 15’ 25’

  22. Project Two Stirling Engine

  23. Team Projects • Grading: The best 3 out of 4 projects will be used for the course project grade. • Project 3: Mousetrap Boat • Travel 8 feet. • Project 4: Three Story Egg Drop • Use only a 8” x 11” sheet of paper. • Due Date: Wednesday of Dead Week • Note that we may have to stay late on that day to finish both projects.

  24. Solution • Define 1) System: City of Hometown, USA 2) Extensive quantity: Population (people) 3) Time period 1980 and 1990 • Then • Final = 10,112, Initial = 8,926 • Input = 945, Output = 108 • Generation = 516, Consumption = ?

  25. Solution • UAE: Final-Initial = In. - Out. + Gen. - Con. 10,112 - 8,926 = 945 - 108 + 516 - Con. Consumption = 167 (people that died)

  26. Solution a.) Accumulation = Final - Initial = 10,112 - 8,926 = 1,186 b.) Net Input = Input - Output = 945 - 108 = 837 c.) Net Generation = Generation-Consumption = 516 - 167 = 349

  27. Chapter 18 counting Accounting for Mass

  28. Engineering Mass and Weight • Pound-Mass • 1 lbm weighs 1 lbf • 1 lbm ≠ 1 lbf • Pound-Force • lbf • It is the same as a pound (lb). • 1 lbf = 1 lb

  29. In-class Exercise Indicate whether each of these is a weight unit or a mass unit. • kilogram • Newton • slug • pound • lbm • lbf

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