thermodynamics reviewer
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Thermodynamics
Thermodynamics
1. The temperature of a close cylinder containing air at 25 deg C and 76 cm mercury is raised to 100 deg C. What is the new pressure?Ans. 95.1 cm Hg
2. A cold tire contains 1000 cubic inches of air at 24 psig and 32 deg F. What is the pressure in the tire if the temperature and volume are increased to 35 deg F and 1020 cu. in respectively?Ans. 38.17 psia
3. What is the pressure of 4.87 grams of hydrogen that occupy 6.8 liters at 10 deg C?Ans. 8.31 atm
4. Water 100 psia and 80 deg F is mixed with 100 psia, 80% quality steam. Hot water at 20 psia and 180 deg F results. If 4000 lbm of hot water are produced each hour, what are the weight flows of the input ingredients?Ans. m1 = 3584.4 lbm/hr, m2 = 415.6 lbm/hr
5. How much heat is required to increase the temperature of 10 lbs of air from 90 deg F to 360 deg F in a constant volume process if the average value of cp over this range is 0.245 BTU/lbm-deg R?Ans. 476.6 BTU
6. One-half of a molecular weight of a perfect gas exist at a pressure of 100 psia. A heat transfer of 200 BTU at constant volume causes the temperature to change by 100 deg F. Find the specific heat for constant pressure processes on a molar basis.Ans. 5.99 BTU/pmole-deg R
7. What is the rise in water temperature of water dropping over a 200 foot waterfall and settling in a basin below?Ans. T = 0.257 deg F
8. A 200 gram glass jar (cp = 0.2) contains 2000 grams of 20 deg C water. A 1/10 hp motor drives a stirrer for 15 minutes. What is the final water temperature neglecting other losses?Ans. T2 = 27.86 deg C
9. What is the specific enthalpy of 4 pounds of water which is initially at 80 deg F and to which 240 BTU are added?Ans. 108.02 BTU/lbm
10. Air expands in steady flow from 60 deg F and 500 psia to 14.7 psia and 100 deg F. Find the change in entropy, the work output, and the isentropic efficiency of the process.Ans. S = 0.1536 BTU/lbm-deg R, W = -38.3 BTU/lbm, eff = 48.3%
11. 3 pmoles of an ideal gas are throttled per second from 9.2 psia to 6.4 psia. What is the entropy change?Ans. 2.162 BTU/sec-deg R
12. A turbine uses 100,000 lbm/hr of steam which enters with an enthalpy of 1400 BTU/lbm and essentially zero entrance velocity. 10,000 hp are developed. The exit velocity of the steam is 500 fps. Expansion is adiabatic. What is the exit enthalpy?Ans. h2 = 1140.5 BTU/lbm
13. 4 lbm/sec of steam enter a turbine with velocity of 65 ft/sec and enthalpy of 1350 BTU/lbm. The steam enters the condenser after being expanded to 1075 BTU/lbm and 125 ft/sec. The total heat loss from the turbine casing is 50 BTU/sec. What power is generated by this turbine?Ans. 1500 hp
14. What is the enthalpy of water at 200 psia and 900 deg F?Ans. 1476.2 BTU/lbm
15. What is the final enthalpy of steam which is expanded isentropically through a turbine from 100 psia and 500 deg F (superheated) to 3 psia?Ans. 1016.2 BTU/lbm
16. A 2 pound block of steel (c = 0.11 BTU/lbm-deg F) is removed from a furnace and quenched in a 5 pound aluminum (c = 0.21 BTU/lbm-deg F) tank filled with 12 pounds of water. The water and tank are initially in equilibrium at 75 deg F, and their temperature rises to 100 deg F after quenching. What is the initial steel temperature?Ans. 1583 deg F
17. What is the rms velocity of oxygen at 70 deg F?Ans. 5.29 x 10-21 J/molecule
18. What is the average velocity of a nitrogen molecule at 20n deg C?Ans. 470.5 m/secdevilbatPage 1