Chapter 2 Solution manual of Thermodynamics By hipolito STa. maria

Solution manual of

Thermodynamics By hipolito STa. maria

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Chapter 2 1). Assuming that there are no heat effects and no frictional effects, find the kinetic energy and speed of a 3220-lb body after it falls 778 ft from rest. Start with the steady flow equation, deleting energy terms which are irrelevant.

Solution: No heat transfer; Q=0

h=778 ft

kE=?

No enthalpy; H=0

m=3220-lb

V=?

PE=KE

V=224ft/s

2. A reciprocating compressor draws in 500 cubic feet per minute of air whose density is 0.079 lb/cu.ft and discharges it with a density of 0.304 lb/cu.ft. At the suction, p1= 15 psia; at discharge, p2= 80 psia. The increase in the specific internal energy is 33.8 Btu/lb and the heat transferred from the air by cooling is 13 Btu/lb. Determine the work on the air in Btu/min and in hp. Neglect change in kinetic energy.

Solution:

W = - 2384.378 BTU/min

W= 56.235 hp

3. Steam enters a turbine with an enthalpy of 1292 Btu/lb and leaves with an enthalpy of 1098 Btu/lb. The transferred heat is 13 Btu/lb. What is the work in Btu/min and in hp for a flow of 2lb/sec?

Solution:

W= 512.264 hp

W= 21719.994 BTU/min

4. A thermodynamic steady flow system receives 4.56 kg per min of a fluid where p1=137.90 kPa, v1=0.0388 m3/kg, Ѵ1=122 m/s, and u1=17.16 kJ/kg. The fluid leaves the system at a boundary where p 2=551.6 kPa, v2=0.193 m3/kg, Ѵ2=183 m/s and u2=52.80 kJ/kg. During the passage through the system the fluid receives 3000 J/s of heat. Determine the work.

Solution:

W= - 486 kJ/min

5. Air flows steadily at the rate of 0.5 kg/s through an air compressor, entering at 7 m/s speed, 100 kPa pressure and 0.95 m3/kg specific volume, and leaving at 5 m/s, 700 kPa, and 0.19 m 3/kg. The internal energy of the air leaving is 90 kJ/kg greater than that of the air entering. Cooling water in the compressor jackets absorbs heat from the air at the rate of 58 kW. Compute the work in kW.

Solution:

W= - 122 kW

6. In a steady flow apparatus, 135 kJ of work is done by each kg of fluid. The specific volume of the fluid, pressure, and speed at the inlet are 0.37 m3/kg, 600 kPa, and 16 m/s. The inlet is 32 m above the floor, and the discharge pipe is at the floor level. The discharge conditions are 0.62m3/kg, 100 kPa, and 270 m/s. The total heat loss between the inlet and discharge is 9 kJ/kg of fluid. In flowing through this apparatus, does the specific internal energy increase or decrease, and by how much?

Solution:

7. Steam enters a turbine stage with an enthalpy of 3628 kJ/kg at 70 m/s and leaves the same stage with an enthalpy of 2846 kJ/kg and a velocity of 124 m/s. Calculate the work done by the steam.

Solution:

W= -776.762 kJ/kg