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Unformatted text preview: Solutions HW-5 1.Nitrogen gas flowing in a 30-mm diameter pipe at 27C, 100 kPa, at the rate of 180 kg/hr, encounters a partially closed valve. If there is a pressure drop of 10 kPa across the valve and essentially no temperature change, what are the velocities upstream and downstream of the valve? Solution: Same inlet and exit area: A = /4 (0.03)2 = 0.0007068 m2 Ideal gas: vi = RTi/Pi = (0.2968 300)/100 = 0.8904 m3/kg From Eq.6.3, V i = m . viA = (0.05 0.8904)/0.0007068 = 62.98 m/s Ideal gas: ve = RTePe = 0.2968 300/90 = 0.9893 m3/kg V e = m . veA = 0.05 0.9893/.0007068 = 69.98 m/s 2.In a jet engine a flow of air at 1100 K, 100 kPa and 50 m/s enters a nozzle, where the air exits at 900 K, 90 kPa. What is the exit velocity assuming no heat loss? Solution: C.V. nozzle. No work, no heat transfer Continuity m . i = m . e = m . Energy : m . (hi + 1/2 V i2) = m . (he+ 1/2 V e2) Due to high T take h from table A.7.1 1/2 V e2 = 1/2 V i2 + hi - he = (1/2)(50) 2 + (1161.8 933.15) *10^3 J V e = 678.08 m/s 3. Water at 2 MPa, 120C, is throttled adiabatically through a valve to 100 kPa. The inlet 3....
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- Spring '09