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topjm [15]
3 years ago
14

2- A 2-m3 insulated tank containing ammonia at -20 C, 80% quality, is connected by a valve to a line flowing ammonia at 2 MPa, 6

0 C. The valve is opened, allowing ammonia to flow into the tank. At what pressure should the vale be closed if the manufacturer wishes to have 15 kg of ammonia inside at the final state?​
Engineering
1 answer:
alekssr [168]3 years ago
8 0

Answer:

The valve should be closed at 1081 kPa ⇒ 11 bar

Explanation:

Q_{C_V} + m_ih_i = m_2u_2 - m_1u_1 + W_{C_V}

Q_{C_V} = W_{C_V} = 0

m_1 = \frac{V}{v_1}  = \frac{2}{0.49927} = 4.006 kg

m_i = m_2 - m_1 = 15 - 4.006 = 10.994 kg

u_1 = 1057.5, h_i = 1509.9

u_2 =  m_ih_i + m_1u_1

m_2 = \frac{[10.994*1509.9] + [4.006*1057.5]}{15}  = 1389.1 kJ/kg

v_2 = \frac{V}{m_2} = \frac{2}{15} = 0.1333 m^3/kg

Therefore, v₂, u₂ fix state 2.  

​By trial and error, P₂ = 1081 kPa & T₂ = 50.4° C

1081 kPa ⇒ 11 bar

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