A water pump increases the water pressure from 15 psia to 70 psia. Determine the power input required, in hp, to pump 0.8 ft3 /s of water. Does the water temperature at the inlet have any significant effect on the required flow power

Respuesta :

Answer:

[tex]Power=11.52hp[/tex]

Explanation:

Given data

[tex]p_{1}=15psia\\p_{2}=70psia\\V_{ol}=0.8ft^{3}/s[/tex]

As

[tex]m=p*V_{ol}[/tex]

Assuming in-compressible flow p is constant

The total change in system mechanical energy calculated as:

Δe=(p₂-p₁)/p

The Power can be calculated as

[tex]P=W\\P=m(delta)e\\P=p*V_{ol}*(p_{2}-p_{1})/p\\ P=V_{ol}*(p_{2}-p_{1})\\P=44(psia.ft^{3}/s )*[(\frac{1Btu}{5.404psia.ft^{3} } )-(\frac{1hp}{0.7068Btu/s } )]\\P=11.52hp[/tex]    

The power input required to pump 0.8 ft³/s of water is; P = 11.52 hP

We are given;

Initial pressure; P1 = 15 psia

Final pressure; P2 = 70 psia

Volume flow rate; V' = 0.8 ft³/s

The formula for the mass flow rate is;

m' = ρV'

The total change in the mechanical energy of the system is;

△E = (P2 - P1)/ρ

Now, formula for power is;

P = m' × △E

P = ρV' × (P2 - P1)/ρ

P = V'(P2 - P1)

P = 0.8(70 - 15)

P = 44 psia.ft³/s

Converting to Btu/s gives;

P = 8.142 btu/s

Converting Btu/s to HP from conversion tables gives; P = 11.52 hP

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