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A pump collects water (rho = 1000 kg/m^3) from the top of one reservoir and pumps it uphill to the top of another reservoir with an elevation change of Δz = 800 m. The work per unit mass delivered by an electric motor to the shaft of the pump is Wp = 8,200 J/kg. Determine the percent irreversibility associated with the pump.

User Rlatief
by
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1 Answer

6 votes

Answer:

4.29%

Step-by-step explanation:

Given:

Density of water, ρ = 1000 kg/m³

elevation change of Δz = 800 m

work per unit mass delivered, Wp = 8,200 J/kg

Now,

The percent irreversibility =
(1-n_p)*100

where,


n_p(W_(actual))/(W_(theoretical))

also,


W_(actual)=(g\Delta z)/(1000)

Where, g is the acceleration due to the gravity

on substituting the values, we get


W_(actual)=(9.81*800)/(1000)

or


W_(actual)=7.848\ KJ/kg

or


W_(actual)=7848\ J/kg

Therefore,

The percent irreversibility =
(1-n_p)*100

on substituting the values, we get

The percent irreversibility =
(1-(7848)/(8,200))*100

or

The percent irreversibility = 4.29%

User Cellepo
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