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Homework Statement
An insulated pistoncylinder device contains 5 L of saturated liquid water at a constant pressure of 175 kPa. Water is stirred by a paddle wheel while a current of 8 A flows for 45 min through a resistor placed in the water, If onehalf of the liquid is evaporated during this constant pressure process and the paddle wheel work amounts to 400 kJ, determine the voltage of the source. Also, show the process on a Pv diagram with respect to saturation lines.
Homework Equations
ΔE = E_{in}  E_{out}
W_{electric} = VIΔt
if ΔP = 0, ΔH = m(h_{2}  h_{1})
ΔH = ΔU + W_{boundary}
The Attempt at a Solution
V = 5 L
m = 5 kg (by conversion)
P = 175 kPa
I = 8 A
Δt = 45*60 sec = 2700
Assuming that KE, and PE = 0,
ΔE = ΔU
Also since it is insulated we are assuming that the heat lost is 0
W_{e} + W_{sh}  W_{boundary} = ΔU
W_{e} + W_{sh} = ΔU + W_{boundary}
W_{e} + W_{sh} = ΔH
W_{e} + W_{sh} = m(h_{2}  h_{1})
Here is where I get lost. I know that we can find h_{1} from the saturated water tables
h_{1} = 487.01 kj/kg (at P_{sat} = 175 kPa)
I'm confused as to where the second enthalpy value comes from since our state has constant P.
Also the Pv should look something like this I believe:
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