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1 kg of water that is initially 90oC with a quality of 10 percent occupies a spring-loaded piston-cylinder device. At this state, a linear spring is touching the piston and exerting no force on it. The device is now heated to compress the spring until the pressure rises to 800 kPa and the temperature is 250oC. Determine the total work produced during this process, in kJ.

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muhammadalambsmathf1

Answer:

The total work produced is 24 kJ.

Explanation:

Explanation is in the following attachment

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Answer:

The total work produced during this process is 24.43 KJ.

Explanation:

Here we have from steam tables at 90 Ā°C Ā 

Pā‚ = 0.701824 bar = 70.1824 Pa

Since the quality is 10 %, this gives the fraction of liquid present in the steam, hence we have the specific volume given by

vā‚ = 0.00103594 + 0.1 Ɨ (2.35915 - 0.00103594) = 0.236847346 mĀ³/kg

When the steam is then heated, we have from the super heated steam tables at Tā‚‚ = 250 Ā°C and Pā‚‚ = 800 kPa

vā‚‚ =0.293 mĀ³/kg

Therefore the work done is given by

Area under the PV curve, which is

Average pressure Ɨ Change in volume

[tex]\frac{P_1 +P_2}{2} \times Mass \hspace{0.09cm} of \hspace{0.06cm}steam \times Change \hspace{0.09cm} in \hspace{0.06cm}Specific \hspace{0.06cm} Volume[/tex]

[tex]Work \hspace{0.09cm} Done =\frac{70.1824 + 800}{2} \times 1kg\times(0.293 -0.237 )[/tex]

= 24.43 KJ.

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