Darryl English

2022-07-14

A rigid tank initially contains saturated vapor at 0,35 MPa. Then heat transferred to water until its temperature is ${400}^{\circ }C$. Determine the heat transfer during this process, in kJ/kg.

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Saturation Pressure: The pressure exerted by the vapor on the liquid when both liquid and vapor are in equilibrium is known as saturation pressure. the corresponding temperature is known as the saturation temperature.
First Law of thermodynamics: The first law of thermodynamics states that Energy can never be created nor be destroyed but it can be transferred from one form to another form.
First law of thermodynamics is given by formula
dQ = dU + W
dQ is the heat added or rejected
dU is the change in internal energy
W is the work done
Given data: The initial pressure of the saturated vapor
At 0.35 MPa from saturated water steam tables
The specific internal energy of saturated vapour is given by

The saturated vapour is heated until the temperature reaches ${T}_{2}={400}^{\circ }C$
From superheated steam tables at 0.35 Mpa and ${400}^{\circ }C$
The specific internal energy of the vapour is given by

From the first law of thermodynamics
The heat transferred is given by
$Q=\mathrm{△}U+P\mathrm{△}V$
Here volume of the vessel is constant so $\mathrm{△}V=0$

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