Steam initially at 0.3 MPa, 2500C is cooled at constant volume. a) At what temperature will the steam become saturated vapour? b) What is the quality at 800C? What is the heat transferred per kg of steam in cooling from 2500C to 800C?
Answers
Answer:
Basics of Thermodynamics:
* First law of thermodynamics:
The first law of thermodynamics states that the cyclic integral of the net heat transfer is equal to the cyclic integral of the net work tranfer. Mathematically,
∮
2
1
δ
Q
=
∮
2
1
δ
W
Q
1
−
2
=
W
1
−
2
+
Δ
E
1
−
2
Where,
Q
1
−
2
is the heat transfer during the process 1 to 2.
W
1
−
2
is the work transfer during the process 1 to 2.
Δ
E
1
−
2
is the total change in energy during the process 1 to 2.
If we neglect the change in potential anergy and change in kinetic energy, then
Q
1
−
2
=
W
1
−
2
+
Δ
U
1
−
2
Δ
U
1
−
2
is the change in internal energy during the process 1 to 2.
* Stages of Steam:
Steam or vapour is a gaseous phase of water. Steam is widely used for the power generation through steam engines and steam turbines. The following are the three stages of steam:
1. Wet steam
2. Dry steam or dry saturated steam
3. Superheated steam
* Constant Volume Process (V=Const.):
During this process, the volume remains constant. The workdone is zero.