Curves in Thermodynamics:
Thermodynamics can be understood with the help of the curves, where each curve represents a specific process.
In general curves are plotted in a coordinate system where X axis and Y axis represent thermodynamic variables, often two conjugate variables.
The state of a thermodynamic system can be fully specified by the values of any two conjugate thermodynamic properties.
Therefore, in a coordinate plane where
X and Y axes are replaced by any two conjugate thermodymanic properties, each point will represent an unique thermodynamic equilibrium states. Hence, curves joining any arbitrary two points on this plane will represent a thermodynamic processes.
The curves those are used most:
In thermodynamics, p-v diagrams,
T-s diagrams, h-s diagrams are the important diagrams. h-s diagrams of water is also known as Mollier Chart. Curves play a crucial role in studying Thermodynamics.
In thernodynamics all the possible types of processes which are reversible can be represented by a mathemetical relation hence, can be plotted in different thermodynamic planes. It can be represented by a relation pvⁿ = constant and called polytropic process.
In the second law analysis, it is useful to plot the process on diagrams for which has one coordinate is entropy. The two diagrams commonly used in second law analysis are temperature-entropy (T-s) and enthalpy-entropy (h-s) diagrams. For some pure substance, like water, the entropy is tabulated with other properties.
On a P-v diagram, the area under the process curve is equal, in magnitude, to the work done during a quasi-equilibrium expansion or compression process of a closed system. On a T-s diagram, the area under an internally reversible process curve is equal, in magnitude, to the heat transferred between the system and its surroundings. That is,
The T-s diagram of a Carnot cycle is shown on the above figure. The area under process curve 1-2 (area 1-2-B-A-1) equals the heat input from a source (QH). The area under process curve 3-4 (area 4-3-B-A-4) equals the heat rejected to a sink (QL). The area enclosed by the 4 processes (area 1-2-3-4-1) equals the net heat gained during the cycle, which is also the net work output.
Thermodynamics can be understood with the help of the curves, where each curve represents a specific process.
In general curves are plotted in a coordinate system where X axis and Y axis represent thermodynamic variables, often two conjugate variables.
The state of a thermodynamic system can be fully specified by the values of any two conjugate thermodynamic properties.
Therefore, in a coordinate plane where
X and Y axes are replaced by any two conjugate thermodymanic properties, each point will represent an unique thermodynamic equilibrium states. Hence, curves joining any arbitrary two points on this plane will represent a thermodynamic processes.
The curves those are used most:
In thermodynamics, p-v diagrams,
T-s diagrams, h-s diagrams are the important diagrams. h-s diagrams of water is also known as Mollier Chart. Curves play a crucial role in studying Thermodynamics.
In thernodynamics all the possible types of processes which are reversible can be represented by a mathemetical relation hence, can be plotted in different thermodynamic planes. It can be represented by a relation pvⁿ = constant and called polytropic process.
In the second law analysis, it is useful to plot the process on diagrams for which has one coordinate is entropy. The two diagrams commonly used in second law analysis are temperature-entropy (T-s) and enthalpy-entropy (h-s) diagrams. For some pure substance, like water, the entropy is tabulated with other properties.
The T-s Diagrams and its importance
 |  |
The T-s diagram of a Carnot cycle is shown on the above figure. The area under process curve 1-2 (area 1-2-B-A-1) equals the heat input from a source (QH). The area under process curve 3-4 (area 4-3-B-A-4) equals the heat rejected to a sink (QL). The area enclosed by the 4 processes (area 1-2-3-4-1) equals the net heat gained during the cycle, which is also the net work output.
No comments:
Post a Comment