Ericsson Cycle With P-v and T-s Diagram
Ericsson Cycle was invented by Ericsson, which consists of two isothermal and two constant pressure processes. It is made thermodynamically reversible by the action of a regenerator. The p-v and T-s diagrams of the Ericsson cycle are shown in the figure. This cycle is used these days in the manufacture of closed-cycle type gas turbines.
J. Ericsson was an American Engineer, who invented this engine in 1840. He used a hot air engine, working on this cycle, for running a ship (known as Ericsson) in 1853.
Read also: Thermodynamic Cycle: Its Classification, Working, Terms Used in Thermodynamics and More.
Now, let us consider the four-stage of the Ericsson cycle. Let the engine contain m kg of air at its original position represented by point 1 on p-v and T-s diagrams. At this point, let p1, T1, and v1 be the pressures, temperature, and volume of the air.
Ericsson Cycle Processes
Following are the four Processes of an Ericsson cycle:
- 1-2 Process (Isothermal expansion or heat addition)
- 2-3 Process (Constant pressure or isobaric heat rejection)
- 3-4 Process (Isothermal compression)
- 4-1 Process (Constant pressure or isobaric heat absorption)
1. Process 1-2 (Isothermal Expansion or Heat Addition)
The air is heated at constant pressure from an initial temperature T1 to a temperature T2 represented by the graph 1-2 in fig.
2. Process 2-3 (Constant Pressure or Isobaric Heat Rejection)
The air is allowed to expand isothermally (i.e., at constant temperature T2=T3) from initial volume v2 to v3 represented by the graph 2-3 in fig. We know that a part of the heat supplied in the first stage is utilized for doing work in isothermal expansion.
3. Process 3-4 (Isothermal Compression)
The air is now cooled at constant pressure from initial temperature T3 to a temperature T4 represented by the graph 3-4 in fig.
4. Process 4-1 (Constant Pressure or Isobaric Heat Absorption)
Finally, the air is compressed isothermally (i.e., at constant temperature T4=T1) from initial volume v3 to v4 represented by the graph 4-1 in fig. We know that some heat is rejected by the air for doing work on the air.
We know from the above, that heat supplied during the process 1-2 is equal to the heat rejected during the process 3-4 (because of T2-T1=T3-T4).
Work done = Heat supplied – Heat rejected
And efficiency,
Notes:
1. The efficiency of the Ericsson cycle is the same as that of Carnot efficiency.
2. If the regenerator efficiency is nr, then heat taken in from the regenerator during process 4-1 will be mCp (T4-T2) (1-nr). In that case.
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