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# Ericsson Cycle: Efficiency with [P-v and T-s] Diagram

## Ericsson Cycle With P-v and T-s Diagram

Contents

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.

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. 