Ericsson cycle

The Ericsson cycle (after John Ericsson ), also Ackeret -Keller- cycle ( after Jakob Ackeret ), is a thermodynamic cycle. The process is used as a comparison process for a gas turbine system (internal or external heating ) with internal heat transfer from the exhaust gas to the turbine, the compressed gas (eg air). The ideal process is the efficiency of the Carnot cycle.

Description

The Ericsson - process consists of two isobaric and two isotherms. He is shown in the diagrams in the image on the right orange and runs between the vertices 1 -2E 3E 4E -1.

The 4 state changes are:

Isobars extend equidistantly ( seen in horizontal direction? ) In the TS diagram so that the surface of the heat transferred below the corresponding curve of 2E to 3E is the same as the area under the curve of 1 to 4E. For the heat transfer is an ideal counter-current heat exchanger is required. The mean temperature of the external heat supply is the highest process temperature and the mean temperature of the heat dissipation is the lowest, so that the efficiency equal to the Carnot cycle (in the Ts diagram the area enclosed by the circle process area can be in one area the same rectangle with the entropy deform between 1 and 2E and the temperature difference between 3E and 2E).

Real possible processes

Isotherm turbines and compressors are not feasible. Heat transfer across the casing wall, the residence time is insufficient and the surface to be small. Therefore, the approximation to the ideal process only by splitting into different compressor and turbine stages with respective intermediate cooling or intermediate heating is possible. In the diagrams and in the diagram (right) a subdivision is shown in two steps. The internal heat exchange is restricted now to the Ts diagram for the heat absorption and heat dissipation green red marked areas of equal size ( assumed as ideal, ie without the required heat transfer temperature difference). It can be seen from the fact that the approach to the process Ericsson is the better, the more stages are chosen ( for the ideal case would be infinitely many steps required). The construction cost for multiple stages is high.