Ericsson cycle

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If an infinite number of intercoolers, compressors, reheaters, and turbines are added to a basic ideal Brayton cycle, the intercooling and multicompression processes approach an isothermal process. Similarly, the reheat and multiexpansion processes approach another isothermal process. This limiting Brayton cycle becomes an Ericsson cycle. 

The schematic Ericsson cycle is shown in Fig. 4.27. The p-v and T-s diagrams of the cycle are shown in Fig. 4.28. The cycle consists of two isothermal processes and two isobaric processes. The four processes of the Ericsson cycle are isothermal compression process 1-2 (compressor), isobaric compression heating process 2-3 (heater), isothermal expansion process 3-4 (turbine), and isobaric expansion cooling process 4-1 (cooler). 

Air, at a mass flow rate of 1 kg/sec, is compressed and heated from 100 kPa and 100°C in an Ericsson cycle to a turbine inlet at IMPa and 1000°C. Determine the pressure and temperature of each of the four states, power and rate of heat added in each of the four devices, and cycle efficiency. 

Figure 4.30 Schematic Ericsson cycle with a regenerator.

Does the regenerator improve the efficiency of the Ericsson cycle ... 

Suppose an ideal regenerator is added to an Ericsson cycle. The regenerator would absorb heat from the system during part of the cycle and return exactly the same amount of heat to the system during another part of the cycle. What would be the difference between the Ericsson cycle efficiency and the Carnot cycle efficiency ... 

A Braysson cycle (Fig. 4.32) uses air as the working fluid with 1 kg/sec mass flow rate through the cycle. In the Brayton cycle, air enters from the atmospheric source to a compressor at 20° C and 1 bar (state 1) and leaves at 8 bars (state 2) air enters an isobaric heater (combustion chamber) and leaves at 1100°C (state 3) air enters a high-pressure isentropic turbine and leaves at 1 bar (state 4). In the Ericsson cycle, air enters a low-pressure isentropic turbine and leaves at 0.04 bar (state 5) air enters a first-stage compressor and leaves at 0.2 bar (state 6) air enters an isobaric intercooler and leaves at 20°C (state 7) air enters a second-stage compressor and leaves at 1 bar (state 8) and air is discharged to the atmospheric sink. Assume all compressors have 85% efficiency. 

Blank, D.A. and Wu, C., Power limit of an endo-reversible Ericsson cycle with regeneration. Energy Conversion and Management, 37(1), 59-66, 1996. 

Chen, L., Sun, F., and Wu, C., Cooling and heating rate limits of a reversed reciprocating Ericsson cycle at steady state. Proceedings of the Institute of Mechanical Engineers, Part A, Journal of Power and Energy, 214, 75-85, 2000. 

In the classical equilibrium thermodynamics, Stirling and Ericsson cycles have an efficiency that goes to the Carnot efficiency, as it is shown in some textbooks. These three cycles have the common characteristics, including two isothermal processes. The objection to the classical point of view is that reservoirs coupled to the engine modeled by any of these cycles do not have the same temperature as the working fluid because this working fluid is not in direct thermal contact with the reservoir. Thus, an alternative study of these cycles is using finite... 

The Ericsson cycle consisting of two isobaric processes and two isothermal processes is shown in Figure 4. Now, it follows a similar procedure as in the Stirling cycle case. Thus, the hypothesis on constant heating and cooling, now at constant pressure, is expressed as... 

With the change of variables used in the previous section, now the expression for the power output of the non-endoreversible Ericsson cycle is... 

Figure 4. Idealized Ericsson cycle at the V -p (volume vs pressure) plane.

The analysis for the case of ecological function is similar to the case of power output and also leads to similar results. The shape of the function u=u(ZI, Is, << ) is the same as in Equation (87), but the form of Z, =/,(< , Is, A) changes. Thus, because heating and cooling in isobaric processes are considered constant, the change of entropy can be taken only for the isothermal processes. Hence, for the non-endoreversible Ericsson cycle considered, we have... 

The efficiency for Ericsson cycle at maximum ecological function can be written now as... 

Ladino-Luna, D., Portillo-Diaz, P., Paez-Hemandez, R.T. (2013). On the Efficiency for Non-Endoreversible Stirling and Ericsson Cycles. J. Modern Phys., Vol. 4, pp 1-7. 

The Ericsson cycle is similar to.the Stirling cycle except that each of the streams in the regenerator is at a constant (but different) pressure rather than at a constant volume. The P-V and T-S traces are shown in Fig. 5.2-7. 

Indeed, the only computational difference between the Stirling and Ericsson cycles is that the thermodynamic properties at the various points of the cycle are slightly different because of the difference between the constant-pressure and constant-volume paths. 

An Ericsson cycle. with air as the working fluid is operating between a low temperature of 70°C and a high temperature of 450°C, a low pressure of 2 bar, and a pressure compression ratio of S (so that the high pressure is 16 bar). Assume that at these conditions air can be considered to be an ideal gas with Cp constant. Compute the properties at each point in each of these cycles and the cycle efficiencies. 

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