Ericsson Cycle vs. Carnot – Ideal Thermal Efficiency with Perfect Regeneration For an ideal Ericsson cycle (two isothermal and two constant-pressure processes) operating with perfect regeneration between the isobars, the thermal efficiency is equal to that of a Carnot cycle working between the same temperature limits.

Introduction / Context:
The Ericsson and Stirling cycles are regenerative cycles composed of isothermal heat transfer processes. With an ideal (perfect) regenerator, both can theoretically achieve the Carnot efficiency when operating between the same high and low temperatures, despite having different process combinations than Carnot.

Given Data / Assumptions:

• Ideal gas as working fluid.
• Two isothermal and two constant-pressure processes (Ericsson).
• Perfect regenerator shifting heat internally between the two isobars; no pressure losses; fully reversible processes.

Concept / Approach:

Carnot efficiency depends only on the two reservoir temperatures: eta_Carnot = 1 − T_L/T_H. An ideal Ericsson cycle, made fully reversible via perfect regeneration, has no net internal temperature differences during heat transfer other than at the reservoirs, making its efficiency depend solely on T_H and T_L, the same as Carnot.

Step-by-Step Solution:

Verification / Alternative check:

Derivations using T–s diagrams show equal net area (work) relative to heat in/out purely at isotherms when regeneration is perfect. Any regenerator inefficiency or pressure drop reduces efficiency below Carnot in practice.

Why Other Options Are Wrong:

Greater than Carnot is impossible by the second law. Less than applies when regeneration is imperfect, but the ideal statement specifies perfect regeneration. “Undefined” ignores the specified idealization.

Common Pitfalls:

Confusing Ericsson with Brayton (which has adiabatic legs, not isothermal) and overlooking the crucial role of perfect regeneration.

Final Answer:

equal to