Entropy-Based Analysis of Heat Engines
The objective is to find whether there is any consistent relation between the entropy production of a power plant and its thermal efficiency or work production. The study considers two classes of power plants. The first group includes some endoreversible models including the Curzon-Ahlborn engine, the Novikov’s engine, and the Carnot vapor cycle. The second class of power plant studied includes irreversible Otto, Diesel and Brayton cycles. The operational regimes at maximum thermal efficiency, maximum work output and minimum entropy production of these models are compared.
The results reveal that in an endoreversible engine, a reduction in the entropy production corresponds to an increase in the thermal efficiency. However, in an irreversible engine, a reduction in entropy production is neither equivalent to an increase in thermal efficiency; nor to an increase in work output. At the condtion of fixed heat input, minimum entropy production design is identical to maximum thermal efficiency design and maximum work output design. The results demonstrate that for practical applications, power plants should be designed based on maximum thermal efficiency or maximum work output criteria. An entropy-based design should be avoided.