OPTIMIZATION OF A STEADY-FLOW CARNOT CYCLE WITH EXTERNAL IRREVERSIBILITIES FOR MAXIMUM SPECIFIC OUTPUT

A steady-how two-phase Carnot cycle is optimised for maximum specific work output for the case in which temperature differences exist betwee n the cycle isotherms and the external reservoirs for a given heat exc hanger standard (defined as the product of the surface area A and the heat transfer coefficient h(0)). When the heat transfer process betwee n the cycle and the reservoirs is by convection obeying Newton's law t he optimum efficiency is shown to be eta(opt) = 1 - root Tc/Th in whic h T-h and T-c are the temperatures of the hot and cold reservoirs, res pectively. The efficiency is independent of the heat transfer process and is identical to the same expression for a similar non-how irrevers ible Carnot cycle as derived by Curzon and Ahlborn and ideal Joule-Bra yton and Otto cycles when optimised for the same maximum work conditio n. For the case of both the heat transfer processes following the Stef an-Boltzmann law of thermal radiation the efficiency is dependent upon characteristics of the heat transfer process and can be greater than the Curzon-Ahlborn cycle efficiency. Results are also presented of an analysis of several cycles with the heat transfer processes being diff erent combinations of radiation, condensation and convection processes . Copyright (C) 1996 Elsevier Science Ltd.