FINITE-TIME OPTIMIZATION OF A RANKINE HEAT ENGINE

Abstract

We study the power and efficiency of a low grade energy Rankine heat engine which is widely used for power generation from heat recovered or collected at low temperatures. We develop an analytical formula for estimating the finite time Rankine power cycle efficiency at maximum power from heat reservoirs with finite heat capacity rate to obtain a bound on the power conversion systems. This simple formula does not need any detailed thermodynamic data. The accuracy of the procedure is shown by comparisons between the analytical values and those calculated using detailed thermodynamic data. It is also seen that the observed efficiency data on well designed real power plants fall in the domain anticipated theoretically. The efficiency at maximum power provides a measure of the power available in a practical Rankine heat engine.