The Regenerative Cycle: An Efficiency Basis having Special Reference to the Number of Feed Water Heating Stages

Abstract

The efficiency of the regenerative cycle may be defined as the ratio of the heat converted into work (in British Thermal Units per pound of steam) to the heat supplied to 1 lb. of steam in the boiler plant. Where feed heating is employed, however, the heat converted into work is less than the adiabatic heat drop as calculated from the initial and final states of expansion. The difference between these quantities is termed “unavailable heat” in the paper, and the efficiency is therefore given as the ratio of the adiabatic heat drop less the unavailable heat, to the heat supplied to 1 lb. of steam in the boiler plant. The object of the paper is to illustrate the advantage derived from working in terms of unavailable heat. Values of this quantity are given, and the author provides a worked example showing their use. Appendixes I and II deal with investigations of the case in which the number of feed heating stages is infinitely great, i.e. the conditions for the ideal efficiency. The relationship of the ideal efficiency to other efficiencies corresponding to various finite numbers of feed heating stages is indicated.