Considerations Affecting the Improvements in the Thermal Efficiencies of Non-Reheating Plants at High Steam Pressures

Abstract

This contribution is supplementary to the paper presented by Mr. K. Baumann entitled “Improvements in Thermal Efficiencies with High Steam Pressures and Temperatures in Non-Reheating Plant” (see p. 125).† It reviews the basic assumptions made in that paper. Particular attention is drawn to the condition line, to the corrections in the turbine efficiency due to higher pressures and temperatures relative to the basic conditions of 600 lb. per sq. in. gauge and 800 deg. F., and to the assessment of the decrease in the heat consumption due to feed heating. The method applied is demonstrated in detail by a typical calculation of a feed heating heat balance. Consideration is also given to the optimum decrease in heat consumption due to feed heating and also to the economic feed temperature for various operating factors. The factors affecting the improvement in thermal efficiency for the economic feed temperature and the power of the station auxiliaries for river and cooling tower conditions, at various pressures and temperatures at the stop valve, are presented by a series of graphs. The use of these graphs is clarified by a summary of comparative data on the improvement in thermal efficiency relative to 600 lb. per sq. in. gauge and 800 deg. F. The final results of the improvement in thermal efficiency for the economic feed temperature relative to 600 lb. per sq. in. gauge and for temperatures from 800 deg. F. to 950 deg. F. with five stage feed heating are indicated by a group of graphs for a range in pressure of 600 to 1,800 lb. per sq. in. gauge for a vacuum of 29 inches of mercury, both excluding and including power station auxiliaries. Finally, a graph indicates the percentage difference in the heat consumption per inch of mercury between 28 inches and 29 inches for temperatures from 800 to 950 deg. F. The results are summarized in seventeen figures and in two comprehensive tables.