上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lecture 41-42 Chapter 10 Vapor and Combined Power Systems Spring,5/9/2018 通 Prof.,Dr.Yonghua HUANG VALLAMAAA http://cc.sjtu.edu.cn/G2S/site/thermo.html SHANG 1日 ERSITY
Engineering Thermodynamics I Lecture 41‐42 Spring, 5/9/2018 Prof., Dr. Yonghua HUANG Chapter 10 Vapor and Combined Power Systems http://cc.sjtu.edu.cn/G2S/site/thermo.html
Rankine Cycle Improvements Basic Rankine Cycle: T IDEAL CYCLE Turbine 3 Irreversibility in the pump Pressure drop in the boiler 3 Boiler O out Irreversibility Cooling water in the turbine Pump- 2 Condenser ACTUAL CYCLE )4 Pressure drop in the condenser 上游充通大率 May9,2018 2 SHANGHA BAO TONG LINIERSITY
May 9, 2018 2 Rankine Cycle Improvements Basic Rankine Cycle: 1 2 3 4
Rankine Cycle Performance Trends Effect of superheat on performance: ·Purpose: Increase average temperature for heat addition at a given boiler pressure T increase in performance Increase in Wnet superheat T3 is limited by TH and materials Question: Why not increase Tg instead? Answer: Need high steam quality at turbine outlet to avoid corrosion (want x4 0.9,better >0.95) -Would require higher boiler pressure materials,safety 上游充通大￥ May9,2018 3 SHANGHA BAO TONG LINIERSITY
May 9, 2018 3 Rankine Cycle Performance Trends Effect of superheat on performance: • Purpose: Increase average temperature for heat addition at a given boiler pressure increase in performance T 3 is limited by T H and materials Question: Why not increase T B instead? Answer: ‐ Need high steam quality at turbine outlet to avoid corrosion (want x 4 > 0.9, better > 0.95) ‐ Would require higher boiler pressure materials, safety T B superheat
Continue Rankine Cycle Performance Trends Continue effect of superheat on performance: Consequence of superheating: △Tsup〔C) n X4 0 0.186 0.858 54 0.190 0.913 278 0.217 -(superheated) Note: ·Increasing△T'sup does not have big effect on thermal efficiency,but is needed to increase x4 toa“practical'"value！ 上游充通大粤 May9,2018 4 HANGHAI HAO TONG LINIVERSITY
May 9, 2018 4 Continue Rankine Cycle Performance Trends Continue effect of superheat on performance: • Consequence of superheating: Tsup ( oC) x 4 0 0.186 0.858 54 0.190 0.913 278 0.217 ‐ (superheated) Note: • Increasing Tsup does not have big effect on thermal efficiency, but is needed to increase x 4 to a “practical” value!
Continue Rankine Cycle Performance Trends Effect of boiler pressure on performance: T Increasing boiler pressure Increase decreases heat input at in Wnet relatively constant work output Decrease >Increase in efficiency in Wnet Upper limit depends on heat supply temperature and materials 4' Possible? Also decreases quality S 上游充通大粤 May9,2018 5 SHANGHA BAO TONG LINIERSITY
May 9, 2018 5 Continue Rankine Cycle Performance Trends Effect of boiler pressure on performance: ‐ Increasing boiler pressure decreases heat input at relatively constant work output Increase in efficiency ‐Upper limit depends on heat supply temperature and materials ‐ Also decreases quality T B Possible?