The paper presents an exergy analysis of condensate low-pressure heating system of a cogeneration power plant, which consists of one heater, one condensate pump and one pressure reduction valve. The entire system is investigated at three different plant loads. Regardless of the plant load, the highest exergy destruction is noted for the condensate heater (between 416.41 kW and 771.46 kW), after which follows pressure reduction valve with exergy destruction between 57.43 kW and 120.61 kW. Exergy destruction of condensate pump is almost negligible at any plant load and therefore condensate pump has the highest exergy efficiency (between 75.86 % and 77.08 %). Exergy efficiency of condensate heater is between 56.13 % and 59.29 %, while pressure reduction valve has the lowest exergy efficiency of all three analyzed system components and is between 36.98 % and 48.42 %.
Keyword: exergy destruction
Influence of the ambient temperature change on steam pressure reduction valve exergy destruction and exergy efficiency
The paper presents an exergy analysis of pressure reduction valve mounted in the steam propulsion system on conventional LNG carrier. From exploitation are obtained that the valve pressure and temperature decrease become as higher as steam system load increases. Valve exergy power input and output decreases during the increase in steam system load, mostly because of the steam mass flow decrease. Steam system load increase in exploitation also causes a decrease in valve exergy destruction with a simultaneous decrease in valve exergy efficiency (from 68.42 % to 68.09 %). The ambient temperature variation showed that the valve exergy destruction is the lowest for the lowest observed ambient temperature, in any steam system load. The exergy efficiency of the pressure reduction valve is reverse proportional to valve exergy destruction. An increase in the ambient temperature for 10 °C causes a decrease in analyzed valve exergy efficiency for between 2.5 % and 3 %.
EXERGY EFFICIENCY AND EXERGY DESTRUCTION CHANGE OF LOW POWER STEAM TURBINE WITH ONE CURTIS STAGE DURING THE VARIATION IN DEVELOPED POWER
In this paper is presented an exergy analysis of low power steam turbine with one Curtis stage which drives the main feed water pump (MFPT) in the conventional LNG carrier steam propulsion system. It was obtained an insight into the exergy efficiency and the exergy destruction change during the variation in turbine developed power. Measurements of necessary steam operating parameters were performed in seven different turbine operating points. Increase in turbine developed power from 50 kW up to maximum power of 570 kW causes a continuous increase in turbine exergy efficiency and highest exergy efficiency was obtained at the maximum turbine power. Turbine exergy destruction is influenced by steam operating parameters, steam mass flow and turbine current power. MFPT is balanced as the most of the other steam system components – maximum exergy efficiency will be obtained at the highest turbine (steam propulsion system) load on which can be expected the majority of LNG carrier operation.
MATHEMATICAL MODELLING OF TECHNOLOGICAL PROCESSES AND SYSTEMS
ENERGY AND EXERGY ANALYSIS OF SEA WATER PUMP FOR THE MAIN CONDENSER COOLING IN THE LNG CARRIER STEAM PROPULSION SYSTEM
Energy and exergy analysis of sea water pump which is used for the main condenser cooling at lower steam propulsion system loads on conventional LNG carrier is presented in this paper. By using the measured variables from the exploitation, it is presented different influences of pump used power on cumulative energy and exergy power inputs. Energy and exergy pump power losses are reverse proportional, while pump energy and exergy efficiencies are directly proportional to increase in pump load. The highest obtained pump energy efficiency amounts 59.61 %, while the highest obtained pump exergy efficiency amounts 60.25 %. From the viewpoint of efficiencies and power losses, it will be optimal that analyzed pump operates at the highest possible loads.