Presentation is loading. Please wait.

Presentation is loading. Please wait.

ME 400 Energy Conversion Systems Topic 2 Presentation 6 Power Cycles Emad Jassim & Ty Newell Department of Mechanical Science and Engineering University.

Similar presentations


Presentation on theme: "ME 400 Energy Conversion Systems Topic 2 Presentation 6 Power Cycles Emad Jassim & Ty Newell Department of Mechanical Science and Engineering University."— Presentation transcript:

1 ME 400 Energy Conversion Systems Topic 2 Presentation 6 Power Cycles Emad Jassim & Ty Newell Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign © 2012 University of Illinois Board of Trustees. All Rights Reserved.

2 ME 400 Energy Conversion Systems – Lecture 12 Slide 1 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Rankine Cycle - Feedwater Heating -Feedwater heating is the second method we will examine for improving a Rankine cycle -Feedwater heating taps steam from the turbine at intermediate temperature and pressures for heating the water pumped to the boiler -This heating reduces T between liquid going to the boiler and the heat source -Feedwater heating, unlike reheat, should always improve the cycle efficiency

3 ME 400 Energy Conversion Systems – Lecture 12 Slide 2 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. -From our example problem, boiler heat input: Rankine Cycle - Feedwater Heating s T 23C 295C 600C We did not examine heating of the liquid (2 to 2) in detail The liquid changes from 23C to 295C before reaching saturation and starting to boil Feedwater heating adds energy to the low temperature liquid by using some steam that has performed work (which reversibly drops the steam temperature)

4 ME 400 Energy Conversion Systems – Lecture 12 Slide 3 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. ~ 34% of boiler energy is for heating liquid to saturation Rankine Cycle - Feedwater Heating An energy balance on the portion of the boiler where the liquid water is heated to saturation results in: At state 2, Therefore,

5 ME 400 Energy Conversion Systems – Lecture 12 Slide 4 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. 2 types of feedwater heating: Open feedwater heater –2 liquid pumps and a mixing tank required Closed feedwater heater –1 liquid pump, 1 heat exchanger –Isolates steam pressure from boiler feedwater pressure Abbott PP uses one of each –Open for low temperature heating (15psig steam) –Closed for high temperature (~130psig steam) Rankine Cycle - Feedwater Heating

6 ME 400 Energy Conversion Systems – Lecture 12 Slide 5 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Rankine Cycle with Reheat and Open Feedwater Qc W p1 W p2 QbQb W t1 QrQr W t2 m tot -m feed m feed Open feedwater heater

7 ME 400 Energy Conversion Systems – Lecture 12 Slide 6 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Open Feedwater Heater at Abbott PP Open feedwater heater (~15psig~200kPa abs & 120C) Gases in water evolve from the heating and are collected in the top

8 ME 400 Energy Conversion Systems – Lecture 12 Slide 7 © 2012 Emad Jassim & Ty Newell. All Rights Reserved.

9 ME 400 Energy Conversion Systems – Lecture 12 Slide 8 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Open Feedwater Heater Level Controller Pneumatic controller pneumatic pressure operates valve in the feedwater pump line Small tank with float Torque tubeLevel control in the feedwater heater is similar to other industrial processes where a liquid level must be maintained Often, some type of float mechanism Other common systems are dip tubes, optical sensors, and capacitance sensors

10 ME 400 Energy Conversion Systems – Lecture 12 Slide 9 © 2012 Emad Jassim & Ty Newell. All Rights Reserved.

11 ME 400 Energy Conversion Systems – Lecture 12 Slide 10 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Open Feedwater Heater Goal: find fraction of mass flow to be diverted to the feedwater heater P 2 = P 2 = P 3 = P 3 x 2 = 0 P 2 = P 2 = P 3 m feed =?

12 ME 400 Energy Conversion Systems – Lecture 12 Slide 11 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Closed Feedwater Heater Qc W p1 QbQb W t1 QrQr W t2 m tot -m feed m feed Closed feedwater heater valve P 2 =P 2 =P 3 T 2 ~T 3

13 ME 400 Energy Conversion Systems – Lecture 12 Slide 12 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Closed Feedwater Heater at Abbott PP Closed feedwater heater is often a shell & tube heat exchanger Boiler feedwater is at boiler pressure (~500psig for gas boilers and ~1200psig for coal boilers) Steam pressure ~115psig (high pressure extraction from turbines)

14 ME 400 Energy Conversion Systems – Lecture 12 Slide 13 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Closed Feedwater Heater Goal: find fraction of mass flow to be diverted to the feedwater heater P 2 = P 2 = P 2 = P 3 T 2 ~ T 3 Valve (const h) m feed =?

15 ME 400 Energy Conversion Systems – Lecture 12 Slide 14 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Goal: Find feedwater mass flowrate. Then, determine cycle efficiency – Example - Rankine Cycle with Reheat and Open Feedwater Assume conditions found for previous Rankine cycle example with reheat. Formulate 1 st Law on the feedwater heater

16 ME 400 Energy Conversion Systems – Lecture 12 Slide 15 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Example - Rankine Cycle with Reheat and Open Feedwater 3 2 2

17 ME 400 Energy Conversion Systems – Lecture 12 Slide 16 © 2012 Emad Jassim & Ty Newell. All Rights Reserved. Example - Rankine Cycle with Reheat and Open Feedwater To be continued…..


Download ppt "ME 400 Energy Conversion Systems Topic 2 Presentation 6 Power Cycles Emad Jassim & Ty Newell Department of Mechanical Science and Engineering University."

Similar presentations


Ads by Google