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Lecture Objectives:

Lecture Objectives:. Finish with absorption cooling Power generation Rankine cycles Connect power generation with heating and cooling CHP CCHP. Useful information about LiBr absorption chiller.

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Lecture Objectives:

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  1. Lecture Objectives: • Finish with absorption cooling • Power generation • Rankine cycles • Connect power generation with heating and cooling • CHP • CCHP

  2. Useful information about LiBr absorption chiller • http://www.cibse.org/content/documents/Groups/CHP/Datasheet%207%20-%20Absorption%20Cooling.pdf Practical Tips for Implementation of absorption chillers • Identify and resolve any pre-existing problems with a cooling system, heat rejection system, water treatment etc, before installing an absorption chiller, or it may be unfairly blamed. • Select an absorption chiller for full load operation (by the incorporation of thermal stores if necessary) as COP will drop by up to 33% at part-load. • Consider VSD control of absorbent pump to improve the COP at low load.

  3. System with no pump(Platen-Munter system) • H2O-NH3 + hydrogen http://www.youtube.com/watch?v=34K61ECbGD4

  4. Power generation

  5. Power generation in steam turbines(Rankine cycle) Pump Nuclear Coal

  6. Steam powered turbine

  7. Ideal Rankine Cycle 1-2 isentropic pump 2-3 constant pressure heat addition 3-4 isentropic turbine 4-1 constant pressure heat rejection

  8. Ideal Rankine Cycle • h1=hf saturated liquid • Wpump (ideal)=h2-h1=vf(Phigh-Plow) • vf=specific volume of saturated liquid at low pressure • qin=h3-h2 heat added in boiler • Usually either qin will be specified or else the high temperature and pressure (so you can find h3) • qout=h4-h1 heat removed from condenser) • wturbine=h3-h4 turbine work

  9. Deviations from Ideal in Real Cycles • Pump is not ideal • Turbine is not ideal • There is a pressure drop across the boiler and condenser • We need to sub-cool the liquid in the condenser to prevent cavitation in the pump.

  10. For increasing system efficiency of Rankine Cycle • Lower condenser pressure • We should have at least 10°C DT between condenser and cooling water or air temperature for effective heat transfer • The quality at exit to prevent turbine problems shouldn’t go less than about 88% • Superheat the steam more • Tmax ~ 620° due to material stress • Increase boiler pressure (with same Tmax) • Pmax ~ 30 MPa • This affects the quality at exit!

  11. Reheat Cycle • It allows increase boiler pressure without problems of low quality at turbine exit

  12. Regeneration • Preheats steam entering boiler using a feed-water heater, improving efficiency

  13. Further improvements

  14. Analogy with cooling cycles

  15. Gas powered turbine http://www.youtube.com/watch?feature=player_embedded&v=rxps0sZ8T3Y

  16. Combustion product gas powered turbines • Limited to gas or oil as a major source of fuel • Approximately 55 to 65% of the power produced by the turbine is used for compressor. • Gas temperatures at the turbine inlet can be 1200ºC to 1400ºC • Because of the power required to drive the compressor, energy conversion efficiency for a simple cycle gas turbine plant is ~ 30%

  17. Combined Cycle(gas and steam) http://www.youtube.com/watch?feature=player_embedded&v=D406Liwm1Jc

  18. Combined heat and power(cogeneration CHP or three generation CCHP) Here, we use thermal energy for heating and/or cooling

  19. Other method for CHP Here, we use mechanical energy for powering vapor compression cooling systems

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