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Lecture Objectives:

Lecture Objectives:. Analyze absorption cooling. Mixtures (T-x diagram). Dew point curve. Saturated vapor. Mixture of liquid and vapor. Saturated liquid. Bubble point curve. For P= 4 bar. h-x diagram. h fg for H 2 O. h fg for NH 3. Isotherms are showmen only in liquid region.

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Lecture Objectives:

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  1. Lecture Objectives: • Analyze absorption cooling

  2. Mixtures(T-x diagram) Dew point curve Saturated vapor Mixture of liquid and vapor Saturated liquid Bubble point curve For P= 4 bar

  3. h-x diagram hfg for H2O hfg for NH3 Isotherms are showmen only in liquid region

  4. Composition of h-x diagram Saturated vapor line at p1 Equilibrium construction line at p1 1e Used to determine isotherm line in mixing region! Start from x1; move up to equilibrium construction line; move right to saturated vapor line; determine 1’; connect 1 and 1’. Isotherm at P1 and T1 Adding energy B A x1 X1’ mass fraction of ammonia in saturated vapor

  5. h-x diagramat the end of your textbook you will find these diagramsfor 1) NH3-H2O2) H2O-LiBr LiBr is one of the major liquid descants in air-conditioning systems

  6. Adiabatic mixing in h-x diagram(Water – Ammonia) From the textbook (Thermal Environmental Eng.; Kuehen et al)

  7. Absorption cooling cycle Rich solution of Heat H2O + NH3 H2O H2O Rich solution of H2O + NH3

  8. Mixing of two streams with heat rejection (Absorber) mixture of H2O and NH3 m3 m2 =pure NH3 (x2=1) m1 m3 m2 2 m1 Q cooling 3’ Mixture of 1 and 2 Heat rejection Mass and energy balance: (1) 1 3 (2) (3) x3 x From mixture equation: Substitute into (2) Substitute into (3) From adiabatic mixing (from previous slide)

  9. Change of pressure(pump) Sub cooled liquid at p2 2 Saturated liquid at p1 1 p1 ≠p2 m1 =m2 p2 Saturated liquid at x1 =x2 2 p1 Saturated liquid at 1 x1=x2

  10. Heat transfer with separation into liquid and vapor (Generator) Saturated vapor Heat =2V Sub cooled liquid Saturated liquid We can “break” this generator into 2 units heating m4 Q12 /m1 2L= m1 =m2 Separator mixture sub cooled liquid x1 m3 Q12 Apply mass and energy balance In the separator : Apply mass and energy balance In the heat exchanger defines point 2 in graph Defines points 3 and 4 in graph

  11. Heat rejection with separation into liquid and vapor (Condenser) Saturated vapor at p1 m1 Saturated vapor 1 heat rejection m2 Q1-2/m1 m1 =m2 Saturated liquid at p1 x1 =x2 2 p1 =p2 x1=x2

  12. Throttling process (Expansion valve) Saturated vapor 1 2V 1 2 T1 h1 =h2 2 p1 Saturated liquid at p1 ≠p2 T2 2L Saturated liquid p2 m1 =m2 p1 ≠p2 Saturated liquid at x1 =x2 x1 =x2

  13. Simple absorption system 3V 3L 3LLP

  14. Simple absorption system Saturated vapor at p2=p3=p4 3V 6 3 5V mixing 1’ Needed thermal energy Useful cooling energy 4 3L 5 3LLP 2 Saturated liquid at p2=p3=p4 Saturated liquid at p1=p5=p6=p3_LLP 1 5L

  15. More detailed absorption cooling Refrigeration and air conditioning (Ramesh et al)

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