1

4th INTERNATIONAL CONFERENCE ON ADVANCES IN ENERGY RESEARCH

ENERGY ANALYSIS OF SINGLE AND TWO STAGE ABSORPTION

COOLING AND POWER CYCLES

Dr.C.P.JawaharAssociate Professor

Department of Mechanical EngineeringKarunya University

Coimbatore - 641 114, India

Indian Institute of Technology Bombay, Mumbai10-12 December 2013

INTRODUCTION

Combined cycle

Combination of Rankine cycle and absorption refrigeration cycle which produces power and cooling simultaneously with a single heat source

Employs binary working fluid such as ammonia-water

Advantages of ammonia-water

• Good thermo-physical properties

• Environment friendly

SINGLE STAGE ABSORPTION COOLING AND POWER CYCLE

QSH

PRESSURE REDUCING VALVE

P

weak solution

strong solution

refrigerant

QG

SOLUTION PUMP

ABSORBER

GENERATOR

SOLUTION HEAT EXCHANGER

RECTIFIER

SUPER HEATER

2

1

3 4

5

6

7

89

QR

QA

10

TURBINE

16

EXPANSION VALVE

11

EVAPORATOR

CONDENSER

QE

QC

13

12

14

15

QSH

PRESSURE REDUCING VALVE

P

weak solution

strong solution

refrigerant

weak solution

strong solution

refrigerant

QG

SOLUTION PUMP

ABSORBER

GENERATOR

SOLUTION HEAT EXCHANGER

RECTIFIER

SUPER HEATER

2

1

3 4

5

6

7

89

QR

QA

10

TURBINE

16

EXPANSION VALVE

11

EVAPORATOR

CONDENSER

QE

QC

13

12

14

15

TWO STAGE ABSORPTION COOLING AND POWER CYCLE

QG2

P

PRV1

PRV2

A2SP1

A1

SP2

G2

G1

SHX1

SHX2R1

R2R3

SH

2

1

3 4

5

6

7

89

16

17

18 19

20

21

24

30

25

2322

QR1

QR2

QSH

QR3

QA1

QA210

T

14

29

EV

11

E

C

QE

QC

12

13

27

28

26

15

QG2

P

PRV1

PRV2

A2SP1

A1

SP2

G2

G1

SHX1

SHX2R1

R2R3

SH

2

1

3 4

5

6

7

89

16

17

18 19

20

21

24

30

25

2322

QR1

QR2

QSH

QR3

QA1

QA210

T

14

29

EV

11

E

C

QE

QC

12

EV

11

E

C

QE

QC

12

11

E

C

QE

QC

12

13

27

28

26

15

THERMODYNAMIC ANALYSIS - ASSUMPTIONS

• The system operates under steady state conditions.

• Pump work and the frictional pressure drop in the cycle are neglected except through the expansion valve.

• The weak solution leaving the absorber(s), strong solution leaving the generator(s) and the refrigerant at the outlet of condenser and evaporator are saturated.

• The concentration of the refrigerant leaving the rectifier(s) R1 and R3 is 0.999.

THERMODYNAMIC ANALYSIS - ASSUMPTIONS

• The effectiveness of solution heat exchanger(s) is 0.75 and the temperature of super heater is 200°C.

• Split ratio (S) is assumed to be 0.75.

• The degassing width in the single stage cycle is assumed as 0.10, while the degassing width in the first and second stage of the two stage cycle is assumed to be 0.04 and 0.06 respectively.

THERMODYNAMIC ANALYSIS - ASSUMPTIONS

• Mass flow rate of the weak solution from the absorber to the generator is 1 kg/s.

• Temperature of the weak solution leaving the second stage absorber is 0.10°C higher than the temperature of the strong solution leaving the first stage generator.

• Mass flow rate of the refrigerant vapour leaving the first stage rectifier is same as that of the one entering the second stage rectifier and first stage absorber.

PERFORMANCE ANALYSIS - EQUATIONS

Single stage combined cycle

QA = m6 h6 + m13 h13 + m16 h16 - m1 h1

QC = m10(h10 - h11)

QE = m13(h13 - h12)

QG = m4h4 + m7h7 - m3h3 - m8h8

QR = m7h7 - m8h8 - m9h9

PERFORMANCE ANALYSIS - EQUATIONS

QSHX = m3(h3 - h2)

QSH = m15(h15 - h14)

PT = m15 (h15 - h16)

CR = (Xr - Xss) / (Xws - Xss)

COP = QE/QG

ƞ = [PT+ (ec/ƞII,ref)] /(QG+QSH)

PERFORMANCE ANALYSIS - EQUATIONS

Two stage combined cycle

QA1 = m6h6 + m26m26h26 - m1h1

QC = m10(h10 - h11)

QE = m13(h13 - h12)

QR1 = m7h7 - m8h8 - m9h9

QSHX1 = m3(h3 - h2)

PERFORMANCE ANALYSIS - EQUATIONS

PT = m28 (h28 - h29)

QA2 = m15h15 + m21h21 + m29h29 - m16h16

QR2 = m22h22 - m23h23 - m24h24

QR3 = m24h24 - m25h25 - m30h30

QSHX2 = m18(h18 - h17)

PERFORMANCE ANALYSIS - EQUATIONS

QSH = m28(h28- h27)

CR1 = (Xr1 - Xss1)/ (Xws1 - Xss1)

CR2 = (Xr3 - Xss2)/ (Xws2 - Xss2)

COP = QE/QG2

ƞ = [PT+ (ec/ƞII,ref)] /(QG2+QSH)

COOLING CAPACITY Vs ABSORBER TEMPERATURE

POWER OUTPUT Vs ABSORBER TEMPERATURE

COEFFICIENT OF PERFORMANCE Vs ABSORBER TEMPERATURE

EFFECTIVE FIRST LAW EFFICIENCY Vs ABSORBER TEMPERATURE

COOLING CAPACITY Vs CONDENSER TEMPERATURE

POWER OUTPUT Vs CONDENSER TEMPERATURE

COEFFICIENT OF PERFORMANCE Vs CONDENSER TEMPERATURE

EFFECTIVE FIRST LAW EFFICIENCY Vs CONDENSER TEMPERATURE

COOLING CAPACITY Vs EVAPORATOR TEMPERATURE

POWER OUTPUT Vs EVAPORATOR TEMPERATURE

COEFFICIENT OF PERFORMANCE Vs EVAPORATOR TEMPERATURE

EFFECTIVE FIRST LAW EFFICIENCY Vs EVAPORATOR TEMPERATURE

CONCLUSION

Cooling capacity and Power output of single stage cycle is higher than that of a two stage cycle.

Coefficient of performance and Effective first law efficiency of the two stage cycle is found to vary between 21 to 66% and 20 to 60% respectively, more than the single stage cycle.

It is also observed that the two stage combined cycle could effectively utilize a high temperature heat source than the single stage one.

THANK YOU