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