1. Introduction
For reducing global warming and ozone depletion and
maximizing the use of natural and renewable energy resources with minimal
environmental impacts is key building of an energy efficient sustainable
system. Although completely sustainable energy efficient system would require a
fully reversible process, exploits the second law of thermodynamics which proves
is not possible, which indicating that all real processes are irreversible and
impact on the environment. Approaching sustainability can yield greater
benefits both the current and future environment. The utilization of natural
and renewable resources in a responsible fashion and by using efficient methods
is important aspect when developing new technologies and analyzing current
refrigeration and air conditioning systems. The conventional vapour compression
refrigeration systems and vapour absorption systems utilize different working
fluids. Many of the vapour compression systems use the ozone depleting
chloro-fluoro-carbon refrigerants (CFCs), Hydro-chloro-fluoro-carbon
refrigerants (HCFCs), Hydro-fluoro-carbon refrigerants (CFCs), because of the
thermo-physical properties obtainable by them. Many industrial processes
frequently produce a significant amount of thermal energy; regularly by burning
fossil fuels for heat or steam. The opportunities to convert wastes or excess
heat into useful cooling can be done by integration of absorption refrigeration
systems into these systems. Szargut et al [1]. suggested that exergy methods
should be considered to better realize increased efficiencies and environmental
impacts because exergy is normally considered to be the measure of work
potential (i.e. maximum work) that can be obtained from a system with respect
to its environment. The exergy, is a non-conserved quantity, and exergy balances
account for inputs, losses and wastes of a process. the exergy input and
destruction rates provide an accounting of the utilized efficiency of resources
used. Rosen and Dincer [2] have given links between energy, exergy and
sustainable development, which shows that exergy may allow for measuring
impacts on the environment
Gebreslassie et al
[3] had evaluated exergy in Lithium bromide (Li/Br) absorption systems by using
structural method to obtain a simplified equation to estimate the optimum heat exchanger
area for absorption cooling system and assessed the relationship between heat
exchange area and exergy. Also concluded that in the optimum case, the maximum
exergy destruction was in the solution heat exchanger and the condenser while
in all other components, the destruction rates decreasing as increased heat
exchange area and presented at detailed analysis of exergy for half to triple
effect absorption chillers. Bereche et al [4] analyzed single and double-effect
LiBr systems using a thermo-economic analysis and exergy and concluded that the
single-effect absorption refrigeration systems are suitable utilizing waste
heat or operating in cogeneration systems because of their operation at lower
temperatures compared to double-effect chillers, Morosuk and Tsatsaron [5] is
presented an exergy analysis of the internal components of absorption
refrigeration machines. And concluded that the absorber and generator destroyed
about 40% of their exergy and are main (primary) candidates for improvement.
Kilic and Kaynakli [6] carried out a second law(exergy) thermodynamic analysis
of water and lithium bromide absorption refrigeration and found the evaporator
is a major component for the exergy loss rates and concluded that the
generator, absorber and evaporator were the largest sources of exergy
destruction. Garimella et al [7] proposed
absorption/vapour compression cascade refrigeration system driven by waste heat
used in naval ship and concluded that electricity consumption is reduced by 31%
than that of conventional vapour compression refrigeration system.
The large number
of research studies on cascade refrigeration systems have been done. These
research studies provide valuable insights about energy and exergy analysis of
VCR, VAR cycles in the single, double and triple stage and
compression-absorption in the form of cascade cycles. Most of the research
studies considered till date emphasize on VCR and VAR cycles (single and double
effect, triple and half effect in Li/Br-H2O and NH3H2O).
Mishra [8] carried out exergy- energy analysis of compression-absorption
(combined) or cascade cycles. Though, exhaustive research has been carried out
on cascade cycles, but very less consideration has been given to explore the
thermodynamic performance using HFO refrigerants in the range from -30oC
to -150oC and none of the research work is available on performance
analysis of compression-absorption cascade refrigeration system using HFO
refrigerants. Radhey Shyam Mishra [9-10] carried out
thermodynamic performance of the HFO refrigerants in the medium temperature
compression stage between 5oC to -50oC and NH3H2O,
Li/Br-H2O refrigerants in the absorption stage and its overall
effect on the cascade system. The effect of these HFO refrigerants on the
intermediate temperature in the range of (-50oC to 95oC)
using R245fa of medium temperature cycle cascade system using R32 refrigerant/
hydrocarbons in ultra-low evaporator temperature first and second law
performances using the pair of NH3–H2O in the high
temperature absorption stage and HFO refrigerants at the evaporator temperature
of 223K (-50oC) and R245fa in the medium temperature compression
cycle for evaporator temperature of -95oC evaluated the effect of
various performance parameters of multi cascade refrigeration system in which a
compression system at the low temperature stage using R32 in low temperature
cycle at evaporator temperature of -130oC . It is found that R1233zd
(E), R1225ye(Z) and HFO-1336mzz(z) gives better thermodynamic performances than
using R1243yf. The studies carried out so far on the double and
triple effect cycles in the use of HFO
refrigerants up to evaporator temperature of -50oC in cascaded
vapour compression refrigeration systems. to some extent, the effect of HFO
refrigerants in the intermediate temperature cycle at -75oC and -95oC
is missing. Also the effect of HFO –refrigerants in ultra-low temperature cycle
of compression –absorption refrigeration systems have not been investigated so
far. The present study has therefore
been carried out the effect of HFO refrigerants in intermediate temperature
cycle(ITC) up to -95oC and LTC evaporator of -135oC and -150oC.
2.
Results and
Discussion
System-1
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1233zd(E) in medium temperature cycle at evaporator temperature =-50oC, R-1225ye(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -150oC.
System-2
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1233zd(E) in medium temperature cycle at evaporator temperature =-50oC, HFO-1336mzz(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using R-1225ye(Z) in lower temperature cycle at evaporator temperature = -150oC.
System-3
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234yf in medium temperature cycle at evaporator temperature =-50oC, R-1225ye(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -150oC.
System-4
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234yf) in medium temperature cycle at evaporator temperature =-50oC, HFO-1336mzz(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using R-1225ye(Z) in lower temperature cycle at evaporator temperature = -150oC.
Following numerical values have been used
for validation of code developed for Integrated single effect Li/Br-H2O
VARS using eco-friendly refrigerants.
· Generator temperature= 110oC
·
Absorber
temperature=35oC
·
Condenser
temperature =35oC
·
VARS
evaporator temperature=10oC
·
load
on VARS Evaporator= 175 kW
·
Ambient
(dead state) temperature=25oC
·
Temperature
overlapping in MTC = 10oC
·
VCR
evaporator temperature of MTC=-50oC
·
VCR
evaporator temperature of ITC=-95oC
·
VCR
evaporator temperature of LTC=-150oC
·
VCR
compressor efficiency of MTC= 80%
·
VCR
compressor efficiency of ITC= 80%
·
VCR
compressor efficiency of MTC= 80%
·
Ambient
(dead state) temperature=25oC
Thermodynamic first law energy performances
of integrated single effect Li/Br-H2O VARS system cascaded with
three stages vapour compression cascaded systems shown in table 2(a)
respectively. It was observed that system-6 has lowest thermodynamic
performances than system-5, however first law thermodynamic performance
improvement is less. Similarly, Thermodynamic second law exergy performances of
cascaded single effect Li/Br-H2O VARS system cascaded with three
stages vapour compression cascaded systems shown in table-2(b) respectively. It
was observed that system-6 has higher thermodynamic exergetic performances than
system-5.
Table-1(a) Thermodynamic first law (energetic) Performances of Integrated single effect Li/Br-H2O VARS using ecofriendly refrigerants at evaporator temperature=-150oC
Integrate system |
COP_VARS |
COP _MTC |
COP _ITC |
COP _ L TC |
% Improvement in
COP _MTC |
% Improvement in
COP _ITC |
% Improvement in
COP _ LTC |
System-1 |
0.7560 |
0.8759 |
0.9847 |
0.9236 |
15.86 |
30.65 |
22.17 |
System-2 |
0.7560 |
0.8759 |
0.9847 |
0.9282 |
15.86 |
30.26 |
22.79 |
System-3 |
0.7560 |
0.8102 |
0.9120 |
0.8634 |
7.168 |
20.64 |
14.22 |
System-4 |
0.7560 |
0.8102 |
0.9120 |
0.8674 |
7.168 |
20.31 |
14.74 |
Table-1(b)
Thermodynamic second law (exergetic) Performances of Integrated single effect
Li/Br-H2O VARS using ecofriendly refrigerants at evaporator
temperature=-150oC
Integrate system |
ETA_VARS |
ETA_MTC |
ETA_ITC |
ETA_ L TC |
% Improvement in
ETA_MTC |
% Improvement in
ETA_ITC |
% Improvement in
ETA_ LTC |
System-1 |
0.1564 |
0.321 |
0.5331 |
0.5539 |
77.98 |
195.3 |
206.8 |
System-2 |
0.1564 |
0.321 |
0.5293 |
0.5639 |
77.98 |
193.1 |
212.3 |
System-3 |
0.1564 |
0.2680 |
0.4561 |
0.4890 |
48.94 |
152.6 |
170.9 |
System-4 |
0.1564 |
0.2689 |
0.4530 |
0.4974 |
48.94 |
150.9 |
175..5 |
Table-1(c)
Thermodynamic exergy destruction ratio of Integrated single effect Li/Br-H2O
VARS using ecofriendly refrigerants at evaporator temperature= -150oC
Integrate system |
EDR_VARS |
EDR_MTC |
EDR_ITC |
ED R_ L TC |
% Improvement in
EDR_MTC |
% Improvement in
EDR_ITC |
% Improvement in
EDR_ LTC |
System-1 |
4.539 |
2.112 |
0.8754 |
0.8053 |
-53.47 |
-80.7 |
-82.26 |
System-2 |
4.539 |
2.112 |
0.8894 |
0.7735 |
-53.47 |
-80.4 |
-82.96 |
System-3 |
4.539 |
2.719 |
0.8754 |
0.8053 |
-40.10 |
-73.72 |
-76.98 |
System-4 |
4.539 |
2.719 |
0.8754 |
0.8053 |
40.10 |
-73.40 |
-77.74 |
However, second law thermodynamic
exergetic performance improvement for -150oC evaporator temperature is
less. It means by putting HFO-1336mzz(Z) in lower temperature cycle in system-5
gives lower first and second law thermodynamic performances than using R-1225ye(Z)
in low temperature cycle. However, first law(energy) and second law exegetic
performances of double stage cascaded integrated system-5 is higher than double
stage cascaded integrated system-6 at evaporator temperature of -95oC.It
means by putting HFO-1336mzz(Z) in intermediate temperature cycle gives lower
first and second law thermodynamic performances than using R-1225ye(Z). The
exergy destruction ratio of whole cascaded system is shown in Table-2(c)
respectively.
System-5
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234ze(Z) in medium temperature cycle at evaporator temperature =-30oC, R1225ye(Z) in intermediate temperature cycle at evaporator temperature = -75oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-6
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234ze(Z) in medium temperature cycle at evaporator temperature =-30oC, HFO-1336mzz(Z) in intermediate temperature cycle at evaporator temperature = -75oC and using R1225ye(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-7
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234ze(E) in medium temperature cycle at evaporator temperature =-30oC, R1225ye(Z) in intermediate temperature cycle at evaporator temperature = -75oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-8
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234ze(E) in medium temperature cycle at evaporator temperature =-30oC, HFO-1336mzz(Z) in intermediate temperature cycle at evaporator temperature = -75oC and using R1225ye(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-9
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1243zf in medium temperature cycle at evaporator temperature =-50oC, R-1225ye(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-10
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1243zf in medium temperature cycle at evaporator temperature =-30oC, HFO-1336mzz(Z)in intermediate temperature cycle at evaporator temperature = -75oC and using R-1225ye(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-11
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1233zd(E) in medium temperature cycle at evaporator temperature =-50oC, R-1225ye(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-12
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1233zd(E) in medium temperature cycle at evaporator temperature =-50oC, HFO-1336mzz(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using R-1225ye(Z) in lower temperature cycle at evaporator temperature = -150oC.
System-13
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234yf in medium temperature cycle at evaporator temperature =-50oC, R-1225ye(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -135oC.
System14
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234yf in medium temperature cycle at evaporator temperature =-50oC, HFO-1336mzz(Z) in intermediate temperature cycle at evaporator temperature = -95oC and using R-1225ye(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-15
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R-1225ye(Z) in medium temperature cycle at evaporator temperature =-50oC, R1233zd(E) in intermediate temperature cycle at evaporator temperature = -95oC and using HFO-1336mzz(Z) in lower temperature cycle at evaporator temperature = -135oC.
System-16
Li/Br-H2O single effect vapour absorption refrigeration system at 10oC of evaporator temperature cascaded with three stages vapour compression refrigeration system using R1234yf in medium temperature cycle at evaporator temperature =-50oC, R1233zd(E) in intermediate temperature cycle at evaporator temperature = -95oC and using R-1225ye(Z) in lower temperature cycle at evaporator temperature = -135oC.
Following numerical values have been used
for validation of code developed for Integrated single effect Li/Br-H2O
VARS using ecofriendly refrigerants
·
Generator
temperature= 110oC
·
Absorber
temperature=35oC
·
Condenser
temperature =35oC
·
VARS
evaporator temperature=10oC
·
load
on VARS Evaporator= 175 kW
·
Ambient
(dead state) temperature=25oC
·
Temperature
overlapping in MTC = 10oC
·
VCR
evaporator temperature of MTC=-30oC
·
VCR
evaporator temperature of ITC=-75oC
·
VCR
evaporator temperature of LTC=-135oC
·
VCR
compressor efficiency of MTC= 80%
·
VCR
compressor efficiency of ITC= 80%
·
VCR
compressor efficiency of MTC= 80%
·
Ambient
(dead state) temperature=25oC
Thermodynamic first law energy performances of integrated single effect Li/Br-H2O VARS system cascaded with three stages vapour compression cascaded systems shown in table 2(a) respectively. It was observed that system-2 has lowest thermodynamic performances than system-1, however first law thermodynamic performance improvement is less
Table-2(a) Thermodynamic first law (energetic) Performances of Integrated single effect Li/Br-H2O VARS using ecofriendly refrigerants at evaporator temperature=-135oC
Integrate system |
COP_VARS |
COP _MTC |
COP _ITC |
COP _ L TC |
%Improvement in
COP _MTC |
%Improvement in
COP _ITC |
% Improvement in
COP _ LTC |
System-5 |
0.7560 |
1.002 |
1.145 |
1.05 |
32.56 |
51.44 |
38.96 |
System-6 |
0.7560 |
1.002 |
1.143 |
1.057 |
32.58 |
51.15 |
39.82 |
System-7 |
0.7560 |
0.9662 |
1.104 |
1.020 |
27.81 |
46.032 |
34.92 |
System-8 |
0.7560 |
0.9662 |
1.102 |
1.057 |
27.81 |
45.82 |
35.75 |
System-9 |
0.7560 |
0.9698 |
1.108 |
1.057 |
28.29 |
46.62 |
35.35 |
System-10 |
0.7560 |
0.9698 |
1.106 |
1.057 |
28.29 |
46.36 |
36.16 |
System-11 |
0.7560 |
0.9961 |
1.138 |
1.057 |
31.76 |
50.53 |
38.28 |
System-12 |
0.7560 |
0.9961 |
1.138 |
1.045 |
31.76 |
50.53 |
38.28 |
System-13 |
0.7560 |
0.9431 |
1.078 |
1.0 |
24.76 |
42.62 |
32.31 |
System-14 |
0.7560 |
0.9431 |
1.076 |
1.006 |
24.76 |
42.37 |
32.08 |
System-15 |
0.7560 |
0.9634 |
1.102 |
1.018 |
2744 |
45.74 |
34.68 |
System-16 |
0.7560 |
0.9794 |
1.120 |
1.039 |
29.56 |
48.13 |
37.5 |
Table-2(b)
Thermodynamic second law (exergetic) Performances of Integrated single effect
Li/Br-H2O VARS using ecofriendly refrigerants at evaporator
temperature=-135oC
Integrate system |
ETA_VARS |
ETA_MTC |
ETA_ITC |
ETA_ L TC |
%Improvement in
ETA_MTC |
% Improvement in
ETA_ITC |
%Improvement in
ETA_ LTC |
System-5 |
0.1560 |
0.322 |
0.5278 |
0.5383 |
78.49 |
192.3 |
198.1 |
System-6 |
0.1560 |
0.3223 |
0.5255 |
0.5491 |
78.49 |
191.0 |
204.1 |
System-7 |
0.1560 |
0.2970 |
0.4936 |
0.5126 |
64.50 |
173.5 |
183.5 |
System-8 |
0.1560 |
0.2970 |
0.4917 |
0.5227 |
64.5 |
172.3 |
189.5 |
System-9 |
0.1560 |
0.2992 |
0.4972 |
0.5152 |
65.86 |
175.4 |
185.3 |
System-10 |
0.1560 |
0.2995 |
0.4951 |
0.5253 |
65.86 |
174.5 |
191.0 |
System-11 |
0.1560 |
0.3170 |
0.5219 |
0.5339 |
76.04 |
189.1 |
195.7 |
System-12 |
0.1560 |
0.3170 |
0.5219 |
0.5339 |
76.04 |
189.1 |
195.7 |
System-13 |
0.1560 |
0.2817 |
0.4723 |
0.4958 |
55.96 |
161.6 |
174.6 |
System-14 |
0.1560 |
0.2816 |
0.4704 |
0.5054 |
55.96 |
160.5 |
179.9 |
System-15 |
0.1560 |
0.2950 |
0.4918 |
0.5110 |
55.96 |
172.4 |
183.0 |
System-16 |
0.1560 |
0.3061 |
0.5068 |
0.5347 |
69.54 |
180.7 |
196.1 |
Table-2(c)
Thermodynamic exergy destruction ratio of Integrated single effect Li/Br-H2O
VARS at evaporator temperature=-135oC
Integrate system |
EDR_VARS |
EDR_MTC |
EDR_ITC |
ED R_ L TC |
% Improve in EDR_MTC |
%Improvement in
EDR_ITC |
%Improvement in
EDR_ LTC |
System-5 |
4.539 |
2.103 |
0.9031 |
0.8212 |
-53.66 |
-80.10 |
-81.91 |
System-6 |
4.539 |
2.103 |
0.8947 |
0.8577 |
-53.66 |
-80.29 |
-81.1 |
System-7 |
4.539 |
2.367 |
1.025 |
0.9529 |
-47.85 |
-77.41 |
-79.05 |
System-8 |
4.539 |
2.367 |
1.034 |
0.9133 |
-47.82 |
-77.23 |
-79.88 |
System-9 |
4.539 |
2.339 |
1.011 |
0.9410 |
-48.46 |
-77.72 |
-79.23 |
System-10 |
4.539 |
2.339 |
1.02 |
0.9036 |
-48.46 |
-77.53 |
-80.09 |
System-11 |
4.539 |
2.146 |
0.916 |
0.8729 |
-52.71 |
-79.82 |
-80.77 |
System-12 |
4.539 |
2.146 |
0.916 |
0.8729 |
-52.71 |
-79.82 |
-80.77 |
System-13 |
4.539 |
2.551 |
1.117 |
1.017 |
-43.79 |
-75.39 |
-77.6 |
System-14 |
4.539 |
2.551 |
1.126 |
0.9785 |
-47.37 |
-77.23 |
-78.92 |
System-15 |
4.389 |
2.551 |
1.033 |
0.9569 |
-43.79 |
-75.19 |
-78.44 |
System-16 |
4.539 |
2.267 |
0.9730 |
0.8703 |
-50.06 |
-78.56 |
-80.83 |
Similarly, Thermodynamic second tlaw exergy performances of cascaded single effect Li/Br-H2O VARS system cascaded with three stages vapour compression cascaded systems shown in table-2(b) respectively. It was observed that system-2 has higher thermodynamic exergetic performances than system-1. However, second law thermodynamic exergetic performance improvement for -150oC evaporator temperature is less. It means by putting HFO-1336mzz(Z) in lower temperature cycle in system-1 gives lower first and second law thermodynamic performances than using R-1225ye(Z) in low temperature cycle. However, first law(energy) and second law exegetic performances of double stage cascaded integrated system-1 is higher than double stage cascaded integrated system-2 at evaporator temperature of -95oC.It means by putting HFO-1336mzz(Z) in intermediate temperature cycle gives lower first and second law thermodynamic performances than using R-1225ye(Z). The exergy destruction ratio of whole cascaded system is shown in Table-2(c) respectively.
Thermodynamic first law energy performances
of integrated single effect Li/Br-H2O VARS system cascaded with
three stages vapour compression cascaded systems with varying evaporator
temperature is shown in table -3 respectively. It was observed that by
increasing VAR evaporator temperature, the thermodynamic first law (energy)
performance is increases while second law (exergy)efficiency is decreases and
exergy destruction ratio is increases. Similarly, Thermodynamic second law
exergy performances of cascaded single effect Li/Br-H2O VARS system
cascaded with three stages vapour compression cascaded systems with variation
of absorber temperature is shown in table-4 respectively. It was observed
thermodynamic performances
is decreases, by increasing absorber
temperature.
Table-3 Thermodynamic (exergy) performances of Integrated single effect Li/Br-H2O VARS using R1233zd(E) ecofriendly refrigerants at MTC evaporator temperature=-65oC, T_Eva_VARS= 5oC, Approach=, 5oC
Evaporator
temperature of VARS (oC) |
COP_VARS |
EDR |
Exergetic
Efficiency |
COP_ cascade |
EDR_ cascade |
Exergetic
Efficiency_ cascade |
% Improvement in COP
_ cascade |
% Decrement in
EDR _ cascade |
%Improv-ment in
Exergetic Efficiency _ cascade |
3 |
0.7360 |
2.783 |
0.2643 |
0.7789 |
1.933 |
0.3410 |
5.03 |
-30.56 |
29.0 |
4 |
0.7410 |
2.964 |
0.2523 |
0.7808 |
1.970 |
0.3367 |
5.03 |
-33.55 |
33.48 |
5 |
0.7560 |
3.163 |
0.2402 |
0.7827 |
2.008 |
0.3325 |
5.03 |
-36.52 |
38.41 |
6 |
0.7438 |
3.382 |
0.2282 |
0.7848 |
2.046 |
0.3283 |
5.03 |
-39.49 |
43.84 |
7 |
0.7466 |
3.624 |
0.2163 |
0.7869 |
2.085 |
0.3241 |
5.03 |
-42.46 |
49.87 |
8 |
0.7496 |
3.894 |
0.2043 |
0.7892 |
2.125 |
0.320 |
5.03 |
-45.42 |
56.60 |
9 |
0.7525 |
4.197 |
0.1924 |
0.7916 |
2.166 |
0.3159 |
5.16 |
-48.40 |
64.16 |
10 |
0.7560 |
4.539 |
0.1805 |
0.7940 |
2.207 |
0.3119 |
5.03 |
-51.38 |
72.73 |
Table-4
Effect of Absorber temperature on thermodynamic performances of Integrated
single effect Li/Br-H2O VARS using R1233zd(E) ecofriendly refrigerants at MTC
evaporator temperature=-65oC, T_Eva_VARS= 5oC, Approach=,
5oC
Absorber
temperature of VARS (oC) |
COP_VARS |
EDR |
Exergetic
Efficiency |
COP _
cascade |
EDR_ cascade |
Exergetic
Efficiency_ cascade |
% Improvement in
COP _ cascade |
% Decrement in
EDR _ cascade |
% Improvement in Exergetic
Efficiency _ cascade |
30 |
0.7486 |
3.121 |
0.2427 |
0.7885 |
1.997 |
0.3337 |
5.323 |
-36.02 |
37.51 |
35 |
0.7410 |
3.163 |
0.2402 |
0.7827 |
2.008 |
0.3325 |
5.627 |
-36.52 |
38.41 |
40 |
0.7353 |
3.195 |
0.2384 |
0.7784 |
2.016 |
0.3315 |
5.856 |
-36.90 |
39.09 |
45 |
0.7312 |
3.219 |
0.2370 |
0.7752 |
2.022 |
0.3309 |
6.023 |
-37.17 |
39.59 |
Thermodynamic first law energy performances of integrated single effect Li/Br-H2O VARS system cascaded with three stages vapour compression cascaded systems with varying Condenser temperature is shown in table -5 respectively. It was observed that by increasing VARS Condenser temperature, the thermodynamic first law (energy) performance is decreases while second law (exergy)efficiency is decreased and exergy destruction ratio is increases. Similarly, Thermodynamic performances of cascaded single effect Li/Br-H2O VARS system cascaded with three stages vapour compression cascaded systems with variation of generator temperature is shown in table-6 respectively. It was observed thermodynamic performances is decreases, by increasing generator temperature.
Table-5
Effect of condenser temperature on thermodynamic performances of Integrated
single effect Li/Br-H2O VARS using R1233zd(E) ecofriendly
refrigerants at MTC evaporator temperature=-65oC, T_Eva_VARS= 5oC,
Approach=, 5oC
Condenser
temperature of VARS (oC) |
COP_VARS |
EDR |
Exergetic
Efficiency |
COP _
cascade |
EDR_ cascade |
Exergetic
Efficiency_ cascade |
% Improvement in COP _
cascade |
% Decrement in
EDR _ cascade |
%Improv-ment in
Exergetic Efficiency _ cascade |
30 |
0.7472 |
3.129 |
0.2422 |
0.7874 |
2.003 |
0.3330 |
5.38 |
-36.11 |
37.61 |
32 |
0.7449 |
3.141 |
0.2415 |
0.7857 |
2.004 |
0.3328 |
5.470 |
-36.26 |
37.94 |
34 |
0.7423 |
3.156 |
0.2406 |
0.7837 |
2.006 |
0.3327 |
5.574 |
-36.44 |
38.25 |
35 |
0.7410 |
3.163 |
0.2402 |
0.7827 |
2.008 |
0.3325 |
5.627 |
-36.52 |
38.41 |
36 |
0.7398 |
3.170 |
0.2398 |
0.7818 |
2.070 |
0.3323 |
5.678 |
-36.61 |
38.56 |
38 |
0.7374 |
3.183 |
0.2390 |
0.780 |
2.013 |
0.3319 |
5.773 |
-36.76 |
38.84 |
40 |
0.7353 |
3.195 |
0.2384 |
0.7784 |
2.016 |
0.3315 |
5.856 |
-36.90 |
39.09 |
42 |
0.7336 |
3.205 |
0.2378 |
0.7771 |
2.019 |
0.3313 |
5.925 |
-37.01 |
39.30 |
44 |
0.7322 |
3.213 |
0.2373 |
0.7760 |
2.021 |
0.3310 |
5.983 |
-37.11 |
39.47 |
45 |
0.7315 |
3.217 |
0.2371 |
0.7755 |
2.022 |
0.3309 |
6.009 |
-37.15 |
39.55 |
Table-6
Effect of generator temperature on thermodynamic performances of Integrated
single effect Li/Br-H2O VARS using R1233zd(E) ecofriendly
refrigerants at MTC evaporator temperature=-65oC, T_Eva_VARS= 5oC,
Approach=, 5oC
Generator
temperature of VARS (oC) |
COP_VARS |
EDR_VARS |
Exergetic
Efficiency_VARS |
COP _MTC |
EDR _MTC |
Exergetic
Efficiency _ M TC |
%Improve-ment in
COP _MTC |
%Improve-ment in
COP _ITC |
%Improv-ment in
COP _ LTC |
90 |
0.7596 |
2.277 |
0.3052 |
0.8194 |
1.599 |
0.3849 |
7.881 |
-29.79 |
26.10 |
95 |
0.7532 |
2.510 |
0.2849 |
0.8145 |
1.657 |
0.3761 |
8.132 |
-33.98 |
32.10 |
100 |
0.7478 |
2.737 |
0.2676 |
0.8103 |
1.715 |
0.3684 |
8.346 |
-37.37 |
37.67 |
105 |
0.7437 |
2.955 |
0.2528 |
0.8070 |
1.770 |
0.3611 |
8.509 |
-40.13 |
42.82 |
110 |
0.7410 |
3.163 |
0.2402 |
0.8049 |
1.822 |
0.3544 |
8.618 |
-42.40 |
47.53 |
115 |
0.7388 |
3.364 |
0.2291 |
0.8031 |
1.873 |
0.3481 |
8.709 |
-44.34 |
51.93 |
120 |
0.7399 |
3.541 |
0.2202 |
0.8040 |
1.917 |
0.3428 |
8.665 |
-45.87 |
55.68 |
Thermodynamic first law energy performances
of integrated single effect Li/Br-H2O VARS system cascaded with
three stages vapour compression cascaded systems with varying generator
temperature for constant evaporator temperature of -75oC in lower
vapour compression cycle is shown in tables -7 for R1233zd(E), R1225ye(Z) and
HFO-1336mzz(Z) respectively. It was observed that by increasing VARS Condenser temperature, the thermodynamic
first law (energy) performance is decreases while second law (exergy)efficiency
is decreases and exergy destruction ratio is increases. Similarly,
Thermodynamic performances of cascaded single effect Li/Br-H2O VARS
system cascaded with three stages vapour compression cascaded systems with
variation of generator temperature is shown in table-6 respectively. It was
observed thermodynamic performances
Table-7(a) Effect of generator temperature on thermodynamic performances of Integrated single effect Li/Br-H2O VARS using R1233zd(E) ecofriendly refrigerants at MTC evaporator temperature=-75oC, T_Eva_VARS= 5oC, Approach=, 5oC
Generator
temperature of VARS (oC) |
COP_Cascade |
EDR_ Cascade |
Exergetic Efficiency_
Cascade |
90 |
0.8194 |
1.599 |
0.3849 |
95 |
0.8145 |
1.657 |
0.3761 |
100 |
0.8103 |
1.715 |
0.3684 |
105 |
0.8070 |
1.770 |
0.3611 |
110 |
0.8049 |
1.822 |
0.3544 |
115 |
0.8031 |
1.873 |
0.3481 |
120 |
0.8040 |
1.917 |
0.3428 |
Table-7(b) Effect of generator temperature on improvement in thermodynamic performances of Integrated single effect Li/Br-H2O VARS using R1233zd(E) ecofriendly refrigerants at MTC evaporator temperature=-75oC, T_Eva_VARS= 5oC, Approach=, 5oC
Generator
temperature of VARS (oC) |
% improvement in
COP_ Cascade |
% decre-ment in
EDR_ Cascade |
% improvement in
Exergetic Eff_ Cascade |
90 |
7.881 |
-29.79 |
26.10 |
95 |
8.132 |
-33.98 |
32.10 |
100 |
8.346 |
-37.36 |
37.67 |
105 |
8.509 |
-40.13 |
42.82 |
110 |
8.618 |
-42.40 |
47.53 |
115 |
8.709 |
-44.34 |
51.93 |
120 |
8.665 |
-45.87 |
55.68 |
able-7(c) Effect of generator temperature on thermodynamic performances of Integrated single effect Li/Br-H2O VARS using HFO1336mzz(Z) ecofriendly refrigerants at MTC evaporator temperature=-75oC, T_Eva_VARS= 5oC, Approach=, 5oC
Generator
temperature of VARS (oC) |
COP_ cascade |
EDR_ cascade |
Exergetic Efficiency_
cascade |
90 |
0.7950 |
1.790 |
0.3594 |
95 |
0.7902 |
1.852 |
0.3507 |
100 |
0.7478 |
1.911 |
0.3435 |
105 |
0.7437 |
1.968 |
0.3369 |
110 |
0.7410 |
2.022 |
0.3309 |
115 |
0.7388 |
2.075 |
0.3252 |
120 |
0.7399 |
2.122 |
0.3204 |
able-7(d) Effect of generator temperature on percentage improvement in thermodynamic performances of Integrated single effect Li/Br-H2O VARS using HFO1336mzz(Z) ecofriendly refrigerants at MTC evaporator temperature=-65oC, T_Eva_VARS= 5oC, Approach=, 5oC
Generator
temperature of VARS (oC) |
% improvement in
COP_cascade |
% decrement in
EDR_ cascade |
% improvement in
Exergetic Efficiency_
cascade |
90 |
4.662 |
-21.36 |
17.43 |
95 |
4.914 |
-26.26 |
23.10 |
100 |
5.129 |
-30.18 |
28.38 |
105 |
5.293 |
-33.41 |
33.26 |
110 |
5.402 |
-36.06 |
37.73 |
115 |
5.493 |
-38.32 |
41.92 |
120 |
5.449 |
-40.09 |
45.49 |
able-7(e) Effect of generator temperature on thermodynamic performances of Integrated single effect Li/Br-H2O VARS using R1225ye(Z) ecofriendly refrigerants at MTC evaporator temperature=-65oC, T_Eva_VARS= 5oC, Approach=, 5oC
Generator
temperature of VARS (oC) |
COP_ cascade |
EDR_ cascade |
Exergetic Efficiency_
cascade |
90 |
0.7851 |
1.874 |
0.3479 |
95 |
0.7532 |
1.936 |
0.3406 |
100 |
0.7478 |
1.997 |
0.3337 |
105 |
0.7437 |
2.055 |
0.3274 |
110 |
0.7410 |
2.11 |
0.3216 |
115 |
0.7388 |
2.163 |
0.3161 |
120 |
0.7399 |
2.211 |
0.3115 |
able-7(f) Effect of generator temperature on percentage improvement thermodynamic performances of Integrated single effect Li/Br-H2O VARS using R1225ye(Z) ecofriendly refrigerants at MTC evaporator temperature=-75oC, T_Eva_VARS= 5oC, Approach=, 5oC
Generator
temperature of VARS (oC) |
% improve-ment in
COP_ cascade |
% decre-ment in
EDR_ cascade |
% improvement in
Exergetic Efficiency_
cascade |
90 |
3.359 |
-17.69 |
17.43 |
95 |
3.612 |
-22.87 |
23.10 |
100 |
3.827 |
-27.06 |
28.38 |
105 |
3.991 |
-30.48 |
33.26 |
110 |
4.10 |
-33.29 |
37.73 |
115 |
4.192 |
-35.70 |
41.92 |
120 |
4.148 |
-37.58 |
45.49 |
3. Conclusions
Following
conclusions were drawn from present investigations
· By reducing the exergy destruction rate by using HFO refrigerants therefore, sustainability improved.
·
The
best thermodynamic performances were observed by using R1234ze(Z) and
R1233zd(E), HFO-1336mzz(Z), and R1225ye(Z) and R1234ze(E) and R1243zf
performance
·
The lowest thermodynamic performances were
fund by using R1234yf in cascaded system in lower circuit up to a VCR
evaporator temperature
·
In
single cascading with VARS, at low temperature applications up to -30oC
evaporator temperature, HFO ecofriendly refrigerants (R-1234ze(Z), R-1234ze(E),
R1233zd(E), R-1243zf, R1225ye(Z), HFO-1336mzz(Z) and R1234yf will be certainly
useful for replacing HFC, HCFC and CFC refrigerants, while R1224yd(Z) will be
suitable for -10oC above evaporator temperature for replacing R134a.
·
In
single cascading with VARS, at low temperature applications up to -50oC
evaporator temperature, HFO ecofriendly refrigerants (R1225ye(Z), R1233zd(E), HFO-1336mzz(Z)
and R1234yf will be certainly useful for replacing HFC, HCFC and CFC
refrigerants.
·
In
the double cascading with VARS, at low temperature applications up to -75oC
evaporator temperature, HFO ecofriendly refrigerants (R1225ye(Z), R1233zd(E), HFO-1336mzz(Z)
will be certainly useful for replacing HFC, HCFC and CFC refrigerants and can
be better than replacing R134a
·
In
the triple cascading with VARS, at ultra-low temperature applications up to
-150oC evaporator temperature, HFO ecofriendly refrigerants
(R1225ye(Z), HFO-1336mzz(Z) will be certainly useful for replacingR32, and,
HCFC and CFC refrigerants.
References
[1] Szargut, J.; Morris, D.R.; Steward, F.R. (1987), Exergy Analysis of Thermal, Chemical, and Metallurgical Processes; Hemisphere Publishing: New York, NY, USA.
[2] Rosen, M.A.;
Dincer, I. (2005), Efficiency analysis of a cogeneration and district energy
system. Applied
Thermal Engineering, 25, 147–159
[3] Gebreslassie, B.H.;
Medrano, M.; Boer,D. (2010), Exergy analysis of multi-effect water-LiBr
absorption systems: From half to triple effect. Renew. Energy, 35,
1773–1782.
[4] Bereche, R.P.;
Palomino, R.G.; Nebra, S.A. (2009), Thermoeconomic analysis of a single and
double-effect LiBr/H2O absorption refrigeration system. International
journal of thermodynamics, 12, 89–96
[5] Morosuk, T.;
Tsatsaronis, G. (2008), A new approach to the exergy analysis of absorption
refrigeration machines. Energy ,33, 890–907
[6] Kilic, M.;
Kaynakli, O. (2007), Second law-based thermodynamic analysis of water-lithium
bromide absorption refrigeration system. Energy, 32,
1505–1512.
[7] Garimella, S.,
Brown, A.M., Nagavarapu, A.K., (2011), Waste heat driven
absorption/vapor-compression cascade refrigeration system for megawatt scale, high-flux,
lowtemperature cooling. International journal of refrigeration, 34, 1776–1785.
[8] Radhey Shyam Mishra,
(2019), Thermal performance of cascaded vapour compression absorption systems,
International Journal of Research in Engineering and Innovation, 3 (1), 61-67.
[9] Radhey Shyam Mishra,
(2019), Performance evaluation of half effect Li/Br-H2O vapour absorption
systems using multi cascading of vapour compression cycles for ultra-low
temperature applications International Journal of Research in Engineering and
Innovation, 3 (1), 509-526.
[10] Radhey Shyam Mishra,
(2020), Single and multiple cascading of VCRS in NH3H2O
vapour absorption refrigeration systems for improving thermodynamic
(energy-exergy) performances using five ecofriendly new HFOs and other low GWP
refrigerants for replacing R134a, International Journal of Research in
Engineering and Innovation, 4 (2), 96-104.
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