Abstract
The ozone depletion and global warming due to the
use of various refrigerants is very serious for environmental degradation which
affect living of human standard Therefore , it is essential to search and use
new and low GWP and zero ODP eco-friendly refrigerants. Thermodynamic first and second law performances (
energy-exergy efficiencies) of cascade vapour compression refrigeration system
using new HFO eco-friendly refrigerants for reducing global warming and ozone
depletion performance parameters such as COP, exergetic efficiency and exergy
destruction ratio and power required to run whole systems have been presented
in this paper. The various combinations
of using six different ecofriendly refrigerants used in high temperature cycle
in the temperature range of from 50oC
to 0oC for which other five ecofriendly low GWP refrigerants in the
temperature range of from 0oC
to-50oC have been compared. It is found that The first and second law
performances of cascade vapour compression refrigeration system using R1234ze (Z) in higher temperature cycle and
R1233zd (E) in low temperature cycle gives a best thermodynamic performance as
compared to R1234ze(E) and R1224ze(z) and R1243z in high temperature cycle.
Moreover, lowest performances were found by using R1234yf in high or low
temperature cycles as compared to other HFO refrigerants. The comparison was made between HFO-1234yf and HFC-134a in low temperature cycle up to temperature of -50oC and also found the first and second law efficiencies are 3.245% lower than using R-1234yf in low temperature cycle as compared to HFC-134a in low temperature cycle and R1234ze(Z) in high temperature cycle with 5.195% decrement in the exergy destruction ratio.
1.
Introduction
Refrigeration plays a very
significant role in industrial, domestic and commercial sectors for cooling,
heating and food preserving applications. There are numerous applications of
such systems and they are the major consumer of electricity around the world
because energy utilization is directly proportional to the economic development
of any nation. However, this area is in huge interest nowadays because of the increase in the cost of conventional fuels and environmental concerns globally.
The scientists are searching for new/alternate renewable energy sources in
order to reduce the costs. Due to the ever-increasing energy demand and
degradation of the environment due to global warming and depletion of ozone layer
etc, there is an urgent need of efficient energy utilization and waste heat
recovery for useful applications. A refrigerant is a
substance or mixture, usually a fluid, used in a refrigeration cycle. In most
cycles it undergoes phase transitions from a liquid to a gas and back again.
Many working fluids have been used for such purposes. The researchers
are paying attention on the alternate and environment friendly refrigerants,
especially HFCs after the Kyoto and the Montreal protocols. However, it is
essential to find alternate and environment friendly refrigerants such as HFOs
and others in terms of Blends of HFCs with HFOs, for the energy efficiency of
the equipment having HFC refrigerants. Although, natural and conventional refrigerants are also very important in the present age of
competitive dealing community because the aim of the scientific group of people
all over the world is to find out
the new and renewable energy
sources besides, efficient utilization of all conventional sources. The use of refrigerant was
started in early 1800 century with use of natural refrigerants, which were
replaced by CFCs in 1928 with increase in thermal performance, which were
banned under Montreal Protocol (1987) due to their high ozone layers depletion
(ODP) properties and then they are substituted by hydrocholoro carbon (HCFCs)
and hydrocarbons in 1980s. Thereafter researchers noted that HCFCs are
responsible for ozone depletion and bear high global warming potential. As per
guidelines of Kyoto Protocol (1997), HCFCs have to be phased out by 2020-2030
and HFCs by 2025-2040.
1.1
Low GWP ecofriendly Refrigerants
In current operating low
temperature applications, the working refrigerants of the hydrocarbons (HC) and
hydrofluorocarbons (HFC) groups are dominating. More recently, new working
refrigerants have been used by Mishra [10] which are in the
hydro-fluoro-olefines (HFO) and hydro chloro-fluoro-olefines (HCFO) group. The
HFO R1234yf and R1234ze (E) as well as the HCFO R1233zd(E) and R1224yd(Z) are
especially promising low-GWP alternatives to the HFC R134a and R245fa.For
instance, the German Environment Agency intends to prohibit the application of
R1233zd(E), due to its ODP of 0.00024. However, R1233zd(E) has several
favorable aspects, such as a very low GWP and no flammability and toxicity
(safety classification of A1). This proves, that the very small ODP by
R1233zd(E) and R1224yd lead to no significant increase of the external costs.
Thus, a general prohibition of potentially promising refrigerants with a very
small ODP appears not be justifiable based on the presented results. The
electrical powers are lower by using HCFO-1233zd-E as compared to R134a As a
conclusion, it can be stated, that both novel fluids R1233zd(E) and R1224yd(Z)
are suitable for the drop-in replacement of R245fa in refrigeration systems . However, the results show, that the
compatibility of R1233zd(E) and R1224yd(Z), with the is compared to replace
R245fa and R134a , it is found that when
R1233zd(E)is used , for finding the system performances , the highest power
output is still obtained with the high-GWP fluid R245fa and R134a which is 7%
to 9% The exergy of fuel with R245fa is
0.42% higher compared to R1233zd(E) and 8% higher compared to R1224yd(Z). In
terms of thermal efficiency of the ORC system, R1233zd(E) leads to
approximately 2% higher values compared to R245fa. In contrast to that, the
thermal efficiency of R245fa and R1224yd(Z) is equal over a wide range of
operation conditions.
1.2
HFO-1336mzz(E) and R1336mzz(Z)
R1336mzz(Z) (also referred to as HFO1336mzz(Z)) provides
approximate thermodynamic property data for
cis-1,1,1,4,4,4-Hexafluoro-2-butene, MW 164.056 gm/mole, CAS# 692-49-9). The fundamentals of choosing a good working refrigerants
are based on system optimization to maximize the thermodynamic performance
characteristics in terms of first and second law efficiencies, these novel HFOs
are being developed, like HFO-1336mzz(E) and R1336mzz(Z), to meet the more
stringent regulations of low GWP and no ODP and they demonstrate the known
characteristics of a good working fluids – stability, compatibility, favorable
toxicity and performance even at high temperatures. The HFO-1336mzz(E) has 7.5oC
boiling point, critical temperature of 137.7oC and critical pressure
of 3.15 MPa. Whereas R-1336mzz(Z) has slightly higher boiling point of 33.4oC,
critical temperature of 171.3oC and lower critical pressure of 2.90
MPa. The compressor efficiency, superheat (∆Tsh), sub cooling (∆Tsc)
and lift temperatures were fixed variables is this calculation, the condensing
temperatures were adjusted so higher temperature effects could be evaluated for
each working fluid. HFO1336mzz isomers (E and Z) and had the excellent first
law efficiency (COPs) amongst than the HFC Refrigerants (such as R134a, R410a, R404a, R407c, R507a,
R125a) but lower than R245fa due to and power required to run
compressors is 8.63% higher than R245fa.
1.3
R1243zf
The HFO
(hydrofluoroolefin) are going to be our future refrigerants with low ozone
depletion potential (ODP) and low global warming potential (GWP).The basic
properties of new future HFO refrigerants expected as R410a and R32
alternatives which are presently used in refrigerators and room air
conditioners. R1243zf is expected to be a good alternative with its flammability,
which is A2 category for replacing R134a.
Triple point data of a refrigerant, is very important for refrigerating
industry defined the lowest temperature range at which any refrigerant may
circulate in liquid state. The triple point of R1243zf is 122.8K and the normal
boiling temperature and critical pressure are 247.73 K and 3630.6 kPa,
respectively.
2.
Thermodynamic (Energy-Exergy) Performances of vapour
compression refrigeration system
A cascade refrigeration cycle is a multi-stage thermodynamic cycle. An example two-stage process is shown at right. The cascade cycle is often employed for devices such as ultra-low temperature freezers as shown in fig-1. Cascade refrigeration system is a low temperature refrigeration system
and is used for very low temperature range about (-40C to -130C). At such low
temperature simple Vapour Compression Refrigeration Cycle (VCRS) is not
efficient due to very high compression ratio that further leads to high
discharge problem and low volumetric efficiencies whereas, cascade
refrigeration is much efficient for such conditions. Cascade refrigeration
cycle is nothing but simply a combination of two VCRS cycles named as low and
high temperature circuit that are combined together by a cascade condenser.
This cascade condenser unit act as evaporator for low temperature circuit and
condenser for high temperature circuit, the low temperature circuit uses low
boiling refrigerants such as R23, R744 etc. and high temperature uses high
boiling point refrigerants such as R717, R290, R404A, R1270, R507A etc.
To
condense refrigerants that are capable of achieving ultra-low temperatures that
would not be able to condense at room temperature. This is achieved by using a
low temperature evaporator of one system as the condenser the other, condensing
and sub cooling the liquid before entering the metering device.
Normally
in a cascade refrigeration system two
types of compressors, are used and they
run individually with different ecofriendly
refrigerants, connected among them so that evaporator of first high
temperature cycle used for cooling of
second (low temperature} cycle condenser (i.e. the evaporator with the first
unit cools the condenser of the second unit). In practice, an alternative
approach using a common capacitor with a booster circuit to provide two
separate temperature limits of the evaporator. The cascade refrigeration cycle
is a combination of two vapour compression cycles which utilizes two different
refrigerants. The primary refrigerant flows from low temperature circuit
evaporator to low stage compressor and condensed in cascade condenser which
also acts as evaporator for high temperature circuit. The heat rejected from
condenser of low temperature circuit is extracted by evaporator of high
temperature circuit containing secondary refrigerant then, this secondary
refrigerant gets compressed in high stage compressor and finally condensed to
outer atmosphere. The desired refrigerating effect is occurred from evaporator
of low temperature circuit. The temperature difference in cascade condenser is
an important design parameter that decides the COP of the entire refrigeration
system.
The following advantages of
cascade vapour compression systems are as follow.
·
In
the cascade vapour compression refrigeration system using different
refrigerants, it is possible to select an ecofriendly refrigerant is best
suited for different temperature range. Therefore, very high pressure can be
avoided as in case of simple vapour compression refrigeration system.
·
In
the cascade vapour compression refrigeration system migration of lubricating
oil from one compressor to the other compressor is prevented.
·
The
saving of energy is more because the system allows use of refrigerants that
have suitable temperature limits characteristics for each of the
higher-temperature side and the lower-temperature side.
·
It
allows especially for stable ultra-low-temperature operation around -160oC
using four stages cascading repair and maintenance is also easy.
·
The
objective of present research work is the technology is development in the
field of refrigeration and air conditioning, remarkable comfort for reducing
global warming and ozone depletion by using newly low GWP and around zero ODP
are achieved by using energy & exergy analysis.
First
law analysis (energy analysis) is restricted to calculate only coefficient of
performance of system but exergy analysis is the one of the most useful
analyses to evaluate the plant losses, the actual amount of energy flow through
process exergetic efficiency and exergetic destruction Ratio. Exergy based
investigation of the VCRS and evaluated thermodynamic performance of
hydrocarbons, mixture of hydrocarbons, & R134a carried out. Additionally,
they found that higher exergy destruction occurred in compressor as rivaled
with other VCRS’ components and they emphasized on the possibilities of
researches in the field of exergy analysis in various vapor compression
refrigeration systems. Exergy losses, exergetic efficiency, and irreversibility
of the system components as well as in the vapour compression system using
R134a, R290 and R600a refrigerants [1]. Exergy parameters in the compressor,
evaporator, condenser and expansion devices are computed and found that
the exergy losses depend on evaporator
temperatures, condensing temperature, type of
refrigerants and ambient temperature and concluded that maximum exergy
destruction occured in the condenser and
lowest in the Expansion devices. He also observed the exergy destruction using
butane or isobutene are less than using R134a refrigerant in the VCRS. In the
higher evaporating temperature exergy loss is decreased for all refrigerants
because exergetic efficiency is also higher for butane as compared to isobutene
and R-134a as refrigerants. Exergy loss
in the compressor is higher than that in the other parts of the system i.e.
around 70% of the total exergy loss occurs in the system. The experimental
analysis of 2TR (ton of refrigeration) vapor compression refrigeration cycle
for different percentage of refrigerant charge using exergy analysis [2]. An
experimental setup has been developed and evaluated on different operating
conditions using a test rig having R22 as working fluid. The coefficient of
performance, exergy destruction, and exergetic efficiency for variable quantity
of refrigerant has been calculated. The present investigation has been done by
using 2TR window air conditioner. A 2TR window air conditioner equipped with
different pressure, temperature, and flow measuring devices has been studied
experimentally using energy and exergy analysis. The unit is charged with
refrigerant R-22 in four steps, i.e., 25, 50, 75, and 100%, respectively, and
the system performance is analyzed in each case. The reference temperature is
measured to be 25oC. The results indicate that the losses in the
compressor are more pronounced, while the losses in the condenser are less
pronounced as compared to other components, i.e., evaporator and expansion
device. The total exergy destruction is highest when the system is 100%
charged, whereas it is found to be least when the system is 25% charged. Theoretical
analysis of actual VCRS with liquid vapour heat exchanger & also carried
out analysis on basis of energy, entropy, & exergy in specific temperature
range of evaporator and condenser. Besides, they concluded that R502 fluid was
best refrigerant as compared to R404A and R507A fluid. The main objective is to
investigate the thermodynamic performances of a cascade vapour compression
refrigeration systems (VCRS) based on energy-exergy principles. In this investigations , several new HFO
refrigerants flowing in the high temperature circuit between temperature range
from 50oC to 0oC have been compared in terms of first law
efficiency known as coefficient of performance (COP) and second law efficiency
commonly known as exergetic efficiency (Exergy Efficiency) and exergy
destruction ratio (EDR_System) and other ecofriendly new HFO
refrigerants are also compared with HFC-134a, R245fa and R32 in low temperature
circuit up to -50oC by doing
exergy analysis [3-4]. The thermodynamic performances of vapour compression
refrigeration system using multiple evaporators and compressors with individual
or multiple expansion valves have been considered by using first law and second
law analysis. Numerical models for parallel and series expansion valves in the VCR.
Thermodynamic analysis in terms of energy and exergy analysis of multiple
evaporators and compressors with individual expansion valves (system-1) and
multiple evaporators and compressors with multiple expansion valves (system-2)
have been carried out and following conclusions was drawn from present
investigation. For same degree of subcooling, fixed evaporators and condenser
temperatures system-2 is the best system with comparisons of system-1. R600,
R600a and R152A show better performances than other refrigerants for both
systems (system-1 & system-2) but due to inflammable property of R600 and
R600a, R134a is preferred for both systems. First law efficiency and second law
efficiency of system-2 is 3%- 6% higher than System-1 [5]. Thermodynamic
analysis of an R744–R717 cascade refrigeration system and concluded that by
increasing the condenser temperature which increases refrigerant mass flow
rates and also the decreasing COP. Similarly by increasing evaporating temperature increased COP of the
system and decreases mass flow ratios. By increasing temperature difference in
cascade condenser reduced both COP and mass flow ratios and by
increasing isentropic efficiency of compressors also increases COP linearly [6]. Experimental investigation on a domestic
refrigerator and concluded that compressor’s exergetic destruction was highest
in contrast to other components [7]. The detailed energy and exergy analysis of
multi-evaporators at different temperatures with single compressor and single
expansion valve using liquid vapour heat exchanger vapour compression
refrigeration systems have been done in terms of performance parameter for
R507a, R125, R134a, R290, R600, R600a, R1234ze, R1234yf, R410a, R407c, R707,
R404a and R152a refrigerants. The numerical computations have been carried out
for both systems. It was observed that first law and second law efficiency
improved by 20% using liquid vapour heat exchanger in the vapour compression
refrigeration systems. The First law efficiency (COP) and Second law efficiency
(Exergetic efficiency) of vapour compression refrigeration systems using R717
refrigerant is higher but is has toxic nature can be used by using safety
measure for industrial applications. COP and exergetic efficiency for R152a and
R600 are nearly matching the same values are better than that for R125 at 313K
condenser temperature and showing higher value of COP and exergetic efficiency
in comparison to R125. For practical applications R-134a is recommended because
it is easily available in the market has second law efficiency slightly lesser
than R-152a which was not applicable for commercial applications. The increase
in dead state temperature has a positive effect on exergetic efficiency and
EDR, i.e. EDR decreases and exergetic efficiency increases with increase in
dead state temperature. [8-10]. The numerical investigation of VCRS by using R134a, R143a,
R152a, R404A, R410A, R502, & R507A fluid and reported that temperature of
evaporator and condenser have crucial effect on both COP & exergetic
efficiency. In addition, they found that R134a fluid has better performance
than R407C fluid [11]. The energy analysis of vapour compression
refrigeration system using refrigerants R134a, R152a, R600a , R290 , R1234yf
and R1234ze(E) (HFOs) and found that these can be a good alternative to R134a
without compromising the performance of refrigeration system [12].
The above investigators did not
carried out detailed thermodynamic first and second law analysis using energy
and exergy principles for predicting performances using latest and new ecofriendly of low GWP
refrigerants of cascade refrigeration systems for replacing high GWP refrigerants in near future . In this paper ,
thermodynamic first law efficiency in terms of coefficient of performance (COP)
and second law efficiency in terms of exergetic efficiency have been computed
for low temperature applications used
for bio medical applications and best solution for replacing High GWP refrigerants and important results have been
presented in next section.
3.
Results and Discussion
Following
input data have been chosen for numerical computations in the– cascade vapour
compression refrigeration system using new HFO eco-friendly refrigerant for
reducing global warming and ozone depletion:
·
Temperature
of low temperature evaporator using
eco-friendly refrigerants = -50oC,
·
Compressor
efficiency of low temperature cycle compressor =80%
·
Temperature
overlapping between low temperature condenser and intermediate temperature
evaporator =10oC
·
Load on low temperature evaporator = 175 “kW”
·
Compressor
efficiency of high temperature cycle
compressor = 80%
·
Temperature
of high temperature evaporator using
ecofriendly refrigerants = 0oC,
·
Temperature
of high temperature condenser using
ecofriendly refrigerants = 50o
Table-1 shows the effect of various ecofriendly refrigerants
in high temperature circuit between temperature range of 50oC to 0o
C and R134a in the low temperature cycle
at -50oC of evaporator with 10 oC temperature overlapping (approach) and found that R1234ze(Z) gives best/highest thermodynamic
performances with lowest exergy
destruction ratio as compared to R1224yd(Z) and R1234ze(E) and R1243zf. However
lowest performances was observed by using R1234yf in high temperature circuit
and R134a in low temperature cycle. Table-2
show the effect of various ecofriendly refrigerants in high temperature circuit between
temperature range of 50oC to 0o C and HFO-1234yf in the low temperature cycle
at -50oC of evaporator with 10 oC temperature overlapping (approach) and found
that R1234ze(z) gives best/highest thermodynamic performances with lowest
exergy destruction ratio as compared to R1224yd(Z) and R1234ze(E) and
R1243zf.However lowest performances was observed by using R134a in high
temperature circuit and R1234yf in low temperature cycle. The thermodynamic
performances of cascade vapour compression refrigeration systems was compared
between HFC-134a and HFO-1234yf and it is found that HFC-134a gives better
cycle thermodynamic performances 4.845 % higher than R1234yf and overall
cascade system thermodynamic first law performances 6.708% The second law
performance (exergetic efficiency) using R134a in low temperature cycle is
6.665% higher than using R1234yf in low temperature cycle. Table-3 shows the
effect of various ecofriendly refrigerants
in the low temperature circuit
between temperature range of -50oC to 0o C and R1234ze(Z) in the high temperature cycle at 50oC of
evaporator with 10 oC
temperature overlapping
(approach) and found that R1233zd(E)gives best/highest thermodynamic
performances with lowest exergy destruction ratio as compared to R1224yd(Z) and
HFO1336mzz(Z). However lowest performances was observed by using R1234yf in
high temperature circuit and R134a in low temperature cycle. The power required
to run both compressors in whole cascade system is lowest by using R1233zd(E)in
lower temperature while highest by using
R1234yf in low temperature cycle. The second law performance using R1233zd(E)
is higher than using HFO-1336mzz(Z) or R1225ye(Z) in lower temperature
circuit. It was also observed that the
thermodynamic performances using HFO-1336mzz(Z)
and R1225ye(Z) are nearly same
nearly 0.5% differences. The
lowest thermodynamic first and second law performances was found by using
R1234yf in the low temperature circuit.
Table-4 shows the effect of various ecofriendly
refrigerants in the low temperature circuit between temperature range
of -50oC to 0o C
and R1234ze(E) in the high
temperature cycle at 50oC of evaporator with 10 oC temperature overlapping (approach) and found that R1233zd(E)gives
best/highest (more than 2.183%
thermodynamic performances with lowest exergy destruction ratio as
compared to R1225ye(Z) and HFO1336mzz(Z).However lowest performances was
observed by using R1234yf in high temperature circuit and R134a in low
temperature cycle. The power required to run both compressors in whole cascade
system is lowest by using R1233zd(E)in lower temperature while highest by using
R1234yf in low temperature cycle. The second law performance using R1233zd(E)
is higher than using HFO-1336mzz(Z) or R1225ye(Z) in lower temperature
circuit. It was also observed that the
thermodynamic performances using HFO-1336mzz(Z)
and R1225ye(Z) are nearly same
nearly 0.5% differences. The
lowest thermodynamic first and second law performances was found by using R1234yf
in the low temperature circuit. Table-5 shows the effect of various ecofriendly
refrigerants in the low temperature circuit between temperature range of -50oC
to 0o C and R1224zd(Z) in the
high temperature cycle at 50oC
of evaporator with 10 oC
temperature overlapping (approach) and found that R1233zd(E) gives
best/highest (more than 2.183%
thermodynamic performances with lowest exergy destruction ratio as
compared to R1225ye(Z) and HFO1336mzz(Z). However lowest performances was
observed by using R1234yf in high temperature circuit and R134a in low temperature
cycle. The power required to run both compressors in whole cascade system is
lowest by using R1233zd(E)in lower
temperature while highest by using R1234yf in low temperature cycle. The second law performance using R1233zd(E)
is higher than using HFO-1336mzz(Z) or R1225ye(Z) in lower temperature
circuit. It was also observed that the
thermodynamic performances using HFO-1336mzz(Z)
and R1225ye(Z) are nearly same
nearly 0.5% differences. The
lowest thermodynamic first and second law performances was found by using
R1234yf in the low temperature circuit. Table-6 shows the effect of various
ecofriendly refrigerants in the low temperature circuit between temperature range
of -50oC to 0o C
and R1243zf in the high temperature cycle at 50oC of
evaporator with 10 oC
temperature overlapping
(approach) and found that R1233zd(E)gives best/highest (more than
2.183% thermodynamic performances with
lowest exergy destruction ratio as compared to R1225ye(Z) and
HFO1336mzz(Z).However lowest performances was observed by using R1234yf in high
temperature circuit and R134a in low temperature cycle. The power required to
run both compressors in whole cascade system is lowest by using R1233zd(E)in
lower temperature while highest by using R1234yf in low temperature cycle. The
second law performance using R1233zd(E) is higher than using HFO-1336mzz(Z) or
R1225ye(Z) in lower temperature circuit.
It was also observed that the thermodynamic performances using
HFO-1336mzz(Z) and R1225ye(Z) are nearly
same nearly 0.5% differences. The lowest thermodynamic first
and second law performances was found by using R1234yf in the low temperature
circuit.
Table-1: Thermodynamic (Energy-Exergy )
performance Parameters of– cascade) vapour compression refrigeration system
using new HFC (R134a) refrigerant in low
temperature circuit and following ecofriendly refrigerant in high temperature circuit for reducing global
warming and ozone depletion
First
& second Law performances
|
R1234ze(Z)
|
R1234ze(E)
|
R1224yd(Z)
|
R1243zf
|
R1234yf
|
High temperature First Law Efficiency (COP_HTC
)
|
3.669
|
3.215
|
3.448
|
3.169
|
2.986
|
Low temperature First Law Efficiency (COP_LTC
)
|
2.294
|
2.294
|
2.294
|
2.294
|
2.294
|
Overall Cascade First Law Efficiency (COP_Overall Cascade)
|
1.209
|
1.133
|
1.173
|
1.125
|
1.091
|
Overall Cascade Second law efficiency
|
0.4065
|
0.3811
|
0.3945
|
0.3783
|
0.3668
|
System Exergy Destruction Ratio (EDR_
Overall Cascade)
|
1.46
|
1.621
|
1.535
|
1.644
|
1.726
|
Total power required to run whole system (kW)
|
144.8
|
154.5
|
149.2
|
155.6
|
160.4
|
Table- 2: Thermodynamic (Energy-Exergy )
performance Parameters of cascade) vapour compression refrigeration system
using new HFO (R1234yf) refrigerant in
low temperature circuit and following ecofriendly refrigerant in high temperature circuit
First
& second Law performances
|
R1234ze(Z)
|
R1234ze(E)
|
R1224yd(Z)
|
R1243zf
|
R1234yf
|
High temperature First Law Efficiency (COP_HTC
)
|
3.669
|
3.215
|
3.448
|
3.169
|
2.986
|
Low temperature First Law Efficiency (COP_LTC
)
|
2.188
|
2.188
|
2.188
|
2.188
|
2.188
|
Overall Cascade First Law Efficiency (COP_Overall
Cascade)
|
1.171
|
1.099
|
1.137
|
1.091
|
1.104
|
Overall Cascade Second law efficiency
|
0.3938
|
0.3695
|
0.3824
|
0.3669
|
0.3713
|
System Exergy Destruction Ratio (EDR_
Overall Cascade)
|
1.54
|
1.706
|
1.615
|
1.726
|
1.693
|
Total power required to run whole system (kW)
|
149.5
|
159.3
|
153.9
|
160.4
|
158.5
|
Table- 3: First law performance
Parameters of– cascade) vapour compression refrigeration system using new HFO
(R1234ze(Z) in high temperature circuit and following ecofriendly refrigerant
in low temperature circuit
First & second Law performances
|
HFO-1336mzz(Z)
|
R1234yf
|
R1225ye(Z)
|
R1233zd(E)
|
R124
|
R245fa
|
R32
|
High
temperature First Law Efficiency (COP_HTC )
|
3.669
|
3.669
|
3.669
|
3.669
|
3.669
|
3.669
|
3.669
|
Low
temperature First Law Efficiency (COP_LTC )
|
2.286
|
2.188
|
2.289
|
2.363
|
2.312
|
2.349
|
2.249
|
Overall
Cascade 1st Law Effi (COP_Overall
Cascade)
|
1.206
|
1.171
|
1.20
|
1.233
|
1.218
|
1.228
|
1.193
|
Overall
Cascade Second law efficiency
|
0.4058
|
0.3998
|
0.4036
|
0.4147
|
0.4087
|
0.4130
|
0.401
|
System
Exergy Destruction Ratio (EDR_ Overall Cascade)
|
1.466
|
1.540
|
1.478
|
1.412
|
1.447
|
1.421
|
1.493
|
Total power
required to run whole system (kW)
|
145.1
|
149.5
|
145.8
|
141.9
|
144.0
|
142.5
|
146.7
|
High
temperature First Law Efficiency (COP_HTC )
|
58.86
|
58.86
|
58.86
|
58.86
|
58.86
|
58.86
|
58.86
|
Table- 4: Thermodynamic (Energy-Exergy )
performance Parameters of– cascade) vapour compression refrigeration system
using new HFO refrigerant (R1234ze(E) in high temperature circuit and following
ecofriendly refrigerant in low temperature circuit
First
& second Law performances
|
HFO1336
mzz(Z)
|
R1234yf
|
R1225ye(Z)
|
R1233zd(E)
|
R32
|
R245fa
|
R124
|
High temperature First Law Efficiency (COP_HTC
)
|
3.215
|
3.215
|
3.215
|
3.215
|
3.215
|
3.215
|
3.215
|
Low temperature First Law Efficiency (COP_LTC
)
|
2.286
|
2.188
|
2.289
|
2.363
|
2.249
|
2.349
|
2.312
|
Overall Cascade First Law Efficiency (COP_Overall Cascade)
|
1.139
|
1.109
|
1.125
|
1.155
|
1.119
|
1.151
|
1.139
|
Overall Cascade Second law efficiency
|
0.3802
|
0.3695
|
0.3784
|
0.3885
|
0.3762
|
0.3870
|
0.383
|
System Exergy Destruction Ratio (EDR_
Overall Cascade)
|
1.63
|
1.540
|
1.642
|
1.574
|
1.493
|
1.421
|
1.611
|
Total power required to run whole system (kW)
|
154.8
|
159.3
|
155.5
|
151.5
|
156.7
|
154.1
|
153.7
|
Table 5: Thermodynamic (Energy-Exergy )
performance Parameters of– cascade) vapour compression refrigeration system
using new HFO refrigerant (R1224zd(Z) in high temperature circuit and following
ecofriendly refrigerant in low temperature circuit
First
& second Law performances
|
HFO1336
mzz(Z)
|
R1234yf
|
R1225ye(Z)
|
R1233zd(E)
|
R32
|
R245fa
|
R124
|
High temperature First Law Efficiency (COP_HTC
)
|
3.448
|
3.448
|
3.448
|
3.448
|
3.448
|
3.448
|
3.448
|
Low temperature First Law Efficiency (COP_LTC
)
|
2.286
|
2.188
|
2.269
|
2.363
|
2.249
|
2.349
|
2.312
|
Overall Cascade First Law Efficiency (COP_Overall Cascade)
|
1.142
|
1.131
|
1.192
|
1.196
|
1.158
|
1.192
|
1.179
|
Overall Cascade Second law efficiency
|
0.4007
|
0.3824
|
0.4007
|
0.4023
|
0.3894
|
0.4007
|
0.3966
|
System Exergy Destruction Ratio (EDR_
Overall Cascade)
|
1.495
|
1.615
|
1.445
|
1.486
|
1.568
|
1.445
|
1.521
|
Total power required to run whole system (kW)
|
146.9
|
153.9
|
146.9
|
146.3
|
151.1
|
146.9
|
148.4
|
Table- 6 : Thermodynamic (Energy-Exergy
) performance Parameters of– cascade) vapour compression refrigeration system
using new HFO (R1243zf) refrigerant in
high temperature circuit and following ecofriendly refrigerant in low
temperature circuit
First
& second Law performances
|
HFO1336
mzz(Z)
|
R1234yf
|
R1225ye(Z)
|
R1233zd(E)
|
R32
|
R245fa
|
R124
|
High temperature 1st law Efficiency
(COP_HTC )
|
3.169
|
3.169
|
3.169
|
3.169
|
3.169
|
3.169
|
3.169
|
Low temperature 1st law Efficiency
(COP_LTC )
|
2.286
|
2.188
|
2.269
|
2.363
|
2.249
|
2.349
|
2.312
|
Overall Cascade 1st law Eff (COP_Overall
Cascade)
|
1.122
|
1.091
|
1.117
|
1.141
|
1.111
|
1.142
|
1.131
|
Overall Cascade Second law efficiency
|
0.3774
|
0.3669
|
0.3750
|
0.3856
|
0.3735
|
0.3841
|
0.3802
|
EDR_ Overall Cascade
|
1.649
|
1.726
|
1.662
|
1.594
|
1.677
|
1.604
|
1.630
|
Total power required to run whole system (kW)
|
155.9
|
160.4
|
156.7
|
152.6
|
157.6
|
153.2
|
154.8
|
4.
Conclusions
The following conclusions were drawn from the present investigation.
·
The first and second law performances of cascade vapour compression
refrigeration system using R1234ze(Z ) in higher temperature cycle is highest.
·
The first and second law performances of cascade vapour compression
refrigeration system using R1234ze(Z ) in higher temperature cycle and HFO and HFC refrigerants in
lower temperature is higher than R1234ze(E) R1224zd(Z ) and (R1243zf) in high temperature cycle.
·
The power
required to run both compressors in whole cascade system is lowest by using
R1233zd(E)in lower temperature while
highest by using R1234yf in low
temperature cycle while using R1234ze(z), R1234ze(E), R1224ze(Z)
and (R1243zf) in high temperature
cycle
·
The
thermodynamic performances using HFO-1336mzz(Z)
and R1225ye(Z) in low temperature
cycle are nearly same nearly 0.5% differences using R1234ze(z) or R-1234ze(E)
in high temperature cycle. The lowest
thermodynamic first and second law performances was found by using R1234yf in
the low temperature circuit.
·
R1243zf gives lower thermodynamic performance as compared to using
R1234ze(Z) and R1234ze(E) in high
temperature cycle.
·
The thermodynamic performances using R1234yf in higher temperature
cycle and even in low temperature cycle gives lower performances as compared to
other HFO refrigerants.
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