Abstract
Currently, the refrigeration and air conditioning is looking for energy efficient technologies which will reduce the electric power consumption from causing the damage to the environment. The ejector refrigeration system is found to be energy efficient system which will be able to provide the cooling by utilizing the environment friendly refrigerants. In this paper HFO refrigerants are used in ejector refrigeration system and comparison were made with other HFC and HCFC refrigerants
1.
Introduction
In the context of recent developments in the field of energy, the aspect related to energy consumption is of excessive importance for experts. Many industries trust on refrigeration technologies; a great challenge being stated in energy savings in this sector. In this respect, efforts oriented towards efficient industrial refrigeration systems have revealed the necessity of a proper design. The most commonly used method of cooling is based on vapor compression cycles.
Ejector
refrigeration technology is the one which can have utilized the waste heat to
compress the refrigerant instead of compressor. Therefore, electrical energy
was saved which can have employed to meet the other demand. When ejector is
integrated with vapour compression refrigeration system, then system will use
less compressor power to provide the natural cooling of products.
2.
Ejector Refrigeration system
In the vapour compression refrigeration system, throttle
device is used to expand the refrigerant from high pressure prevailing in the
condenser to low pressure evaporator. Capillary tube and thermostatic expansion
valve, used in the throttling devices in the vapour compression refrigeration
system has highly irreversible process which causes larger amount of wastage of
the kinetic energy of the refrigerant. Vapour compression refrigeration systems
uses CFCs, HFCs and HCFC refrigerants and their leakage from the system causes
emissions in the environment hence degrading its air quality. This emission can
be direct emission or indirect or both. Therefore, energy efficient
technologies which reduced the electric power consumption apart from the
causing the damage to the environment. Ejector refrigeration system is an
energy efficient device which is able to compress the refrigerant in the system
and providing the cooling by utilizing the environment friendly refrigerant
Chen,
J, [1] studied theoretically, the application of different nine working fluids
in the ejector vapour refrigeration system and found theR600 gives higher first
law efficiency (COP) of ejector refrigeration system. Chen, J, [2] had performed
exergy analysis of an ejector refrigeration system using ecofriendly R134a refrigerant
and found that by reducing the exergy destruction in the parts improves the
quality of exergy analysis in terms of exergetic efficiency and concluded the
maximum exergy destruction in ejector followed by generator and evaporator and
tried for reducing ejector exergy destruction by improving the ejector
efficiencies. Similarly, generator (boiler) exergy destruction can be reduced
by improving design of other components of the system. Memet and A Preda [3] carried out theoretical analysis of
ejector refrigeration system using R134a and found that when by increasing the
generating temperature, the coefficient of performance(COP) is increasing
together and the best COP value being 0.178. also the generating temperature
increase leads to the increase of the work input to the pump. Li, H. et.al. [4]
had compared thermodynamic performance characteristics of ejector expansion
refrigeration cycle using R1234yf and R134a as a refrigerants and found that
R1234yf gives better performance than R134a at 40oC of condenser
temperature and 5oC of evaporator temperature. Trung Kien Nguyen & Chi Hiep Le [5] carried out
the first and second law of thermodynamics, an ejector vapour compressor
cascade refrigeration system using R134a and R410A refrigerant for the ejector
and compressor sub-cycle, respectively. Also an intercooler was inserted for
setting temperature at 26.5 °C for minimizing total exergy loss in the
system. The effects of generator temperature, evaporator temperature, condenser
temperature, intercooler temperature and intercooler temperature difference are
studied and found that a combined cycle can improve 30.8% of COP in single
compressor cycle and 122% when compared to the single ejector cycle. M Yari, M Sirousazar [6] carried out the first and second law
(exergy) analysis of the ejector-vapour compression refrigeration cycle using
internal heat exchanger and intercooler for enhancing the performance of the
cycle and investigated the effects of the evaporative and condenser temperatures
on the coefficient of performance (COP), second law efficiency, exergy
destruction rate and entrainment ratio. and found that the COP and second law
efficiency values of the new ejector-vapour compression refrigeration cycle are
on average 8.6% and 8.15 % higher than that of the conventional ejector-vapour
compression refrigeration cycle using R125. It was also observed that the COP
of the new ejector-vapour compression cycle is 21 per cent higher than that of
the conventional vapour compression cycle.
Yapici
and Ersoy [7] had compared the thermodynamic performance of constant pressure
and constant area mixing ejector using HR123 refrigerant and found the optimum
coefficient of performance and area ratio determined by using the constant area
flow model are greater than those of constant pressure model. Yin-Hai Zhu & Peixue Jiang [8]
developed refrigeration system which combines a basic vapour
compression refrigeration cycle with an ejector cooling cycle. The ejector
cooling cycle is driven by the waste heat from the condenser in the vapor
compression refrigeration cycle. The additional cooling capacity from the
ejector cycle is directly input into the evaporator of the vapor compression
refrigeration cycle. The governing equations are derived based on energy and
mass conservation in each component including the compressor, ejector,
generator, booster and heat exchangers. The system performance was analyzed for
the design conditions and found that the COP is improved by 9.1% for R22
system. Chaiwongsa and Wongwishes [9] have carried out experimental
investigation on two phase ejector as expansion device using R134a and R12
refrigerants and observed the COP improvement at lower sink temperature because
motive mass flow rate is highly dependent on heat sink temperature. Chaiwongsa
and Wongwishes [10] have carried out experimental investigation on the effect
of throat diameter of the nozzle on the performance on the refrigeration system
using ecofriendly R134a refrigerant in the two phase ejector as expansion
device and found maximum cooling capacity and COP at 0.8mm throat diameter. by
varying the dimension of nozzle diameter with cooling capacity. Da‐Wen Sun [11] described a new integrated refrigeration cycle based on the
combination of an ejector cycle with a vapour compression cycle for maximizing performance
of the conventional ejector cycles and providing high COP for refrigeration and
observed that this cycle has a significant increase in system performance over
the conventional systems and its COP values are competitive to the absorption
machines. In this modified system, the waste heat was used and, higher COP
value was observed. The system performance can be further improved if dual refrigerants
are used. Lucas and Kochler [12] found experimentally the improvement in COP of
the vapour compression refrigeration cycle using R744 (CO2) as
refrigerant and found the entrainment ratio and ejector efficiency increases
with increase in high side pressure and also concluded that ejector efficiency
is maximum decrement with decreasing evaporator pressure. Kornhauser A.A [13]
analyzed thermodynamic performance of the ejector-expansion refrigeration cycle
on constant mixing pressure using R12 and found 21% improvement in COP. Nehdi
[14] carried out theoretical investigation on the performance of
ejector-expansion refrigeration cycle with ecofriendly synthetic refrigerants
and found maximum performance of 22% using R141b. Also investigated maximum first
law performance (COP) using ejector as expansion device occurred at 9.9 area
ratio and found best performance for using R141b and R408A for a given
operating condition. Bilir and Ersoy [15] investigated theoretical improvement
of ejector refrigeration cycle using two phase ejector using R134a refrigerant
and observed that COP increases with decreasing evaporator temperature and also
by increasing condenser temperature. Saleh B., [16] had numerical investigated
parameter analysis of ejector refrigeration cycle with different refrigerants
using ejector refrigeration cycle and found best thermodynamic performance
using R245fa. Sarkar [17] carried out optimization of geometric parameters of
the ejector expansion refrigeration cycle using natural refrigerant (R717) and
hydrocarbon (R600a and R290) refrigerants and observed 21.55% maximum COP
improvement using isobutane (R600a), 18% using propane(R290).12% using
ammonia(R717).
Lot
of work have been done by several investigators using CFCs, HFCs, natural and
hydrocarbon refrigerants in the ejector refrigeration systems and still very
less work has been done using HFO refrigerant. In this paper the utility of HFO
refrigerants in ejector refrigeration system are highlighted for improving
thermodynamic performances.
3.
Results and Discussion
Following Numerical values have been chosen
for numerical computation
|
Cooling Load(Qeva) |
4.75 KW |
|
Boiler temperature(T_boiler) |
333 K |
|
Evaporator temperature (T_eva) |
273 K |
|
Condenser temperature (T_cond) |
303 K |
|
Ambient temperature (To) |
300 K |
|
T_ref |
T_eva+5 |
Ejector
geometric input
|
(Length / Diameter} ratio of constant area mixing
chamber(L/D) |
10 |
|
Diameter of primary nozzle throat (D_throat) |
0.5/1000 |
|
Diameter
of mixing chamber(d_m) |
1.4/1000 |
|
Exit
diameter of primary nozzle (d_p) |
0.8/1000 |
|
Diffuser
angle (theta) |
3 |
|
Diffuser
Length (L_d) |
112/1000 |
|
Refrigerant |
R1234zf |
|
Area
Ratio |
7.84 |
Table- 1(a): Effect of ecofriendly refrigerants on the
variation of thermal performance parameters of vapour
compression refrigeration system using ejector
|
Refrigerant |
COP |
EDR |
2nd law Efficiency |
|
R-1234ze(Z) |
6.483 |
4.007 |
0.1997 |
|
R-1234ze(E) |
6.213 |
3.56 |
0.2193 |
|
HFO-1336 mzz(Z) |
4.723 |
3.573 |
0.2187 |
|
R-1243zf |
6.016 |
3.754 |
0.2103 |
|
R1234yf |
5.788 |
3.298 |
0.2327 |
|
R-1233zd(E) |
5.799 |
3.833 |
0.2069 |
|
R-1224yd(Z) |
5.163 |
3.468 |
0.2238 |
|
R-1225ye(Z) |
5.734 |
3.212 |
0.2374 |
|
R-124 |
5.333 |
3.256 |
0.2349 |
|
R123 |
5.141 |
3.545 |
0.220 |
Table-1(a)
shows the variation of first law efficiency (COP) of vapour compression
refrigeration system using ejector using ecofriendly refrigerants and it was
observed that maximum COP was observed by using R1234ze(Z) and minimum by using
R123. Similarly, maximum second law efficiency was observed by using
R-1225ye(Z)
Table-1(b) Effect of ecofriendly refrigerants on the
variation of thermal performance parameters of vapour compression refrigeration
system using ejector
|
Refrigerant |
Entrainment Ratio(shy) |
Compression Ratio (Mu1) |
Mu2 |
|
R-1234ze(Z) |
1.454 |
1.942 |
7.089 |
|
R-1234ze(E) |
1.383 |
1.970 |
6.804 |
|
HFO-1336 mzz(Z) |
1.535 |
2.347 |
5.328 |
|
R-1243zf |
1.359 |
1.807 |
6.543 |
|
R1234yf |
1.353 |
1.987 |
6.313 |
|
R-1233zd(E) |
1.477 |
2.07 |
6.403 |
|
R-1224yd(Z) |
1.467 |
2.229 |
5.714 |
|
R-1225ye(Z) |
1.386 |
2.151 |
5.858 |
|
R-124 |
1.396 |
2.162 |
5.827 |
|
R123 |
1.496 |
2.254 |
5.648 |
|
R125 |
1.326 |
2.155 |
5.32 |
Table-1(b)
shows the variation of Entrainment Ratio (shy) of vapour compression
refrigeration system using ejector using ecofriendly refrigerants and it was
observed that maximum Entrainment Ratio was observed by using HFO-1336mzz(Z)
and minimum by using R125. Similarly, maximum compression Ratio was observed by
using R-1225ye(Z).
Table-1(c) Effect of ecofriendly refrigerants on the
variation of thermal performance parameters of vapour compression refrigeration
system using ejector
|
Refrigerant |
Effective ness |
a |
b |
|
R-1234ze(Z) |
0.07336 |
2.072 |
1.02 |
|
R-1234ze(E) |
0.08521 |
1.963 |
1.03 |
|
HFO-1336 mzz(Z) |
0.1063 |
2.134 |
0.9652 |
|
R-1243zf |
0.08476 |
1.904 |
1.035 |
|
R1234yf |
0.09896 |
1.891 |
1.033 |
|
R-1233zd(E) |
3000.08411 |
2.097 |
1.022 |
|
R-1224yd(Z) |
0.1034 |
2.063 |
0.9902 |
|
R-1225ye(Z) |
0.1094 |
1.933 |
1.016 |
|
R-124 |
0.1085 |
1.959 |
1.011 |
|
R123 |
0.1030 |
2.092 |
0.9832 |
Table-1(c) shows the variation of
Effectiveness of vapour compression refrigeration system using ejector using
ecofriendly refrigerants and it was observed that maximum Effectiveness was
observed by using R-1225ye(Z).
Table- 2(a): Variation with Generator
(Boiler) temperature of ejector fitted vapour compression refrigeration system
using R1243zf
|
T_Boiler (K) |
Exergetic
efficiency |
EDR |
shy |
|
333 |
0.2103 |
3.754 |
1.359 |
|
338 |
0.2.091 |
3.782 |
1.359 |
|
343 |
0.2080 |
3.807 |
1.359 |
|
348 |
0.2071 |
3.829 |
1.359 |
|
353 |
0.2062 |
3.848 |
1.359 |
|
358 |
0.2056 |
3.863 |
1.359 |
|
363 |
0.2053 |
3.871 |
1.359 |
Table-2(a) shows the variation of Exergetic efficiency
of ejector coupled vapour compression refrigeration system using HFO-1243zf with
variation of boiler temperature and it was observed that boiler temperature is increasing,
second law efficiency (Exergetic efficiency) is decreasing.
Table- 2(b): Variation
with Generator (Boiler) temperature of ejector fitted vapour compression
refrigeration system using R1243zf
|
T_Boiler (K) |
a |
b |
mu1 |
|
333 |
1.398 |
0.6952 |
1.665 |
|
338 |
1.449 |
0.7046 |
1.627 |
|
343 |
1.497 |
0.7132 |
1.593 |
|
348 |
1.542 |
0.7218 |
1.563 |
|
353 |
1.582 |
0.7296 |
1.537 |
|
358 |
1.619 |
0.7373 |
1.514 |
|
363 |
1.648 |
0.7444 |
1.495 |
Table-2(b) shows the variation of Compression Ratio of
ejector coupled vapour compression refrigeration system using HFO-1243zf with
variation of boiler temperature and it was observed that boiler temperature is increasing,
Compression Ratio of ejector coupled vapour compression refrigeration
system is decreasing.
Table- 3(a):
Variation with condenser temperature of ejector fitted vapour compression
refrigeration system using R1243zf
|
T_Cond(K) |
Exergetic
efficiency |
EDR |
shy |
|
300 |
0.2127 |
3.701 |
1.663 |
|
303 |
0.2138 |
3.676 |
1.807 |
|
306 |
0.2149 |
3.651 |
1.961 |
|
308 |
0.2158 |
3.634 |
2.069 |
|
309 |
0.2162 |
3.625 |
2.124 |
Table-3(a) shows the variation of Exergetic efficiency
of ejector coupled vapour compression refrigeration system using HFO-1243zf with
variation of condenser temperature and it was observed that condenser
temperature is increasing, second law efficiency (Exergetic efficiency) is
increasing. Similarly, entainment ratio is also increasing while exergy
destruction ratio is decreasing
Table- 3(b): Variation with condenser temperature of
ejector fitted vapour compression refrigeration system using R1243zf
|
T_Cond(K) |
COP |
mu1 |
Mu2 |
|
300 |
1.363 |
1.807 |
1.486 |
|
303 |
0.9115 |
1.807 |
0.9951 |
|
306 |
0.6283 |
1.807 |
0.6867 |
|
308 |
0.4595 |
1.807 |
0.5376 |
|
309 |
0.4337 |
1.807 |
0.4746 |
Table-3(b) shows the variation of first law efficiency (COP) of ejector coupled vapour compression refrigeration
system using HFO-1243zf with variation of condenser temperature and it was
observed that condenser temperature is increasing, first law efficiency (COP)
is decreasing.
Table-3(c) shows the variation of first law efficiency (COP) of ejector coupled vapour compression refrigeration
system using HFO-1243zf with variation of condenser temperature and it was
observed that condenser temperature is increasing, first law efficiency (COP)
is decreasing.
Table- 3(c):
Variation with condenser temperature of ejector fitted vapour compression
refrigeration system using R1243zf
|
T_Cond(K) |
COP |
a |
b |
|
300 |
1.363 |
1.582 |
0.8595 |
|
303 |
0.9115 |
1.489 |
0.8092 |
|
306 |
0.6283 |
1.413 |
0.7676 |
|
308 |
0.4595 |
1.368 |
0.7436 |
|
309 |
0.4337 |
1.348 |
0.7326 |
Table-4(a): Variation
with evaporator temperature of ejector fitted vapour compression refrigeration
system using R1243zf
|
T_EVA[K] |
Exergetic
efficiency |
EDR |
shy |
|
268 |
0.3826 |
1.613 |
3.002 |
|
273 |
0.3347 |
1.988 |
2.517 |
|
278 |
0.2791 |
2.583 |
2.126 |
|
283 |
0.2138 |
3.676 |
1.807 |
Table-4(a) shows the variation of second law efficiency (exergetic efficiency) of ejector coupled vapour compression refrigeration
system using HFO-1243zf with variation of evaporator temperature and it was
observed that evaporator temperature is increasing, second law efficiency (exergetic efficiency)
is decreasing.
Table-4(b): Variation
with evaporator temperature of ejector fitted vapour compression refrigeration
system using R1243zf
|
T_EVA[K] |
COP |
mu1 |
Mu2 |
|
268 |
0.3692 |
1.602 |
0.4163 |
|
273 |
0.4888 |
1.665 |
0.5451 |
|
278 |
0.6556 |
1.732 |
0.7233 |
|
283 |
0.9115 |
1.807 |
0.9950 |
Table-4(b) shows the variation of first law efficiency (COP) of ejector coupled vapour compression refrigeration
system using HFO-1243zf with variation of evaporator temperature and it was
observed that evaporator temperature is increasing,
first law efficiency (COP) is decreasing and
entrainment ratio is also increasing.
Table- 4(c): Variation with evaporator temperature of
ejector fitted vapour compression refrigeration system using R1243zf
|
T_EVA[K] |
COP |
a |
b |
|
268 |
0.3692 |
1.359 |
0.6478 |
|
273 |
0.4888 |
1.398 |
0.6952 |
|
278 |
0.6556 |
1.441 |
0.7483 |
|
283 |
0.9115 |
1.489 |
0.8092 |
Table-4(c)
shows the variation of first law efficiency (COP) of ejector coupled vapour compression
refrigeration system using HFO-1243zf with variation of evaporator temperature and
it was observed that evaporator temperature is increasing, first law efficiency
(COP) is decreasing and
entrainment ratio is also increasing.
4.
Conclusions
Following
conclusions were drawn from this investigation.
·
Maximum first law efficiency of ejector coupled vapour
compression refrigeration system using HFO-1234ze(Z) while maximum second law efficiency
was observed by using R-1225ye(Z)
·
maximum Entrainment Ratio of ejector coupled vapour
compression refrigeration system was observed by using HFO-1336mzz(Z) and
minimum by using R125.
·
Maximum Effectiveness of ejector coupled vapour
compression refrigeration system was observed by using R-1225ye(Z)
·
When boiler temperature of ejector coupled vapour
compression refrigeration system is increasing, second law efficiency
(Exergetic efficiency) is decreasing.
·
When boiler temperature of ejector coupled vapour
compression refrigeration system is increasing, compression Ratio of ejector
coupled vapour compression refrigeration system is decreasing.
·
When condenser temperature of ejector coupled vapour
compression refrigeration system is increasing, second law efficiency
(exergetic efficiency) is increasing. Similarly, entrainment ratio is also
increasing while exergy destruction ratio is decreasing
·
condenser temperature of ejector coupled vapour
compression refrigeration system using R1243zf is increasing, first law
efficiency (COP) is decreasing.
·
When evaporator temperature of ejector coupled vapour
compression refrigeration system using HFO-1243zf is increasing, first law
efficiency (COP) is decreasing and entrainment ratio is also increasing.
·
When evaporator temperature of ejector coupled vapour
compression refrigeration system using HFO-1243zf is increasing, second law
efficiency (exergetic efficiency) is decreasing.
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