THERMODYNAMIC AND THERMOPHYSICAL ASSESSMENT OF DIMETHYL ETHER AND ITS BLENDS APPLICATION IN HOUSEHOLD REFRIGERATOR

Abstract

¬This study deals with the Thermodynamic evaluation of the use of Di-methyl ether refrigerants in household refrigeration systems which utilize R134a as a working fluid. A theoretical computational analysis was developed for R134a, Di-methyl ether (RE170) and the selected mixtures (R429A, R435A and R510A) in the standard refrigeration cycle ASHRAE, using the REFPROP 9.0 software. The results of computational simulations between the fluids were compared to find the evidence of the best alternative for R134a. In this sense, it is observed that the Di methyl ether reduced the levels of pressure on the condenser and evaporator. It also reduces the mass to be charged in the system. The use of these refrigerants reduces mass flow rate and increases refrigerating capacity of the system.

Full text

THERMODYNAMIC AND THERMOPHYSICAL ASSESSMENT OF
DIMETHYL ETHER AND ITS BLENDS APPLICATION IN
HOUSEHOLD REFRIGERATOR
A. Baskaran
#1
, N. Manikandan
#2
, V.P.Sureshkumar
#3
#
Department of mechanical Engineering, P.A. College of Engineering and Technology, Pollachi – 642002.
1
boss120367@gmail.com
Abstract —
This study deals with the Thermodynamic evaluation of the use of Di-methyl ether refrigerants in household
refrigeration systems which utilize R134a as a working fluid. A theoretical computational analysis was developed for R134a,
Di-methyl ether (RE170) and the selected mixtures (R429A, R435A and R510A) in the standard refrigeration cycle ASHRAE,
using the REFPROP 9.0 software. The results of computational simulations between the fluids were compared to find the
evidence of the best alternative for R134a. In this sense, it is observed that the Di methyl ether reduced the levels of pressure on
the condenser and evaporator. It also reduces the mass to be charged in the system. The use of these refrigerants reduces mass
flow rate and increases refrigerating capacity of the system.
Keywords—
Di methyl ether, R429A, R435A , R510A, Refrigerator
I. INTRODUCTION
For the past half century, chlorofluorocarbons (CFCs) have been used extensively in the field of refrigeration due to
their favorable characteristics. In particular, R12 has been predominantly used for small refrigeration units including
domestic refrigerator/freezers. Since the advent of the Montreal Protocol (1987) [1], as the R12 has high ODP and
GWP the refrigeration industry has been trying to find out the best substitutes for ozone depleting substances. For a
past decade, R134a has been used to replace R12 used in refrigerators and automobile air conditioners. R134a has
such favorable characteristics as zero ozone depleting potential (ODP), non-flammability, stability, and similar
vapour pressure to that of R12.In 1997, the Kyoto protocol was agreed by many nations calling for the reduction in
emissions of greenhouse gases including HFCs [2]. Since the Global warming potential (GWP) of R134a is
relatively high (GWP1300) and also expensive, the production and use of R134a will be terminated in the near
future. Now it is imperative to identify the alternative refrigerant with low GWP in accordance with the limit fixed
by EU Regulations [3].
Fatouh and El Kafafy [4] conducted a theoretical study about HC mixture (60% /40% R290/R600) as a possible
alternative for HFC -134a based domestic refrigerators under various climate conditions. Nicholascox [5] reported
that Di methyl ether (RE170, DME) makes a better refrigerant than R290 / R600a blends as it has no temperature
glide and doesn’t separate during leakage.
Valentinapostol et al. [6] conducted a thermodynamic study in vapor-compression refrigeration system for pure
substances and zoetrope mixtures, The results indicates that Di methyl ether can be used as alternative refrigerant for
R12 and R134a. B.M. Adamson [7] reported that the Di methyl ether (DME, C2H6O) possesses a range of desirable
properties as a replacement for R-134a. These include better heat transfer characteristics than R-134a, a
pressure/temperature relationship very close to R134a, compatibility with mineral oils, low cost and ready
availability. It is also highly environmentally friendly. (ODP =0; GWP =1; atmospheric lifetime = 6 days) DME is
compatible with most materials commonly found in refrigeration systems.
Baskaran.et al. [8-14] reported the performance of a vapor compression refrigeration system with Di methyl ether
and its blends. The results showed that the Di methyl ether and its blends have better performance when compared
with R134a.
Ki-Jung Park.et al. [15] investigated both numerically and experimentally in an effort to replace R134a used in the
refrigeration system of domestic water purifiers. Test results show that the energy consumption and the compressor
discharge temperature of R429A is 28.9% and 13.40 C lower than that of R134a with50% of the refrigerant charge ,
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Overall,R429Ais a new long term environmentally safe refrigerant, is a good alternative for R134a requiring little
change in the refrigeration system of the domestic water purifiers.
Choedaeseong, Dangsoo Jung [16]. presented an experimental study on the application of R435A (mixture of DME
and R152a) to replace R134a in domestic water purifiers. Test results show that the energy consumption and
discharge temperature was 12.7% and 3.7°C lower than that of R 134a
Ki-Jung Park/Yohan Lee/Dongsoo Jung [17] investigated both numerically and experimentally in an effort to
replace HFC134a used in the refrigeration system of domestic water purifiers. Test results show that the energy
consumption and the compressor discharge temperature of R510A is 22.3% and 3.70 C lower than that of R134a
with50% of the refrigerant charge , Overall, R510Ais a new long term environmentally safe refrigerant, is a good
alternative for R134a requiring little change in the refrigeration system of the domestic water purifiers.
II.
THEORETICAL
MODEL
A theoretical analysis is implemented for the use of R134a, Di methyl ether (RE170) and selected mixtures
(RE170/R600a/R152a 60%/30%/10%, RE170/R152a 80%/20% and RE170/R600a 88%/12%) in the ASHRAE
standard cycle (evaporation temperature: -23.3ºC, condensation temperature: 54.4°C, temperature of liquid and
suction: 32.2ºC) using the REFPROP 9.0 software [18]. The objective of the analysis is to identify refrigerants that
performed close to R134a. Figure 1 show the thermodynamic cycle model used in theoretical and computational
analysis.
In order to simulate the vapor-compression refrigerator the following assumptions are necessary.
a) Steady state operation
b) No pressure loss occurs in the pipes
c) Gain or loss of heat is neglected
d) Compressor volumetric efficiency and isentropic efficiency of 75 % [4]
The properties of the selected refrigerants in this study are reported in Table1. [19] The model used here is
CYCLE_D developed by NIST [20]. The system simulated by CYCLE_D consists of a compressor, discharge line,
condenser, expansion device, evaporator, compressor suction line, and an optional suction line heat exchanger
(SLHX). Thermodynamic properties are regenerated through the Carnahan- Starling-DeSantis (CSD) equations of
state. The simulated cycle is outlined by 11 states corresponding to key locations in a real system as shown in Fig. 1.
These states are as follows: (1) Inlet to the shell of the hermetic compressor; (2) Cylinder inlet before the
compression process; (3) Cylinder outlet after the compression process; (4) Condenser inlet; (5) Saturated vapor in
the condenser; (6) Saturated liquid in the Condenser; (7) Condenser outlet; (8) inlet to the adiabatic expansion
device; (9) Expansion device outlet or evaporator inlet; (10) Saturated vapor in the evaporator and (11) Evaporator
outlet.
Figure1. Real thermodynamic cycle of a household refrigerator
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For drop-in acceptance of a working fluid in a refrigeration system that already exists, some important performance
characteristics should be considered. These are: operating pressure, volumetric cooling capacity, coefficient of
performance and compressor discharge temperature [4].The refrigerant must have a minimum number of essential
characteristics favorable, among which the most significant are: low density in the liquid phase, high latent heat of
vaporization, low specific volume in the vapor phase and low specific heat in the liquid phase. The volumetric
cooling capacity (Qvol) is a measure of the compressor size for the required operating conditions expresses the
effect of cooling obtained per 1m3 of refrigerant entering in compressor. It should be noted that, as the volumetric
cooling capacity increases, the size of compressor required is reduced. The pressure ratio (PR) is defined as the ratio
between the condensation pressure (Pcond) and evaporation pressure (Pevap). The condensation and evaporation
pressures are determined according to the condensation and evaporation temperatures, respectively. The coefficient
of performance (COP) relates the cooling capacity and power required and indicates the overall power consumption
for a desired load. High COP means low energy consumption for absorption of the same cooling capacity of space to
be refrigerated. In the cycle analysis, the same cooling capacity was applied to all simulations of refrigerants
considered. The cycle cooling capacity of 120 W was obtained by a 180L household refrigerator, provided by the
manufacturer.
Table: 1. Properties of Investigated Refrigerants
S.No Refrigerant
mixture Composition (% mass f.) NBP
(C) GWP Molecular
Mass
Critical
Temperature
Critical
Pressure
1
R134a
--------
-
26.1
1430
102.3
101.1
4.06
2
RE170
-------
-
24.8
10
46.07
127.2
5.34
3 R 429A
RE170/R600a/R152a
(60/30/10) -26.0 14 50.76 123.5 4.86
4 R 435A DME/R 152a (80/20) -26.1 <31 49.04 125.2 5.39
5 R 510A DME/R 600a (88/12) -25.2 <3 47.24 127.9 5.33
Table 2. Computational Parameters of Investigated Refrigerants (ASHRAE cycle)
Refrigerant R134a RE170 R429A R435A R510A
Condensation pressure @ 54.4ºC (kPa)
1469.8 1270.4 1253.3 1323.2 1261.1
Evaporation pressure @ -23.3ºC (kPa)
114.8 108.2 111.6 113.4 109.5
Pressure Difference(kPa)
1355 1162.2 1141.7 1209.8 1151.6
Pressure ratio
12.8 11.75 11.23 11.67 11.52
Refrigeration effect(Kj/Kg)
185.58 411.09 362.43 382.96 396.21
Volumetric cooling capacity(kJ/m3)
875.2 822.6 827.3 856.2 824
COP
2.05 2.039 2.074 2.033 2.053
Refrigeration capacity(W)
120 120 120 120 120
Mass flow(kg/h)
2.3278 1.0509 1.192 1.128 1.0903
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Discharge temperature(
0
C)
139.5 163.2 145.4 162.3 156
Capillary tube inlet temperature (oC)
32.2 32.2 31.8 32.1 32.2
Suction specific volume (m3/kg)
0.212 0.5 0.438 0.447 0.481
Liquid specific heat (kJ/kgK)
1.4559 2.4084 2.3954 2.2997 2.4267
Liquid density (kg/m3)
1179.6 645.18 614.63 678.56 626.34
LHV(KJ/kg)
90.5 201.6 174.7 188.4 193
III. RESULTS
AND
DISCUSSIONS
Applying the simulation on the thermo dynamic cycle showed in Fig.1 under predetermined conditions of operation
(ASHRAE cycle) and using software REFPROP 9.0 .The results were obtained and presented in Table 2.
Figure 2 shows that the variation of vapour density of the selected refrigerants which are lower than that of R134a
for the whole range of operating temperatures. This leads to reduction compressor work required. The reduction in
density is a more important factor than the latent heat of vaporization of the fluid.[21] The vapour densities under
the suction conditions of the mixtures and di methyl ether presents smaller than those of R134a, corresponding to a
less fluid charge required in the system in relation to R134a [4] As shown in figure 3, the R429A and R510A give
the lowest liquid densities, providing thereby reducing frictional losses in the system.[4]
- 5 0 - 4 0 - 3 0 - 2 0 - 1 0 0 1 0 2 0 3 0 4 0
0
5
1 0
1 5
2 0
2 5
3 0
3 5
4 0
Vapour Density(kg/m
3
)
S a t u ra t io n T e m p e ra t u re (
o
C )
R 1 3 4 a
R E 1 7 0
R 4 2 9 A
R 4 3 5 A
R 5 1 0 A
Figure 2.Variation of Vapour density with saturation temperature.
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-5 0 -4 0 -3 0 -2 0 -10 0 1 0 20 30 4 0
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
Liquid Density(kg/m3)
S at ur a tio n Te m p e ra tu re (oC )
R 1 3 4 a
R E 1 7 0
R 4 2 9 A
R 4 3 5 A
R 5 1 0 A
Figure3.Variation of Liquid density with saturation temperature.
-5 0 -4 0 -3 0 -2 0 -1 0 0 1 0 2 0 3 0 40
0 .0 0
0 .0 5
0 .1 0
0 .1 5
0 .2 0
0 .2 5
0 .3 0
0 .3 5
0 .4 0
0 .4 5
0 .5 0
0 .5 5
0 .6 0
0 .6 5
0 .7 0
0 .7 5
0 .8 0
0 .8 5
0 .9 0
Vapour Volume(m3/kg)
S a t u ra t io n T e m p e r a tu r e ( oC )
R 1 3 4 a
R E 1 70
R 4 2 9 A
R 4 3 5 A
R 5 1 0 A
Figure 4.Variation of vapour volume with saturation temperature.
Figure 4 shows the variation in the suction specific volume conditions of the compressor. It is observed that higher
values of specific volume in the compressor suction provides a higher volumetric cooling capacity, resulting in the
need for higher displacement of the compressor to the same cooling capacity of the system. It is observed that in
order to carry out a drop-in of refrigeration system, the substitute refrigerant must have similar volumetric cooling
capacity to the existing refrigerant so as not to be necessary to replace the compressor. In this study, it is observed
that the Di methyl ether shows the highest specific volume and R429A has lower value.
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Analysing the Table 2 can be noted that the latent heat of vaporization (refrigeration effect) of the R510A is about
twice that of R134a. However, due to the low specific volume of R134a in the suction, the volumetric cooling
capacity of the two fluids is nearly similar.
IV. CONCLUSIONS
Di methyl ether and its blends are environmentally friendly; the use of these substances as refrigerants in domestic
refrigerators is very feasible. It is found from the thermodynamic analysis, the pressure level in the condenser and
evaporator are lower. The use of Di methyl ether and mixtures involving hydrocarbons provides a doubling of the
latent heat of vaporization compared to R134a. This factor leads to a reduction in charge mass (50%) of refrigerant
in the cooling system for a same capacity of the equipment. The coefficient of performance of the system with Di
methyl ether and mixtures (R510A and R429A) is having similar and higher values compared to R134a respectively.
In order to consolidate the di methyl ether and their mixtures as substitutes for R134a, the refrigeration industry
should focus its efforts on developing compressors suitable for volumetric cooling capacity of these alternative
refrigerants,
REFERENCES
[1] United Nations Environmental Programme, 1987.Montreal protocol on substances that deplete the ozone layer, Final act,
United Nations, New York, USA.
[2] Global Environmental Change Report, 1997.A brief analysis of the Kyoto protocol, IX (24).
[3] Regulation (EU) No 517/2014 of the European Parliament and of the Council of 16 April 2014 on fluorinated greenhouse gases
and repealing Regulation (EC) No 842/2006 (eurlex.europa.eu/legal-
content/EN/TXT/PDF/?uri=CELEX:32014R0517&from=EN)
[4] Fatouh, M., and El Kafafy, M., 2006, Assessment of Propane/Commercial Butane Mixtures as Possible Alternatives to R134a in
Domestic Refrigerators, Energy Conversion and Management, Vol. 47, pp. 2644- 2658.
[5] Nicholas Cox, 2010.Developments and opportunities using hydrocarbon refrigerant blends. Presented to Transforming
Technologies Conference, London. www.earth care products.co.UK
[6] valentinapostol_etl 2009 Thermodynamic Study Regarding the Use of Dimethylether as Eco Refrigerant REV. CHIM.
(Bucureºti) 60Nr. 7,2009 http/www.revistadechimie.ro
[7] Adamson, B.M. 1998, Dimethyl Ether As An R-12 Replacement IIR - Commissions B & E - Oslo, Norway – 1998
[8] A Baskaran, P. Koshy Mathews, 2012, “A Performance Comparison of Vapour Compression Refrigeration System Using Eco
Friendly Refrigerants of Low Global Warming Potential, International Journal of Scientific and Research Publications, vol. 2
(Issue 9), pp.1-8
[9] A Baskaran, P. Koshy Mathews, 2012, “A Performance comparison of vapour compression refrigeration system using various
alternative refrigerants”, International Journal of Scientific & Engineering Research, vol.3 (issue.10), pp.1-7
[10] A Baskaran, P. Koshy Mathews, 2012, “Thermal analysis of vapour compression refrigeration system with R152a and its
blends R429A, R430A, R431A and R435A”, International Journal of Scientific & Engineering Research, vol.3 (issue.10), pp.1-8.
[11] A Baskaran, P. Koshy Mathews, 2012, “Comparative Study of Environment Friendly Alternatives to R12 and R134a in
Domestic Refrigerators”, European Journal of Scientific Research, vol92 (issue.2), pp.160-171.
[12] A Baskaran, P. Koshy Mathews, 2013, “Energy and Exergy Analysis of a vapour Compression Refrigeration System with R134a,
R152a and RE170”, Archives Des Sciences, vol.66 (issue3), pp.1-15
[13] A Baskaran, P. Koshy Mathews, 2014, “Investigation of New Eco Friendly Refrigerant Mixture Alternative to R134a in
Domestic Refrigerator”, Australian Journal of Basic and Applied Sciences, vol.9 (issue 5), pp.297-306
[14] A. Baskaran, P. Koshy Mathews, 2015, “Thermodynamic Analysis of R152a and Dimethylether Refrigerant Mixtures in
Refrigeration System”, Jordan Journal of Mechanical and Industrial Engineering, vol. 9 (issue.4), pp.289-296
[15] Ki-Jung Park, Dong Gyu Kang and Dongsoo Jung C, S Cooling Performance of Alternative Refrigerant R429A in Domestic
Water Purifiers Department of Mechanical Engineering, Inha University, Incheon, Korea
[16] Choedaeseong, Dangsoo Jung, Performance of R435A on refrigeration system of domestic water purifiers. Int. J. Sarek. 11,
366 - 371.,2010.
[17] Ki-Jung Park Yohan Lee Dongsoo Jung., Cooling performance of R510A in domestic water purifiers The Journal of
Mechanical Science and Technology, vol. 24, no. 4, pp.873-878, 2010.
[18] REFPROP: Reference fluid thermodynamic and transport properties. NIST Standard reference data base 23-version 9.0,
Gaithersburg (MD): National institute of standards and technology.
[19] J.M.Calm,G.C. Hourahan, Physical safety and environmental data for current and alternative refrigerants,ICR2011,August-21-
26-Prague,Czech Republic.
[20] CYCLE_D: Vapour compression cycle design NIST Standard reference data base 23 - version 4.0 Gaithersburg (MD): National
institute of standards and technology.
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[21] Poggi, F., Macchi-Tejeda, H., Leducq, D., and Bontemps, A., 2008, Refrigerant Charge in Refrigeration Systems and Strategies
of Charge Reduction, International Journal of Refrigeration, Vol. 31, pp. 353-370.
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