INTERNATIONAL JOURNAL or REFRIGERATION 36 (2013) 870 880
`
`Available online at wwwscienoedinectoom
`
`Sciverse Sciencebirect
`
`
`
`journal homepage: www.elsevier.com/locate/ijrefrig
`
`Experimental analysis of R1234yf as a drop-in
`replacement for R134a in a vapor compression
`
`system
`
`I. Navarro-Esbn""*, ].M. Mendoza-Miranda ", A. Mata-Babiloni “, A. Barragcin-Ceruera “,
`].M. Belman-Flores”
`
`‘Department of Mechanical Engineering and Construction, Campus de Riu Sec s/n, University Jaume 1, E12071 Castelldn, Spain
`"Engineering Division, Campus lrapuato Salamanoa, University of Guanajuato, Carr. Salamanca Valle de Santiago lam 3.5+1.8 km,
`Comunidad de Palo Blanco, C.P. 36885, Salamanca, Gto., Mexico
`
`ARTICLE INFO
`
`ABSTRACT
`
`Article history:
`Received 19 September 2012
`Recdved in revised form
`22 November 2012
`
`Accepted 16 December 2012
`Available online 26 December 2012
`
`Keywords:
`Drop in
`R1234yf
`R134a
`
`Vapor compression system
`Internal heat exchanger
`Low GWP
`
`This paper presents an experimental analysis of a vapor compression system using
`R1234yf as a drop in replacement for R134a. In this work, we compare the energy perfor
`mance of both refrigerants, R134a and R1234yf, in a monitored vapor compression system
`under a wide range of working conditions. So, the experimental tests are carried out
`varying the condensing temperature, the evaporating temperature, the superheating de
`gree, the compressor speed, and the internal heat exchanger use. Comparisons are made
`taking refrigerant R134a as baseline, and the results show that the cooling capacity
`obtained with R1234yf in a R134a vapor compression system is about 9% lower than that
`obtained with R134a in the studied range. Also, when using R1234yf, the system shows
`values of COP about 19% lower than those obtained using R134a, being the minor difference
`for higher condensing temperatures. Finally, using an internal heat exchanger these dif
`ferences in the energy performance are significantly reduced.
`© 2013 Elsevier Ltd and HR. All rights reserved.
`
`Analyse expérimentale du R1234yf comme frigorigéne de
`remplacement immédiat du R134a dans un systéme a
`compression de vapeur
`
`Mots clés : remplacement immédiat ; R1234yf ; R134a ; systéme a compression de vapeur ; échangeur de chaleur interne ; faible GWP
`
`‘ Corresponding author. Tel.: +34 964728137; fax: +34 964728106.
`E mail address: navarroj@emc.uji.es (J. Navarro Esbri).
`0140 7007/$
`see front matter © 2013 Elsevier Ltd and IIR. All rights reserved.
`http://dx.doi.org/10.1016/j.ijrefrig.2012.12.014
`
`Page 1 of 11
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`Arkema Exhibit 1134
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`i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 3 6 ( 2 0 1 3 ) 8 7 0 8 8 0
`
`871
`
`Nomenclature
`
`COP
`Cp
`
`f
`
`GR
`
`GS
`h
`_m
`N
`P
`Qo
`s
`
`coefficient of performance
`specific heat (kJ kg 1 K 1)
`compressor drive frequency (Hz)
`superheating degree (K)
`subcooling degree (K)
`specific enthalpy (kJ kg 1)
`mass flow rate (kg s 1)
`compressor rotation speed (rpm)
`pressure (kPa)
`heat transfer rate (kW)
`specific entropy (kJ kg 1 K 1)
`
`T
`VG
`hv
`rasp
`
`temperature (K)
`geometric volume (m3)
`volumetric efficiency
`density at suction (kg m 3)
`
`Subscripts
`
`brine
`k
`o
`pi
`po
`ref
`
`Propileneglycol brine
`condensation
`evaporation
`evaporator inlet (brine side)
`evaporator outlet (brine side)
`refrigerant
`
`1.
`
`Introduction
`
`(CFCs) and hydro
`chlorofluorocarbons
`During 1900’s,
`chlorofluorocarbons (HCFCs) were extensively used in refrig
`eration and air conditioning vapor compression systems.
`When their ozone depleting potential became recognized, the
`Montreal Protocol was adopted by many nations to begin the
`phase out of both CFCs and HCFCs (UNEP, 1987). So, hydro
`fluorocarbons (HFCs) were developed as long term alternative
`to substitute CFCs and HCFCs, and while they were non ozone
`depleting, they did have large global warming potential (GWP).
`In 1997, HFCs were considered as greenhouse gases (GHGs)
`and currently they are target compounds for GHG emission
`reduction under the Kyoto Protocol (GCRP, 1997). In this way,
`the growing international concern over relatively high GWP
`refrigerants has motivated the study of low GWP alternatives
`for HFCs in vapor compression systems. One of those re
`frigerants is R134a, with a GWP (100 years) of 1430, extensively
`used in refrigeration and air conditioning (banned in Europe
`for new mobile air conditioners according to Directive, 2006/
`40/EC). The main candidates to replace R134a in vapor com
`pression systems are natural refrigerants like ammonia, car
`bon dioxide or hydrocarbons (HC) mixtures; low GWP HFCs,
`highlighting R32 and R152a; and HFO, specifically R1234yf,
`developed by Honeywell and DuPont (Spatz and Minor, 2008).
`Among the various studies of hydrocarbons mixtures using
`propane (R290), those using butane (R600) and isobutane
`(R600a) have given good results in comparison with R134a.
`The best performance is reached with the mixture propane/
`butane/isobutane (50/40/10 in mass) (Wongwises et al., 2006).
`The main disadvantage of the implementation of hydrocar
`bons mixtures is their flammability (BSI, 2004). For the case of
`drop in in domestic refrigeration with medium class flam
`mability refrigerants, like R152a and R32, the average COP
`obtained using R152a is higher than the one using R134a,
`while the average COP of R32 is lower than the one using
`R134a (Bolaji, 2010). R1234yf has been proposed as a replace
`ment for R134a in mobile air conditioning systems (Spatz and
`Minor, 2008), and its similar thermophysical properties makes
`R1234yf a good choice to replace R134a in other applications of
`refrigeration and air conditioning.
`Focusing on R1234yf, this refrigerant does not contain
`chlorine, and therefore its ODP is zero (WMO, 2007), and its
`
`GWP is as low as 4 (Nielsen et al., 2007; Papadimitriou et al.,
`2008). About security characteristics, R1234yf has low tox
`icity, similar to R134a, and mild flammability, significantly
`less than R152a (Koban, 2009). Analyzing other environmental
`effects of R1234yf, in the case that this refrigerant would be
`released into the atmosphere, it is almost completely trans
`formed to the persistent trifluoroacetic acid (TFA), and the
`predicted consequences of some studies of using R1234yf
`(Henne et al., 2012) show that future emissions would not
`cause significant increase in TFA rainwater concentrations.
`Several works can be found in the literature presenting
`theoretical studies to determine the feasibility of direct sub
`stitution (or with slight modifications) using R1234yf in facil
`ities working with R134a (Akasaka et al., 2010), being most of
`them based on mobile air conditioning systems. Lee and Jung
`(2012), measured theoretically the drop in performance of
`R1234yf in a simple bench tester and examined the possibility
`of substituting R134a in mobile air conditioning systems. Zilio
`et al. (2011) experimented with R1234yf in a typical R134a
`European automotive air conditioning system with some
`modifications. Bryson et al. (2011) tested a car air conditioning
`system using refrigerants R152a and R1234yf to replace R134a.
`In other refrigeration and air conditioning applications there
`is also a trend of using low GWP refrigerants as alternative and,
`furthermore,
`future legislation will probably encourage
`a greater use of them. Particularly, it has been studied the pos
`sibility of replacing R134a and R410A, which have a GWP of 1890,
`by other low GWP refrigerants. This has been done following the
`established trend in the automotive industry of replacing high
`GWP refrigerants. Reasor et al. (2010) evaluated the possibility of
`R1234yf to be a drop in replacement for a pre designed system
`with R134a or R410A, comparing thermophysical properties and
`simulating operational conditions. Leck (2010) discussed
`R1234yf, and other new refrigerants developed by DuPont, as
`replacement for various high GWP refrigerants. Endoh et al.
`(2010) modified a room air conditioner that had been using
`R410A to meet the properties of R1234yf, and also evaluated the
`cycle performance capacity. Okazaki et al. (2010) studied the
`performance of a room air conditioner using R1234yf and R32/
`R1234yf mixtures, which was originally designed for R410A,
`with both the original and modified unit.
`The aim of this work is to present an experimental study of
`R1234yf as a drop in replacement for refrigerant R134a in
`a vapor compression system in a wide range of working
`
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`872
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`INTERNATIONAL JOURNAL OI-‘ REFRIGERATION 36 (2013) 870 880
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`conditions. An energetic characterization with both re
`frigerants is carried out using as main perfomiance pararne
`ters
`the cooling capacity,
`the compressor volumetric
`efficiency, the compressor power consumption, and the COP.
`This experimental analysis has been executed varying the
`condensing temperature, the evaporating tempaature, the
`superheating degree, the compressor drive frequency, and the
`use of an internal heat exchanger. The results obtained with
`R134a are taken as baseline for comparison.
`The rest ofthe paper is organized as follows. In Section 2, the
`refrigeration tat bench used to obtain the experimental data is
`described. In Section 3, the experimental procedure andthe data
`validation considerations are briefly exposed. In Section 4, the
`experimental results are presented and discussed Finally, in
`Section 5, the main conclusions of the paper are summarized.
`
`2.
`
`Experimental refrigeration plant
`
`In this work, the tats are carried out in an experimental tat
`facility that consists of a vapor compression system, Fig. 1,
`working with refrigerants R134a and R1234yf. The test bench
`is completed with two secondary circuits: condensing water
`loop and load simulation system, which allow chang'ng the
`heat load as well as the evaporating and condensing condi
`tions. The condenser water loop consists of a closed type
`cooling system, which allows controlling the temperature of
`the water and its mass flow rate. The load simulation system
`also regulates the secondary coolant (water/propylene glycol
`brine) tempuature through a set of immersed PID controlled
`electrical resistances; meanwhile its mass flow rate can be
`adjusted using a variable speed pump.
`The main components of the vapor compression plant are:
`an open type reciprocating compressor, a shell and tube
`condenser (with refrigerant flowing along the shell and the
`
`Table 1 — Range of operating conditions in the
`experimental tests.
`
`Controlled parameters
`
`Condensation temperature ('I'.,)
`Evaporation temperature (To)
`Use of ll-[X
`Superheating degree (GR)
`Comprer drive frequency (f)
`
`Range values
`
`313.15 333.15 (K)
`265.65 280.15 (K)
`ON/OFF
`5 10 (K)
`35 50 012)
`
`tube in tube heat
`water inside the tubes), an internal
`exchanger (II-IX), a set of expansion valves, and a shell and
`tube evaporator, where the refrigerant flows inside the tubes
`and abrine water propylene gycol (65/35% by volume) is used
`as secondary fluid flowing along the shell.
`The thermodynamic states of the refrigerant are obtained
`measuring pressure and temperature at the inlet and outlet of
`each basic component of the test facility, using eleven K type
`thermocouples and eight piezoelectric pressure gauges. The
`temperature sensors are calibrated in our own laboratory
`using certified references, obtaining an uncertainty of i0.3 K;
`while the pressure transducers, within a range of 0-3000 kPa,
`have an uncertainty of 10.1% of the full scale range. The
`refrigerant mass flow rate is measured by a Coriolis mass flow
`meter located at the liquid line, with a certified accuracy
`within :t0.22% of the reading. The compressor electric con
`sumption is measured using a digital wattrneter, with a cali
`bration specified uncertainty of :t0.5%; and the compressor
`rotation speed is also measured using a capacitive sensor
`(with an uncertainty of :I:1%). The thermodynamic properties
`are calculated using REI-‘PROP (Lemmon et al., 2007).
`The volumetric flow rates of the secondary fluids are
`measured using two electromagnetic flow meters. Immersed
`themiocouples (with an accuracy of 10.1 K) are motmted in
`order to obtain secondary fluid temperatures.
`
`THERMOSTATIC
`EXPANSION VALVE
`
`Tpo
`
`Pig. 1 — Schematic diagram of the test bench.
`
`Page 3 of 11
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`INTERNATIONAL JOURNAL or-' REFRIGERATION 36 (201 3) 870 880
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`873
`
`7(X)0
`
`Pressure
`
`(kPa) 5‘O
`
`70
`
`150
`
`2(1)
`
`250
`
`310
`
`350
`
`400
`
`450
`
`Fig. 2 — Experimental test variation range.
`
`Finally, all the measurements are gathered with a National
`Instruments data acquisition system and monitored through
`a Personal Computer.
`
`3.
`
`Experimental procedure
`
`3.1.
`
`Experimental steady-state test
`
`Table 2 — Uncertainties for calculated parameters.
`
`Experimental estimation
`
`0.60%
`
`Qo (kW)
`
`C01’
`
`0.74%
`
`11..
`
`1.01%
`
`and evaporating pressurejtemperature ranges for the exper
`irnental tests are prsented in Fig. 2.
`The process of selecting a steady state consists of taking
`a time period of 20 min, with a sample period of 0.5 s, in which
`the condensing and evaporating pressure are within an in
`terval of ;I:2.5 kPa. Furthermore, in these tests all the tem
`peratures are within :t0.5 K and refrigerant mass flow rate is
`within i0.0005 kg s 1. Then, once a steady state is achieved
`(with 2400 direct measurement), the data used as a steady
`state test are obtained averaging over a time period of 5 min
`(600 measurements). Fig. 3 shows the variation about the
`mean value in a random test for the condensing pressure, the
`evaporating pressure,
`the superheating degree and the
`refrigerant mass flow rate.
`
`3.2.
`
`Propagation of errors in the estimated parameters
`
`To have a general understanding on the associated uncer
`tainty with the parameters calculated from measurements,
`the characteristic parameters uncertainty propagation is
`obtained using the RSS method (Taylor, 1997), Table 2.
`
`3.3.
`
`Data validation
`
`In order to check the accuracy of the measurements, a com
`parison between the heat load removed by the refrigerant and
`
`Po(kPa)
`
`
`
`Mnf(kgls)
`
`In order to obtain the experimental data to characterize the
`energy performance of the test bench using both refrigerants,
`104 steady state tests are carried out in a wide range of
`operating conditions, as shown in Table 1. The condensing
`1320 —
`1318 ‘
`1316 ‘
`1314 ‘
`1312
`1310 ‘
`1313
`135 ‘
`1304 ‘
`1302 ‘
`131!)
`'
`
`Pk(kPa)
`
`
`
`Time (3)
`
`GR(K)
`
`Time (3)
`
`(C)
`
`Fig. 3 — Fluctuation of operating parameters in a random steady-state test. (a) Condensing pressure, (b) evaporating
`pressure, (c) superheating degree, (d) refrigerant mass flow rate.
`
`Page 4 of 11
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`

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`874
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`INTERNATIONAL JOURNAL or-' REFRIGERATION 36 (2013) 870 880
`
`the heat supplied by the brine at the evaporator is carried out.
`So, I-ig. 4 shows a comparison between the cooling capacity
`measured at the refrigerant side and at the propylene glycol
`brine side, including all the experimental tests used in this
`work with both refrigerants.
`The cooling capacity at the refrigerant side is obtained as
`the product of the experimental refrigerant mass flow rate
`(m,.,) and the refrigerating effect, computed from the meas
`ured refrigerant thennodynamic states at the evaporator inlet
`(its) and outlet (he). So, the cooling capacity is expressed as:
`
`Q».-er
`
`75l:«(hs
`
`715)
`
`(1)
`
`'l'he cooling capacity at the brine side is obtained using the
`measured brine flow rate and the temperatures at the evap
`orator inlet (TF5) and outlet ('I',,,):
`
`Qn.h-he
`
`Vilw-eCpJ=rine("'pi T1»)
`
`(2)
`
` A R134a
`
`o R1234yf
`
`2
`
`3
`
`4
`
`5
`
`6
`
`7891011121314
`Qo.brlno(kW)
`
`14
`
`13
`
`12
`
`11
`
`10
`
`§ 9
`:5
`
`8
`'1',
`8‘ 7
`
`6 5 4 3 2
`
`Pig. 4 — Cooling capacity at the evaporator (comparing
`refrigerant side and brine side).
`
`4.
`
`Results and discussion
`
`4.1.
`
`‘theoretical expected raulls
`
`T|(=323.15 K, I= 50 Hz. GR= 5 K
`
`I R1343
`1R1234y1
`
`IHX=OFF
`
`lHX=ON
`
`In order to analyze the influence of the operafing parameters
`(evaporating
`temperature,
`condensing
`temperature,
`24.0
`22.0
`20.0
`18.0
`16.0
`"14.0
`$12.0
`81o.o
`6.0
`6.0
`4.0
`2.0
`0.0
`
`IHX=OFF
`
`
`
`280.65
`
`265.65
`
`273.15
`To (K)
`
`(b)
`
`24.0
`
`22.0
`20.0
`18.0
`
`16.0
`$14.0
`512.0
`310.0
`8.0
`
`|HX=OFF.I= 50 HL GR= 5K
`
`116361315K
`
`T|t=G23.15K
`
`‘I’k=333.15K
`
`TI-313.15K
`
`Tl-323.15K
`
`'21:)”
`
`§
`
`1'3
`
`,
`
`3
`"
`
`.
`1
`
`,
`E
`1
`5‘-‘
`
`'2’
`
`.
`
`i1
`
`6.0
`4.0
`
`1
`31
` 273.15
`
`265.65
`
`280.65
`
`To (K)
`
`(a)
`
`-We
`-R1234y1
`
`GRI5K
`
`GR=10K
`
`
`
`265.65
`
`27315
`To (K)
`
`28065
`
`$14.0
`512.0
`0
`010.0
`8.0
`6.0
`4.0
`2.0
`0.0
`
`24.0
`22.0
`
`.
`IR134a wm'1oul|HX
`DR1234y1wnhIHX
`I-50!-lz
`20'0
`13_o GR=5K
`16.0
`
`
`
`x
`.,
`“‘
`5
`g
`
`E
`5.;
`E
`
`2
`g
`9
`2
`é
`
`x
`3‘
`'1
`an
`3
`E
`3
`
`
`3
`g
`E
`
`E’
`,£
`15
`
`,
`9
`::.‘
`71'
`l'-‘
`
`x
`¥
`3
`E
`
`
`
`265.65
`
`273.15
`To (K)
`
`280.65
`
`Fig. 5 - Theoretical cooling capacity variation versus evaporating temperature T,: (a) varying condensing temperature,
`(b) with and without ll-Ix (c) varying superheating degree, (d) comparing R1234yf with IHX and R1349 without IHX.
`
`(c)
`
`(d)
`
`Page 5 of 11
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`

`
`INTERNATIONALJOURNAl.OFREFRIGERATION 36(2or3)87o 880
`
`875
`
`superheating degree, and the use of ll-IX) on the cooling ca
`pacity and the COP, a previous simple theoretical study is
`carried out. In this theoretical study the following assump
`tions are made:
`
`o the evaporator outlet temperature is established as the
`evaporation temperature plus the superheating degree
`(with two levels of superheating degree: 5 K and 10 K),
`o there pressure drops are negected,
`o the comprssion procss is assumed isentropic,
`o volumetric efficiency of 1,
`o there is no heat transfer to the surroundings,
`0 a subcooling degree of 2 K is considered at the condenser
`outlet
`
`o the possibility of using an II-IX (efliciency of 50%)
`considered
`
`is
`
`o isenthalpic process is considered at the expansion valve.
`
`The refrigerant mass flow rate is calculated as follows:
`
`.
`N
`mm P..pVc(5)
`
`(3)
`
`where N is the compression rotation speed in rpm, and pup is
`the density of the refrigerant at the compressor suction.
`The cooling capacity is defined as the product of the
`refrigerant mass flow rate and the refrigerating effect
`(enthalpy difierence between evaporator outlet and inlet):
`
`(4)
`(p.,».vc) (he no
`a.
`The theoretical COP only depends on thermodynamic states
`at the inlet and outlet of the evaporator and the compressor,
`and is defined as:
`
`COP
`
`lie
`,1
`
`in
`,:
`
`(5)
`
`where I11 is the specific enthalpy at compressor discharge,
`obtained by using the condensation pressure and specific
`entropy at the inlet of the compressor (s5).
`Figs. 5 and 6 show the variations of the theoretical cooling
`capacity and COP using both refrigerants varying the operat
`ing pressures, the superheating degree and with and without
`IHX. These theoretical rsults reveal that the cooling capacity
`with R1234yf would be 8—11% lower than using R134a (Fig. 5a),
`
`10.0
`
`9.0 -
`8.0
`
`7.0
`
`6.0
`
`I.
`O 5.0
`O
`4.0
`
`3.0
`2.0
`
`1.0
`0.0
`
`10.0 - T
`
`90'
`nR1234yf
`8.0
`
`
`
`§
`"
`15
`
`3
`9
`§
`‘5
`=
`‘
`
`
`‘.5
`"'
`5
`E
`3
`E
`
`
`3
`
`x
`,-3
`%‘
`3!
`
`7.0
`6.0
`3 so
`0 ’
`4.0
`3.0
`2.0
`
`1.0
`
`0.0
`
`2&).65
`
`265.65
`
`273.15
`T000
`
`(3)
`
`10.0 -
`
`10.0
`
`n.
`8 5.04.0
`3.0 —
`
`7
`
`ll-IX (FFJ SIHLTI 3315K
`
`
`
`8.0
`7.0
`
`6.0
`
`2.0
`
`1.0
`
`0.0
`
`2$55
`
`flaw
`T°(K)
`
`mam
`
`COP
`
`11:-an.1an<
`
`9.0
`8.0 -
`7.0
`
`6.0
`
`5.0
`
`4.0
`3.0
`
`2.0
`
`1.0
`
`0.0 '|'kfl23.1lK
`
`Fig. 6 — Theoretical COP variation versus evaporation temperature T,: (a) varying condensing temperature, (b) with and
`without ll-Ix (c) varying superheating degree, (d) comparing R1234yf with Ill)! and R1341: without ll-Ix.
`
`(c)
`
`(d)
`
`Page 6 of 11
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`

`
`876
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`INTERNATIONAL JOURNAL or REFRIGERATION 36 (2013) 870 880
`
`meanwhile the COP is also about 5—10% lower (Fig. 6a). When
`an ll-[X (efficiency
`50%) is used with both refrigerants, the
`difference between the theoretical cooling capacity and COP
`obtained with R134a and R1234yf is reduced, with a difference
`about 3-6% in cooling capacity and 2-4% in COP (Fig. Sb and
`Fig. 6b). It is also observed that the difference between the
`theoretical cooling capacity and COP using both refrigerants is
`slightly reduced when the condensing temperature is
`decreased, and having no significant influence the super
`heating degree (Fig. 5c and Fig. 6c). The differences in the
`energy performance are practically total reduced when an I1-IX
`is used with R1234yf compared with theoretical results using
`R134a without II-IX.
`
`4.2.
`
`Experimental results
`
`This section describes the experimental results obtained in
`the test bench using R1234yf and R134a, showing the main
`enagy performance parameters: cooling capacity, com
`pressor power consumption, and COP.
`Fig. 7 prsents the obtained results for the cooling capacity
`using R1343 and R1Z34yf. Experimental tests show that the
`
`cooling capacity using R123-Ilyf in a drop in replacement is
`about 9% lower than using R134a. This difference remains
`approximately constant when the evaporating and condens
`ing temperature are varied (Fig. 7a). It can alsobe seen that the
`difference between the cooling capacities using both re
`frigerants diminishes when an IHX is used (Fig. 7b), being this
`difference about 9—10% without IHX and about 7% when an
`
`IHX is used (despite the ll-IX efficiency is about 20%). Fur
`thermore, comparing the values of cooling capacity obtained
`using R1234yf with II-IX with those obtained using R134a
`without II-IX, the difference is reduced until about 5%.
`Observing Fig. 7c, it can be extracted that there is not
`a significant influence of the superheating degree on the
`difference of cooling capacities obtained with both re
`frigerants. Analyzing Fig. 7d, it can be seen that the cooling
`capacity increases when compressor drive frequency is
`increased. When the compressor frequency increases from
`35 Hz to 50 Hz, there is an increase in the cooling capacity
`using R134a about 19-45%, similar to that obtained using
`R1234yf (27—40%), maintaining the difference of the values of
`cooling capacity obtained using both refrigerants approx
`irnately constant
`
`X
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`Fig. 7 — Experimental cooling capacity variation regarding evaporating temperature T, varying: (a) condensing temperature,
`(b) use of ll-Ix, (c) superheating degree, (d) compressor drive frequency.
`
`Page 7 of 11
`
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`INTERNATIONAL JOURNAL or REFRIGERATION 36 (201 3) 870 880
`
`877
`
`In Fig. 8 the influence of the compression ratio on the
`compressor volumetric effidency using both refrigerants is
`presented. It has to be noted that the compressor volumetric
`efficiency using R1234yfis 5% lower compared with that using
`R134a. Furthermore, in this figure, one can observe that the
`dispersion obtained for the R1234yf volumetric efficiency is
`larger than that presented by R134a data. This fact is moti
`vated by the larger influence of the compressor speed on the
`volumetric efficiency when R1234yf is used, which can be
`partly explained by higher pressure drops using this
`refrigerant.
`Fig. 9 presents the compressor power consumption using
`both refrigerants at different working conditions. Fig. 9a
`presents that the power consumption obtained using R1234yf,
`when the operating pressures are changed in the test range, is
`between 1 and 2% (for a condensing temperature of 33.15 K)
`and 18-27% (for a condensing temperature of 313.15 K) higher
`than that obtained using R134a. So, the minimum difference
`in the power consumption is given for high condensing tem
`peratures, when the refrigerant mass flow rate is low and the
`pressure drops are also low. Furthermore, it can be seen that
`the measured power consumption decreases when the con
`densing temperature decreases, mainly due to a reduction in
`
`4.0
`
`1.00
`
`0.95 ~
`
`0.90 ~
`
`0.85 ~
`
`0.80 ~
`
`0.75 ~
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`0.70 ~
`
`0.65 ~
`
`0.60 ~
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`0.55 ~
`
`0.50
`
`AR134a
`
`o R1234yf
`
`
`
`5
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`omprasslon Ratio
`
`Pig. 8 — R134a and R1234-yf volumetric eficiency versus
`compression ratio.
`
`
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`Fig. 9 — Experimental power consumption (Pa) regarding evaporation temperature T. varying: (a) condensing temperature,
`(In) superheating degree, (c) compressor drive frequency.
`
`Page 8 of 11
`
`'l'|F313.1§K ‘ThI33I.1!K
`
`

`
`878
`
`INTERNATIONAL JOURNAL or-' REFRIGERATION 36 (2013) 870 880
`
`the compression ratio, being the slope of the power con
`sumption reduction presented by R134a sharper than the one
`presented by R1234yf.
`Analyzing the influence of the superheating degree on the
`compressor power consumption, Fig. 9b,
`it
`is observed
`a decrease in the power consumption when the superheating
`degree increases from 5 K to 10 K, remaining the difference
`between both refrigerants approximately constant. Finally,
`analyzing the influence of the compressor frequency, Fig. 9c,
`we can see that the difference between both refrigerants
`power consumption at 35 Hz is lower than that observed at
`50 Hz. This fact is due to the higher pressure drops using
`R1234yf in comparison with those presented when using
`R134a. So, when the compressor frequency drive increases
`from 35 Hz to 50 Hz, the pressure drops increases about 0%
`using R1234yf, meanwhile pressure drops using R134a only
`increases about 38%.
`
`Fig. 10 shows the variation of the COP with the operating
`parameters. It is observed that the COP obtained using R1234yf
`is about S—27% lower than that observed when using R134a
`when the operating pressures are changed in the test range
`(Fig. 10a). This difference in the value of the COP using both
`refrigerants is lower for higier condensing temperatures,
`
`being about 8% for condensing temperatures of 333.15 K and
`about 25% for condensing temperatures of 313.15 K. It can be
`also seen that the ll-IX has a significant influence on the COP
`differences between both refrigerants (Pig. 10b). So, the values
`of the COP for R1234yf are 11-24% lower than those obtained
`for R134a when the IHX is not used and about 6—17% when the
`IHX is used.
`
`Analyzing the influence of the superheating degree on the
`COP, Pig. 10c, it can be observed that the difference about the
`values of the COP obtained using R134a and R1234yf increass
`when the superheating degree rises. ‘The influence of the com
`pressor drive frequency on the COP is shown in Fig. 10d, where it
`can be seen that the difference between the COP obtained using
`R123-4yf and using R1343 is increased when the compressor
`speed augments, again mainly due to higher pressure drops
`using R1234yf. This factis given because the higher incrementin
`compressor power consumption using R1234yf, in comparison
`with the increment presented by R1343, when the compresor
`frequency is raised from 35 Hz to 50 Hz.
`Finally, Table 3 summarizes the results presented in Figs. 7,
`9 and 10. This table shows the relative differences ofthe main
`
`energy parameters analyzed using R134a and R1234yf in the
`test range.
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`Fig. 10 — Experimental COP variation regarding evaporation temperature T. varying: (a) condensing temperature, (b) use of
`IHX, (c) superheating degree, (d) compressor drive frequency.
`
`Page 9 of 11
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`
`INTERNATIONAL JOURNAL or REFRIGERATION 36 (2oI3) 870 880
`
`879
`
`%Q.,..,,
`
` Table 3 — Experimental variation for cooling capacity, compressor power consumption and GOP taking R134a as baseline.
`T (K) T]: (K)
`Qo.R134a Qo,R134yf
`1’ R134:
`Pc,R134yf
`C0PR134a
`c0PR1.34yf
`°
`|QD3l‘m| x 1oo %I>,_,,,,
`|‘h3m| x 1m %coI>.,,,
`copmh
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`2.34%
`12.37%
`265.65 33.15
`13.46%
`14.47%
`24.40%
`265.65
`313.15
`12.37%
`18.24%
`3.82%
`273.15 33.15
`4.36%
`1.32%
`5.60%
`273.15 33.15
`8.85%
`12.53%
`19.00%
`273.15
`313.15
`5.27%
`24.38%
`3.84%
`280.65 33.15
`5.68%
`0.15%
`5.82%
`280.65 33.15
`8.36%
`9.23%
`16.11%
`280.65
`313.15
`8.39%
`27.03%
`27.89%
`
`|
`
`x 100
`
`T0
`
`IHX
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`265.65 OFF
`265.65 ON
`273.15 OFF
`273.15 ON
`280.65 OFF
`280.65 ON
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`Qp.R134a Qo,R134
`P 3134:
`1’ R1234
`C0Pru34.
`C0P1u234
`%Q.,,..,, TH x me 999..., |fi| x we %cop..,, | x 1oo
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`14.34%
`24.31%
`8.98%
`10.18%
`17.39%
`8.85%
`12.53%
`19.00%
`7.40%
`10.77%
`16.41%
`8.36%
`3.03%
`11.05%
`6.47%
`0.19%
`6.65%
`
`7
`°
`265.65
`265.65
`280.65
`280.65
`
`T
`°
`265.65
`265.65
`273.15
`273.15
`280.65
`280.65
`
`GR
`
`5
`10
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`10
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`f
`
`35
`50
`35
`50
`35
`50
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`Qo,R134n Qo,R134yf
`Pc.lu34a
`1’ ,R134yf
`C0PR134a Copmzuyr
`%Q.,.,,, 331 x 100 %P,._,,,, |fi| x 100 %co1>,,,,, | x 100
`13.46%
`22.99%
`29.64%
`8.51%
`31.67%
`3.52%
`8.36%
`3.03%
`11.05%
`11.40%
`2.42%
`13.49%
`
`Qo,Iu34a
`Qo_R1234yf
`P 1113!:
`1’ ,R1234yr
`C0Pm3aa C0PR134yf
`%Q,_..,, 3| x 100 %P.,.,,, #1 x 100 %cop.,,, | x 100
`13.46%
`11.11%
`22.12%
`13.83%
`10.5%
`22.28%
`8.85%
`1253%
`19.00%
`13.82%
`24.59%
`3.83%
`8.36%
`9.23%
`16.11%
`2.16%
`33.28%
`26.59%
`
`.
`
`5
`
`on 11510115
`C d _
`
`In this paper, an experimental analysis of a vapor com
`pression system using R1234yf as a drop in replacement for
`R134a has been presented. In order to obtain a wide range of
`working conditions a total of 104 steady state tests have been
`carried out. The tests have been performed varying the con
`densing pressure, evaporating pressure, superheating degree,
`the compressor speed and the IHX use.
`The energetic comparison is performed on the basis of the
`cooling capacity, the volumetric efficiency, the compressor
`power consumption, and the COP. The main conclusions of
`this paper can be summarized as follows.
`
`a The cooling capacity of R134yf used as a drop in replace
`ment in a R134a refrigerant facility is about 9% lower than
`that presented by R134a in the test range. This difference in
`the values of cooling capacity obtained with both re
`frigerants decreases when the condensing temperature in
`creases and when an IHX is used.
`
`c The volumetric efficiency using R1234yf is about 5% lower
`in
`comparison with
`that
`obtained with R134a.
`
`I-‘urthennore, the compressor volumetric efficiency using
`R1234yf shows a greater dependence on the compressor
`speed.
`c The values of the COP obtained using R1234yf are between
`5% and 30% lower than those obtained with R134a. Here, it is
`observed that when the condensing temperature raises
`from 313.15 K to 333.15 K this difference decreases from 25%
`
`until 8%, even more in the case of using an IHX.
`
`Finally, it can be concluded, from the experimental re
`sults, that the energy performance parameters of R1234yf in
`a drop in replacement are close to those obtained with
`R134a at high condensing temperatures and making use of
`an IHX.
`
`Acknowledgments
`
`This study was sponsored by Fundacié Caixa Castellé Ban
`caixa under the project P1132010 24 “Aplicacién de nuevos
`refrigerantes con bajo potencial de efecto invernadero en
`sisternas de frio comercial y climatizacién".
`
`Page 10 of 11
`
`

`
`880
`
`i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 3 6 ( 2 0 1 3 ) 8 7 0 8 8 0
`
`r e f e r e n c e s
`
`Akasaka, R., Tanaka, K., Higashi, Y., 2010. Thermodynamic
`property modeling for 2,3,3,3 tetrafluoropropene (HFO
`1234yf). Int. J. Refrigeration 33, 52 60.
`Bryson, M., Dixon, C., St Hill, S., 2011. Testing of HFO 1234yf and
`R152a as mobile air conditioning refrigerant replacements.
`Ecolibrium, 30 38. May.
`BSI, 2004. Determination of Explosion Limits of Gases and
`Vapours. BS EN 1839:2003. The British Standards Institution
`(BSI), London, UK.
`Bolaji, B.O., 2010. Experimental study of R152a and R32 to replace
`R134a in a domestic refrigerator. Energy 35, 3793 3798.
`Directive 2006/40/EC of The European Parliament and of the
`Council of 17 May 2006 relating to emissions from air
`conditioning systems in motor vehicles and amending
`Council Directive 70/156/EC. Official J. of the European Union,
`2006. Retrieved online at: http://eur lex.europa.eu/LexUriServ/
`LexUriServ.do?uri¼OJ:L:2006:161:0012:0018:EN:PDF, November
`8, 2011.
`Endoh, K., Matsushima, H., Takaku, S., 2010. Evaluation of cycle
`performance of room air conditioner using HFO1234yf as
`refrigerant. In: Int. Refrig. and Air Cond. Conf. at Purdue, West
`Lafayette, IN, USA. Paper No. 1050.
`Global Environmental Change Report GCRP, 1997. A Brief Analysis
`Kyoto Protocol, vol. IX, p. 24.
`Henne, S., Shallcross, D.E., Reimann, S., Xiao, P., Brunner, D.,
`O’Doherty, S., Buchmann, B., 2012. Future emissions and
`atmospheric fate of HFC 1234yf from mobile air conditioners
`in Europe