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Int. J. Mech. Eng. & Rob. Res. 2014 Alok Bharadwaj et al., 2014

THERMODYNAMIC ANALYSIS OF HFC R152aREFRIGERANT AS AN ALTERNATIVE TO HFC

R134a

Alok Bharadwaj1*, Anirudh V Kaushik1, Aditya S N1 and Aayush Tandon1

*Corresponding Author: Alok Bharadwaj,[email protected]

A detailed study of thermodynamic properties of an emerging refrigerant R152a has beendiscussed with respect to other conventional and non-conventional refrigerants like R12, R22,R404a, R410, R134A, etc. More emphasis has been laid on the environmental friendliness ofthe refrigerant with Ozone Depletion Potential (ODP) and Global Warming Potential (GWP)forming the basis. Further, the optimum working conditions of R152a, in terms of its propertiesas well as design parameters, are considered and compared with other refrigerants, beingused presently, in order to propose it as the most suitable and economically viable substitute tothe conventional refrigerants. Lastly, solutions have been suggested to some of the problems ofR152a so that it can be used as a replacement for R134a in refrigerators and ACs.

Keywords: Alternative refrigerant, R152a, ODP, GWP, Performance, Safety

INTROUDUCTIONConcept of Ozone DepletionPotential (ODP) and GlobalWarming Potential (GWP)The Ozone Depletion Potential (ODP) of achemical compound is the relative amount ofdegradation to the ozone layer it can cause,with trichlorofluoromethane (R-11 or CFC-11)being fixed at an ODP of 1.0.Chlorodifluoromethane (R-22), for example,has an ODP of 0.055. CFC 11, or R-11 hasthe maximum potential amongst chlorocarbons

ISSN 2278 – 0149 www.ijmerr.comVol. 3, No. 3, July 2014

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Int. J. Mech. Eng. & Rob. Res. 2014

1 Department of Mechanical Engineering, R V College of Engineering, Bangalore, India.

because of the presence of three chlorineatoms in the molecule.

Global-Warming Potential (GWP) is arelative measure of how much heat agreenhouse gas traps in the atmosphere. Itcompares the amount of heat trapped by acertain mass of the gas in question to theamount of heat trapped by a similar mass ofcarbon dioxide. A GWP is calculated over aspecific time interval, commonly 20, 100 or 500years. GWP is expressed as a factor of carbondioxide (whose GWP is standardized to 1).

Research Paper

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Selection Criteria for AlternateRefrigerants

Performance CriterionThe alternative refrigerant must have its COPvalues better than or equal to the originalrefrigerants. The selection of alternaterefrigerants should not hamper theperformance of the refrigeration systembecause it leads to fall in the demand of therefrigerant.

EnvironmentEnvironment criterion is the most critical inchoosing the alternative. The new refrigerantmust have ZERO ozone depletion potentialand as low as possible global warmingpotential.

SafetyThe refrigerant chosen must be stable in theworking condition. It should be non-toxic andnon-flammable.

Thus, possible alternatives being presentedare HFC 404a, HFC 410a and HFC 152a. Anexhaustive literature survey was carried out inorder to select the best among the three (incomparison with R22 and R134a).

THEORITICAL ANALYSIS• Refrigerants analyzed

– To be phased out refrigerant: R22

– Currently popular

– Alternatives chosen: R404a[6], R410a[2],R152a[7]

• Analysis was carried out theoretically

• Assumptions:

– Ideal vapour compression cycle

– Tevap = –15 °C and Tcond = 40 °C

– Unit mass flow rate (1 Kg/s)

• Thermodynamic Cycle

– Ideal Standard Steady State Cycle

• Formula

– COP = (H1 – H4)/(H2 – H1)

– PR = P2/P1

– RE = H1 – H4

– Compressor Work = H2 – H1

COP – Coefficient of Performance

H1, H2, H3 and H4 are enthalpy (KJ/Kg)

PR – Pressure Ratio

RE – Refrigeration Effect (KW)

Compressor Work (KW)

ODP 1.0 1.0 0.05

GWP 4750 10900 1810

Table 1: ODP and GWP of Phased OutRefrigerants

R11 R12 R22

RefrigerantsODP and GWP ofPhased Out

Figure 1: Basic Vapour CompressionRefrigeration Cycle

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PERFORMANCE ANALYSISTheoretical COP of R152a is higher than theother refrigerants in consideration over therange of Evaporator temperature chosen.Hence it can work efficiently for bothRefrigeration and Air Conditioningapplications.

Discharge temperature for R152a is fairlylow, because of which chemical stability of thefluid medium is maintained.

Pressure ratio for R134a and R152a issimilar over the entire range; hence switchingthe refrigerants does not require structuralmodification.

For a given Compressor work per kg ofrefrigerant, R152a gives maximum RE.

Figure 2: COP vs Evaporator Temp

Figure 3: Refrigeration Effect vsCompressor Work

Figure 4: Discharge Temp vs EvaporatorTemp

Figure 5: Pressure Ratio vs EvaporatorTemp

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R152a has the least GWP among theselected refrigerants and has a ZERO ODP. Itis thus the better refrigerant among thoseconsidered.

Figure 6: Comparison of GWPfor Various Refrigerants

Refrigerant Safety Group

R12 A1

R134a A1

R404a A1

R410a A1

R152a A2

Table 2: Safety Group Classificationof Refrigerants

Safety group of R152a “A2” indicates therefrigerant is mildly flammable. There is a needto reduce its flammability and research hasbeen done in this aspect.

The flammability of R152a can be reducedby using a suitable fire hazard reducing agent.NovecTM 1230 is a suitable choice for thispurpose.

It is used as emulsion/solution in theflammable refrigerant with a particle size of

Figure 7: 1, 1, 1, 2, 2, 4, 5, 5, 5-Nonafluoro-4-(Trifluoromethyl)-3-

Pentanone

10 µm or less. Concentration is sufficient toreduce flammability to acceptable levels.

100 0 12 Mild, lightblue flame R152a only

90 10 1 Very faint, Substantialblue flame Reduction of

flame

80 20 No flame No flame Elimination offlame

Table 3: Result of Addition of Novec™to R152A’s Flamability

R152a(%age)

Novec1230

(%age)

Result

FlameLength(inch)

FlameQuality Observation

CONCLUSIONThe study has proved theoretically that R152ais a suitable alternative to the currently popularR134a. It has lesser GWP than any of thealternatives currently researched on and hasfavorable working characteristics. It has higherCOP than any other refrigerants consideredin the study.

Although mildly flammable, R152a can beused comfortably using a fire hazard reducingagent, NovecTM 1230 as proved by theresearch.

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REFERENCES1. Ashrae (2001), Thermophysical

Properties of Refrigerants, Chapter 20,Vol. 20, pp. 1-67, ASHRAE Fundamental,Inc., Atlanta.

2. Bolaji B O, Akintunde M A and Falade TO (2011), “Comparative Analysis ofPerformance of Three Ozone-FriendsHFC Refrigerants in a VapourCompression Refrigerator”.

3. Canadian Patent Number CA 2543985(2013), “Compositions and Methods forReducing Fire Hazard of FlammableRefrigerants”.

4. Daniel J S, Velders G J M, Douglass A R,Forster P M F, Hauglustaine D A, IsaksenI S A, Kuijpers L J M, McCulloch A,Wallington T J, Ashford P, Montzka S A,Newman P A, Waugh D W (2007),“Changes in Atmospheric Constituentsand in Radiative Forcing”.

5. Forster P M F, Ramaswamy V, Artaxo P,Berntsen T, Betts R, Fahey D W, HaywoodJ, Lean J, Lowe D C, Myhre G, Nganga J,Prinn R, Raga G, Schulz M and VanDorland R (2007), “HalocarbonScenarios, Ozone Depletion Potentials,and Global Warming Potentials”.

6. Hongqi Li and Zhigang Zhao (2008),“Analysis of the Operating Characteristicsof a Low Evaporation Temperature R404aRefrigeration System”.

7. Stephanie L Outcalt and Mark O McLinden(1995), “A Modified BWR Equation ofState for the Thermodynamic Propertiesof R152a”.

8. US EPA (2007), “Global WarmingPotentials of ODS Substitutes”, Science-Ozone Layer Protection, Retrieved 2010-12-16.

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