Available online at ScienceDirect. Energy Procedia 109 (2017 )

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1 Available online at ScienceDirect Energy Procedia 109 (2017 ) International Conference on Recent Advancement in Air Conditioning and Refrigeration, RAAR 2016, November 2016, Bhubaneswar, India Comparative evaluation of an automobile air - conditioning system using and its alternative refrigerants Prof. Jignesh K. Vaghela a* a Assistant Professor, ITM Universe, Vadodara , India Abstract This research involves the theoretical aspects of automobile air conditioning system. The main aim of the research is to evaluate the different alternative refrigerants as a drop in substitute of theoretically. For this purpose, thermodynamic properties of different alternative refrigerants i.e.,,,,, and are compared to. Thermodynamic evaluation of standard rating cycle of vapour compression refrigeration system is carried out. Engineering equation solver and refprop soft wares have been used for the thermodynamic analysis purpose. From thermodynamic analysis, it is derived that is best suitable alternative refrigerants as a drop in substitute of. has lower coefficient of performance as compared to ; however it is best suitable alternative refrigerants as a drop in substitute because it has very low global warming potential and can be substituted in the existing automobile air conditioning system with minimum modification The The Authors. Authors. Published Published by Elsevier by Elsevier Ltd. This Ltd. is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of the organizing committee of RAAR Peer-review under responsibility of the organizing committee of RAAR Keywords: Automobile Air Conditioning System,, alternative refrigerants, low GWP,. 1. Introduction: Since 1995, the standard refrigerant in the automobile industry has changed from R12 to due to ozone layer protection measures given by the montreal protocol (1989). However, concerns about global warming have since led to the creation of the global environment change report (1997). In this report, the goal was set to reduce the emissions of greenhouse gas up to refrigerant, which is widely used in current automobile air conditioning systems, is one of the controlled substances in the kyoto protocol (1997). In United Nations, the current air conditioning system was banned for refrigerants that have a Global Warming Potential (GWP) of over 150 by In India, Higher GWP refrigerants are also going to be banned in near future. The first response to the kyoto protocol by the automobile manufacturers was thus to improve systems by reducing leakage. However, efforts are being made to find an The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of the organizing committee of RAAR doi: /j.egypro

2 154 Jignesh K. Vaghela / Energy Procedia 109 ( 2017 ) alternative refrigerants to replace due to its high GWP of 1430 [1]. Hence this study involves finding of suitable alternative refrigerants of AAC system so that kyoto protocol requirements are fulfilled. Nomenclature AAC CFC COP GWP h HCFC HFC HFO m N NIST ODP P PR q RE SCD T v VCR w W Automobile Air Conditioning ChloroFluoroCarbon Coefficient of Performance Global Warming Potential specific enthalpy (kj /kg) HydroChloroFluoroCarbon HydroFluoroCarbon HydroFlouroOlefin mass flow rate (kg/s) Speed (rpm) National Institute of Standard and Technology Ozone Depletion Potential Pressure (MPa) Pressure Ratio Heat transfer (kj/kg) Refrigerating Effect (kj/kg) Specific Compressor Displacement (m 3 /kj) Temperature ( c) Specific volume (m 3 /kg) Vapour Compression Refrigeration Work (kj/ kg) Work (kw) Subscripts 1 refrigerant inlet condition to compressor a air c compressor ca compressor actual ci compressor isentropic co condenser D or 2n discharge E evaporator r refrigerant sat saturation AAC is a competitive and technology-oriented industry; so the open literature on the experimental performance of AAC systems is very limited. Because of the Montreal Protocol, some investigators determined the performance of AAC systems using refrigerants alternative to R12, which was the refrigerant widely used in AAC systems until Although the automobile industry has been using as a standard replacement for CFC12 since 1994, refrigerant has a very high global warming potential. Therefore, some recent studies have aimed to lower the global warming caused by the AAC systems by designing systems requiring less amounts of or using CO 2 or hydrocarbons or HFO as an alternative to [2]. J. Steven Brown, Samuel F. Yana-Motta, Piotr A. Domanski [3] had carried out comparative analysis of an automotive air conditioning systems operating with CO 2 and. The analysis showed having a better COP than CO 2 with the COP disparity being dependent on compressor speed and ambient temperature.

3 Jignesh K. Vaghela / Energy Procedia 109 ( 2017 ) S. Devotta et. al [4] has searched alternatives to HCFC-22 for air conditioners. NIST CYCLE_D has been used for the comparative thermodynamic analysis. Among the refrigerants studied (HFC134a, HC290,,, and three blends of HFC32, HFC134a and HFC125), HFC134a offers the highest COP, but its capacity is the lowest and requires much larger compressors. Mahmoud Ghodbane [5] had done an investigation of and hydrocarbon refrigerants in mobile air conditioning. He concluded that and cyclopropane (RC270) exhibit superiority as refrigerants when compared to. Pamela Reasor et al. [6] carried out a refrigerant performance comparison investigation. Comparisons are made between,, and, and simulations are conducted to determine the feasibility of using as a replacement for or. B. Takabi et al. [7] had carried out an effects of Al 2 O 3 -Cu/water hybrid nanofluid on heat transfer and flow characteristics in turbulent regime. The results indicate that employing hybrid nanofuid improves the heat transfer rate with respect to pure water and nanofuid, yet it reveals an adverse effect on friction factor and appears severely outweighed by pressure drop penalty. B. Takabi et al. [8] had also done an augmentation of the heat transfer performance of a sinusoidal corrugated enclosure by employing hybrid nanofluid. To predict the average number of nanofluid and hybrid nanofluid, two correlations have been developed. These equations are based on the modeling results and calculated by employing the classical least square method. Kakaç et al. [9] had done an analysis of convective heat transfer enhancement by nanofluids: single-phase and two-phase treatments. Despite the advantages of the mixture model, such as implementation of physical properties and less computational power requirements, some studies showed that the results of the single-phase and two-phase models are very similar. Only the main difference consists in the effect of the drift velocities of the phases relative to each other Objectives: The main aim of the project is to evaluate the different alternative refrigerants as a drop in substitute of. To evaluate thermodynamic properties of and its alternative refrigerants. To carry out thermodynamic evaluation of standard Rating cycle of VCR system. 2. Thermodynamic Property Analysis: Table 1. Thermodynamic properties comparison of different refrigerants [4] [5] [6] Refrigerants Chemical composition Molecular weight [kg/kmol] Normal boiling Point[ C] Critical Temp[ C] Critical Pressure [MPa] Safety class Propane () CH 3-CH 2-CH A ODP GWP Isobutane () CH 3-CH-CH 3 CH A3 0 3 R32+R125+R134(23/25/ 52) A1/A R32+R125(50/50) A1/A R125+R134+R143(44/4/ 52) A1/A CH 2FCF A CH 3-CH-F A CF 3CF=CH A2L 0 4

4 156 Jignesh K. Vaghela / Energy Procedia 109 ( 2017 ) The thermodynamic properties of different refrigerants as well as safety and flammability data are described in Table 1. The saturation pressure of the different refrigerants for wide range of temperatures (between 30 and 70 C) is compared in fig. 1. This is done by using Refprop and Engineering Equation Solver (EES) softwares. Fig. 1 depicts the variation of saturation pressure of,,,,,, and against temperature. It is observed that and have approximately the same saturation vapour pressure as. Hence system can operate with minimum modification in the existing system in case of and. 5 SATURATION PRESSURE [Mpa] TEMPERATURE [ C] Fig. 1. Saturation pressure Vs Temperature 3. Thermodynamic Cycle Analysis Procedure: Fig. 2. Schematic Diagram of VCR [10] Fig. 3. Pressure-Enthalpy Chart of VCR [10] AAC system works on Vapour Compression Refrigeration (VCR) cycle. The representation of cycle on schematic and the p-h diagram are shown in fig. 2 and 3, respectively; when the vapour at the end of compression is assumed to -be superheated. Assuming that 1 kg of refrigerant flows in the system, we can analyse the system as follows with help of steady flow energy equation. Thermodynamic analysis is as follows [10]: (a) Isentropic Compressor work, W ci : W ci = h 2s - h 1, kj/kg (1) Actual Compressor work, W ca : W ca = h 2n - h 1, kj/kg (2) (b) Heat rejected at the condenser, q co :

5 Jignesh K. Vaghela / Energy Procedia 109 ( 2017 ) q co = h 3 h 4, kj/kg (3) Condenser pressure, P co = P sat (T co ) (4) (c) Expansion device: h 5 = h 6, kj/kg (5) (d) Refrigerating effect, RE: RE = h 7 h 6, kj/kg (6) Evaporator pressure, P E = P sat (T E ) (7) (e) COP: COP = RE/W ca COP = (h 7 -h 6 )/(h 2n -h 1 ) (8) (f) Compressor Power, W c : W c = m r (h 2n - h 1 ), kw (9) (g) Mass of refrigerant to be circulated, m r per sec: m r =Q/q e, kj/s (10) (h) Specific Compressor Displacement, m 3 /kj: SCD = v 1 /q 0 (11) Assumptions : Pressure drops in suction and discharge lines are neglected. Cooling capacity of evaporator is assumed to be 4 kw. Analysis is based on steady-state condition. The size of tiny air bubbles and solid particles in refrigerant are assumed so small that they do not have a significant effect on the thermo-mechanical properties of the basic refrigerant. 4. Results and Discussion: Table 2. Calculated thermodynamic data of and its alternatives for Evaporating temperature=7.2 c, Condenser temperature= 55 c, compressor inlet temperature=35 c Refrigerant Discharge Temp. T 2n ( C) Pressure Ratio COP Refrigerating Effect RE (kj/kg) Compressor Work W (kw) By using data of standard rating cycle and by making simulation program in EES soft-ware, the thermodynamic analysis of and its alternative refrigerants is performed. This is done by varying its evaporator temperature for the given cooling capacity. Condenser temperature is 55 c and Evaporator temperature varies from 0 c to 12 c. For different evaporator temperature, the different parameters are measured. There is noticeable change in performance of different refrigerants for the same condition due to their characteristics. Table 2 presents the calculated theoretical (thermodynamic) data of and its alternative refrigerants. Fig. 4 shows the pressure ratio of and its alternative refrigerants for various evaporating temperatures for T C =55 c. As shown in fig. 4, with decrease in evaporating temperature, pressure ratio increases. If the pressure ratio is higher, then the compressor efficiency is lower.

6 158 Jignesh K. Vaghela / Energy Procedia 109 ( 2017 ) PRESSURE RATIO P R DISCHARGE TEMPERATURE T 2n [ C] EVAPORATING TEMPERATURE T E [ c] Fig. 4. PR Vs T E for Tc=55 c EVAPORATING TEMPERATURE T E [ c] Fig. 5. T D Vs T E for Tc=55 c The pressure ratio is highest for and lowest for for the entire range of T E in this study. This is because of higher molecular weight and normal boiling pressure of compared to. and have lower pressure ratio compared to and hence volumetric efficiencies of and are higher. Fig. 5 shows the discharge temperature of and its alternative refrigerants for various evaporating temperatures for T C =55 c. As shown in fig. 5, with decrease in evaporating temperature, discharge temperature increases. For better lubricant and refrigerant stability, lower discharge temperature is beneficial. At lower discharge temperature, compressor is expected to be running at slow speed. Compressor life is higher in case of slow speed. has slightly higher discharge temperature while has lowest discharge temperature compared to. Compressor life in case of is higher. COMPRESSOR WORK W [kw] COP EVAPORATING TEMPERATURE T E [ c] Fig. 6. W Vs T E for Tc=55 c EVAPORATING TEMPERATURE T E [ c] Fig. 7. COP Vs T E for Tc=55 c Fig. 6 shows the compressor work of and its alternative refrigerants for various evaporating temperatures for T C =55 c. As shown in fig. 6, with decrease in evaporating temperature, compressor work increases. Lower compressor work is desirable for better overall system efficiency. The compressor work is highest for

7 Jignesh K. Vaghela / Energy Procedia 109 ( 2017 ) and the lowest for for the entire range of T E in this study. Compared to, has higher while has lower compressor work respectively. Fig. 7 shows the COP of and its alternative refrigerants for various evaporating temperatures for T C =55 c. As shown in fig. 7, with decrease in evaporating temperature, COP decreases. Higher COP is always desirable parameter for refrigerants. The COP is highest for and the lowest for for the entire range of T E in this study. Compared to, has higher while has lower COP respectively Thermodynamic cycle analysis Results relative to : The summary of the derived thermodynamic data for all mentioned alternative refrigerants is presented in Table 3. The data have been derived by taking as a basic refrigerant. Table. 3. Summary of Thermodynamic cycle analysis Evaporating temperature=7.2 c, Condenser temperature= 55 c, compressor inlet temperature=35 c REFRIGERANT %COP RELATIVE TO COP Refrigerating effect, RE (kj/kg) Pressure ratio Compressor Work, W (kw) Discharge temp. T 2n ( c) and (Hydrocarbons): has about 2.4% lower COP but has 17.9% lower pressure ratio compared to. Hence compressor efficiency is higher. Discharge temperature is about 2.1% lower. Main advantage of is having low GWP i.e. 11.Main disadvantage is that it falls in A3 safety class. Flammability of is very high but it can be used if safety aspects are addressed and diminished. has about 3% higher COP and has 4.2% lower pressure ratio compared to. Hence compressor efficiency is higher. Discharge temperature is about 12% lower. Main advantage of is having low GWP i.e. 3 only. Main disadvantages are that it falls in A3 safety class and requires higher SCD hence larger capacity of compressor is required. It is also highly flammable but can be used if safety aspects of using are addressed and diminished., and (Zeotropic mixtures):, and have about 7.8%, 11.9% and 14.7% lower COP compared to respectively. They have about 2.7%, 12.9% and 13.7% lower pressure ratio compared to respectively. Hence compressor efficiency is higher. Discharge temperature is about 13.3% and 16.1% higher in case of and while it is 4% lower in case of. Main advantage of zeotropic mixtures are that they falls in A1 safety class. It is nonflammable refrigerants. Main disadvantages are that they are high discharge pressure refrigerants and hence pipelines connecting main components of AAC must be very reliable that can sustain high pressure. They have high GWP also. (Hydro Fluorocarbon): (1, 1-difluoroethane) can be possible substitute of if safety measures are provided. Refrigerating effect is 64.8% higher while compressor work is 3.9% lower compared to. Discharge temperature is 13.2% is

8 160 Jignesh K. Vaghela / Energy Procedia 109 ( 2017 ) higher but COP is 4.1% higher compared to. Pressure ratio is almost similar to that of. Main advantages of refrigerant are that it has low GWP and higher COP compared to. Main disadvantage are that it is flammable refrigerant and discharge temperature is higher than. (HydroFlouroOlefin): (2, 3, 3, 3-Tetrafluoropropene) is new categorical HFO refrigerant. Discharge temperature is lowest among the above all refrigerants that is 16% lower compared. has lower COP of about 6.3% compared to. Pressure ratio is 7.4% lower compared to. Main advantages of 1234yf refrigerant are that it has very low GWP (i.e. 4) compared to (i.e GWP) and has lowest discharge temperature. Also it can be substitute in the existing AAC system without any modification since SCD is close to. Main disadvantage is that; Since is just newly launched; its price is high in commercial market. 5. Conclusions Thermodynamic properties of different alternative refrigerants i.e.,,,,, and are compared to which is used in AAC system. and cannot be substituted in AAC system due to high flammability issue. From thermodynamic property analysis it is clear that, and having very high saturation pressure so it cannot be used in current AAC system. can be substituted of if and only if safety mitigations are provided. From thermodynamic cycle analysis, it is derived that has 6.3% lower COP compared to ; however it is best suitable alternative refrigerants as a drop in substitute of AAC system because it has very low GWP and can be substituted in the existing AAC system with minimum modification. This study is useful to design engineers of AAC system for future aspect. Acknowledgments The author would like to thank Dr. Ragesh G. Kapadia, Principal, SVMIT, Bharuch, Gujarat, India for their valuable input during the course of this investigation. The author would also like to thank Mr. Chintan Lad, AP, S.S. Agrawal College, Navsari; Mr. Harshit Trivedi, AP, ITM Universe, Vadodara; Mr. Ravi Parekh, Lecturer, KJP, Bharuch and Mr. Dhaval Prajapati, Engineer, IPR, Ahmedabad for their help in this study. References [1] S.Y. Yoo, D.W. Lee, Experimental Study On Performance Of Automotive Air Conditioning System Using R-152a Refrigerant, International Journal of Automotive Technology, Vol. 10, No. 3, p [2] Alpaslan Alkan, Murat Hosoz, Comparative performance of an automotive air conditioning system using fixed and variable capacity compressors, International Journal of Refrigeration 33, p [3] J. Steven Brown,Samuel F. Yana-Motta, Piotr A. Domanski, Comparative analysis of an automotive air conditioning systems operating with CO 2 and, International Journal of Refrigeration 25, p [4] S. Devotta, A.V. Waghmare, N.N. Sawant, B.M. Domkundwar, Alternatives to HCFC-22 for air conditioners, Applied Thermal Engineering 21, p [5] Ghodbane M., An Investigation of and Hydrocarbon Refrigerants in Mobile Air Conditioning, SAE International, SAE technical paper series, [6] Pamela Reasor,Vikrant Aute,Reinhard Radermacher, Refrigerant Performance Comparison Investigation, International Refrigeration and Air Conditioning Conference, School of Mechanical Engineering, Purdue University, Purdue e-pubs. [7] B. Takabi, H. Shokouhmand, Effects of Al2O3-Cu/water hybrid nanofluid on heat transfer and flow characteristics in turbulent regime, International Journal of Modern Physics C; Vol. 26, No. 4, [8] B. Takabi, S. Salehi, Augmentation of the Heat Transfer Performance of a Sinusoidal Corrugated Enclosure by Employing Hybrid Nanofluid, Advances in Mechanical Engineering, Vol. 6, [9] Kakaç, S., A. Pramuanjaroenkij, Analysis of Convective Heat Transfer Enhancement by Nanofluids: Single-Phase and Two- Phase Treatments, Journal of Engineering Physics and Thermophysics, Vol. 89, No. 3, p [10] 10.pdf