Experimental the same as refrigeration units.Refrigeration has

Experimental assessment of R134a and its lower GWP alternativesR152a &R290                                                                           Pancham Sahu                                     M-Tech Scholar                              Email- ID:  [email protected] of Mechanical Engineering, TIT, Bhopal                    Prof.

Dr. Rupesh Goyal               Email-ID: [email protected] of Mechanical Engineering, TIT, Bhopal  AbstractR134a (1,1,1,2-tetrafluoroethane) has been used in domestic as well as commercial purpose in many vapor compression refrigeration system. It has zero ozone depleting potential but high global warming potential of 1301. Due to its high global warming potential it needs to phase out from vapor compression refrigeration cycle application.

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The EU regulation would take effect from January 1,2015. The regulation implies an HFCs phase-out from 2015 to 2030 by means of bans on high GWP refrigerants. Especially R134a is under pressure and likely to be phased out of all commercial systems. The widely used R134a in the refrigeration and air conditioning fields need to identify new alternative of low GWP. Accordingly, in this work two low-GWP refrigerants tests in same system design for R134a under same operating conditions.

The refrigerants used in this work are R134a (HFCs), R152a (HFCs) and R290 (HCs). All of them test on same refrigeration test facility without any changes, that is direct drop-ins.the results obtained from the experimental tests are presented and details analyzed in the work from energetic point of view..IntroductionRefrigeration may be a method of moving heat from one location to a different. The work of warmth transport is historically driven by mechanical work, however may also be driven by heat, magnetism, electricity, laser, or alternative suggests that. Refrigeration have many house hold , commercial freezers, cryogenics and air con. applications.

Heat pumps could use the warmth output of the refrigeration method, and conjointly is also designed to be reversible, however are otherwise the same as refrigeration units.Refrigeration has had an outsized impact on business, lifestyle, agriculture and settlement patterns. The thought of protective food dates back to the traditional Roman and Chinese empires. However, refrigeration technology has speedily evolved within the last century,Vapour compression coolingA vapour compression cooling uses a refrigerant sealed in associate airtight and leak proof mechanism. The refrigerant is circulated through the system and it undergoes a no of changes in its state whereas passing through varied elements of the system. Every such modification within the state of vapor is termed a method.

The method of repetition of the same order of operation is termed a cycle.               The compression cycle is given this name as a result of it’s the compression of the refrigerant by the mechanical device which allows transfer of warmth energy. The refrigerant absorbs that from one place and releases it to a different place.Due to great contribution in climate change HFCs were included in green house gas basket by Kyoto protocol (UN1997). HFCs refrigerant R404A, R134a and R410A fluid were widely used in many system like air conditioning and refrigeration system. In developed and developing country, the most common refrigerant used is R134a in many system in medium temperature range besides phase out R12 and R22.

             In EU regulation no 517/2014 (the European parliament and council of European Union,2014) established the phase ut of higher  GWP refrigerants used in different application. As this R134a is banned in domestic refrigeration  since publishing of this regulation act and will be phase out in all application till 2022, and hence for  this refrigerant it is mandatory to found an alternative refrigerant. For those application where it still in used, low GWP alternatives (McLinden et al,2014) should be prioritized to prevent impact on environment, consequences of climate change (velders e al,2015).          Mota babilani et al,2017 perform the experimental assessment of R513A (mixture of R134a and R1234yf in 44/56 by weight) as alternative of R134a and R513A has GWP 573 and results shows  an increase of 5% cop while power consumption also increases.        Jignesh k vaghela et al 2016, evaluate the thermodynamic property of R290,R600a, R407C, R410A, R404A, R152a and R1234yf on automobile air conditioning compared to R134a with the help of engineering of equation solver and REFPROP software.

Cabello et al,2015 presented an experimental comparison on test bench which result an increase of 13% COP with decrease in cooling capacity of about 10% with respect to R134a B.O. Bolaji state the method  of selecting environmental-friendly refrigerants that have zero ozone depletion potential (ODP) and low global warming potential (GWP).

Nowadays R152a, R143a, R134a and R125 from ethane derivatives are the main refrigerants that are nontoxic, having low flammability, which are in use of most application. These refrigerants must theoretical and experimentally analyzed  to investigate their performance in the system.Samira Benhadid-Dib and Ahmed Benzaoui, have showed that the uses of halogenated refrigerants are harmful for environment and the use of “natural” refrigerants become a possible solution.

Here natural refrigerants are used as an alternative solution to replace halogenated refrigerants. The solution to the environmental impacts of refrigerant gases by a gas which contains no chlorine no fluorine and does not reject any CO2 emissions in the atmosphere. The researchers showed that emissions have bad effects on our environment. They also concerned by a contribution to the reduction of greenhouse gases and by the replacement of the polluting cooling fluids (HCFC). Mao-Gang He, Tie-Chen Li, Zhi-Gang Liu and Ying Zhang , have analyzed that the R152a/R125 mixture in the composition of 0.

85 mass fraction of R152a has a similar refrigeration performance with the existing refrigerant R12.K. Mani and V. Selladurai, have analyzed a vapour compression refrigeration system with the new R290/R600a refrigerant mixture as drop-in replacement was conducted and compared with R12 and R134a. The VCRS was initially designed to operate with R12.

The results showed that the refrigerant R134a showed slightly lower COP than R12. The discharge temperature and discharge pressure of the R290/R600a mixture was very close to R12. The R290/R600a (68/32 by wt %) mixture can be considered as a drop-in replacement refrigerant for R12 and R134a. Minxia Li, Chaobin Dang and EijiHihara, have investigated that Hfo1234yf has been proposed for mobile air-conditioners due to its low GWP and performance comparable to that of R134a. However, its performance is inferior to that of R410a.

This makes it difficult to be applied to residential air-conditioners. In order to apply the low GWP refrigerant to residential air-conditioners, refrigerant mixtures of Hfo1234yf and R32 are proposed. The hydro-fluoro olefins from last decade come into existence as environmental friendly alternative of refrigerants. The R1234yf and R1234ze(E) mostly  implemented in many application having their GWP is equal or below unity (Sethi et al., 2016). HFOs fluids issues low flammability or insufficient cooling capacity related to their use in existing system of R134a (Mota-babiloni et al,2014).Main characteristics of R134a, R152a and R290R134a is used most of HVAC application but according to EU   it must phase out from all application and system designed for R134a no more in use so it is compulsory to find an alternatives which can directly used in place of current refrigerants. To meet  Montreal protocol many HCs ,HFO, And some of HFCs having lesser GWP and zero ODP refrigerants should be used in all application of air conditioning.

  R152a is another also HFCs refrigerant, it has an GWP of about 137 for 100 year. It is nontoxic and slightly flammable than R134a but it can easily flame tested for leakage testing. the safety is measure concern because inhalation of R152a very much harmful for human being health.  The NBP temperature of R152a is near about of R134a so it not affect the system.      R290 is an HCs refrigerant which has negligible GWP about 3 over 100yrs and zero ODP. It is highly flammable and non toxic refrigerant so required more safety in operation.

          According to thermo-physical property of refrigerant R152a and R290 shows higher liquid thermal conductivity, specific heat, latent heat and lower density. Hence theoretically these refrigerants produce more refrigerating effect while these shows lower mass flow rate.  Table 1 Characteristics of R134a, R152a .NO. Properties R1 R2 R31 Refrigerant R134a R152a R2902 Chemical formula C2H2F4 C2H2F2 C3H83 Composition Pure Pure Pure4 ASHRAE Safety classification A1 A2 A35 ODP 0 0 06 GWP 100yr  (ASHRAE ) 1301 137 37 Molecular weight 102.06 66.

05 44.18 Critical temperature (0C) 101.1 113.26 96.749 Critical pressure (MPa) 4.

059 4.517 4.25110 NBP (0C) -26.4 -24.02 -42.

1111 Liquid density  (kg/m3) 1295.3 960 52912 Vapor density (kg/m3) 14.35 6.858 4.06013 Liquid Cp (kj/kg.k) 1.

341 1.697 2.50614 Vapor Cp (kj/kg.k) 0.897 1.012 1.63515 Latent heat (?) at NBP (KJ/kg) 198.6 307.

11 374.816 HOC (MJ/kg) 4.2 16.5 50.

417 Liquid thermal conductivity (W/m.0C) 92.08 109 105.

518 Vapor thermal conductivity (W/m.0C) 11.50 11.75 15.17 Experimental procedures Experimental setup To perform the experimental comparison between R134a, R152a and R290 a fully instrumented vapor compression refrigeration system was used (fig 1). The components used in system are shown in a schematic view (fig2). It is composed of  many components and measuring device for temperature, pressure measurement and mass flow rate.

The oil was used for R152a and R290 is also same as R134ai.e. POE as compatibility information presented by the compressor manufacturer for R290 and R134a (Embraco,2007), for R152a (Uemura et al 1992) and also for hydrocarbon R290 by Tecumesh (2010).  The system is composed of mainly four part common to every vapor compression system- A full hermetic centrifugal compressor designed for R134a. the motor running at 50 Hz (approximately 2900 rpm) the oil used in compressor is POE and is ensured return to compressor by the oil separator. The air cooled condenser and evaporator are coil tube type and heat rejection/ extraction is directly with contact.

   An Rota meter designed for R134a is used  in system which measure the mass flow rate. An R134a thermal expansion valve (TXV) with an electronic solenoid switch, this switch also controller allow the p-h diagram to be updated in same order to maintain similar superheating in evaporator. An oil receiver at outlet of condenser with a by pass connections to compressor for returning of oil to compressor.

     Fig.1: schematic diagram of vapor compression refrigeration system Measurement The measuring instruments of the system are describe in following: Temperature is measured at each inlet and outlet of main component with thermocouple thermometer and reading is notedwith uncertainty of + 0.10%. Pressure is also measured at each inlet outlet of main component by pressure transducer   of dial type with uncertainty + 0.10%. Power consumption of system is measured with help of wattmeter connected in electrical circuit of system.

  Mass flow rate is directly measured with Rota meter connected in flow of system after drier as shown in figure.       Finally all data are collected in tabular form for each main component. In this system is assumed isolated to environment and minimum loss to environment.             Tests conditions The performed tests are simulate the operating condition of small refrigerating system.

Two evaporating and three condensing temperatures were established for each of refrigerant tested. When alternative of refrigerants are introduced in system an retrofit adjustment done for system by thermal expansion valve. For each of condition an average value of temperature and pressure is note down over one hour.EquationsAfter reading we first calculate the cooling capacity by eq.(1).  The enthalpy at inlet and outlet of evaporator is calculated using REFPROP Software (lemmon et al, 2013) and temperature and pressure measurement. The mass flow rate is directly measured from system by Rota meter.(Q ?_evap ) ?=(m ?_ref ) ?  ?(h_out-h_in)?_evp        (1)                     The  cooling capacity is validated by a power meter that registers the electrical power consumed by the heater.

  Then the Cop of the refrigeration system is calculated by using COP formula as given in eq.(2).COP= Q ?_evap/P_comp                   (2)  Table 2:  Test value of R134a                                          Experinment value for R134acompressor condenser expansion device evaporator m Q Pcomp COPPsuc Tsuc Pdis Tdis Po Ti To Tc Pexp Texp Pevi Pevo Tev Tevo kg/h watt watt  1.9 8.5 6.6 72.5 6.6 61 21 25 6.

75 22.5 2 1.92 -10 0.8 13 616 294 2.12 8.2 8.8 77.4 8.

8 65 31 35 8.9 29.5 2.1 2 -10 2 13 589 315.7 1.91.9 9.2 11 85 11 72 40 45 11.

6 35.5 2.1 1.

98 -10 1.7 12 521 335 1.62.8 15 6.7 68.9 6.

7 61 21 25 6.65 21.5 2.9 2.8 0 13 21 1034 350 32.9 15 8.

9 76 8.8 67 31 35 9 29 3 2.95 0.

6 14 20 960 385 2.52.8 14 12 83 12 73 41 45 12 36 3 2.

9 0.2 13 20 863 415 2.1Table 3:  test value of R152aexperinment result value for R152acompressor condenser expansion device evaporator m Q Pcomp COPPsuc Tsuc Pdis Tdis Po Ti To Tc Pexp Texp Pevi Pevo Tev Tevo kg/h watt watt  1.8 11 6 76.9 6 62 23 25 6.

2 24.5 1.8 1.8 -10 1.7 8 598 275 2.

21.8 10 7.9 82 8 66 32 35 8.17 29.5 1.9 1.

82 -9 1.7 7.9 572 292 21.8 12 10 90.

5 10 71 42 45 10.6 35.4 1.8 1.78 -10 2.1 7.

2 500 312 1.62.5 14 6 73 5.9 63 23 25 6 23.8 2.6 2.

56 0.2 10 12 945 312 32.5 14 8 81.

5 8 69 33 35 8.3 31 2.7 2.6 0.2 9.5 12 865 340 2.52.6 14 10 88 10 74 43 45 10.

5 37.6 2.7 2.6 0 9.9 11 789 370 2.

1Table 4: test value of R290                    experinment result value for R290compressor condenser expansion device evaporator m Q Pcomp COPPsuc Tsuc Pdis Tdis Po Ti To Tc Pexp Texp Pevi Pevo Tev Tevo kg/h watt watt  3.4 1.8 9.

6 62.8 9.5 56 23 25 9.75 22.7 3.6 3.45 -10 -4.1 12 1038 401 2.

63.4 2 12 74.2 12 65 34 35 12.4 33.2 3.6 3.45 -10 -3.

4 11 898 439 2.13.4 2 15 83.5 15 73 43 45 15.

6 41.9 3.5 3.45 -10 -3.

7 11 771 485 1.64.7 5.3 9.7 59.

2 9.6 55 22 25 9.7 23.2 4.8 4.

73 0.2 5.6 17 1516 443 3.44.7 11 12 69.5 12 63 33 35 12.

4 32.5 4.9 4.75 0.3 6.9 16 1359 502 2.74.

7 9.5 15 77.7 15 70 41 45 15.5 39.9 4.8 4.75 0.

1 5.8 16 1201 560 2.1 Results and discussion This section presents and discuss the used parameter to analyze the behavior of the lower GWP alternatives to R134a,R152a and R290.the main parameters are mass flow rate, cooling capacity, COP and discharge temperature of compressor.

These parameters are presented against three condensing temperature at two constant evaporator temperature. The ambient temperature assume equal to room temperature. The relative value with respect to R134a can be calculated by eq.(3).

%X=((X_ref-X_R134a)/X_R134a ).100                     (3)Where X is varying parameter. Tc Tevp ?m ?_ref(%) ?Pcomp(%) ?Tdis (K) ?Q ?_ev (%) ?COP (%)0C 0C R152a R290 R152a R290 R152 R290 R152a R290 R152a R29025 -10 -38.46 -8.46 -6.46 36.39 4.

4 -9.7 -2.92 68.

50 2.84 22.7435 -39.69 -13.74 -7.

50 39.05 4.6 -3.2 -2.

88 52.46 4.84 10.2145 -41.46 -13.

0 -6.86 44.77 5.5 -1.5 -4.03 47.

98 3.22 2.5825 0.2 -40.00 -17.56 -10.85 26.57 4.

1 -9.7 -8.60 46.60 2.36 15.

5435 -41.37 -19.7 -11.

68 30.38 5.5 -6.5 -9.89 41.56 2.

00 8.8345 -42.05 -20.0 10.85 34.93 5.0 -5.

3 -8.57 39.16 2.40 12.

50 Table 5: Difference of different property analysis with respect to R134a Refrigerants Mass flow rateThe refrigerant mass flow rate is a parameter that is directly measured by device installed in the refrigeration facility. This parameter depends upon many variables in accordance with eq. (4). m ?_ref= (?_(v.) V ?_G)/v_compi =(?_(v.) V_(G ).N)/(v_compi.60)                 (4)  The geometrical volume (VG) only depends upon geometry of compressor: stroke, bore number of rotation.

According to data given by compressor manufacture the volumetric capacity of 15.4 cc and approx.2850rpm at 50Hz electrical frequency.

From table 1 it is clear that vapor density of R152a and R290 is smaller than R134a, therefore by theoretical point of view mass flow rate is smaller for these refrigerant expected as in fig.2 represent the mass flow rate for all three refrigerant at different operating conditions.  Thus, taking into account what is shown in fig experimental results confirm the lower mass flow rate of R152a and R290. The difference with respect to R134a is greater for R152a and smaller difference for R290.These results also corresponds to specific volume difference since for lower density specific volume is high so it driven lower mass flow rate by compressor (eq.4).

    Fig 2: Mref vs condensing temperature (Tc) (0C) Compressor power consumptionThe electrical power consumed by compressor is directly measured by wattmeter connected in power circuit of system. Also power consumption of compressor depends on mass flow rate (mref), the isentropic specific compressor work (Ws) and global efficiency (?G) as shown in equation (5).P_comp=(m ?_ref.W_s)/?_G                       (5)     Fig 3 : Pcomp v/s condensing temperature (Tc) (0C) At constant evaporating temperature The results obtained from test are presented in figure which shows higher power is consumed by R290 (up to (26.57 to 44.7)% more and while R152a consumed less power up to (6.

46 to11.68)% with reference to R134a, calculated by eq.3. this behavior corresponds to the variability registered in mass flow rate, where specific compressor works and ?G also change the trends.

The global efficiency is a complex variable associated to compressor efficiencies; mechanical efficiency, electrical efficiency and isentropic efficiency(Da Riva and Del col.2011;sanchez et al,2010). It established relationship which shows minimum power consumed by compressor to compress the refrigerants at given conditions.  This also concludes that for above variation one may be cause of compressor design for specific refrigerant.Discharge temperature The discharge temperature is parameter that especially affected by compressor design, inlet condition and refrigeration system used for compressor. The hermetic compressor is used with coaxial motor in system.

Figure shows that variation in discharge temperature for all refrigerant tested. As depicted from figure R152a represent an increase of up to 5.5K in temperature while R290 shows an decrease of temperature up to 10K.

  this also not measured effect to all other values in operation of system.    Fig 4: Tdis v/s Tc at constant evaporating temperature Cooling capacity Cooling capacity is obtained as product of mass flow rate driven by compressor and specific cooling capacity defined by evaporating temperature and inlet/outlet conditions as in eq.1.As for compressor all conditions are same for all three refrigerants and the volumetric refrigerating effect depends on specific cooling capacity and specific volume at the compressor inlet. From result presented in figure it is clear that cooling capacity of R290 is high ~68.5% than R134a and for R152a is lower (~9.89%) than R134a.

But this highly increase of cooling capacity means that the higher volume swept by compressor and as it also consumed more power for R290 than R134a. R152a can be used direct drop in a refrigeration system facility designed for R134a because of similar power consumption and small drop in cooling capacity.Coefficient of performanceThe COP of refrigeration system is defined as the ratio of  the cooling capacity and power consumed by the system. In accordance of eq.2 COP obtained for each condition is shown in figure and in table. Considering the experimental presented in table it can be say that use of R152a or R290 in the place of R134a improve the COP of the system what may be conditions.

For R152a the improvement level ranges between 2.0% to 4.8% while for R290 it swings more from 2.58% to 22.74% (low improvement is obtained when compression ratio is high).     Fig 5: Qevp  v/s Tc at constant evaporating temperature   Fig 6: COP v/s Tc (0C) at constant evaporating temperature Conclusion  The R134a in future in most of application must be not used due high GWP.

In this work an experimental analysis of two refrigerant having lower GWP done on same refrigerating system and same conditions of operation designed for R134a. the refrigerants used to perform in this analysis are R152a(HFCs) and R290 (HCs) with reference to R134a and they were direct drop-ins without any special change in system facility. All tests were carried out by considering same operating condition that includes two evaporating temperature and three condensing temperature (25, 35&450C).  Based on tests different thermo-physical property discuss and following conclusion were drawn for refrigerants. The hydro-fluorocarbon R152a presents an average reduction in cooling capacity and in power consumption by compressor designed for R134a on an average by 6.14% and 6.02% respectively. These of two mostly equal however an increase in COP about 2.

00% to 4.84 % registered. Accordingly, this is direct drop-ins suitable for this facility to R134a taking into account of safety requirement. The hydrocarbon R290 (propane) obtains the best performance in terms of cooling capacity and COP, an increase of about 49.37% and 12.

06 % respectively  on average.  However it requires more power up to 44.77%, which reveals that an use of electrical motor larger than the R134a used. So it is not suitable for direct drop-ins alternative for R134a facility.

    

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