Replacing harmful refrigerant R22 in a bulk milk cooler

51 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) ISSN: 0974- 6846 Replacing harmful refrigerant R22 in a bulk milk cooler *Alka Bani Agrawal, R.K. Dave and Vipin Shrivastava Dept of Mech Engg., Univ. Instt. of Tech.,RGPV, Bhopal, India [email protected] Abstract: Many milk coolers are presently using village level co-operatives with .241 million farmer refrigerant R22 which has substantial ozone depleting members. It has collection units all over M.P with potential along with high global warming potential. As per capacities ranging from 1000 to 20000 liters per day the commitment of Montreal and Kyoto protocol, R22 is (LPD) where milk is chilled to 4°c with the help of Milk required to be replaced by a suitable eco-friendly chillers before dispatching it daily in insulated tanks to big refrigerant and this paper explores the various options plants for processing. MPSDCF has total milk-chilling available. First the performance of 13 eco-friendly capacity of 448000 LPD and after processing, markets its refrigerants was compared by simulating their milk and milk products under the trade name of ‘Sanchi’. performance with the help of CYCLE D. Then detailed Milk Coolers, using HCFC22 as refrigerant, contribute study of binary and ternary mixture refrigerants has been 17.5 % of its total milk chilling capacity. done for selecting a Retrofit mixture for use in place of At present HCFC22 is the most widely used R22 in the existing milk cooler. Elucidating the refrigerant in the world both for refrigeration and airperformance,ODP and GWP values of refrigerants, it is conditioning. Although HCFC's are considered to be only clear that R1270 is best choice for replacing R22 with 5% ozone depleting refrigerant but as they contain zero ODP and negligible GWP. Out of four mixtures, chlorine giving it the potential to damage the ozone and R32/R152 is best with zero ODP and low GWP. therefore has been targeted since the 1990's for eventual Keywords: Refrigerant, CFC22, Retrofitting, milk cooler. phase out by the Montreal Protocol, an international Introduction treaty signed under the UNEP for control of substances Refrigeration plays a very vital role in dairy industry damaging the protective Ozone Layer of the Earth as milk and milk products are highly susceptible to (Agrawal, 2001). bacteria growth in very short time. Fresh milk does not In October 2000, EC Regulation no. 2037/2000 was form any bacteria for the first 40 minutes, after that brought into force as the last step in eliminating ozonebacterium multiplies every 20 minutes in unprocessed depleting substances (ODSs) as per the Montreal milk. So the quality of collected milk is preserved by Protocol. This binding regulation is the legislative cooling it as quickly as possible to below 4 °C at milk instrument used by the European Union to phase-out collection centers with the help of Milk Coolers before ozone depleting substances and stipulates that the use dispatching it daily in insulated tanks to big plant for and sale of virgin hydro chlorofluorocarbons (HCFCs) will be banned from 1 January 2010. HCFCs (most commonly further processing. Production of milk in India is very widely scattered in in the form of R-22) are used in a variety of refrigeration the rural areas and at vast distances from the places of and air conditioning installations (both stationary and high consumption in the urban areas. Dairy Farming as mobile commercial refrigeration, cold and freezing stores. In 2007 and 2008, the U.S. Environmental Protection such is not a professional occupation but part of the over all agriculture operation. The hygienic conditions and Agency (EPA) published an industry model of the environment of milk production in the rural area are still expected HCFC market size and the related demand for not up the desired standards. High ambient temperature R-22. Based on the market demand model , EPA too throughout the year in a tropical country like India is an proposed rules for meeting the 2010 phase-down called additional disadvantage since the bacterial growth is very for by the Montreal Protocol of R-22 and other HCFC rapid if the temp of milk is not brought down immediately refrigerants. The first rule regards the 2010 allocation of after the production. It is very essential to cool the milk production and import rights of R-22. The second immediately after milking to maintain the quality of milk as proposal is on the ban on production, import, and sale of final transporting to processing plant may take 8 hours or R-22 in new equipment post January 1st, 2010. These more from the time of milking. In fact the chilling of milk at rules regarding the phase out of R-22 refrigerant gas will or near the production centers is the most important become effective January 1st, 2010. India became a party to the Montreal Protocol in 1993 factor which has influenced the growth of milk industry. The chilling of milk to about 4 °C or less is done to check and has since made significant progress in decreasing its the growth of bacteria and preserve the quality as dependence on CFC. Additionally, India must also begin produced, until it is subjected to pasteurization process. to take steps to decrease its dependence on HCFCs. This is done at collection centers using Instant Milk According to an accelerated HCFC phase out schedule, developing countries must begin to reduce their use of Chilling Units and Bulk Milk Coolers. Madhya Pradesh (M.P.) is one of the biggest states of HCFCs from the baseline consumption-set at the average India of more than 10 million people. M.P. State Dairy Co- of 2009 and 2010 consumption (Singhal, 2008). operative Federation (MPSDCF) is the apex body of 5 Therefore search for alternatives for this important milk unions of the state which collect milk from 4522 refrigerant is a very important area of research. Even Research article Indian Society for Education and Environment (iSee) “Refrigerant” http://www.indjst.org Agrawal et al. Indian J.Sci.Technol. 52 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) ISSN: 0974- 6846 flammable refrigerants set out in the joint Australia-NZ standards for safe use of refrigerants. In Indonesia, number of milk cooling units have been retrofitted by Hydrocarbon refrigerants after the research work done in the Bandung Institute of Technology (Pasek et al., 1990). In this research, a milk cooling unit designed for R22 was directly switched to propane/butane refrigerants (propane/isobutane and propane/ n-butane). It was found that propane/n-butane refrigerant is the most efficient followed by propane/iso-butane and R22 refrigerant. Criteria for selection of retrofit refrigerant An integrated approach that includes economic, performance and safety criteria will be required while finding a solution to the problem of phase out of harmful refrigerants in a developing country like India as milk is one of the basic necessities of life. Either purchase or replacement or major modification of existing equipment will add on to the cost of the milk. Hence it is a must that existing equipment with useful life in it remain in operation. Retrofitting i.e. changing over of current refrigerant by suitable alternative is the most effective solution in India. This will require a selection of a drop-in substitute as a replacement to R-22. In principle a drop in alternative should fulfill the following criteria: • The new refrigerant should have zero or very small ozone depleting potential along with minimum global warming potential. • Any drop in substitute should have the same volumetric refrigeration capacity as of R-22 in the milk chiller to use the same compressor (Jung et al.,1999) • The cooling unit should have matching or better coefficient of performance (C.O.P.) with the alternative refrigerant. • The new refrigerant should be compatible with the material of construction and lubricant used in the compressor. • The toxicity and flammability potential should be evaluated carefully before selecting an Table 1.1. Thermodynamic & environmental properties of R22 & selected alternative. And if the refrigerant is refrigerant at the design conditions of bulk milk cooler flammable, all necessary safety Volu Specific V1 Refriger N.B.P metric measures and controls should be Hfg P.R. heat ODP GWP 3 ant Efficie (m /kg (°C) incorporated in the system. ratio ncy • If the alternative is a mixture, it should R142b -9.25 5.40 .781 .154 264.8 1.13 0.065 1600 have temperature glides less than 5 to R600a -11.61 4.94 .791 .244 443.8 1.09 0 3 7o C to avoid changes in composition R124 -11.96 5.41 .781 .0992 202 1.13 0.022 430 due to any leakage. R227ea -15.61 5.31 .785 .0653 167.2 1.13 0 2900 • Availability of the alternative refrigerant R152a -24.02 5.04 .797 .1250 374.6 1.134 0 140 with its cost will also be important factor R134a -26.07 5.09 .788 .0720 252.1 1.102 0.00015 1200 in selection of drop in alternative. R717 -38.94 5.38 .743 .3060 1443 1.31 0 0 Materials and methods R22 -48.81 4.37 .827 .0492 250.2 1.13 0.055 1500 after continuous research and development, no single refrigerant has been identified for replacing R22. Now Industry, with its need to meet various dead lines, has begun an intensive effort to adapt various mixtures to act as a long term working fluids in new equipment, and, when possible, as a drop in or retrofit alternative in existing equipment. Objective Harda Chilling Centre of Bhopal Dugdh Sangh has a Bulk Milk Cooler of 5000 litre per day capacity with a direct expansion vapour compression refrigeration system operating on refrigerant R22(HCFC22). In this paper, an exhaustive study has been undertaken to find a suitable eco-friendly refrigerant for replacing the harmful R22 so that milk cooler can be used for an extended time. The effort is to find a retrofit i.e. drop-in refrigerant which would replace R22 with minimum of cost and component change. Case studies Retrofitting of a milk silo refrigeration system operating on R22 has been done in New Zealand Dairy Research Institute, Palmerton North, New Zealand (Cleland & Keedwell, 1998). They have compared the performance of HCFC22 with hydrocarbon refrigerants from the Care range in a typical NZ milk silo refrigeration system under tightly controlled laboratory conditions. Energy efficiency increased by 5-8% for the hydrocarbon refrigerants trialed and there was minimal change in cooling capacity of the system if the hydrocarbon mixture is appropriately chosen. On farm trials were undertaken to confirm laboratory tests that showed the benefits of using hydrocarbons as drop in replacement to fluorocarbon refrigerants in milk silo refrigeration system (Keedwell & Cleland,1998). Only potential disadvantage of hydrocarbon refrigerant is its flammability. But milk silo refrigeration systems generally contain less than 5 kg of charge and most farm systems are located either outside or in well ventilated enclosures with restricted access. Therefore most farms would meet the criteria for use of R290 R143a R1270 R125 R32 -42.1 -47.22 -47.69 -48.14 -51.65 4.02 4.16 3.90 4.23 4.33 .842 .836 .848 .833 .829 .1000 .0383 .0844 .0248 .0479 Research article Indian Society for Education and Environment (iSee) 472.8 244.7 470.6 180.5 382.6 1.126 1.13 1.13 1.13 1.13 0 0 0 .00003 0 “Refrigerant” http://www.indjst.org 3 3800 3 2500 650 Technical detail of bulk milk cooler The Harda Chilling Center of Bhopal Dugdh Sangh has Installed Chilling Capacity of 5000 LPD of milk. It is a Bulk Milk Cooler with direct expansion cooling Agrawal et al. Indian J.Sci.Technol. 53 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) ISSN: 0974- 6846 Table 1.2. Performance parameters of selected eco-friendly refrigerants when used in bulk milk cooler for giving same cooling capacity condensing temperature (Alfa Lavel) and Charged with 14 kg of Freon22 Refrigera M P QK RE V.R.C. VRC/V DT which is injected by the expansion COP nt (kg/sec) (kW) (kW) (kJ/kg) (kJ/m3) RC12 (°C) valve in the evaporator. R142b .191 9.86 38.40 150.12 762.5 .328 76.0 2.90 For simulation of Bulk Milk Cooler, R600a .126 10.37 39.00 227.32 738.3 .318 63.3 2.76 the Copeland Compressor QR 90 input R124 .284 10.48 39.11 100.68 792.6 .341 66.4 2.73 values of Isentropic Efficiency value R227a .452 12.36 40.99 63.35 761.8 .328 55.0 2.32 .80, Compressor Volumetric Efficiency R152a .135 10.08 38.71 212.24 1357.8 .584 89.0 2.84 as calculated for selected refrigerant, R134a .232 10.77 39.40 123.60 1352.6 .582 75.2 2.66 Electrical Motor Efficiency of 1.0 and R717 .028 9.99 38.52 1009.36 2452.7 1.05 169.4 2.87 System Cooling Capacity of 28.64 kW R22 .207 10.62 39.25 138.41 2324.6 1.00 97.7 2.70 are used. These values are taken from R290 .125 11.10 39.76 229.82 1927.9 .829 74.0 2.58 the technical data of the condensing R143a .288 12.83 41.46 99.43 2168.0 .933 75.7 2.23 unit and in consultation with Design R1270 .121 11.53 39.76 236.60 2377.6 1.02 81.9 2.57 Engineer of the Alfa Lavel Agri (India) R125 .503 15.23 43.86 56.97 1915.1 .824 67.8 1.88 Limited, Pune. R32 .135 11.41 40.04 212.08 3672.5 1.54 118.4 2.51 Results system. The cooling unit of the bulk cooler is adequately Performance study of 13 alternative eco-friendly designed to cool milk from 35°C to 4° C according to ISO5708 norms. The compact condensing unit is simple, refrigerants was done using simulation programme easy to install and comprises of Reliable hermitic Cycle_D which is developed by NIST (National Institute of compressor Co-plant QR90 of 8TR capacity operating at Standard and Technology), Gaithersburg, USA and used extensively for selecting a suitable alternative refrigerant 0 °C evaporating temperature and 55 °C Table 1.3. Performance simulation of binary mixtures with equal volumetric refrigeration capacity of R22 in bulk milk cooler Refrigerant/ Mixture Ratio R22 R 32/ R142 .63/.37 R32/R152a .49/.51 R 32/ R 600a .55/.45 R 32/ R 124 .45/.55 M (kg/ sec) .207 P (kW) Qk (kW) 10.62 39.25 V1 (m3/k g) .0492 .134 10.67 39.30 .128 10.63 .139 .188 Te ( °C ) Te ( °C ) Pe (kPa) Pc (kPa) RE (kJ/kg) V.R.C 3 (kJ/ m ) D.T. ( °C ) P.R. COP 0 0 498.0 2175.1 138.41 2324.6 97.7 4.37 2.70 .0741 11.9 12.6 466.1 2288.6 213.80 2323.8 116.5 4.91 2.68 39.26 .0781 5.4 6.2 469.8 2254.5 223.10 2321.7 108.2 4.80 2.69 11.71 40.34 .0719 21.9 15.9 557.6 2557.4 205.94 2318.7 99.7 4.59 2.44 11.26 39.89 .0530 9.4 8.5 512.2 2455.8 152.28 2311.9 101.9 4.79 2.54 R 32/ R 134a .39/.59 .175 10.99 39.62 .0569 4.2 4.5 501.5 2406.1 163.79 2328.6 97.5 4.80 2.60 R 32/ R 143a .08/.92 .271 12.76 41.39 .0377 3.7 0.5 659.8 2749.6 105.77 2336.3 79.0 4.17 2.24 Table 1.4 - Performance of ternary mixtures with equal volumetric refrigeration capacity and higher C.O.P. and small temp glides in bulk milk cooler Refrigerant/ Mixture Ratio R22 R 32/R152a R600a .47/.35/.18 0 RE (kJ/k g) 138.41 V.R.C (kJ/ m3) 2324.6 5.8 6.5 202.65 506.2 2422.2 4.4 4.8 .0697 490.6 2341.1 6.1 39.31 .0752 481.0 2302.3 39.55 .0671 497.4 2330.7 39.25 V1 (m3/k g) .0492 11.07 39.70 .176 11.01 .140 M (kg/ sec) .207 P (kW) Qk (kW) 10.62 .141 D.T. ( °C ) P.R. COP 97.7 4.37 2.70 2336.4 97.5 4.58 2.59 162.90 2314.2 97.8 4.79 2.60 6.7 203.84 2344.3 107.1 4.77 2.66 5.4 6.4 218.32 2337.8 108.0 4.79 2.68 5.1 5.4 190.90 2335.1 99.8 4.69 2.62 Te ( °C ) Te ( °C ) 498.0 2175.1 0 .0699 525.7 2406.5 39.64 .0562 10.76 39.39 .131 10.68 .150 10.92 Pe (kPa) Pc (kPa) R 32/ R600a/R134a .40/.05/.55 R 32/ R 152a/ R 124 .050/.35/.15 R 32/ R152a/ R134a .50/.45/.05 R 32/ R 152a/ R 142a .35/.40/.25 Research article Indian Society for Education and Environment (iSee) “Refrigerant” http://www.indjst.org Agrawal et al. Indian J.Sci.Technol. 54 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) ISSN: 0974- 6846 Table 1.5. Selected retrofit refrigerant for replacing R22 in bulk milk cooler Refrigernt/ Mixture Ratio R22 R1270 R32/R152a .49/.51 R 32/ R 134a .39/.61 R 32/ R600a/R134a .40/.05/.55 R 32/ R152a/ R134a .50/.45/.05 ∆Te (°C ) ∆Tc (°C ) Pe (kPa) Pc (kPa) R.E. (kJ/kg) D.T. V.R.C (kJ/ m3) ( °C ) P.R. COP .0492 .0844 0 0 0 0 498.0 585.9 2175.1 2286.1 138.41 236.67 2324.6 2377.6 97.7 81.9 4.37 3.90 2.70 2.57 39.26 .0781 5.4 6.2 469.8 2254.5 223.10 2321.7 108.2 4.80 2.69 10.99 39.62 .0569 4.2 4.5 501.5 2406.1 163.79 2328.6 97.5 4.80 2.60 .176 11.01 39.64 .0562 4.4 4.8 506.2 2422.2 162.90 2314.2 97.8 4.79 2.60 .131 10.68 39.31 .0752 5.4 6.4 481.0 2302.3 218.32 2337.8 108.0 4.79 2.68 M (kg/sec) P (kW) (kW) Qk .207 .124 10.62 11.38 39.25 40.65 .128 10.63 .175 V1 (m3/kg) properties as compared to R22. It for a vapour compression refrigeration Table 1.6. Environmental properties has a very high latent heat along system. The possible alternate of selected retrofit refrigerant with high specific volume. refrigerants have been selected because G.W.P Refrigerant O.D.P Therefore the mass flow of their favorable environmental properties R22 0.055 1500 requirement is very small. Its and comparative assessment of their 3 0 R1270 performance is better than R22 properties at design condition of milk 390 0 R32/R152a system with COP of 2.76 with lower cooler have been given in Table 1.1 and (.49/.51) discharge temperature at Graph 1.1(a &b ). The performance 986 0 R32/R134a (.39/.61) compressor outlet due to low simulations have been done with different 710 0 R32/R152a/R134a specific heat ratio. This refrigerant refrigerant to obtain same cooling capacity (.50/.45/.05) works very well with the lubricant as with R22. The results of simulation, in 920 0 R32/R600a/R134a when it replaces R22. But because terms of mass flow of refrigerant (m), (.40/.05/.55) of it has high specific volume, power consumption (P), Heat rejected in condenser (Qk), Volumetric Refrigeration Capacity, R600a has a very small volumetric refrigeration capacity Refrigerating Effect (VRJ), Discharge Temperature at requiring 70% more compressor displacement as compressor outlet (Tc) and Co-efficient of Performance compared to R22. R124 is refrigerant with low (COP) of the Bulk Milk Cooler Graph 1.1 (a) – ODP values of R22 and selected pure refrigerants ODP and GWP value but with when alternative refrigerants are higher-pressure ratio and specific used in place of R22, are ODP volume as compared to R22 at presented in Table 1.2. Also operating condition of Bulk milk Comparisons of COP, Mass Flow cooler. Its operating pressures are rate, Discharge Temp. at lower than R22. The COP of the compressor outlet and requirement system with R124 is better than of Compressor displacement for R22. It has a quite low discharge R22 and selected refrigerants have temperature as compared to other been shown in Graph 1.2 (a) to refrigerants. It will require 65 % Graph 1.2(d). higher compressor displacement Discussion R142b has a higher pressure ratio and lower than R22. Therefore the milk cooler with R124 will need a operating pressures in the system but its performance much bigger compressor. R227ea is an HFC refrigerant with no ozone was best of all refrigerants with a very high COP of 2.90. depletion but considerable global warming potential. Its The discharge temperature at Graph 1.1 (b) – GWP values of R22 and pressure ratio and specific compressor out let is 76°C as selected pure refrigerants volume is higher than R22. compared to 97.7°C for R22. For the same cooling For the equal cooling capacity, GWP capacity the mass flow R142b system will require requirement is very high as approximately 70% larger compared to other displacement volume as refrigerants .It requires a 67 compared to R22. The R142b % larger compressor is compatible with the mineral displacement for giving oil used with R22 system. same cooling capacity. R600a is a natural R52a is an HFC occurring hydrocarbon with refrigerant with highly very favorable environmental Research article “Refrigerant” Agrawal et al. Indian Society for Education and Environment (iSee) http://www.indjst.org Indian J.Sci.Technol. 55 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) ISSN: 0974- 6846 favorable environmental parameter. It performed well with milk cooler. Its energy consumption is little higher than R22 resulting in lower COP of a very high COP of 2.84. Its 2.58 but it gives a very pressure ratio is higher than COP favorable discharge R22. As compared to other temperature. The drawback of refrigerants, its charge this refrigerant is its high requirement is very less. flammability which will requires R152a is compatible with Graph 1.2 (a) –COP values of R22 and extra safety measures for use mineral oil but it is slightly selected pure refrigerants in place of R22 which is non flammable which require flammable. extra safety measures R290 is freely available during operation. Another advantage is its lower discharge temperature than R22.For the same cooling capacity R152a requires 42% increased compressor displacement as compared to R22 compressor. R134a is one of the most well known members of the HFC family of refrigerants. It has similar physical and thermodynamic properties to R152a. It does not have ozone depleting potential but a substantial global warming potential. R134a has compatibility problem with mineral oil and requires change of lubricant when used in a R22 system. Also it has a small volumetric refrigeration capacity than R22 therefore requires 42% higher compressor displacement for producing the same cooling effect in the milk cooler. R22 is a HCFC refrigerant being used in Bulk milk cooler and is scheduled to be phased out in developing countries. It has a pressure ratio of 4.37 and specific volume of 0.0492. It gives COP of 2.70 and results in a high discharge temp of 97.7 °C. It is an easily available refrigerant with non-flammable property. R290 is a natural refrigerant with very favorable environmental and physical properties as a possible substitute to R22 with no ozone depletion or global warming impact. It has a high volumetric efficiency associated with a small charge requirement for performing the same cooling capacity in the Research article Indian Society for Education and Environment (iSee) Graph 1.2 (b) –Mass flow of R22 and selected pure refrigerants M (kg/sec) DT Graph 1.2 (c) –Discharge temp. of R22 and selected pure refrigerants Graph 1.2 (d) –Compressor volume of R22 and selected pure refrig. VRC/VRC12 Graph 1.3 (a) –Temp. glide of R22 and selected binary refrigerants o C “Refrigerant” http://www.indjst.org and comparatively of lower cost then other substitutes. The R290 system will be compatible with the mineral oil used as a lubricant in the milk cooler. This is very important from the point of view of retrofitting cost and acceptability. But it can not be used as a direct drop in refrigerant in milk chiller as it has lower volumetric refrigeration capacity than R22. An equivalent R290 system will require 18% larger compressor displacement for giving same cooling in the system. R143a is also a HFC family refrigerant but higher global warming potential than R32, R134a and R152a. It has higher pressure ratio than R22 with a higher volumetric efficiency at the designed conditions. It gives poor performance with COP of 2.23 as compared to 2.70 of R22. It also has a very high mass flow rate as compared to R22. The discharge temperature is very smaller resulting in cool operation. The operating pressures are again much higher for R143a needing extra precaution against leakage. R143a has very small volumetric refrigeration capacity difference for giving the same cooling effect in the milk chiller. The displacement required is only 7% more as compared to Agrawal et al. Indian J.Sci.Technol. 56 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) ISSN: 0974- 6846 2.70 of R22 refrigerant but R22 compressor displacement. gives a very high discharge R1270 is an unsaturated o temperature. This may require hydrocarbon with no ozone C extra cooling of compressor for depletion and a negligible smooth operation. The global warming potential. It is volumetric refrigeration the one of the two refrigerants Graph 1.3 (b) –Temp. glide of R22 and capacity is very high with R32. which gives a higher cooling selected binary refrigerants Therefore for the same cooling capacity like R32. Its COP is capacity, it will require 58% smaller at 2.57. It results in a smaller compressor low discharge temperature displacement as compared to than R22. Its charge R22. requirement is very low due to From the analysis of the its very high specific volume. results of simulation of pure R1270 has a high volumetric o refrigerants, it is clear that refrigeration capacity which is C refrigerant Propylene (R1270) just 2% more than R22 for giving has a very similar the same cooling capacity in the Graph 1.4 (a) –Temp. glide of R22 and thermodynamic property cooler. Therefore it is the best selected ternary refrigerants refrigerant that can be used in candidate which can be used in place of R22 in the Bulk Milk place of R22 as a possible Cooler. But the co-efficient of Retrofit refrigerant. The performance of R1270 is small operating pressures are on little as compared to R22 and higher side but can be used with therefore it will increase the other system components with consumption of power, which slight adjustment. will contribute, to the problem of R125 is a lower boiling Global Warming. R1270 is refrigerant of HFC category. very flammable (A3) also It has negligible ozone o C causing problem in using it depletion potential but has Graph 1.4 (b) –Temp. glide of R22 and without strict extra safety substantial global warming selected ternary refrigerants measures. The efforts potential of 2500. It has a should be in finding a high volumetric efficiency refrigerant which can due to smaller pressure increase the efficiency i e ratio. It also gives quite high COP of the system and with cooling capacity due to limited flammability which increased mass flow rate. It can be safely managed. The has the highest charge Graph 1.5 (a) –COP of R22 and selected solution could be in using a requirement of all the retrofit refrigerants mixture refrigerant refrigerants because of its CO consisting of any two or smallest specific volume. It three pure refrigerants, results in smaller discharge which will give an increased temperature at compressor performance in terms of outlet, which is preferable for COP and desired system safe operation. The system has compatibility in terms of a very small COP as compared flammability. to R22 due to large mass floe From the analysis it is resulting in higher power clear that there are consumption in compressor. refrigerants which give The biggest drawback is its low critical temperature which is very near to the condensing improved performance in terms of COP and they are also temp of 55°C .For the same cooling capacity, the R125 less flammable like R142b and R152a. But because of their lower volumetric refrigeration capacity, they can not system will require 18% large compressor displacement. R32 is a HFC refrigerant with zero ozone depletion be used in pure form in place of R22. But by combining it effect and very small global warming potential. It has with a higher volumetric refrigeration capacity, a small pressure ratio as compared to R22, which results refrigerant mixture can be prepared which can be an ideal into increased volumetric efficiency of the compressor. It Retrofit candidate to replace R22. R32 is a higher has a co-efficient of performance of 2.51 as compared to volumetric refrigeration capacity refrigerant, which can be Research article Indian Society for Education and Environment (iSee) “Refrigerant” http://www.indjst.org Agrawal et al. Indian J.Sci.Technol. 57 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) ISSN: 0974- 6846 combined with a higher performance, but lower cooling capacity of the milk chiller as compared to R32/R134a mixture. But both volumetric refrigeration capacity Graph 1.5 (b) –Mass flow of R22 and results in higher discharge refrigerant. The R142b, R152a, selected retrofit refrigerants temperature at the outlet of R124 and R600a are selected for condenser as compared to mixture study. R290, R143a and M R22. The R32/R152a mixture R 134a refrigerants have also suction pressure is slightly been selected for further study as smaller and R32/R134a mixture these have been associated with suction pressure is slightly mixture refrigerants being widely higher than R22 system. researched for finding a most From the study of binary suitable refrigerant mixture as an refrigerants, it is clear that all ideal replacement of R22. binary mixtures give lower The performance of Binary mixtures, combining R32 with R142b, R152a, R600a, C.O.P. values with a much higher discharge R124, R134a and R143a, has been studied by simulation temperatures at outlet of compressor. The ternary of the performance of Bulk Milk Cooler. The analysis of mixtures combination of selected mixture may give a R290/R32 binary mixture was not possible because their more efficient refrigerant, which can be used for replacing mixture had critical temperatures very near to the R22 in the Bulk Milk Cooler. The R32 has been combined condensing temp of the refrigeration cycle. The Binary with two lower volumetric refrigeration capacity fluids at a time to have 15 ternary combination of R1270 with combinations of the selected other refrigerants was not o refrigerants. The mixture possible as R1270 has a C ratios were altered to get a nearly equal volumetric combination with matching refrigeration capacity to R22 Graph 1.5 (c) –Temp glide of R22 and selected retrofit refrigerants volumetric refrigeration and therefore binary capacity of R22 in milk combinations give a pure cooler. 15 Ternary mixtures R1270 results. The with matching refrigeration simulations of binary capacity but with varying mixtures have been done for degree of temperature glides giving the same cooling capacity. The volumetric of 5°C to 13 °C were efficiency of the mixture refrigerants has been taken as identified and studied. Ternary mixtures give better the average of the constituent refrigerants. Table 1.3 results than binary mixtures with higher C.O.P. values. shows the Binary mixture results with equal Volumetric The C.O.P. of many mixtures is higher than C.O.P. of Refrigeration Capacity of R22 in the Bulk milk Cooler. pure possible refrigerant R1270 (with C.O.P. of 2.57). These mixtures can theoretically replace R22 in the Bulk Therefore all ternary mixtures with equal or higher C.O.P. milk cooler but none of the refrigerants give better result than 2.57 and with temp glides in the range 5°C to 7°C in terms of C.O.P. of the system as compared to R22. can be selected as possible retrofit ternary refrigerant and This proves the research results of last several years that have been given in Table 1.4 and Temp Glides variation it is very difficult to find a suitable eco-friendly alternative have been shown in Graph 1.4(a&b). for replacing R22 in the refrigeration application. From Out of the five ternary mixtures, refrigerants mixtures practical application point of view, high temp glide R32/R152a/R134a and R 32/ R600a/R134a give best mixtures should not be used in practical applications. This performance results with highest C.O.P. of 2.68 and 2.60 is necessary to avoid changes in the composition of the are selected to replace R22 in milk cooler. These mixtures due to unavoidable leakage in any system. The refrigerants require smaller charge as compared to R22 mixture of R32/R142b gives a temperature glides of because of their large refrigerating effect in the cycle. The 11.9°C and 12.6 °C respectively in evaporator and operating suction pressures in the system of the selected condenser and will not be suitable retrofit candidate. refrigerants are close to R22 suction pressure but Therefore only those mixtures with temperature glides in discharge pressures are at slightly higher sides. the range of 5°C to 7°C and with C.O.P higher than 2.57 Conclusion Now all the five Retrofit refrigerants have been are being selected as Retrofit refrigerant for replacing R22 and their comparative temp glides have been shown tabulated in Table 1.5 for their comparative assessment in Graph 1.3(a&b) Two binary mixtures namely of performance. Also comparison of their environmental, R32/R134a and R32/R152a mixtures are possible Retrofit thermo physical and safety properties is done (Table 1.6; refrigerant which can be practically used for replacing the Graph 1.5(a) to Graph1.5(e)) for achieving the objectives R22 in the refrigeration system of Bulk Milk Cooler. of the research. From the study of the ODP and GWP R32/R152a requires a smaller charge for giving the same values of refrigerants given in table, it is clear that R1270 Research article Indian Society for Education and Environment (iSee) “Refrigerant” http://www.indjst.org Agrawal et al. Indian J.Sci.Technol. 58 Indian Journal of Science and Technology Vol.2 No. 9 (Sep 2009) is best choice for replacing R22 with zero ODP and negligible GWP. Out of four mixtures R32/R152 mixture is best with zero ODP and low GWP. The Safety requirement of the refrigerants will be much more stringent as compared to R22 as all the five retrofit refrigerants are flammable. R1270 and R600a are highly flammable (A3), R134a is non-flammable (A1) and R32 and R152a are slightly flammable (A2). But all these are non toxic as R22 (Agrawal & Dave,1999). The oil compatibility of the selected Retrofit Refrigerants is very important factor and should be carefully considered. Propylene (R1270) and Isobutane (R600a) are hydrocarbon refrigerants and fully compatible with the mineral oil used with R22. But HFC refrigerants R32 and R134a are not compatible with mineral oil. But HFC refrigerant R152a gives good results with mineral oil also (McLindon & Didion, 1987). Therefore out of the five selected Retrofit refrigerants only R32/R134a binary refrigerant will require a change of lubricant used. All four other Retrofit refrigerants can be used in place of R22 without change of lubricant in the refrigeration system of Bulk Milk Cooler. The performance of the identified Retrofit refrigerants will be tested by following the Cooling Test Method given in International Standards ISO- 5708. Then the best performing refrigerant can be selected for replacing refrigerant R22 in the milk cooler. ISSN: 0974- 6846 3. Cleland J and Keedwell RW (1998) Use of HC refrigerants in on farm milk cooling equipment. AIRAH J. 52 (7)19-23. 4. Jung DS and Radermacher R (1991) Performance simulation of single evaporator domestic refrigerators charged with pure and mixed refrigerants. Intl. J. Refrigeration. 14 (3), 223- 231. 5. Keedwell RW and Cleland DJ (1998) Use of hydrocarbon refrigerants to replace HCFC22 in on farm milk cooling equipment. In: Proc. IRHACE Technical Conf., Nelson, NewZeland, April. pp:10-18. 6. McLindon MO and Didion DA (1987) Quest for alternatives. ASHRAE J. 29 (12), 32-36, 38, 40 & 42. 7. Pasek AD, Suwono A and Tandian HM (1999) Indonesian experience in retrofitting some milk coolers. In: Proc. Seminar on ODS phase out-Bali. Indonesia, May 5-7. pp: 124-134. 8. Singhal Kapil (2008) The R12 and R22 phase out in India: preparing for critical changes in the refrigerant landscape. Air-conditioning & Refrigeration J. 11 (4), 103-106. Graph 1.5 (e) –ODP & GWP of R22 and selected retrofit refrigerants o C Graph 1.5 (d) –Temp. glide of R22 and selected retrofit refrigerants Acknowledgement The research was carried out at Rajiv Gandhi Technical University, Bhopal in association with Bhopal Dugdh Centre, Habibganj of Madhya Pradesh State Dairy Co-operative Federation. Bhopal. The Authors wish to acknowledge the constant help and support given by the authorities of University and Madhya Pradesh State Dairy Co-operative Federation, Bhopal in successful outcome of the research. References 1. Agarwal Alka and Dave RK (1999) Alternatives to CFC: a discussion of options. In: 20th Intl. Conf. Refrigeration, Sept. 19-24, Sydney, Australia. 2. Agrawal RS (2001) Impact of Montreal Protocol on refrigeration and air conditioning industry. In: Proc, Intl. Conf. on Emerging Technol. in Air - Conditioning & Refrigeration, New Delhi, India, Sept 26-28. pp:13-25. Research article Indian Society for Education and Environment (iSee) “Refrigerant” http://www.indjst.org Agrawal et al. Indian J.Sci.Technol.