Applied Mechanics and Materials Vol. 612 (2014) pp 181-185 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.612.181
ECOFRIENDLY REFRIGERANTS Prashant P.Pandav1, a, S.B.Lokhande2, b, Shivprakash B.Barve3, c, 1, 2, 3
Mechanical Engineering Department, MAEER’s MIT College of Engineering, Kothrud, Pune,India. a
[email protected],
[email protected],
[email protected]
Keywords: Hydrofluoroarbon, Hydrocarbon, Refrigerants, Ecofriendly, Depletion of ozone layer, Green house effect.
Abstract: The depletion of ozone layer and green house effects are worldwide problem. Refrigerants are part and source of depletion of ozone layer. As we using these Ecofriendly refrigerants then harm to ozone reduces. These are best option for recently running refrigerants. Eco-friendly refrigerant like hydroflurocarbons and hydrocarbons are replacing chlorofluorocarbons application.CFC is the most important member of CFC refrigerants. This paper, gives alternate to refrigerants that are causes ill effect on environment. Their performance with respect to recently used refrigerant compared. By this comparison benefits of Ecofriendly refrigerants discussed. Introduction The ozone depleting potential (ODP) and global warming potential (GWP) have become the most important criteria in the development of new refrigerants apart from the refrigerants CFCs due to their contribution to ozone layer depletion and global warming. The HFC refrigerants are considered as one of the six target greenhouse gases under Kyoto protocol of United Nations frame work convention on climate change (UNFCCC). In1997 [1, 2] Kyoto protocol was approved by many nations called for the reduction in emission of green house gas including HFC refrigerants. Hydrocarbon refrigerants are environmentally friendly, non-toxic, non-ozone depleting replacement for chlorofluorocarbons (CFCs), hydro chlorofluorocarbons (HCFCs) and hydro fluorocarbons (HFCs). From a chemical point of view, a hydrocarbon is the simplest organic compound, consisting entirely of hydrogen and carbon. Hydrocarbons (HC) are naturally occurring substances. The majority can be found in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen. The presence of fluorine atoms in HFC134a is responsible for the major environmental impact (GWP) with serious implications for the future development of the refrigeration based industries. HFC’s are free from chlorine have zero ODP but relatively high GWP. HFC’s are main candidates at present to replace CFCs and HCFCs especially in refrigeration, air-conditioning and Heat pump applications. GWP of most of the HFCs is lower than CFCs but it is much higher than HCs which are the probable candidates to be considered in place of HFCs. [3] R22 has been widely used for many decades in vapor compression refrigeration system. It is generally accepted and most suitable refrigerant for air-conditioners. Unfortunately, it belongs to the family of hydro-chlorofluorocarbon (HCFC) refrigerants, which were considered as harmful working fluids to the environment. As we discuss about Ecofriendly refrigerants these are of different varieties of hydro-fluorocarbons (HFCs) that are used in conventional vapor compression cycles such as R134a, R413A, R410A, and R407C? Natural fluids which includes propane (R290) and ammonia (R717) alternative cycles that include absorption systems, and use of trans- critical fluid CO2 (R744) and air cycles.50% of Propane (R290) and 50% of Isobutene (R600a) by mass fraction is used as a refrigerant. The R290/R600a (68/32 by wt %) is a zeotropic refrigerant mixture. A zeotropic refrigerant [10, 12] needs a temperature range to condense or to evaporate at a given pressure, with the dew point temperature always higher than the corresponding bubble point temperature. This leads to a shift in the composition of the phase changing mixture. .
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Literature review Many studies have been concentrated on the research of substitutes for R12. Some of the investigations are Richardson and Butterworth [1], Jung et al. [2], Hammad and Alsaad [3],Kuijpers et al. [6], Jung et al. [7], Akash and Said [8] and Fatouh and Kafafy [9]. Recently Dalkilic and Wongwises [10] studied the performance of refrigerants HFC134a, HFC152a, HFC32, HC290, HC1270, HC600 and HC600a for different ratios in a traditional vapor compression refrigeration system and compared with CFC12, CFC22 and HFC134a. Their results showed that refrigerant blend of HC290/HC600a (40/60 by wt.% instead of CFC12 found to be replacement refrigerant among other alternatives. Bolaji [5] provided comparative experimental steady is carried out of there refrigerator R-152a R-32 & R-134a to replace R-134a R-152a & R-32 are new refrigerant having zero ODP & GWP finally, he considered that Cop of R-152a 4.7% higher than R-134a & Cop of R-32 is 8.5% less than R-134a. Pull down time is achieved early than R-32. Power is considerably reduced with R-152a than the R-32 R-134a. Shegstan Bi et al R-600a is mixed with nano refrigerants ratio2, by mixing this nano refrigerants power consumption is reduced & miscibility of oil with refrigerants is increased. Finally results indicated that tio2-R-600a nano refrigerants work normally and safely in the refrigerator. In the present investigation the proposed R290/R600a (68/32 by wt %) mixture is a HC blend composed of propane 68% and iso-butane 32% on mass basis and performed better than the other propane/iso-butane mixtures so far studied by various investigators. Materials and methods The refrigeration system is made up of four major components: condenser, evaporator, compressor and expansion device. In the evaporator, the liquid refrigerant vaporizes by absorbing latent heat from the material being cooled, and the resulting low pressure vapor refrigerant then passes from the evaporator to the compressor. Compressor is the heart of the refrigeration system. It pumps and circulates refrigerant through the system, and supplies the necessary force to keep the system operating. It raises the refrigerant pressure and hence the temperature, to enable heat rejection at a higher temperature in the condenser. Condenser is a device used for removing heat from the refrigeration system to a medium which has lower temperature than the refrigerant in the condenser. The high pressure liquid refrigerant from the condenser passes into the evaporator through an expansion device or a restrictor that reduces pressure of the refrigerant to low pressure existing in the evaporator. Expansion device regulates or controls the flow of liquid refrigerant to the evaporator. [8] Performance characteristic of Ecofriendly refrigerants Figure (1) shows the variation of the refrigerating capacity (RC) for various evaporating temperatures. It is observed that as Te increases, the refrigerating capacity of the refrigerants is increased. The refrigerating capacity of R290/R600a is 21%-25% higher for temperatures above 13°C and 43% higher at -19°C than that with R12. The increasing percentage of propane in the hydrocarbon mixture reduces the specific volume of the refrigerant vapor results in increase refrigerant circulated per unit of time and the refrigerating capacity. The RC of R134a showed a very close match with R12 for all the operating conditions. This is due to the similar thermo physical properties of R134a to R12. R290/R600a mixture showed a higher cooling rate than that with R12 and R134a at higher evaporating temperatures [10].
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Fig1: Effect of evaporating temperature on RC
Fig2: Effect of evaporating temperature on PC
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Fig3:Effect of evaporating temperature on COP
The relationship between the power consumption and the evaporating temperature of R12, R134a and R290/R600a mixture is shown in fig.2. It is found that when the Te increases, the power consumed by the compressor increases. This is due to the increased mass flow rate of refrigerants at higher evaporator temperatures. The power consumed by the system with R290/R600a mixture is higher by 11%-20% and 13%-21.9% than that with R12 and R134a respectively. The refrigerant R134a consumed 2.5%-4.1% lesser power than that with R12 for all the operating conditions. Refer figure (3) the coefficient of performance for R12, R134a and R290/R600a mixture for various evaporating temperatures. It is observed that the COP of R290/R600a mixture is 10.2%-22.9% higher than that of R12 due to the increased refrigerating capacity. The COP of R134a closely matches with that of R12.
Fig:4Effect of pressure ratio and condensing temperature
Fig5: Effect of volumetric efficiency and condensing temperature.
According to part load performance analysis of vapor refrigerants system with hydrocarbon refrigerants by P.Thangavel & P.Somasunderam they obtain following results. From fig (4) & (5) shows that R600&r290 highest and lowest pressure ratio. The pressure ratio of proposed mixture is about 16-25% & 4.5-9%less than pressure ratio or R134a & R12. Reduction in pressure ratio leads increase in volumetric efficiency of compressor compared with 134a & R12.Eco friendly refrigerants have highest efficiency than other refrigerants. Compared to conventional refrigerants like R12 effect is produced by stirrer which is attached with R134a, HCM having the highest volumetric system to attain the uniform cooling effect. The instruments like pressure measurement, temperature volumetric efficiency of R600a is closer to R134a measurement. Data logging system is also incorporated with the refrigeration system in order to store the pressure and temperature at various places. Hydrocarbons mixture of R290 and R600a is charged measured by using the thermocouples with accuracy of as a refrigerant with 50% each (by mass) in the+0.1°C. Pressure gauges with the working range of refrigerator. [11]
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Effect of evaporator temperature on volumetric cooling capacity: Fig. shows the variation of volumetric cooling capacity with varying evaporator temperature for the four refrigerants. It also show that the VCC increases with increase in evaporator temperature. Average value of VCC for R-290 is 26.3% and 25% higher than that of R-134a and R-12 respectively. While Average value of VCC for R- 152a is 1.3% and 3.5% lower than that of R-134a and R-12 respectively. It is clear that R- 290 has the highest VCC. It means that for the same refrigerating capacity it would require less displacement than other refrigerants, and R-290 requires small compressor comparative to other three refrigerants. In other hand VCC for R-152a is close to theR-134a and R-12.therefore R-152a requires same Compressor size which is used for R-134a and R-12. [12]
Fig. 6: Variation of volumetric cooling capacity (VCC)
Fig.7: Power per ton of refrigeration vs. evaporator temperature
Effect of evaporator temperature on Power per ton of refrigeration: The variation of power per ton of refrigeration with evaporator temperature is illustrated in fig. from this fig. the power per ton of refrigeration decreases as the evaporator temperature increases for the per ton of refrigeration with varying evaporator temperature constant condensation temperature of 46˚C and evaporator temperature range -20 to 20˚C.The average Power per ton of refrigeration for R-290 is 3% and 4% higher than that of R-134a and R-12 respectively. While the average power per ton of refrigeration for R-152a is 4% and 3.5% lower than that of R-134a and R12respectively. It means that R- 152a requires less power per ton of refrigeration in comparison to other three refrigerants. [12] Conclusion This paper shows an eco-friendly and energy efficient refrigerants for refrigerators and airconditioners. In accordance with Montreal and subsequent protocols on substances that deplete the Ozone layer, CFC’s and HCFCs refrigerants are subjected to total phase-out in a scheduled time frame.R-134a, R-290,R-404A,R-407C,R-410A and R-507 are the refrigerants will end up replacing various application of R-22. (1)R-152a is the better substitute of R-134a and R-12. R-152a has GWP lower than that of R-134a and R-12. (2)Propane (R-290) has higher volumetric cooling capacity Therefore it requires small size of compressor. (3)Propane has lowest pressure ratio is good for compressor life. (4)R- 152a requires less power per ton of refrigeration in comparison to other.
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References [1] Richardson, R.N., Butterworth, J.S., The Performance of Propane/Isobutane Mixtures in a Vapour Compression Refrigeration System,International Journal of Refrigeration, 18 (1995), pp. 58-62 [2] Dongsoo Jung, Chong B.Kim, Byoung H.Lim, Hong W.Lee, Testing of a Hydrocarbon Mixture in Domestic Refrigerators, ASHRAETransactions, Symposia AT-96-19-3, (1996), pp. 10771084 [3] Hammad, M.A., Alsaad, M.A., The use of Hydrocarbon Mixture as Refrigerants in Domestic Refrigerators, Applied Thermal Engineering,19 (1999) pp. 1181-1189 [4] Amjad Khan, Kuldeep Ojha, Prakash Gowali,Analysis of ecofriendly refrigerants, International journal of engineering, 6(2013), pp177-185 [5] Bukola olalekan bolaji, Zhongjie Huan, Computational analysis of the performance of ozoneFriendly r22 alternative refrigerants in vapor compression air-conditioning systems, Environment Protection Engineering, Vol. 38 (2012),pp 38-45 [6] Kuijpers, L.J.M., De Wit, J.A., Janssen, M.J.P., Possibilities for the Replacement of CFC12 in Domestic Equipment, International Journal of Refrigeration, 11 (1998), pp. 284-291 [7] Jung, D., et al., Testing of Propane/Isobutene Mixture in Domestic Refrigerators, International Journal of Refrigeration, 23, (2000), pp.517- 527 [8] Bilal A. Akash., Salem A. Said, Assessment of LPG as a Possible Alternative to R12 in Domestic Refrigerators, Energy conversion and Management, 44 (2003) pp. 381-388 [9] Fatouh, M., Kafafy, M.E., Experimental Evaluation of a Domestic Refrigerator Working with LPG, Applied Thermal Engineering, 26 (2006), pp. 1593-1603 [10]Kolandavel MANI, Vellappan SELLADURAI, Experimental Investigations with eco-friendly Refrigerants using design of experiments technique–mathematical modeling and experimental Validation, International Journal of Refrigeration, 23, (2011),pp56-64 [11]P.thangavel,P.Somasundaram,Part load performance analysis of vapor compression system by Hydrocarbon refrigerants, Journal of science and industrial research,vol 72,july2013,pp445-460 [12]Kavita Paroche, Performance Analysis of Reciprocating Compressor Using Eco-Friendly Refrigerant,, International Journal of Refrigeration,11(2012),pp234-242
