COMPATIBILITY TEST OF HERMETIC COMPRESSOR WITH LPG (HYDROCARBON BLEND)

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 10, October 2018, pp Article ID: IJMET_09_10_089 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed COMPATIBILITY TEST OF HERMETIC COMPRESSOR WITH LPG (HYDROCARBON BLEND) Saurabh Gupta Assistant Professor, Mechanical Engineering Department, G H Raisoni College of Engineering and Management, Wagholi, Pune, Maharashtra, DrP. Srinivas Associate Professor, Mechanical Engineering Department, School of Technology, GITAM(Deemed To Be) University, Rudaram Mandal, Sangareddy District, Patancheru, Hyderabad, Telangana, India ABSTRACT In order to protect the environment by implementing the Kigali Amendment of Montreal Protocol, It is imperative that the industry of developing countries like India adopts, as early as possible, non-hfc refrigerants and energy-efficient designs for refrigeration systems. A number of refrigerants such as R290, R600a,LPG, Hydrocarbon mixtures and ternary blends are being actively considered as alternative to HFC. Since it is preferable to continue using the existing HFC-134a compressors, there is urgent need to study their compatibility while operating with more eco-friendly refrigerants. A few of these combinations have been used and various chemical and physical tests have been performed on the different components of the hermetic compressor in test rig. The results of these tests are compared with those obtained when the compressor is handling HFC-134a.It is hoped that this paper fills a vital need in attempting to prepare a database of material compatibility of compressor components with various refrigerant-lubricant combinations. Keywords: HFC (Hydro Flouro Carbon), HC (Hydrocarbon), POE (PolyOlEster), LPG (Liquid Petroleum Gas), R290 (Propane), R600 (Butane), R600a (Iso Butane) Cite this Article: Saurabh Gupta and DrP. Srinivas, Compatibility Test of Hermetic Compressor with Lpg (Hydrocarbon Blend), International Journal of Mechanical Engineering and Technology, 9(10), 2018, pp editor@iaeme.com

2 Saurabh Gupta and DrP. Srinivas 1. INTRODUCTION As per Kigali Amendment of Montreal Protocol in 2016, Developing countries like India has to freeze HFC application in Refrigeration and Air conditioning sector by 2035 and HFC phase down should start from year Hydrocarbons are being actively considered as alternative to HFC. Presently millions of RAC appliances are used across the world with existing HFC refrigerant compressor. It is preferable to continue using the existing HFC hermetic compressors with Hydrocarbons. So, it is necessary to study the compatibility of these existing hermetic compressors with LPG(Hydrocarbon Blend). Hammad and Alsad(9), Wongwises (4,10), Sattar et al. (5), Mohanraj et al (6,7) Purkayastha B (8) and many more investigators experimentally tested mixture of hydrocarbons in four ratio of R290, R600 and R600a in domestic refrigerator and found that HC mixture was the most suitable alternative for refrigerator to replace R12 and R134a. 2. ALTERNATIVE REFRIGERANTS TO HFC-134A The alternative refrigerant should possess various desirable characteristics such as thermal and chemical stability, material compatibility, low cost and operational safety. In addition, there are other environmental compatibility factors such as zero ODP, relatively low GWP and preferably low smog formation potential i.e. should not be a volatile organic compound. Therefore, any substitute should be harmless not only to all forms of life but also to the environment. It is now acknowledged that in order to satisfy the environmental regulations, one has to compromise on other factors such as flammability, energy efficiency, manufacturing feasibility (and hence cost), and additionally one has to resort to re-design of the system. Devotta(2,3) The comparison of the Hydrocarbon refrigerants/blend to HFC-134a are given in Table.1(Arora, 1994) Refrigerant HFC 134a HC 290/HC 600a HC 600a Formula CH 2FCF 3 C 3H 8 C 4H 10 C 4H 10 Molecular Weight Critical Temperature (ºC) Boiling Point (ºC) Flammable Limit (% in air) None (20ºC, 100Kpa) ODP GWP 1300 <0.01 <0.01 LPG is a mixture of propane and butane (butane weight percentage in the order of 30-70%, average 50%). It also contains small percentages of other saturated alkanes, and contaminants, including moisture at an unknown percentage. 3. HERMETIC COMPRESSOR Hermetic compressor is the main component of a household refrigerator. In this type of compressor, compressor pump and its motor are sealed inside the welded shell. The refrigerant gas connections are welded to the shell and the electrical connections to the motor are made through an insulated pass bonded to the metal shell. This hermetic arrangement prevents the loss of oil and refrigerant which could occur through rotating seals or mechanical fitting. In order to protect the environment by implementing the Montreal Protocol (Kigali Amendment,2016), it is mandatory to run the compressor for non-hfc refrigerants. But there are millions of refrigerators in India today (operating with HFC refrigerants) whose life is very likely to stretch beyond the phase out target dates. Therefore, there is urgent need to study their editor@iaeme.com

3 Compatibility Test of Hermetic Compressor with Lpg (Hydrocarbon Blend) reliability while operating with more eco friendly refrigerants. The first step in this approach is to study the compatibility of HFC 134a compressors with LPG(hydrocarbon blend). 4. TEST CYCLE The test rig employs a simplified gas cycle without evaporation and condensation of the refrigerant. The refrigerant gas from the compressor at a high pressure and temperature, the refrigerant gas is cooled in a cooling coil at a constant pressure without condensation as shown in the pressure-enthalpy diagram(fig 1). The operating pressures are determined by the quantity of refrigerant charged and the expansion valve adjustment. The vapour after entering the compressor shell is further superheated in the compressor shell (state point 1 to 1 ). The superheated vapour then enters the cylinder. During compression (state point 1 to 2 ), besides the increase in pressure, the compression increases the temperature of the refrigerant leading further into the superheat region. The superheated vapour is de superheated while flowing from the discharge muffler to shell outlet (state point 2 to 2). The cooling process (state point 2 to 3), is a constant pressure desuperheating process without condensation. The refrigerant still in the superheated vapour region, is expanded to the suction pressure through an expansion valve (state point 3 to 4). The state of the refrigerant after expansion process is shown by state point 4 to complete the cycle. The refrigerant is then cooled at constant pressure from point 4 to 1 to complete the cycle. 5. TEST RIG Test rig(fig 2) consists of all necessary controls, monitoring and measuring devices. A housing with temperature regulated fans allows to run the cycle in a controlled ambient temperatures. Figure 1 Thermodynamic Cycle of the Test Rig editor@iaeme.com

4 Saurabh Gupta and DrP. Srinivas Figure 2 Schematic Layout of Test Rig In this compatibility test, hermetic compressor is tested with HFC 134a/POE and Commercial LPG (Hydrocarbon Blend)/Mineral oil in test rig. Runtime was 2000Hrs. After switching off the power, the gas is released from the system. In case of hydrocarbon refrigerant, care should be taken to release in a properly ventilated area. The compressor is then disconnected from air conditioner and the oil sample is drawn into a flask. The opening of the flask should be closed with a stopper. Immediately after the disconnection, the suction and discharge connections should be closed to restrict the contamination of the oil. The compressor is cut open and dissembled. After the test, the visual rating was made in detail. After the visual rating, photographs of all parts were taken. The compressor parts like piston, piston pin and cylinder were then subjected to the perthography testing. The wear effects of these parts were measured on a perthometer. The comparisons of the perthographs before and after the test gives the wear effect. 5. TESTING OF OIL Analysis of the lubricating oil was carried out for all the test samples, before and after the tests. The oil samples were examined using the following test methods (ARI 1991) 1. Water content test by Karl Fischer Test. 2. Acidity of oil (total acidity number) by KOH solution. 3. Metal content test by spectroscopy. 4. Surface finish measurement by perthography editor@iaeme.com

5 6. RESULTS Compatibility Test of Hermetic Compressor with Lpg (Hydrocarbon Blend) Compatibility tests were conducted for the combinations of HFC 134a and POE and commercial LPG (Hydrocarbon Blend) and mineral oil. The duration of tests was 2000hours. For compressor 1 tested with HFC 134a/POE, parts like piston pin and connecting rods, are not affected by copper plating significantly. The parts like valve plate and discharge valve are also not affected by lacquer and sludge formations. The amount of copper plating is less. The surface finish measurement result show very little wear of the parts except some wear of the piston pin. After running for 2000 hours, the POE oil has more moisture and acidity than that of mineral oil. This is because of the hygroscopic nature of POE oil. The metal content test of the oil shows that the percentage of iron is more than the other metals. For compressor 2 tested with commercial LPG(Hydrocarbon Blend)/Mineral oil combination, some parts like valve plates, discharge valve, piston etc. were covered with varnish like lacquer. This lacquer effect is comparatively larger. Some parts like piston pin and connecting rod are affected by copper plates significantly. The effect of other factors like sludge and wear are very small. The parts tested for surface measurements show comparatively less wear than that of HFC 134a compressor. The oil after the test shows only slight changes. The iron content of 5.79ppm is the only significant change. The global summary shows that the compatibility of compressor parts with commercial LPG/Mineral oil is slightly higher than that of HFC 134a/POE combination. 7. CONCLUSION From the compatibility testing of hermetic compressors, it can be concluded that Commercial LPG (hydrocarbon blend) has a good compatibility with compressor materials and mineral oil. The compatibility of HFC 134a refrigerant with compressor parts is slightly poorer than HC blend and mineral oil. This requires some proper selection of mineral oil for compressor parts particularly for non-metallic parts and motor insulation. From oil test, it can be concluded that mineral oil is the best suited for hydrocarbon refrigerants. But in case of HFC 134a, more attention should be paid while selecting POE, some special additives may be adopted to improve the properties of the oil. It concluded that Commercial LPG is the vital choice as replacement of HFC 134a as per Kigali amendment of Montreal Protocol, only precautions are required due to its flammability. REFERENCES [1] ARI Refrigeration contaminant study final report, Prepared by Spauschus Associates, Inc. Atlanta, Georgia, pp (1991) [2] Devotta S, Assessment of hydrocarbon based refrigerators, Technical report submitted to SDC, New Delhi (1994) [3] Devotta Sukumar, Gupta Saurabh, Indian Scenario of RAC Service sector consumption of CFC and non-cfc refrigerants, proceedings of Conference on Meeting Challenges in Change over to Ecological Refrigeration, IIT New Delhi (2002) [4] Somachai Wongwises, Nares Chimres, Experimental study of hydrocarbon mixtures to replace HFC 134a in a domestic refrigerator, Journal of Energy Conversion and Management, 46(1), 2005 pp [5] Sattar M, Saidur R, Masjuki H., Performance investigation of domestic refrigerator using pure hydrocarbons and blends of hydrocarbons as refrigerants, Proceedings of World Academy of Science, Engineering and Technology, 2007, pp editor@iaeme.com

6 Saurabh Gupta and DrP. Srinivas [6] Mohanraj M, Jayraj S, Muraleedharan C, Improved energy efficiency for HFC 134a domestic refrigerator retrofitted with hydrocarbon mixture (HC290/HC600a) as drop in substitute, Energy Sustainable Development, Dec 2007, 11(4), pp [7] Mohanraj M, Jayraj S, Muraleedharan C, Experimental investigation of R290/R600a mixture as an alternative to R134a in a domestic refrigerator, International Journal of Thermal Sciences, May 2009, 48(5), pp [8] Purkayastha B, Bansal PK, An experimental study on HC290 and a commercial LPG mix as suitable replacements for HCFC22, International Journal of Refrigeration, Jan 1998, 21(1), pp [9] Hammad MA, Alsaad MA, The use of hydrocarbon mixtures as refrigerants in domestic refrigerators, Applied Thermal Engineering, Nov 1999, 19(11) pp [10] Wongwises S, Kamboon A, Orachon B., Experimental investigation of hydrocarbon mixture to replace HFC134a in an automotive air conditioning systems, Energy Conversion and Management, July 2006, 47(11-12), pp BIBLIOGRAPHY Arora C P, Text book on Refrigeration and Air conditioning, Third Edition, The McGraw- Hill publication (2012) editor@iaeme.com