Hata, H.

Ishiyama, A.

Kawashima, K.

lizuka, T.

Sekigami, K.

Sugano, T.

English

Purdue E-Pubs

Purdue UniversityPurdue e-PubsInternational Compressor Engineering Conference School of Mechanical Engineering1994Study of Technology for Refrigerant Applications 2A. IshiyamaHitachiT. lizukaHitachiK. KawashimaHitachiK. SekigamiHitachiH. HataHitachiSee next page for additional authorsFollow this and additional works at: https://docs.lib.purdue.edu/icecThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/Herrick/Events/orderlit.htmlIshiyama, A.; lizuka, T.; Kawashima, K.; Sekigami, K.; Hata, H.; and Sugano, T., "Study of Technology for Refrigerant Applications 2"(1994). International Compressor Engineering Conference. Paper 1206.https://docs.lib.purdue.edu/icec/1206AuthorsA. Ishiyama, T. lizuka, K. Kawashima, K. Sekigami, H. Hata, and T. SuganoThis article is available at Purdue e-Pubs: https://docs.lib.purdue.edu/icec/1206Study of Technology for Refrigerant Applications 2. Lubrication of Rotary Compress()r in HFCbased Alternates Akihiko Ishiyama. Tadashi Iizuka. Ken-ichi Kawashima, Kazuo Sekigami, Hiroaki Hata and Tsuneji Sugano Hitachi. Ltd. Abstract Long term reliability of rotary compressor in HFC refrigerant systems is mainly dependent on lubrication of moving parts in compressor. To maintain better reliability, basic components in rotary compressor, such as refrigeration lubricant, metallic materials and oil supply systems, were evaluated. A new materials. which are compatible in HFC systems, were determined. Also the results of an accelerated life test of rotary compressor using new materials will be presented. Introduction Due to the nature of high efficiency of rotary compressor, they are widely used for home appliance applications. such as room air conditioners, large refrigerators and dehumidifiers (1). Without sacrifice high efficiency of rotary compressor, technical problems associated with lubrication in alternative refrigerants should be made clear. A completely new materials technology to improve long term reliability of rotary compressor, particularly lubrication, is described in this paper. Tribology of Rotary Compressor (I) Lubrication in Liquid Refrigerants, Lubr)cants and their MiXtures To study the lubrication in alternative refrigerant systems. the friction test using actual shaft and roller materials to measure both extreme pressure and wear amount was performed (2). The extreme pressure was determined at the point where the friction coefficient was suddenly increased. At this point, gradually increased load causes adhesive wear. Because wear am.ount at the shaft material was large enough to measure so that this anwunt was chosen to compare the relative lubricity. Some of test results are shown in Figures 2 and 3. The order of lubricity in terms of extreme pressure and wear amount are summarized below. (a) Liquid Refrigerants Extreme Pressure: 22 > 12 >> 134a > 32 Wear: 32 ;:: 134a >> 12 > 22 (b) Lubricants Extreme Pressure: POE-56;:: POE-32 > POE-15 > HAB-56 Wear: HAB-56;:: POE-15 > POE-32;:: POE-56 829 (c) Refrigerant and Lubricant Mixtures Extreme Pressure: 134a/POE-15 > 22/HAB-56 > 12/HAB-56 > 32/POE-32 = 32/POE-56 Wear: 32/POE-32 > 32/POE-56 > 134a/ POE-15 > 12/HAB-56 > 22/HAB-56 where 12: CFC-12, 22: HCFC-22, 134a: HFC-134a, 32: HFC-32, POE-15: Polyol ester VG 15, HAB-56: Hard Alkylbenzene VG 56. In general, HCFCs or CFCs have better lubricity than HFCs. Since HFCs do not have chlorine atom. which would react with iron surfaces to form ferrous chloride layers, lower extreme pressure is expected in HFCs. Therefore following precautions are needed to be considered. (i) The lubricant concentration in lubricant-refrigerant mixture should be kept greater than 50% in order to supply enough lubricant to compressor moving parts. (ii) Selection of new materials, which can survive in HFC systems. (iii) Selection of POE base stock which has better lubricity. (2) Corrosive Wear Polyol esters (POEs) are thought to be the best refrigeration lubricants in HFC systems; however, the formation of acidic products by hydrolysis, oxidation or thermal decomposition of POEs is concerned. Although the acid formation can be minimized, described in previous paper, Falex wear test in acidic media is carried out to investigate the effects of acid. The corrosive wear test was utilized in lubricant with known TAN, prepared by adding the same carboxylic acid as POE produces. Two V-blocks and a journal were immersed in the lubricant and 150lb ofload was applied. Test results are shown in Figure 4. The wear amount of V-blocks is proportional to the TAN. This suggests that the presence of acids accelerates corrosive wear. Again the wear amount of journal was negligible in this test. (3) New Materials for Moving Parts In boundary lubrication regime. direct contact between vane and roller surfaces is occurred. The nature of initial wear of vane and roller in rotary compressors has been well demonstrated but less attention was paid for the difference between various materials. To survive in severe conditions like boundary lubrication. development of new materials was required. In this section. several new materials for vane and roller. listed in Tables 1 and 2. are discussed. The results are shown in Figures 5 and 6. The order of extreme pressure is shown below. (a) Vane Materials Extreme Pressure: SK.H51 <Hard Metal A< Hard Metal B < C/Al complex The ox:ynitriding (ONO) surface treatment dramatically improves extreme pressure shown in Figure 5. (b) Roller Materials Extreme Pressure: FCC250 < FCMNC < FCCVB Increasing primary carbide and steadite quantity is effective to gain better material properties. 830 (4) Refrigeration Lubricants Chemistry of refrigeration lubricant in working condition was investigated using a home-made test apparatus, which duplicates actual working conditions. A schematic diagram of apparatus is shown in Figure 7. A rolling roller was placed between two vanes and the load( F) was applied to two vanes. Lubricant was supplied onto roller /vane contacting parts directly by dropping lubricant droplets. The results are shown in Figure 7. There are liner relationship between friction coefficients and the TAN. and also the consumption of acid catcher. This can be explained by the formation of acids at sliding part of roller and vane. where heat is generated. And formed acids are eliminated by acid catcher. This subtle reaction may lead serious destruction of compressor in long term use. To avoid this reaction, better lubricant supply system. lower friction at sliding parts and selection of thermally stable lubricant are desirable. Compressor Reliability Test The rotary compressor drop-in tests, using new materials mentioned above. were performed. The rotary compressor applied was 0.75kW and used for air-conditioner and HCFC-22 alternative refrigerants were examined. The test was carried out under high pressure and speed condition (ie. discharge pressure: 3.04MPa, suction pressure: 0.59MPa. driving speed: 4,000 to 5.700rpm). The wear amount of vane and roller is shown in Figure 8. The order of wear is; FCMNC/SKI5l(Sulphonitriding) > FCCVB/Hard Metal A (oxynitriding) > FCCVB/C-Al Complex Also increasing both lubricant viscosity (from VG 32 to 56) and amount of acid catcher reduces wear amount into 10 times less. Confirming above findings, much longer term life tests are in progress. Conclusions (1) No benefit of chlorine from HCFC-22 or CFC-12 toward better lubrication is expected. To maintain good lubrication, oil supply to compressor parts is important, keeping greater than 50% oil concentration in oil/refrigerant mixture. (2) Microscopic corrosive wear was identified under severe roller-vane contacting conditions. (3) New materials for roller (FCCVB) and vane (Hard Metal B or CJ Al Complex) were developed and wear loss was dramatically reduced. (4) The combination of new materials and POE VG 56 With acid catcher was proven to be the best one by the accelerated life test of compressor. References l.(a) K. Matsubara et al.," CFC Issue In Hitachi". Hitachi Review. 39 (6) 1990. (b) T. Takagi et al.," Development of Substitutes for Ozone Layer-Destroying CFCs", Hitachi Review. 43 (6) 1993. 2. T. Iizuka et al .. " Improvement of Reliability of Compressors for Domestic Refrigerators Using HFC-134a ". Proc. Int. Compressor Engg. Conf at Purdue. Vol.3. 1992. 831 .--- Hydrodynamic '-- Lubricant Film Mechanical Lubrication ~trength r-- 1-Wear Boundary Material .......----. I Wear r '-- f--Lubrication Cnaracteristics Corrosive Chemical ~tability of '---Wear -Refrigerant and Lubricant Fig.2 Lubricity of Alternative Fig.3 Lubricity of Alternative Refrigerants(Extreme Pressure) Refrigerants(Wear Quantity) ~Lo : : F~F :;: 0.9 ···· ····:··· o· ·:······ ·· V ~lo~-0~~\lock 131: - .0 a~ .... 0. 8 --- ... -- ...... -:·....... ourna :;3 0 7 .,. __ o __ ; ........ :........ F=667N(150lb) B: • : ; V = D. lm/s ~ 0. 6 ·· · ·· · ~- · · · · · · -:- · · · · ·-- · Test Time:2 hr ~ -Vit:gin Oil \._;;l/V Atmosphere:Air : 0•5o.1 10 100 Final TAN (mgKOH/g) Fig.4 TAN Effect to Wear (Falex Test) 832 Table l Composition of Materials for Roller Roller c Other Compos its HRC P.C.& Mat. ( _% ) s. (%) * FCC250 3.48 Si Mn p s Ni Cr Mo Ti - 57 ._Q l.O FCC VB 3.33 Si Mn p s Ni Cr Mo - B 57.0 5.8 FCMNC 3. I 0 Si Mn p s Ni Cr Mo - - !J3.2 1.5 *Primary Carbide and Stead1te Quantity Table 2 Composition of Materials for Vane Vane Mat. c (%) SKH51 0.89 Si Hard Metal A 2. 14 Si Hard Metal B 3.49 Si C_LA I Como I ex 44.6 Si Vane f Material~ Roller~ Material Other Comoosits Mn Cr w Mn Cr w Mn Cr w - - -Oil :POE VG56 Dipping Temp. :GOt Atmosphcre:Air Roller Material:FGG250 Mo v Mo v Mo v - -I IIRC Co - - 59.0 Co - - 66.S Co Ti - 73.2 - - AI 19. 0 Vane Material ~v Micro Structures 25,um SKH51 SKI!Sl(ONO). Hard Metal A A (ONO) Hard Metal B B (ONO) G/Al Complex ll I I I I I I l 0 200 400 600 800 Relative Extreme Pressure SK!I51 ( ONO) I!.M.B(ONO) Fig.5 Characteristic of Vane Material f--1 II. M. A (ONO) Complex Roller Material Vane Matcrial:llard Metal A Micro Structures FCG250 FGMNG FCC VB I I I I 1 0 I 00 200 300 400 Relative Extreme Pressure FCMNC Fig.6 Characteristic of Roller Material 833 50 ,£L m f--1 r 0 0. 01 ..... 0 = < ...... 0~----~----~----~ 0 10 20 30 Relative pPV 0 F = 980N ~A Roller (FCC250) Vane (SKH51 ONO) r » .~ V = 2 m/s c. ~ Test Time:20 hr Oi 1 :POE VG32, 130t Atmosphere:llFCI34a,0.98MPa Fig. 7 Behavior of TAN and Epoxy in POE Oil 100 \ 0.75kW Rotary Compressor >. .... Suction Pressure:0.6MPa Roller Vane ·-.... Discharge Pressure:3.04MPa 1:: Ol .----- Test Time:300 hr == 0 .... <d 50r-c:> 01= Q) > ·-... .a -c:> 0 ~ ilrmmmi .,:; r-Roller FCMNC FCCVB - - -Vane SKIISI Hard Me tal C/Al Hard Metal C/Al A (ONO) Complex A (ONO) Complex POE VG 32 - - 56 -0 i 1 Add.* 100 - - 200 -Refrigerant IIFC32/13 IIFC32/12 5 IIFC32/125 4a - /13 -4a IIFC32/134a /I34a •Add. :Relative Content of Epoxy Fig.8 Result of Accelerated Test for Rotary Compressors 834 

Study of Technology for Refrigerant Applications 2

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Study of Technology for Refrigerant Applications 2

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