Polyalkylene Glycol Lubricant Research Articles

Reducing fuel consumption of a light-duty vehicle by incorporating CuO nanoparticles in compressor lubricant of air-conditioning system

This experimental study aims to investigate the effects of copper (II) oxide (CuO) nanoparticles (~50 nm, 99.9% trace metal basis) incorporation in polyalkylene glycol (PAG) lubricant of a compressor included in air-conditioning (AC) system of a light duty passenger car. Observations on fuel consumption in real-world driving tests while the AC system is fully running were conducted. In order to determine the impacts of CuO nanoparticle incorporation in PAG oil, friction (pin-on-disc tribotester) and wear tests were carried out along with surface visualization analyses of scanning electron microscopy (SEM) and atomic force microscopy (AFM) on the disc samples laser-cut from the spare AC compressor vanes. Morphology and thermal stability of the CuO nanoparticles were also investigated via SEM and thermal gravimetric (TG) analyses, respectively. Wear rate (WR), average coefficient of friction (µa) and surface roughness analyses on the specimen surfaces were conducted to procure a comprehensive knowledge about the tribological improvement of CuO nanoparticles. All analyses were repeated on the identical metal samples in PAG lubricant bath (PL) and CuO nanolubricant (NL) separately under the same conditions and average of the test results were taken into account to minimize error. The results demonstrate that reductions of 15.5% in average coefficient of friction, 33% in wear rate and 9% in average surface roughness were achieved resulting in a decrease of 7.7% in fuel consumption at designated driving conditions.

Dynamic desorption characteristics of propane and polyalkylene glycol lubricants

Natural refrigerant propane has a saturated-liquid density that is only about half that of HFC refrigerants. Compared with traditional refrigerants, the absorption/desorption characteristics of propane with lubricants show great differences. Studies on the dynamic characteristics of refrigerant/lubricant mixtures have mainly focused on the absorption process, especially the absorption process of high-density refrigerants. The desorption of refrigerant from the mixture has been less studied. In this paper, an experimental apparatus was built to observe and measure the dynamic characteristics of refrigerant desorption. The effects of the refrigerant/lubricant combinations, the depressurization rate, the ambient temperature, and the initial concentration on the desorption process driven by depressurization were analyzed. The depressurization rate is the main factor influencing the desorption mass flow rate. As the pressure dropped, the refrigerant solubility decreased fast, causing the supersaturation degree to rise rapidly, which is the main driver of refrigerant desorption. Moreover, the correlation between the desorption mass flow rate and the supersaturation degree was obtained by the experimental results. The absolute deviations between the experimental and simulated concentrations were less than 2.5%.

Stability and Thermal Conductivity of Mono and Hybrid Nanoparticles Dispersion in Double-End Capped PAG Lubricant

Stable nanolubricant mixtures are interrelated with thermal conductivity enhancement, thus improving heat transfer performance in automotive air conditioning (AAC) systems. This paper studies the stability and thermal conductivity of double-end capped polyalkylene glycol (PAG)-based nanolubricants specially designed for R1234yf refrigerant. Mono nanolubricants (Al2O3/PAG and SiO2/PAG) and hybrid nanolubricants (Al2O3–SiO2/PAG) were prepared using a two-step preparation method at different volume concentrations of 0.01 to 0.05%. The stability of these nanolubricants was observed by visual, UV-Vis spectrophotometer, and zeta potential. Thermal conductivity (k) was measured from 30 to 70 °C using a C-Therm thermal properties analyser. The results from the stability analysis show that all nanolubricants were confirmed in excellent stability conditions for more than six months with minimum visual sedimentation, more than 70% concentration ratio, and zeta potentials greater than 60 mV. The Al2O3–SiO2/PAG samples recorded the highest values of thermal conductivity increment, followed by the Al2O3/PAG and SiO2/PAG samples with 2.0%, 1.7%, and 1.5% enhancement. Hybrid nanolubricants have been shown to have greater potential in the AAC system because of their excellent stability and better property enhancement in thermal conductivity.

Mutual diffusivities of difluoromethane and 2,3,3,3-tetrafluoropropylene dissolved in polyalkylene glycol lubricant

In this work, the mutual diffusivities of difluoromethane (R32) and 2,3,3,3-Tetrafluoropropylene (R1234yf) dissolved in Polyalkylene glycol (PAG) lubricant were studied experimentally based on the principle of dynamic light scattering. The pressure range of mutual diffusivity measurement is from 0.142 MPa to 3.371 MPa, and the temperature range is from 293.15 K to 353.15 K. The experimental data were correlated as the equation of temperature and pressure. The average relative deviation between the experimental data and the model is less than 1.34%. The results show that when the temperature is constant, mutual diffusivities of R32/PAG and R1234yf/PAG mixture decrease with the increasing of the solubility of refrigerants. The mutual diffusivity of R1234yf/PAG is less than that of R32/PAG at the same temperature and solubility. This may be due to the longer length of the R1234yf molecule and greater polarity, which results in the difficult diffusion in the lubricant. The molecular radius (0.164 and 0.299 nm) for the mutual diffusivity of R32 and R1234yf in PAG lubricants were obtained according to the Einstein-Stokes equation. The obtained radius values are within a reasonable order of magnitude compared to literature values. Since the molecular radius of R32 is smaller than that of R1234yf, which is also consistent with the experimental results in this work that the mutual diffusivity of R32 dissolved in PAG is larger than that of R1234yf.

Enhancing the thermophysical properties of PAG lubricant using graphene nano-sheets.

One of the most attractive methods to improve the thermo physical and heat transfer properties of conventional coolants and lubricants is the use of nanoparticles in it. Nanofluids are stable colloidal suspensions of nanoparticles and base fluids. The nanofluids exhibit superior thermal performance compared to conventional heat transfer fluids and this leads to the best hope for lubricants based nanofluids as well. Nanolubricant is a new class of lubricant produced by dispersing nano-sized particles of metals, metal oxides, carbon and its allotropes into conventional lubricating oils. In the present study, experiments were conducted to measure the thermophysical and rheological properties of polyalkyleneglycol (PAG) refrigerant compressor oil suspended with graphene nano-sheets. The effect of particle concentration and temperature on thermal conductivity and viscosity of nanolubricant were elucidated. The volume fraction is varied from 0.05 to 0.8% and the temperature range is from 15°C to 85°C. The rheological properties have been investigated at various shear rates, particle concentrations, and temperatures. Furthermore, a correlation is proposed to predict the thermal conductivity of Graphene-PAG nanolubricant. The results revealed that the thermal conductivity and viscosity of the nanolubricant is strongly depends on the volume fraction and temperature. The nanolubricant exhibits higher thermal conductivity and viscosity compared to the PAG oil. Unlike in the case of pure lubricant, the shear rate has a crucial impact on the behavior of nanolubricant. Interestingly, the pure lubricant, which is a Newtonian fluid, is transformed into non-Newtonian when nanoparticles are appended with it. From the studies, it was observed that the nanolubricant having graphene particle concentration of 0.05% is optimum for refrigeration application.

Experimental investigation on thermal and rheological behaviour of PAG lubricant modified with SiO2 nanoparticles

Nanolubricant is prepared by dispersing SiO2 nanoparticles into synthetic refrigerant compressor oil, polyalkylene glycol (PAG) using two-step method. Thermal conductivity and rheological properties of nanolubricant at various volume fractions (0.07 to 0.6vol %) in the temperature range 20°C to 90°C have been investigated. The results show that as the volume fraction increases thermal conductivity and viscosity increase. Conversely, the thermal conductivity and viscosity are found to be decreasing with increase in temperature. The highest thermal conductivity and viscosity of the nanolubricant(volume fraction 0.6%) are 1.31 and 10.34 times greater than that of pure lubricant. The measured thermal conductivity and viscosity are compared with that obtained from classical models and the classical models fail to predict these properties accurately. The non-newtonian shear thinning behaviour of SiO2-PAG nanolubricant was confirmed by computing power law and consistency indices. At higher particle concentrations and lower temperatures, nanolubricant shows thixotropic behaviour.

Comparative study of thermo-physical properties of SiO2 and Al2O3 nanoparticles dispersed in PAG lubricant

Currently, the possibility to enhance fuel efficiency with cutting edge advancements is thoroughly investigated by researchers. One of the best ways to increase the fuel efficiency is by improving the performance of the automobile air conditioning system. As a result, nanoparticles are dispersed in the lubricants of automobile air conditioning compressor for heat transfer and tribology enhancement. In this paper, viscosity and thermal conductivity of the SiO2 nanoparticles dispersed in Polyalkylene glycol (PAG) lubricants for 0.2–1.5% volume concentrations and 303–353K working temperatures was investigated and compared with Al2O3 nanolubricant. The viscosity and thermal conductivity of the nanolubricants increased with volume concentration but decreased with temperature. The paper proposed correlations for viscosity and thermal conductivity of SiO2 nanolubricants at various concentrations and temperatures. The allowable volume concentration of SiO2 and Al2O3 nanolubricants for application in automobile air conditioning compressors are up to 1.0% and 0.3%, respectively. The thermal conductivity of SiO2 nanolubricants at 1.0% concentration is higher than Al2O3 nanolubricants at 0.3% allowable concentration. As a conclusion, it is advisable to use the SiO2 nanolubricants with volume concentration of less than 1.0% for applications in automotive air conditioning system.

Tribological interactions of advanced polymeric coatings with polyalkylene glycol lubricant and r1234yf refrigerant

We report on the tribological performance of an aromatic thermosetting polyester (ATSP) blended with polytetrafluroethylene (PTFE) as a coating material for air-conditioning compressor applications. Tribological experiments were conducted in the presence of environmentally friendly r1234yf refrigerant and polyalkyleneglycol (PAG) lubricant, to compare state-or-the-art polymeric coatings with ATSP/PTFE. Results showed better performance for ATSP/PTFE, compared to PTFE-based and Fluorocarbon- based coatings under both dry and boundary lubricated sliding conditions. Significant reduction of 69% in friction was obtained with the inclusion of PAG lubricant, suggesting a synergistic combination for ATSP/PTFE and PAG/r1234yf. Morphological evolution via scanning electron microscopy revealed surface cracks and voids for PTFE/MoS2, responsible for negative interactions under lubricated condition, which was not the case for ATSP/PTFE coating.

Improved tribological and thermal properties of lubricants by graphene based nano-additives

Enhancing the tribological performance of lubricants with nanoparticle additives is a recent challenge. Addition of graphene based nanostructures in poly-alkylene glycol lubricant could significantly reduce friction and wear for compressors operating with CO2 refrigerant.

Pressure viscosity coefficients and traction properties of synthetic lubricants for wind turbine gear systems

ABSTRACTSynthetic lubricants are increasingly used to provide equipment reliability for wind turbine gear boxes. The majority of synthetic lubricants used today are based on polyalphaolefins. In gear systems where contact pressures are high, the pressure viscosity coefficient and traction values of the lubricant are important fundamental properties. A comparison of these properties for a wind turbine lubricant based on a polyalphaolefin and two lubricants based on polyalkylene glycols has been undertaken. Pressure viscosity coefficients were calculated from viscosity measurements made using an ultra‐high pressure falling needle viscometer at pressures up to 50 000 psi. Significant differences in properties were observed with both polyalkylene glycol lubricants showing lower pressure viscosity coefficients and much lower traction values. A calculation of the film thickness values in the Hertzian contact zone suggests that polyalkylene glycol lubricants may provide elastohydrodynamic films that are approximately 25% thicker than polyalphaolefin lubricants. Copyright © 2012 John Wiley & Sons, Ltd.

Tribological study of high bearing blended polymer-based coatings for air-conditioning and refrigeration compressors

Deposition by spray techniques has made possible to coat different substrate materials found in engineering applications, such as air-conditioning and refrigeration compressors, with blended soft polymeric coatings based on polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), and fluorocarbons (FC). In this study, the tribological performance of four polymeric coatings (PEEK/PTFE, PTFE/MoS 2, FC, and PEEK/Ceramic against 52100 steel) was evaluated using a specialized tribometer simulating aggressive compressor conditions. Experimental results showed that PTFE/MoS 2, and PEEK/PTFE coating systems performed better in terms of their tribological performance compared to the other polymeric coatings under starved lubricated conditions (mixture of R-134a refrigerant and polyalkylene glycol lubricant). Under aggressive unlubricated conditions, scuffing was observed for all the coatings except PEEK/PTFE. By using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray diffraction (XRD), it was found that the good performance of PEEK/PTFE was related to the formation of chemical species from the fragmentation of PTFE, PEEK, and its favorable interaction with the substrate, along with an increase in crystallization of PEEK during testing.

Comparative scuffing performance and chemical analysis of metallic surfaces for air-conditioning compressors in the presence of environmentally friendly CO 2 refrigerant

Carbon dioxide (CO 2) has received significant interest as an alternative refrigerant for air-conditioning compressors due to its environmental benefits. These environmental benefits include zero ozone depletion potential and minimal global warming potential compared to commonly used hydrochlorofluorocarbon and hydrofluorocarbon refrigerants. This study presents results for three typical metallic tribopairs commonly found in air conditioning compressors, namely, Al390-T6, gray cast iron, and Mn–Si brass against 52,100 steel pins. The experiments were performed using a specialized tribometer capable of simulating compressor conditions, and in the presence of CO 2 and polyalkylene glycol lubricant. It was found that the scuffing resistance of gray cast iron and Mn–Si brass was similar and both materials performed better than Al390-T6. Through scanning electron microscopy and energy dispersive spectroscopy it was found that lead in Mn–Si brass melted during scuffing, and prevented sudden catastrophic failure of Mn–Si brass, unlike gray cast iron and Al390-T6 which failed abruptly. X-ray photoelectron spectroscopy conducted on the worn surfaces showed that chemically different species were present on the surfaces and their lubricious effect, originating from different metal oxides, could explain the scuffing behavior of the investigated alloys.

Tribological Studies on Scuffing Due to the Influence of Carbon Dioxide Used as a Refrigerant in Compressors

Because hydrofluorocarbon (HFC) refrigerants in air-conditioning systems are known to have a negative effect on the environment, carbon dioxide (CO2) is a candidate as a replacement refrigerant. Research work related to CO2 as a refrigerant has been focused primarily on its thermodynamic performance, whereas work in the area of tribology related to carbon dioxide is absent. In this study, the effects of CO2 used as a refrigerant on the tribological behavior of surf aces in contact in such systems were investigated. Controlled experiments were performed at constant loads in environments of CO2 and the conventional HFC refrigerant, R134a, as well as under conditions of step-increasing loads in the presence of refrigerant (CO2 or R134a) and polyalkylene glycol lubricant. The experiments were performed on a high-pressure tribometer that is particularly suited for tribological testing of compressor contact interfaces. The tribological behavior of contacting surfaces in a CO2 environment was nearly identical to that in an R134a environment when tested under the same operating conditions.

Flooded Boiling of Ammonia with Miscible Oil Outside a Horizontal Plain Tube

Pool boiling tests were conducted with plain steel tubing using pure ammonia and a mixture of ammonia and a miscible lubricant. By comparing the results, the effect of miscible lubricant on shell-side boiling heat transfer coefficient of ammonia was quantified. The experiment covered saturation temperature from −23.3° C to 7.2°C (−10° F to 45°F) and heat flux up to 60 kW/m2 [19,000 Btu/(h·ft2)]. Nucleate boiling of ammonia took place outside a plain steel tube of 19.1 mm (0.75 in.) diameter. The tube was heated by liquid flowing inside to simulate a real heat exchange device. A polyalkylene glycol lubricant, miscible with ammonia, was tested at 0%, 1%, 5%, and 10% mass concentrations. The experimental results showed that under a particular saturation temperature and heat flux, the heat transfer coefficient generally first decreased with an increase in oil concentration up to 5%. It was then followed by an insignificant increase in the coefficient with a further increase in oil concentration to 10%. At a low temperature and a high heat flux, the heat transfer coefficient decreased with the lubricant concentration and stayed constant. The effect of miscible lubricant strongly depends on saturation temperature and weakly depends on heat flux. The largest degradation of heat transfer performance due to the miscible lubricant occurs at the present low temperature of −23.3°C where the heat transfer coefficient can be reduced by up to 33%. A general correlation was developed for heat transfer coefficients both with and without lubricant effect.

Tribological evaluation of some aluminum-based materials in lubricant/refrigerant mixtures

The tribological characteristics of various aluminum alloys, surface treated 356 aluminum alloy and an aluminum composite are evaluated in lubricant/refrigerant (L/R) mixtures. The evaluation is based on a cylindrical pin/disc line contact geometry. This research program consists of two parts. The first part focuses mainly on materials screening of various aluminum/steel contact pairs lubricated by polyolester/R134a (tetrafluoroethane) and polyalkylene glycol (PAG)/R134a mixtures. For the aluminum alloys tested, the 390-T6 die cast alloy shows the best wear resistance. In general, the amount of wear decreases as the amount of silicon content in AlSi alloys increases. Conventional anodizing does not improve the wear resistance of the 356 aluminum alloy under concentrated contacts. Hard anodizing of 356 and a SiCAl composite provide very good wear resistance, however, they cause increased wear on the counterface. From the wear results obtained, the Ester/R134a mixtures consistently provide better protection of the aluminum alloys compared to the PAG/R134a mixtures. If sufficient amount of R134a exists in the L/R mixture, extensive surface fatigue on 356 aluminum is observed. In the second part, 356-T61 and 390-T61 aluminum alloys are tested in various L/R mixtures. The L/R mixtures tested include ester and PAG lubricants with R134a, mineral and alkylbenzene lubricants with R22 (chlorodifluoromethane), R407C (mixture of difluoromethane, pentafluoroethane and tetrafluoroethane) and R41A (mixture of difluoromethane and pentafluoromethane), as well as ester lubricant with both R407C and R410A. Based on the wear data obtained, the capped PAG seems to be a better lubricant for 356 alloy than the uncapped PAG. However, the lubricity of the PAG's is about the same with the 390 alloy. When the ester lubricant is used, the wear on each alloy is about the same in R134a, R407C, R410A and air environments. There is no significant difference in lubricity of mineral and alkylbenzene lubricants when used with R22 and its possible substitutes R407C and R410A.

Degradation of polyethylene terephthalate films in the presence of lubricants for HFC 134a: a critical issue for hermetic motor insulation systems

Earlier studies conducted in the use of sealed tubes with polyalkylene glycol lubricants and polyethylene terephthalete (PET) films revealed that the PET films exhibited embrittlement and (visual) degradation. This led to an investigation of PET embrittlement mechanisms with the new lubricants used with HFC 134a. The lubricants studied were three polypropylene glycols (the monol, the diol and the completely end-capped glycols), pentaerythritol ester and a blend of monol and ester. The effects of moisture content, temperature and lubricant structure were studied. All lubricants in this study were of viscosity grade ISO-32 (150 SUS). The results were compared to PET film embrittlement in the presence of CFC 12 and mineral oil. This study reconfirmed the earlier findings that the PET films must be dried to lower than 0.1 wt.% moisture content for use in hermetic systems. This paper discusses the effect of the moisture content of the lubricant and the effect of the lubricant structure on PET films. The dependence of the various mechanisms on temperature is shown. Esters and end-capped polyalkylene glycols are recommended for use with HFC 134a.

Polyalkylene Glycol Lubricants MATERIALS HANDLING.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolyalkylene Glycol Lubricants MATERIALS HANDLING.T. W. RodesCite this: Ind. Eng. Chem. 1952, 44, 10, 137A–140APublication Date (Print):October 1, 1952Publication History Published online6 October 2008Published inissue 1 October 1952https://doi.org/10.1021/ie50514a011RIGHTS & PERMISSIONSArticle Views24Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (759 KB) Get e-Alerts