the effect of oil in refrigeration_ current research issues and critical review of thermodynamic aspects

1、ReviewThe effect of oil in refrigeration: Current research issuesand critical review of thermodynamic aspectsMohammed Youbi-Idrissia,1, Jocelyn Bonjourb,*,2aCemagref, Refrigerating Processes Research Unit, Parc de Tourvo

2、ie, BP 44, 92163 Antony Cedex, FrancebCETHIL – UMR5008 CNRS INSA-Lyon Univ. Lyon1, Ba ?t. Sadi Carnot, 9 rue de la Physique, INSA-Lyon,F-69621 Villeurbanne Cedex, Francea r t i c l e i n f oArticle history:Received 10 Ma

3、y 2007Received in revised form17 September 2007Accepted 24 September 2007Published online 2 October 2007Keywords:Refrigeration systemCompression systemReviewLubricationOilProcedureMeasurementSolubilityModellinga b s t r

4、a c tA lubrication agent is necessary in almost all the refrigeration vapour compression systems,particularly for the correct operation of the compressor. However, a certain portion of the oilalways circulates with the r

5、efrigerant through the cycle. This circulation is at the origin ofa deviation from the theoretical behaviour (i.e. based on pure refrigerant) of the components.This article aims at reviewing the oil-related researches in

6、 the field of refrigeration. Previousreviews in the literature focused on the thermo-hydraulic consequences of the presence ofoil; we will analyse here its thermodynamical consequences. In a first part, a brief literatur

7、ereview will give an overview of current scientific and technological issues concerning the im-pact of oil on components or on whole refrigeration systems. The typical approaches andmethods employed to address this probl

8、em will be described. These researches requiresound tools for the evaluation of thermodynamic properties of refrigerant–oil mixtures.The second part of this article is hence a critical review of these tools, and focuses

9、particularlyon liquid–vapour equilibrium, absorption–diffusion, and mixture enthalpy calculation.ª 2007 Elsevier Ltd and IIR. All rights reserved.Effets de l’huile de lubrification dans le domaine du froid :Proble &

10、#180;matiques actuelles et synthe `se critique sur lesaspects thermodynamiques* Corresponding author. Tel.: þ33 (0) 4 72 43 64 27; fax: þ33 (0) 4 72 43 88 11.E-mail addresses: mohammed.youbi@cemagref.fr (M. You

11、bi-Idrissi), jocelyn.bonjour@insa-lyon.fr (J. Bonjour). 1 Tel.: þ33 (0) 1 40 96 65 47; fax: þ33 (0) 1 40 96 62 49. 2 IIR Commission B1 Member.www.iifiir.orgavailable at www.sciencedirect.comjournal homepage: ww

12、w.elsevier.com/locate/ijrefrig0140-7007/$ – see front matter ª 2007 Elsevier Ltd and IIR. All rights reserved.doi:10.1016/j.ijrefrig.2007.09.006i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 3

13、 1 ( 2 0 0 8 ) 1 6 5 – 1 7 9raised in the context of the development of new environmentfriendly refrigerants (or rediscovery of ‘‘old’’ refrigerants) overthe last two decades.For all these reasons, many oil-related resea

14、rches in thefield of refrigeration have been conducted over the last years;we propose to analyse them in this article through a criticalreview. In these works, several themes can be distinguishedand are classified here:1

15、. Technology-oriented researches: these works often dealwith oil injection methods, lubrication efficiency or qualityin compressors, sensors and principles for measurement ofthe mixing ratio of oil to refrigerant in the

16、mixture, .2. Measurement/modelling of thermophysical properties ofoil or refrigerant–oil mixtures (viscosity, density, specificheat, .).3. Heat transfer and pressure drops of refrigerant–oil mix-tures during boiling and

17、condensation.4. Measurement/modelling of thermodynamical properties ofoil or refrigerant–oil mixtures (including solubility, misci-bility and enthalpy).5. Thermodynamical analysis of the impact of oil on a wholesystem, o

18、r on a component.6. Miscellaneous other studies motivated by the presence ofoil in refrigeration (e.g. ice slurry with oil as carrier fluid,cleansing of oil in refrigerating equipment, etc.).Most of the Energy and Therma

19、l Science published mate-rials deal with classes 2, 3, 4 and 5. Indeed, researches belong-ing to the technology class (class 1) are usually rather linked toMechanical Engineering (e.g. tribology), to Industrial Engineer-

20、ing, or to Automation Engineering. These works are hencepublished in journals specialized in these fields, rather thanin journals linked to Energy and Thermal Science. They couldobviously be the subject of a review, but

21、it would be more rel-evant to publish it in the leading journals of these domains.On the contrary, the articles belonging to class 6 (miscella-neous) are too dispersed to allow a critical literature review.The questions

22、of thermophysical properties (class 2) andheat transfer/pressure drops in two-phase flows (class 3) arethe subject of a very large number of publications. Atwo-part review article was published in Shen and Groll(2005a,b)

23、. These themes will hence not be studied here, andwe will focus on classes 4 and 5, which are believed to forma consistent group in that sense that they directly rely on ther-modynamics. Mermond et al. (1999) performed a

24、 review ofseveral correlations allowing the calculation of oil propertiesand compared a few methods used to determine the propertiesof refrigerant–oil mixtures. Conde (1996) focused on somemethods aiming at evaluating th

25、e thermophysical propertiesof oils and their solutions in refrigerants. A part of the presentarticle can be viewed as an updated extension of their works.This article is divided into two main parts. Section 2 is dedi-cat

26、ed to the thermodynamical impact of oil on the behaviour ofcomponents or whole refrigeration systems. Its goal is to givean overview of current technological or scientific issues througha brief analysis of a choice of so

27、me typical recent publications.This will show that these research works require sound toolsfor the evaluation of thermodynamic properties of refrigerant–oil mixtures. Section 3 consists in a critical review of these tool

28、s,and focuses particularly on liquid–vapour equilibrium, dynamiceffects (absorption–diffusion), and mixture enthalpy calculation.2. Thermodynamical analysis of the impact of oil in refrigerationAs exposed in Section 1, w

29、e will not discuss here the effect ofoil on heat transfer in the heat exchangers or on the pressuredrops, but only the thermodynamic effects. The presence ofoil influences the behaviour of almost each component ofrefrige

30、ration units. It is, however, usually admitted that thecondenser is the least sensitive component to the presenceof a lubricant, and the literature is consequently scarce onthat subject, while the compressor, the evapora

31、tor and thepipes or capillary are the subject of a larger number of publica-tions, some of which are analysed in the next sections.2.1. Impact on components2.1.1. CompressorA major effect of the presence of a lubricant i

32、n the compressoris the foaming phenomenon: the foam is due to the oil–refrigerant interaction because of the blade rotation and/orthe vapour blow. For instance, Yanagisawa et al. (1991) exper-imentally investigated the f

33、oaming occurring in a hermeticcasing that simulates a hermetic rotary compressor. They no-ticed that the foaming becomes violent at high compressorblade speed and at high flow rate of the blowing vapour, butthat these bo

34、th effects are not necessarily cumulative. Thefoaming is relatively violent when the pressure is close tothe saturation pressure corresponding to the temperature inthe casing. Some other information such as the foam life

35、time,effects of the oil mixing ratio, of the viscosity, etc., were alsoinvestigated.Another concern with oil is the question of its circulationrate (OCR, Oil Circulation Ratio), or conversely its return tothe compressor.

36、 The OCR seems to be relatively independentof the operating conditions, at least for R-290/POE oil orR-407C/POE oil, but the OCR seems to be slightly higher withPOE oils than with mineral oils (Navarro et al., 1998, 2004

37、,2005). The oil return can be analysed in terms of presumedbenefits of a high miscibility vs. actual lubrication propertiesof the refrigerant–oil mixtures (which are poorer than thoseof pure oil properties, since a porti

38、on of liquid refrigerantcan be dissolved in the oil) and overall energy efficiency.Reyes-Gavilan et al. (1996a,b) showed that a well-chosennon-miscible oil can perform as well as a POE miscible oil ina R-134a household r

39、efrigerator, i.e. both yield about thesame energy efficiency with about the same amount of oiltrapped along the circuit. In some other works, the questionof oil return is linked to specific configurations, such asa pair

40、of compressors working in parallel: Winandy andCuevas (2003) monitored and analysed the oil level of twocompressors linked with line allowing for the pressure andoil-level equalization, with various ON/OFF conditions for

41、each compressor cycle. The oil management must be givena specific care, particularly when the compressors work underpart load.i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 3 1 ( 2 0 0 8 ) 1 6 5 –