A refrigerator oil according to one embodiment of the present invention contains: a base oil containing an oxygen-containing organic compound; a polyphosphate ester compound; and a metal salt of an organic carboxylic acid having 6 to 60 carbon atoms.

A refrigerator oil according to one embodiment of the present invention contains: a base oil containing an oxygen-containing organic compound; a polyphosphate ester compound; and a benzotriazole compound.

The working fluid composition for a refrigerating machine of the present invention comprises a refrigerant comprising a first refrigerant component and a second refrigerant component, and having a global warming potential (GWP) of 500 or less, wherein the first refrigerant component is at least one selected from difluoromethane and tetrafluoropropene, and the second refrigerant component is at least one selected from carbon dioxide and a hydrocarbon having 3 to 4 carbon atoms; and a refrigerating machine oil comprising at least one selected from a polyol ester, a polyvinyl ether and a polyalkylene glycol compound as a base oil, wherein a carbon/oxygen molar ratio of the base oil is 2.5 or more and 5.8 or less.

A refrigerant compressor comprises an electric component; and a compression component which is driven by the electric component and compresses a refrigerant. At least one of slide members included in the compression component is made of an iron-based material. An oxide coating film (150) is provided on a slide surface of the iron-based material, the oxide coating film including a first portion (151), a second portion (152), and/or a third portion (153). The first portion (151) contains at least fine crystals (155). The second portion (152) contains columnar grains (156). The third portion (153) contains layered grains (157).

The use of a refrigerant in organic Rankine cycle systems including at least one hydrofluoroolefin, having at least four carbon atoms represented by the formula (I) R1CHCHR2 in which R1 and R2 independently represent alkyl groups having from 1 to 6 carbon atoms, substituted with at least one fluorine atom, optionally with at least one chlorine atom.

A method and system for lubricating at least one moving part with a lubricating medium includes a chamber configured to house at least one moving part, a lubricant reservoir configured to house a liquid lubricant, a gas reservoir configured to house a gas, and a controller configured to supply a first amount of the gas in the form of bubbles to a second amount of the liquid lubricant to entrain the bubbles of gas in the liquid lubricant. The controller is also configured to regulate proportions of the liquid lubricant and the gas as a function of at least one operating condition, including at least one of pressure, temperature, and flow rate, a solubility relationship between the liquid lubricant and the gas, and a size of the bubbles of gas, and supply the liquid lubricant with entrained bubbles of gas to at least one moving part.

The refrigerator oil according to the present invention includes a base oil including an oxygen-containing organic compound and a phosphorus-based compound represented by the following general formula (1).

##STR00001##

In the formula (1), n represents an integer of 1 to 10; R.sup.1 to R.sup.8 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; and Ar represents a divalent hydrocarbon group having 2 to 20 carbon atoms.

The use of a refrigerant in organic Rankine cycle systems including at least one hydrofluoroolefin, having at least four carbon atoms represented by the formula (I) R1CHCHR2 in which R1 and R2 independently represent alkyl groups having from 1 to 6 carbon atoms, substituted with at least one fluorine atom, optionally with at least one chlorine atom.

Provided is a refrigerating machine oil composition, which is to be used for a refrigerant including a mixture of an unsaturated fluorinated hydrocarbon compound, a saturated fluorinated hydrocarbon compound and CO.sub.2, contains a base oil which includes at least one selected from a polyoxyalkylene glycol, a polyvinyl ether, a copolymer of a poly(oxy)alkylene glycol or a monoether thereof and a polyvinyl ether, and a polyol ester and has a kinematic viscosity at 100 C. of 2 mm.sup.2/s or more and 50 mm.sup.2/s or less and a hydroxyl value of 5 mgKOH/g or less, is able to be used for a refrigerating machine system using a refrigerant having a low global warming potential and usable especially for a car air conditioner or the like and including a mixture of an unsaturated fluorinated hydrocarbon compound, a saturated fluorinated hydrocarbon compound and CO.sub.2, and exhibits not only excellent compatibility with the refrigerant but also excellent stability.

Provided herein are compositions comprising at least one estolide compound of formula:

##STR00001##

in which n is an integer equal to or greater than 0; m is an integer equal to or greater than 1; R.sub.1, independently for each occurrence, is selected from optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; R.sub.2 is selected from hydrogen and optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; and R.sub.3 and R.sub.4, independently for each occurrence, are selected from optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched. Also provided are uses of the compositions described herein.