REFRIGERATION LUBRICANT AND WORKING FLUID INCLUDING THE SAME

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Taiwanese Invention patent application No. 113114329, filed on Apr. 17, 2024, the entire disclosure of which is incorporated by reference herein.

FIELD

The present disclosure relates to a refrigeration lubricant and a working fluid including the same.

BACKGROUND

A refrigeration cycle device, such as air conditioners, refrigerators, heat pump water heaters, etc., typically includes four main refrigeration cycle components, which are a compressor, a condenser, a thermal expansion valve, and an evaporator. A refrigeration cycle consists of four processes, i.e., compression, condensation, expansion, and evaporation which take place in the compressor, condenser, thermal expansion valve, and evaporator, respectively. Briefly, a low-pressure, low-temperature gaseous refrigerant is compressed into a high-pressure, high-temperature gaseous refrigerant in the compressor first. Next, the high-pressure, high-temperature gaseous refrigerant is condensed into a high-pressure, ambient-temperature liquid refrigerant in the condenser. Then, the high-pressure, ambient-temperature liquid refrigerant is expanded and depressurized into a low-pressure, low-temperature liquid-gas mixture refrigerant in the thermal expansion valve. Subsequently, the low-pressure, low-temperature liquid-gas mixture refrigerant is subjected to heat absorption to be evaporated into a low-pressure, low-temperature gaseous refrigerant in the evaporator, followed by repeating the aforesaid four processes in sequence.

In order to reduce the degree of wear during an operation of the compressor so as to extent a service life thereof, decrease the heat generated during the operation of the compressor so as to enhance efficiency and reliability thereof, and prevent refrigerant leakage from the compressor, a refrigeration lubricant that can achieve the aforesaid effects is typically used alongside the refrigerant as a working fluid in the compressor. However, in a refrigeration cycle, the refrigerant continuously circulates through the compressor, the condenser, the thermal expansion valve, and the evaporator, so that the refrigeration lubricant may inevitably leave the compressor along with the refrigerant, and a miscibility between the refrigeration lubricant and the refrigerant may directly affect an efficiency of the refrigeration cycle in a refrigeration cycle device and an operational life of the refrigeration cycle device.

In a low temperature environment of the evaporator, if the miscibility between the refrigeration lubricant and the refrigerant is too low, phase separation between the refrigeration lubricant and the refrigerant may occur, causing the refrigeration lubricant to be accumulated on an surface of the evaporator and unable of returning back to the compressor, which not only reduces a heat transfer efficiency of the refrigerant in the evaporator, but also results in an insufficient amount of the refrigeration lubricant in the compressor so as to cause compressor failure. In contrast, if the miscibility between the refrigeration lubricant and the refrigerant is too high, the refrigerant may be excessively dissolved in the refrigeration lubricant, causing the working fluid's kinematic viscosity to be too low, thereby significantly reducing a lubricity of the working fluid, and hence leading to compressor failure.

In view of the aforesaid, there is still a need to develop a refrigeration lubricant that can be used to prepare a working fluid with a proper miscibility between the refrigeration lubricant and a refrigerant and with a relatively high kinematic viscosity.

SUMMARY

Therefore, an object of the present disclosure is to provide a refrigeration lubricant and a working fluid including the same, which can alleviate at least one of the drawbacks of the prior art.

According to one aspect of the present disclosure, the refrigeration lubricant includes a dipentaerythritol ester which is formed by subjecting a dipentaerythritol and a fatty acid composition to an esterification reaction. The fatty acid composition includes a fatty acid mixture and a C₉ branched chain fatty acid. The fatty acid mixture includes at least two straight chain fatty acids selected from the group consisting of a C₇ straight chain fatty acid, a C₈ straight chain fatty acid, a C₉ straight chain fatty acid, and a C₁₀ straight chain fatty acid.

According to another aspect of the present disclosure, the working fluid includes a refrigerant and the aforesaid refrigeration lubricant. The refrigerant is selected from the group consisting of a hydrofluoroolefin (HFO), a hydrofluorocarbon (HFC), a hydrochlorofluoroolefin (HCFO), and combinations thereof.

DETAILED DESCRIPTION

For the purpose of this specification, it will be clearly understood that the word “comprising” means “including but not limited to”, and that the word “comprises” has a corresponding meaning.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Taiwan or any other country.

Unless otherwise defined, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which the present disclosure belongs. One skilled in the art will recognize many methods and materials similar or equivalent to those described herein, which could be used in the practice of the present disclosure. Indeed, the present disclosure is in no way limited to the methods and materials described.

The present disclosure provides a refrigeration lubricant including a dipentaerythritol ester which is formed by subjecting a dipentaerythritol and a fatty acid composition to an esterification reaction. The fatty acid composition includes a fatty acid mixture and a C₉ branched chain fatty acid.

According to the present disclosure, the fatty acid mixture includes at least two straight chain fatty acids selected from the group consisting of a C₇ straight chain fatty acid, a C₈ straight chain fatty acid, a C₉ straight chain fatty acid, and a C₁₀ straight chain fatty acid, in any proportion. In certain embodiments, the fatty acid mixture includes the C₇ straight chain fatty acid, the C₈ straight chain fatty acid, and the C₁₀ straight chain fatty acid, in any proportion.

According to the present disclosure, the C₉ branched chain fatty acid is selected from the group consisting of 2,2-dimethylheptanoic acid, 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, 3,5,5-trimethylhexanoic acid, 2-ethyl-2,3,3-trimethylbutyric acid, 2,2,4,4-tetramethylpentanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,2-diisopropylpropanoic acid, and combinations thereof.

According to the present disclosure, the fatty acid mixture is present in an amount ranging from 25 wt % to 35 wt % and the C₉ branched chain fatty acid is present in an amount ranging from 65 wt % to 75 wt %, based on the total weight of the fatty acid composition. In certain embodiments, the fatty acid mixture is present in an amount of 25 wt % and the C₉ branched chain fatty acid is present in an amount of 75 wt %, based on the total weight of the fatty acid composition. In other embodiments, the fatty acid mixture is present in an amount of 35 wt % and the C₉ branched chain fatty acid is present in an amount of 65 wt %, based on the total weight of the fatty acid composition.

According to the present disclosure, the C₇ straight chain fatty acid is present in an amount ranging from 20 wt % to 43 wt %, the C₈ straight chain fatty acid is present in an amount ranging from 31 wt % to 40 wt %, and the C₁₀ straight chain fatty acid is present in an amount ranging from 26 wt % to 40 wt %, based on the total weight of the fatty acid mixture. In certain embodiments, the C₇ straight chain fatty acid is present in an amount of 20 wt %, the C₈ straight chain fatty acid is present in an amount of 40 wt %, and the C₁₀ straight chain fatty acid is present in an amount of 40 wt %, based on the total weight of the fatty acid mixture. In other embodiments, the C₇ straight chain fatty acid is present in an amount of 43 wt %, the C₈ straight chain fatty acid is present in an amount of 31 wt %, and the C₁₀ straight chain fatty acid is present in an amount of 26 wt %, based on the total weight of the fatty acid mixture.

According to the present disclosure, a molar ratio of the dipentaerythritol to the fatty acid composition is 1:1.

According to the present disclosure, the refrigeration lubricant has a kinematic viscosity at 40° C. ranging from 120 cSt to 280 cSt.

In certain embodiments, the refrigeration lubricant is prepared by the following steps (a) and (b).

In step (a), the dipentaerythritol and the fatty acid composition are subjected to an esterification reaction in the presence or absence of a catalyst so as to form a crude product containing the dipentaerythritol ester, water, the catalyst (if added), and impurities, followed by subjecting the crude product to a drying treatment so as to remove the water therefrom and reduce a moisture content of the crude product to less than 50 ppm. Examples of the catalyst may include, but are not limited to, tin (II) oxalate, tin (II) oxide, tetrabutyl titanate, tetraisopropyl titanate, and methanesulfonic acid. The esterification reaction may be conducted at a temperature ranging from 150° C. to 250° C.

In step (b), the resultant dried crude product is subjected to a purification treatment, so as to purify the dipentaerythritol ester from the resultant dried crude product. The purification treatment is conducted by subjecting the resultant dried crude product to a neutralization reaction by adding an alkali to neutralize an unreacted fatty acid composition therein or a distillation process to remove the unreacted fatty acid composition therein, so that a hydroxyl value of the thus purified crude product is less than 10 mg KOH/g, followed by adding activated carbon and a filtration aid (i.e., perlite) to filter out the catalyst (if added) and the impurities from the resultant dried crude product.

The present disclosure also provides a working fluid which includes a refrigerant and the refrigeration lubricant. The refrigerant is selected from the group consisting of a hydrofluoroolefin (HFO), a hydrofluorocarbon (HFC), a hydrochlorofluoroolefin (HCFO), and combinations thereof.

In certain embodiments, the refrigerant is selected from the group consisting of a mixture (nomenclature of ASHRAE Standard 34: R-513A) of 2,3,3,3-tetrafluoropropene and 1,1,1,2-tetrafluoroethane, trans-1,3,3,3-tetrafluoropropene (nomenclature of ASHRAE Standard 34: R-1234ze(E)), trans-1-chloro-3,3,3-trifluoropropene (nomenclature of ASHRAE Standard 34: R-1233zd(E)), and 1,1,1,3,3-pentafluoropropane (nomenclature of ASHRAE Standard 34: R-245fa).

According to the present disclosure, the refrigeration lubricant may be present in an amount ranging from 1 wt % to 99 wt % and the refrigerant may be present in an amount ranging from 1 wt % to 99 wt %, based on the total weight of the working fluid. In certain embodiments, the refrigeration lubricant may be present in an amount ranging from 20 wt % to 95 wt % and the refrigerant may be present in an amount ranging from 5 wt % to 80 wt %, based on the total weight of the working fluid.

According to the present disclosure, the working fluid is suitable for circulation in an equipment that undergoes a refrigeration cycle. In certain embodiments, the equipment may be a heat pump water heater, and the refrigerant in the working fluid is R-1233zd(E) or R-245fa. In certain embodiments, the equipment may be a freezer or a chiller, and the refrigerant in the working fluid is R-1234ze(E) or R-513A.

The disclosure will be further described by way of the following examples. However, it should be understood that the following examples are solely intended for the purpose of illustration and should not be construed as limiting the disclosure in practice.

EXAMPLES

Example 1 (EX1): Refrigeration Lubricant

A dipentaerythritol and a fatty acid composition were subjected to an esterification reaction in a molar ratio of 1:1, so as to form a dipentaerythritol ester, which served as a refrigeration lubricant of EX1. To be specific, the fatty acid composition included, based on the total weight of the fatty acid composition, 25 wt % of a fatty acid mixture and 75 wt % of a C₉ branched chain fatty acid. The fatty acid mixture contained, based on the total weight of the fatty acid mixture, 20 wt % of a C₇ straight chain fatty acid, 40 wt % of a C₈ straight chain fatty acid, and 40 wt % of a C₁₀ straight chain fatty acid.

Example 2 (EX2): Refrigeration Lubricant

The procedures and materials for preparing the refrigeration lubricant of EX2 were similar to those of EX1, except that the amounts of the fatty acid composition and the fatty acid mixture were varied. To be specific, the fatty acid mixture was adjusted to be present in an amount of 35 wt % and the C₉ branched chain fatty acid was adjusted to be present in an amount of 65 wt %, based on the total weight of the fatty acid composition. The C₇ straight chain fatty acid was adjusted to be present in an amount of 43 wt %, the C₈ straight chain fatty acid was adjusted to be present in an amount of 31 wt %, and the C₁₀ straight chain fatty acid was adjusted to be present in an amount of 26 wt %, based on the total weight of the fatty acid mixture.

Comparative Example 1 (CE1): Refrigeration Lubricant

A commercially available refrigeration lubricant (Manufacturer: Lubrizol, Model no.: Solest 220) served as a refrigeration lubricant of CE1.

Application Example 1 (AE1): Working Fluid

The refrigeration lubricant of EX1 and trans-1-chloro-3,3,3-trifluoropropene (nomenclature of ASHRAE Standard 34: R-1233zd(E), serving as a refrigerant) were mixed together, so as to obtain a working fluid of AE1.

Application Examples 2 to 8 (AE2 to AE8): Working Fluid

The procedures for preparing the working fluids of AE2 to AE8 were similar to those of AE1, except that the types of the refrigeration lubricant and the refrigerant were varied as shown in Table 1 below.

Comparative Application Example 1 (CAE1): Working Fluid

The refrigeration lubricant of CE1 and R-1233zd(E) (serving as a refrigerant) were mixed together, so as to obtain a working fluid of CAE1.

Comparative Application Examples 2 to 4 (CAE2 to CAE4): Working Fluid

The procedures for preparing the working fluids of CAE2 to CAE4 were similar to those of CAE1, except that the type of the refrigerant was varied as shown in Table 1 below.

The types of the refrigeration lubricant and the refrigerant used for preparing the working fluids of AE1 to AE8 and CAE1 to CAE4 are summarized in Table 1 below.

Property Evaluation

A. Determination of Kinematic Viscosity at 40° C.

The refrigeration lubricant of each of EX1, EX2, and CE1 was subjected to determination of kinematic viscosity at 40° C. using a viscometer (Manufacturer: Anton Paar, Model no.: SVM-3000) in accordance with ASTM D445 (published in 2024). The results are shown in Table 2 below.

B. Determination of Phase Separation Temperature Between Refrigeration Lubricant and Refrigerant

The phase separation temperature between the refrigeration lubricant and the refrigerant was determined in accordance with ANSI/ASHRAE Standard 218-2019 (published in 2019). Briefly, 2 g of a respective one of the refrigeration lubricants of EX1, EX2, and CE1 and 8 g of a refrigerant (i.e., R-1233zd(E), 1,1,1,3,3-pentafluoropropane (nomenclature of ASHRAE Standard 34: R-245fa), trans-1,3,3,3-tetrafluoropropene (nomenclature of ASHRAE Standard 34: R-1234ze(E)), or a mixture (nomenclature of ASHRAE Standard 34: R-513A) of 2,3,3,3-tetrafluoropropene and 1,1,1,2-tetrafluoroethane) were placed into a pressure-resistant glass tube, followed by sealing the pressure-resistant glass tube. Subsequently, the pressure-resistant glass tube was placed in a low temperature oven, followed by gradually reducing a temperature of the low temperature oven, while observing a mixing state of the refrigeration lubricant and the refrigerant inside the pressure-resistant glass tube. When the refrigeration lubricant and the refrigerant inside the pressure-resistant glass tube separated into two layers, the temperature of the low temperature oven at this moment was the phase separation temperature between the refrigeration lubricant and the refrigerant. That is to say, at a temperature greater than the phase separation temperature, the refrigeration lubricant of EX1, EX2, or CE1 and the refrigerant were miscible with each other, whereas at a temperature lower than the phase separation temperature, the refrigeration lubricant of EX1, EX2, or CE1 and the refrigerant were immiscible with each other. The results are shown in Table 2 below.

C. Determination of Solubility of Refrigerant and Refrigeration Lubricant for Forming Working Fluid and Kinematic Viscosity of Working Fluid Containing the Same

First, in a low-temperature and high-vacuum environment, a respective one of the working fluids of AE1 to AE8 and CAE1 to CAE4 was placed in a pressure vessel, followed by heating the working fluid to a temperature of 100° C. and then gradually cooling the working fluid down to a temperature of 0° C. During the cooling process, temperature, pressure, and kinematic viscosity of the working fluid were simultaneously monitored using techniques well-known to those skilled in the art, and the working fluid was sampled to analyze the actual composition of refrigerant and refrigeration lubricant therein. Next, the data (i.e., the monitored temperature, pressure, and kinematic viscosity) thus obtained were plotted to create solubility curves for the refrigerant and the refrigeration lubricant for forming the working fluid, as well as kinematic viscosity curves for the working fluid. By virtue of the solubility and kinematic viscosity curves, the solubility of the refrigerant and the refrigeration lubricant for forming the respective one of the working fluids of AE1 to AE8 and CAE1 to CAE4 and the kinematic viscosity of the respective one of the working fluids of AE1 to AE8 and CAE1 to CAE4 were analyzed under specific operating conditions (i.e., a temperature of an oil tank in a compressor and a pressure of the working fluid in the compressor). The results are shown in Tables 3 to 6 below.

Results

Referring to Table 2, the phase separation temperatures between R-245fa and a respective one of the refrigeration lubricants of EX1 and EX2 were 4° C. and 0° C., respectively, and hence the working fluid containing R-245fa and the respective one of the refrigeration lubricants of EX1 and EX2 were suitable to be applied in evaporators for an air-conditioning purpose and heat pump systems. The phase separation temperatures between R-513A and the respective one of the refrigeration lubricants of EX1 and EX2 were −10° C. and −20° C., respectively, and hence the working fluid containing R-513A and the respective one of the refrigeration lubricants of EX1 and EX2 were suitable to be applied in evaporators for a refrigerating purpose, heat pump systems, and chillers. The phase separation temperatures between a respective one of R-1233zd(E) and R-1234ze(E) and the respective one of the refrigeration lubricants of EX1 and EX2 were all lower than-60° C., and hence the working fluid containing the respective one of R-1233zd(E) and R-1234ze(E) and the respective one of the refrigeration lubricants of EX1 and EX2 were suitable to be applied in evaporators for a freezing purpose, heat pump systems, and chillers.

Referring to Table 3, the solubility of the refrigerant and the refrigeration lubricant for forming the working fluids of AE1, AE2, and CE1 was substantially the same under the same operating conditions (i.e., the temperature of the oil tank in a compressor and the pressure of the working fluid in the compressor), but the kinematic viscosity of each of the working fluids of AE1 and AE2 was higher than that of the working fluid of CAE1 under the same operating conditions. Referring to Table 4, the solubility of the refrigerant and the refrigeration lubricant for forming the working fluids of AE3, AE4, and CAE2 was substantially the same under the same operating conditions, but the kinematic viscosity of each of the working fluids of AE3 and AE4 was higher than that of the working fluid of CAE2 under the same operating conditions. Referring to Table 5, the solubility of the refrigerant and the refrigeration lubricant for forming the working fluids of AE5, AE6, and CAE3 was substantially the same under the same operating conditions, but the kinematic viscosity of each of the working fluids of AE5 and AE6 was higher than that of the working fluid of CAE3 under the same operating conditions. Referring to Table 6, the solubility of the refrigerant and the refrigeration lubricant for forming the working fluids of AE7, AE8, and CAE4 was substantially the same under the same operating conditions, but the kinematic viscosity of each of the working fluids of AE7 and AE8 was higher than that of the working fluid of CAE4 under the same operating conditions. These results demonstrate that the working fluid containing the refrigeration lubricant of the present disclosure (i.e., the refrigeration lubricant of EX1 or EX2) has a proper miscibility between the refrigeration lubricant and the refrigerant, which is better than a miscibility of the working fluid containing the commercially available refrigeration lubricant (i.e., the refrigeration lubricant of CE1), and thus the service life of the compressor can be extended.

In general, under the same operating conditions (i.e., the temperature of the oil tank in the compressor and the pressure of the working fluid in the compressor), higher kinematic viscosity of the working fluid indicates better lubricity thereof, which can extend a service life of the compressor. Referring to Table 3, under the same operating conditions, the kinematic viscosity determined in each of the working fluids of AE1 and AE2 was higher than that in the working fluid of CAE1. Referring to Tables 4 to 6, similar results were observed between the working fluids of AE3 and AE4 compared to the working fluid of CAE2, between the working fluids of AE5 and AE6 compared to the working fluid of CAE3, and between the working fluids of AE7 and AE8 compared to the working fluid of CAE4, indicating that the working fluid containing the respective one of the refrigeration lubricants of EX1 and EX2 had a higher kinematic viscosity than the working fluid containing the refrigeration lubricant of CE1. These results demonstrate that the working fluid containing the refrigeration lubricant of the present disclosure can exhibit excellent lubricity, thereby extending the service life of the compressor.

Summarizing the above test results, it is clear that by virtue of the refrigeration lubricant of the present disclosure including the dipentaerythritol ester, which is formed by subjecting the dipentaerythritol and the fatty acid composition to the esterification reaction, the working fluid prepared from the refrigeration lubricant of the present disclosure has a proper miscibility between the refrigeration lubricant and the refrigerant, and hence has a relatively high kinematic viscosity. Therefore, the working fluid has relatively excellent lubricity, and can effectively extend the service life of the compressor.

In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment(s). It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects; such does not mean that every one of these features needs to be practiced with the presence of all the other features. In other words, in any described embodiment, when implementation of one or more features or specific details does not affect implementation of another one or more features or specific details, the one or more features may be singled out and practiced alone without the another one or more features or specific details. It should be further noted that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure.

While the disclosure has been described in connection with what is(are) considered the exemplary embodiment(s), it is understood that this disclosure is not limited to the disclosed embodiment(s) but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.