KR101343177B1 - Noise Reduction Additive - Google Patents

Abstract

Noise reduction in the compressor used in the cooling system is achieved by introducing 0.01 to 10% by weight of the phosphate ester additive in the compressor lubricant. Phosphoric acid ester additives are of formula (I) Preferred phosphate ester additives are ring substituted aryl esters. Noise reduction over 1 dB is achieved at frequencies 0-20 KHz.

<Formula I>

Wherein each R is independently alkyl, aryl or ring substituted aryl.

Refrigeration system, compressor, compressor grease, refrigerator noise, foaming agent,

Description

Noise Reduction Additives

The present invention relates to the use of phosphate ester additives to reduce noise inside and around a refrigerator compressor and to a method of reducing noise inside and around a refrigerator compressor by adding a phosphate ester additive to the cooling lubricant of the compressor.

Today, one of the driving forces in the chiller industry is the manufacture of more energy efficient cooling systems. This has led to the introduction of cooling systems with more efficient compressors that consume less energy and operate longer. However, one undesirable side effect of increased energy efficiency is that the compressor generates more noise.

In the past, noise reduction in cooling compressors has been proposed by adding an additive which generates foam to the cooling lubricant. Foam was thought to dampen compressor noise by reducing vibration and noise transmission to the compressor outer shell. However, such a noise reduction method in the compressor has a major disadvantage.

First, excessive foaming of the cooling lubricant can cause deleterious effects on the cooling system, such as co-exhaust of excess lubricant when the lubricant is then delivered to other parts of the cooling system outside the compressor. This can lead to lubricant depletion in the compressor, causing the compressor to wear more easily. In addition, when the lubricant moves to and coats the heat transfer surface of the condenser, a decrease in heat transfer in the cooling system occurs.

Second, the most common additives that generate foam in cooling lubricants are those containing silicones, which are known to have disadvantages. For example, it has been found that silicone containing additives block the capillary of the cooling system. It is also known that silicon-containing additives thermally decompose into powdery solids, which can interfere with the cooling process. Thus, care must be taken, for example, when attaching the compressor to the cooling system in areas to be soldered free of residual lubricant and silicone containing additives. Silicone-containing additives are also known to interfere with the painting process.

Triaryl phosphate esters are widely used as antiwear additives in petroleum and synthetic base stock hydraulic fluids, tractor fluids, aircraft turbans and piston engine lubricants. It is widely recognized that triaryl phosphate esters are most effective at levels of up to 2% by weight, preferably 1.5% by weight in the lubricant.

Trialkyl phosphate esters are mainly used as aircraft hydraulic fluid components or as solvents in industrial processes. Their use is noted as anti-wear additives in applications where phenol release from phosphate decomposition is to be avoided, and they are also used in the field of metal working.

Surprisingly, it has been found that adding phosphate ester additives of the kind disclosed above to lubricants in compressors of cooling systems reduces noise inside and around the compressor while minimizing lubricant foam formation. In addition, the phosphate ester additive does not contain silicone.

Accordingly, the present invention is directed to reducing the noise inside and around the compressor of a cooling system of 0.01 to 10% by weight of trialkyl, aryl, aryl substituted by aromatic rings, or arylalkyl phosphate esters by at least 1 dB at a frequency of 0 to 20 KHz. For use in compressor lubricants.

The present invention also includes the addition of 0.01 to 10% by weight of trialkyl, aryl, aryl substituted by aromatic rings, or arylalkyl phosphate esters to the lubricant in the compressor, thereby reducing noise in and around the compressor of the cooling system at frequency 0. To 20 dB or more by 1 dB or more.

The cooling system includes a compressor, a condenser, an expander and an evaporator. The liquid coolant evaporates in the evaporator to provide the cooling required for the cooling system. The coolant gas then passes through a compressor that compresses to condensation pressure. In the condenser, the superheated coolant gas is condensed into liquid using a cooling medium such as water or air. The liquid coolant then passes through the expansion valve to depressurize and return to the evaporator.

The noise originates from the transmission of energy at various frequencies from the noise source to the pressure waves through the solid (compressor case and pipe system), liquid (lubricant) and gas (coolant) media, ie the compressor shell from which the noise occurs. Sources of noise inside and around the compressor include: suction flow inside the compressor as a result of the flow characteristics of the coolant gas determined by the compressor operating conditions; Noise from lubricant agitation inside the compressor required to deliver lubricant to the mechanical part of the compressor for lubrication; Lubricant dipping from the top of the compressor pump and compressor shell and subsequent splashing into the lubricant on the compressor base and compressor shell; Noise from opening and closing of the motor and discharge valve of the compressor itself. Noise from various noise sources ranges from various frequencies, typically from 0.5 to 20 kHz. For example, for a Maris DC compressor, the intake flow is typically 500 Hz, the agitation of lubricant in the compressor is typically 2.5 kHz, dipping and splashing are typically 5 and 6.3 kHz.

Phosphoric acid ester additives used in the present invention are trialkyl, aryl, substituted (on aromatic rings) aryl or arylalkyl phosphate esters, i.e.

Wherein each R is independently alkyl, aryl or ring substituted aryl.

In particular, the phosphate ester additive may be a trialkyl phosphate ester, preferably of formula II.

Wherein each R ¹ may be the same or different and is selected from alkyl groups having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. Each R ¹ may be independently saturated or unsaturated, preferably saturated, and may be independently straight or branched chain.

The phosphoric acid ester additive may be triaryl or tri (ring substituted) aryl phosphate ester, preferably of formula III.

Wherein Ph is phenyl, x is an integer from 0 to 5, and if x is greater than 0, each R ² is an alkyl group which may be the same or different for each Ph group and may be the same or different for each x . Each R ² is preferably an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10, especially 1 to 6 carbon atoms. Each R ² may be independently saturated or unsaturated, preferably saturated, and may be independently straight or branched chain. Preferably, x is an integer ranging from 1 to 5, preferably an integer ranging from 1 to 3, in particular 1 or 2.

The phosphate ester additive may be tri arylalkyl phosphate ester, preferably one of formula (IV) below.

Wherein each R ³ is independently selected from an R ¹ group as defined in Formula II above and a —Ph (R ² ) _x group as defined in Formula III above, provided that at least one R ³ group is R ¹ group and at least one R ³ group is a -Ph (R ² ) _x group.

Preferably, the phosphate ester additive used in the present invention is a ring substituted triaryl phosphate ester of formula III. Specific examples of suitable additives include tricresyl phosphate, tricyllenyl phosphate, tri (isopropyl phenyl) phosphate, tert-butylated triphenyl phosphate, in particular tricresyl phosphate.

The additive is present in the lubricant at a level of 0.01 to 10% by weight, preferably 0.1 to 7% by weight, in particular 1 to 5% by weight.

The noise level inside and around the compressor is reduced by at least 1 dB, preferably at least 1.5 dB, more preferably at least 2 dB.

In order to measure the noise level inside and around the compressor, the compressor is placed on the steel floor in the acoustic chamber.

The acoustic chamber is specifically designed to dampen ambient noise and vibrations. It is made of plasterboard with a piece of fiberglass sandwiched between two plasterboards. The inner surface of the inner plasterboard sheet is coated with an open cell foam. The acoustic chamber itself is raised on a rubber mat. The compressor is connected via a vibration free hose to a cooling system that can be located outside the acoustic chamber and located in a separate space. Appropriate amounts of lubricants and phosphate ester additives and coolants are added to the system. Before measuring the noise level, allow the system to run for a few minutes to reach a stable state because the noise level is expected to be high at the start of the system operation.

Noise levels are measured using a microphone located at various locations, typically four to five locations around the compressor case, and averaged. Typical locations for microphones are one at the center above the compressor case, one at the front and rear of the compressor case, and one at each side of the compressor case. The distance of the microphone from the compressor is optimized for each compressor by testing. Typically, the microphone is placed 5 to 50 cm, in particular 10 to 30 cm, from the compressor. The microphone is attached to a real-time fast Fourier transform (FFT) analyzer that records the signal at each microphone location over a 20 second period. FFT analyzers convert signals over time into noise measurements and frequency spectra.

The presence of additives minimizes foam formation of lubricants in the compressor. Preferably, the foam height measured by bubbling coolant gas in a lubricant containing from 0.01 to 10% by weight of the phosphate ester additive in the measuring cylinder for 10 minutes is 10 mm or less, more preferably 5 mm or less, in particular 4 mm or less. .

The cooling system is equipped with a compressor as described above. The compressor may have on its front a visible glass window that allows to measure the foam height produced when the cooling system is operating when the compressor lubricant contains a phosphate ester additive.

Preferably, the foam height determined by measuring the foam height in the visible glass window of the front of the compressor of the cooling system is 2.5 mm or less, more preferably 2 mm or less when 0.01 to 10% of the phosphate ester additive is added to the compressor lubricant.

Compressor lubricants are selected from polyalkylene glycols, polyol esters, diesters, carbonate esters, polyvinyl ethers, poly alpha olefins and alkylbenzenes, and mixtures thereof. Preferred oils are polyol esters and mixtures of polyol esters with alkyl benzenes, polyvinyl ethers and diesters. Particularly preferred oils are polyol esters or mixtures of polyol esters and alkyl benzenes.

Particularly suitable polyol esters for use in the present invention are prepared from polyhydric alcohols and monobasic carboxylic acids by standard direct esterification methods. The polyol esters may be prepared by transesterification routes. Both routes are described in Synthetic lubricants and high-performance functional fluids, 2nd edition, edited by L. R Rudnick and RL Shubkin, pages 70-71. Especially preferred are polymerization routes that do not use a catalyst. Particularly preferred polyol esters are at least one alcohol selected from neopentylglycol, trimetholpropane and pentaerythritol, and dimers and trimers thereof, and straight and / or branched C ₅ to C ₁₈ acids, in particular C _{From 5} to C ₁₃ acids, more particularly from one or more acids selected from C ₅ to C ₉ acids.

Preferred polyol esters have a dynamic viscosity of at least 5 cSt and at most 240 cSt at 40 ° C. and a dynamic viscosity of at least 1.5 cSt at 100 ° C.

Preferred polyol esters have a pour point below −30 ° C., more preferably below −40 ° C. Preferred polyol esters have an acid number of less than 0.04 mgKOH / g. Preferred polyol esters have a water content of less than 50 ppm. Preferred polyol esters have a hydroxyl number of less than 5 mgKOH / g. Examples of preferred polyol esters include emka rate (EMKARATE) ^® RL acids available polyol ester in a division of the unique e Limited (Uniqema Ltd) of ICI.

Compressor lubricants according to the invention comprise at least one other lubricant additive of known functionality at a level of from 0.0001 to 20% by weight, more preferably from 0.01 to 10% by weight, in particular from 0.01 to 5% by weight, based on the weight of the lubricant. . Suitable additives include antioxidants, antiwear additives, extreme pressure agents, acid scavengers, stabilizers, surfactants, viscosity index enhancers, corrosion inhibitors, metal deactivators or passivators, lubricity Improvers or oily enhancers and friction modifiers.

The coolant of the cooling system suitably comprises hydrocarbon fluorocarbon (HCFC), hydrocarbon fluoride (HFC), a mixture of coolants containing at least one HFC, HCFC or both, carbon dioxide or ammonia. Preferably, the coolant does not contain any chlorine atoms. In particular, the coolant gas is HFC or a mixture of HFCs. Suitable HFC cooling gases include R-134a (1,1,1,2-tetrafluoroethane), R-32 (difluoromethane), R-125 (1,1,1,2,2-pentafluoro Ethane), R-152a (1,1-difluoroethane), R-143a (1,1,1-trifluoroethane) and mixtures thereof, and R-400 and R-500 series. Other components typically found in coolant mixtures may also be included in the cooling gas. These include hydrocarbons, especially hydrocarbons having 1 to 6 carbon atoms, for example propane, isobutane, butane, pentane and hexanes, fluorinated hydrocarbons and other coolants such as carbon dioxide.

The present invention is illustrated with reference to the following non-limiting examples and the accompanying drawings, in which FIG. 1 is a schematic diagram of a simple foam forming test apparatus described in Example 3 below.

For Examples 1 and 2 below, the noise level was measured as follows. The compressor was mounted on the steel floor in the acoustic chamber. The acoustic chamber is a cube of length, width and height 1.5 m made of plasterboard with a sealed door. The acoustic chamber was made from a plasterboard with 2.54 cm thick pieces of fiberglass sandwiched between two 0.64 cm sheet plasterboards. The inner surface of the inner plasterboard sheet was coated with 1.27 cm thick open foam. The acoustic chamber itself was mounted on a rubber mat.

The compressor was connected via a vibration free hose to a cooling system on the adjacent side outside the acoustic chamber. The cooling system was emptied and 235 g of polyol ester lubricant containing 5% of the phosphate ester additive by weight of the lubricant was "suctioned" into the compressor. Thereafter, 60 g of HFC 134a coolant was added to the cooling system. The system was run for a few minutes, typically up to 30 minutes, to allow the noise level to reach a steady state.

The noise level was measured using a 1.27 cm microphone placed in five places around the compressor case (one at the center above the compressor case, one at the front and rear of the compressor case and one at both sides of the compressor case), and averaged the measured values. In each case, the microphone was placed 30 mm from the compressor case. The microphone was connected to a real-time fast Fourier transform (FFT) analyzer that recorded the signal at each microphone location over a 20 second period. The FFT analyzer converted the signal over time into noise measurements (db) and frequency. The noise measurements were then averaged against the measured microphone readings.

Example  One

In this embodiment, the compressor used is a Samsung MK compressor. Table 1 below shows the noise level measured using this method over a frequency range of 0-20 KHz when the compressor lubricant is a unique mica RL10H polyol ester containing 5% by weight of the phosphate ester according to the present invention.

In Table 2 below, the noise levels measured using this method over a frequency range of 350 Hz to 20 KHz are shown when the compressor lubricant is a unique mica RL10H polyol ester containing 5% by weight of the phosphate ester according to the present invention.

In each case, the presence of the phosphate ester additive according to the invention reduced the noise inside and around the compressor by 1 dB or more.

Durad ^® 220 is isopropylated triphenyl phosphate and Durad ^® 220x is trixylenyl phosphate (both FMC Corp.).

Example  2

Table 3 below shows the noise levels measured using the above method for various compressors over a frequency range of 0 to 20 KHz in the ethylene polyol esters in which the compressor lubricant contains 5% by weight of the phosphate ester according to the present invention.

For most different compressor types, the presence of the phosphate ester additive according to the invention reduced the noise inside and around the compressor by more than 1 dB.

Example  3

Foam height (mm) was measured according to a simple foam forming test. The apparatus for the foam formation test is shown in FIG. 1. The water bath 7 was set at 25 ° C. 134a coolant pail 6 was placed in a water bath 7. Fully open the needle valve (5) of the keg (6) and slowly open the system needle valve (5A) located next to the rotameter (4) until a flow rate of 1 L / min is obtained. It was. Then, 5 cm from the bottom of the measuring cylinder 2, the coolant was passed through a sintered glass rod 3 suspended over the compressor lubricant 1 containing the phosphate ester additive. Coolant was bubbled through the sintered glass rod 3 for 10 minutes. The foam levels were then recorded in mm, if present. The results are shown in Table 4 below.

SynOAd 8478 is t-butylated triphenyl phosphate (Akzo).

Table 5 below shows the comparison results when the lubricant additive is a commercially available silicone-containing foam forming additive.

LN is Akrochem 50 (50 cSt polydimethylsiloxane from acrochem / silchem).

DC57 is a copolymer of Dow's polydimethylsiloxane and polyoxyalkylene ether (polyether modified polysiloxane).

Example  4

Foam heights were measured for the cooling systems described in Examples 1 and 2. Samsung compressors were retrofitted with a visible glass window facing the front floor. The compressor was then connected to a cooling system. The cooling system was emptied and 235 g of polyol ester lubricant containing lubricant additive was "suctioned" with the compressor. Thereafter, 60 g of HFC 134a coolant was added to the cooling system. The system was run for a few minutes, typically up to 30 minutes, to allow the noise level to reach a steady state. The foam height was then measured in the glass pane. The results are shown in Table 6 below.

Table 7 below shows the comparison results when the lubricant additive is a commercially available silicone-containing foam forming additive.

Both LN and DC57 are known as foam forming additives used in compressors to reduce compressor noise levels. Typical addition levels can be between 100 ppm and 0.5% or less.

The data of Examples 3 and 4 clearly show that using the phosphate ester according to the invention does not cause excessive foam formation which can cause a detrimental effect on the cooling system. These detrimental effects are as detailed in the first half of this specification.

Claims (33)

Compressor lubricant for reducing the noise inside and around the compressor of the cooling system by at least 1 dB at a frequency of 0-20 KHz, comprising from 5 to 10 weight percent of a phosphate ester additive of formula (I): <Formula I>

Wherein each R is a cresyl group. delete delete delete delete delete delete delete delete delete delete delete The compressor lubricant of claim 1 wherein the phosphate ester additive is present in the lubricant at a level of 5 to 7 weight percent. The compressor lubricant of claim 1, wherein the noise level within and around the compressor is reduced by at least 1.5 dB. A method for reducing noise inside and around the compressor of a cooling system by at least 1 dB at a frequency of 0 to 20 KHz, comprising adding 5 to 10 weight percent of a phosphate ester additive of formula (I) to the lubricant in the compressor: <Formula I>

Wherein each R is a cresyl group. delete delete delete delete delete delete delete delete delete delete delete 16. The method of claim 15, wherein the additive is present in the lubricant at a level of 5 to 7 weight percent. The method of claim 15, wherein the noise level within and around the compressor of the cooling system is reduced by at least 1.5 dB. It contains a coolant, a lubricant, and 5 to 10% by weight of the phosphate ester additive as defined in claim 1, and during operation, the noise inside and around the compressor is at a frequency of zero compared to the operation of the same cooling system without the phosphate ester additive. A cooling system comprising a compressor, a condenser, an expander and an evaporator, reduced by at least 1 dB at from 20 KHz. 30. The cooling system of claim 29, wherein the additive is present in the lubricant at a level of 5 to 7 weight percent. 30. The cooling system of claim 29, wherein, during operation, a noise reduction within and around the compressor of at least 1.5 dB is achieved as compared to the operation of the same cooling system without the phosphate ester additive. 30. The cooling system of claim 29, wherein the lubricant is a fluorohydrocarbon or a mixture of fluorohydrocarbons. 30. The cooling system of claim 29, wherein said lubricant is a polyol ester.

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