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EP1909048A1 - Technik für ölfreies Kältemittel in einer Klimaanlage oder in einem Kühlkreislauf - Google Patents

Technik für ölfreies Kältemittel in einer Klimaanlage oder in einem Kühlkreislauf Download PDF

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Publication number
EP1909048A1
EP1909048A1 EP06020986A EP06020986A EP1909048A1 EP 1909048 A1 EP1909048 A1 EP 1909048A1 EP 06020986 A EP06020986 A EP 06020986A EP 06020986 A EP06020986 A EP 06020986A EP 1909048 A1 EP1909048 A1 EP 1909048A1
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Prior art keywords
oil
refrigeration
compressor
refrigerant
ovf
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EP06020986A
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French (fr)
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Chadalavada Venkatasubramaniam
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
    • F25B43/02—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat for separating lubricants from the refrigerant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/002—Lubrication
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/03—Oil level

Definitions

  • the present invention relates to oil-free refrigerant (OFR) circulation technology for air-conditioning and refrigeration system. More specifically, the present invention relates to oil-free refrigerant (OFR) circulation technology consisting of frictionless 99.99% oil-vapor free (OVF) refrigeration oil, ultra micron oil-aerosol separator with built-in reservoir, and electronic modulating oil level analyzer to increase energy efficiency and reduce maintenance cost.
  • OVF oil-vapor free
  • the oil-aerosol separator can filter solid contaminant particles down to one micron in size and at the same time can deliver 100% oil-aerosol free refrigerant.
  • the electronic modulating oil level analyzer can maintain compressor crankcase oil level recommended by compressor manufacturers for CFC, HCFC, HFC, ammonia and CO 2 refrigeration compressors at any given variable load.
  • Fig. 1 which shows schematically the compressor refrigeration cycle
  • the compressor 1 will drive the refrigerant to the condenser 2 through pipe for condensing, then the liquid refrigerant will go through the expansion device 3 to the evaporator 4 for evaporation by absorbing surrounding heat, and finally the refrigerant vapor will be back to the compressor 1 for recycling.
  • Compressor is the heart and oil is the lifeblood of any air-conditioning and refrigeration compressor.
  • the primary function of the compressor is to circulate refrigerant that has high latent heat carrying capacity to condenser, expansion valve and evaporator. Therefore the compressor capacity determines the capacity of the refrigeration system as a whole. Hence its capacity, reliability, and energy efficiency are significantly influenced by the performance of other components like refrigerant, refrigeration oil, condenser, expansion valve and evaporator.
  • oil vapor is a gas generated by the shearing action of screw compressor rotors or reciprocating compressor pistons and valves during compression process. This oil vapor is subjected to Dalton's Law of Partial Pressures and cannot be removed by any type of oil separator and is the single largest portion of the refrigeration oil (99.99%) carrying over from compressor to the refrigeration system, and continuously contaminates the refrigerant latent heat carrying capacity.
  • Oil related problems cost the industry millions in terms of service calls, energy cost and compressor burnout as published in the ASHRAE Journal April 1995 .
  • the most important oil related problems are:
  • the superheated oil vapor will take up the most valuable surface area used for de-superheating and condensing of superheated refrigerant vapor to liquid. At the same time this superheated oil vapor in the condenser will impede heat transfer and dramatically reduce coefficient of conductance on the condenser wall. Both of these factors will produce smaller temperature difference between the superheated refrigerant vapor and the condensing medium such as air or water.
  • the useful coil area will be less and the pressure drop in the heat exchanger and liquid line will be increased. It will then further accelerate the increase in refrigerant-lubricant viscosity and oil non-equilibrium behavior.
  • Oil contamination in the refrigerant will also reduce the volumetric capacity of the condenser. If 10 percent of the liquid refrigerant and oil solution is oil, then only 90 percent of the solution can be refrigerant and so the unit must operate much longer in order to have the required amount of refrigerant passing through the condenser.
  • thermostatic and electronic expansion valve The primary function of thermostatic and electronic expansion valve is to meter sufficient liquid refrigerant to the evaporator to satisfy the load.
  • TXV and EEV manufacturers require that the refrigerant liquid supplying at the inlet to the valve should be vapor free to guarantee the rated valve capacity but have ignored the effect of oil circulation at the inlet of TXV and EEV.
  • Most of the current correlations of refrigerant-oil mixture are developed from "oil contamination approach". That is not thermodynamically correct.
  • oil contamination approach studies the performance of refrigerant-oil mixture based on pure refrigerant properties. It ignores the influence of oil on the boiling point temperature, specific heat, latent heat, viscosity, density, etc. This in turn alters energy balance, local boiling temperature, superheat, local vapor quality and so on in the data reduction process to calculate heat transfer coefficient and two-phase pressure drop.
  • the tangible method is the "thermodynamic approach" that considers the refrigerant-oil mixture as something like zeotropic refrigerant.
  • the research methods on zeotropic refrigerant have been well understood. It is thermodynamically correct to study the refrigerant-oil mixture as zeotropic refrigerants.
  • the remote bulb of TXV or EEV sensor at the evaporator outlet will have a hard time to sense a true evaporator outlet temperature because of reduction on heat transfer through the line. TXV or EEV will begin to hunt, starve the evaporator and reduce refrigeration system capacity.
  • TXV remote bulb or EEV sensor may sense a warmer-than-normal temperature and therefore may over feed TXV or EEV to run at a low superheat that can result in flooding or slugging the compressor with refrigerant.
  • the compressor pistons can momentarily pump slugs of liquid oil that can build tremendous hydraulic force because of the incompressibility of most liquids and will lead to serious damage on compressor valves and other lubricating parts.
  • Evaporator is the coldest component with largest tubes, thus it has the slowest refrigerant velocity.
  • the higher oil mass fraction (OMF) and thicker oil film viscosity at low temperature can cause excessive oil build-up on the wall of the evaporator tube surface area to cause imperfect refrigerant distribution.
  • the refrigerant-oil mixture enters into evaporator at low temperature and the viscosity of the refrigerant-oil mixture will increase dramatically due to poor viscosity index of the solvent refined mineral oil and POE oil.
  • the solvent refined mineral oil has a viscosity index from 0 to 40.
  • the viscosity of solvent refined mineral oil at -40°C is 32,000 cSt for ISO 22 cSt grade and 1,000,000 cSt for ISO 32 cSt grade, and at -30°C is 170,000 cSt for ISO 68 cSt grade.
  • the pour point for solvent refined mineral oil is in the range of - 30 °C to - 40 °C.
  • POE oil has a viscosity index from 90 to 130.
  • the viscosity of POE oil at - 40 °C is 22,000 cSt for ISO 22 cSt grade and 45,000 cSt for ISO 32 cSt grade, and at -30°C is 70,000 cSt for ISO 68 cSt grade.
  • the pour point for POE oil is in the range of - 35 °C to - 52 °C.
  • the oil excess layer forms during the phase change from liquid to vapor.
  • the oil excess layer has a very large viscosity that causes a large oil volume build-up in the evaporator tube surface area and as a result will take up valuable evaporator surface area used for vaporization.
  • the oil excess layer causes insulation effect to decrease boiling of refrigerant, to increase pressure drop, and to reduce molecular and turbulent transport of refrigerant, therefore dramatically reduces the evaporator heat transfer efficiency.
  • TXV or EEV must feed evaporator with oil free liquid refrigerant at the same rate that it evaporates. Studies have shown that oil presence can reduce system performance as much as 30%.
  • the oil vapor exists as mist typically in the size about 0.001 micron and oil aerosol exists as droplets typically in the size ranging from 0.01 to 0.8 micron.
  • the oil aerosol is generated by the shearing action of the compressor during the compression process. Oil vapor and oil aerosol are trapped in the superheated discharge gas vapor.
  • Solvent refined mineral oil has extremely high volatility properties such as very high vapor pressure, very low viscosity index, very high pour point and very low flash point. Therefore, along with refrigerant-oil dilution effect, the viscosity will be seriously reduced when solvent refined mineral oil is exposed to high superheated discharge gas temperature. As a result the friction will be increased and in turn there will be more quantity of oil vapor generated. It is for this reason, the compressor lubricating oil plays a very important role as it not only determines the oil vapor content in superheated discharge gas vapor but also determines the frequency of oil change.
  • the quantity of oil vapor in the compressor in a large degree depends on the molecular distribution of the oil.
  • solvent refined mineral oil shows a typical broad bell-shaped distribution of the molecular weight with a high proportion of short molecular weight with very large number of short-chain molecules. It is these short-chain molecules that evaporate most easily and at the same time accelerates the generation of oil aerosol.
  • the quantity of HFC refrigerants such as R-134a, R-407c, R-410a and R-404a dissolved in POE oil is more than double when compared with solvent refined mineral oil.
  • the very high miscibility factor of POE oil further causes serious reduction in viscosity and in turn accelerates evaporation of more quantity of oil vapor and oil aerosol.
  • Moisture in a refrigeration system with HCFC and CFC refrigerants and mineral oil can cause formation of hydrochloric and hydrofluoric acids.
  • moisture in a refrigeration system with POE oil and HFC refrigerant can also cause formation of significant amount of organic acids which can lead to seal and gasket failure, lubrication break down, blockage of TXV, copper plating and in worst case scenario bearing erosion and compressor motor burn out.
  • the solvent refined mineral oil has moisture content in the range of 50 PPM to 90 PPM and, when exposed to high discharge gas temperature, will undergo polymerization or de-polymerization due to lack of proper thermal and chemical stability.
  • POE oil also lacks in proper thermal and chemical stability because of highly hygroscopic in nature and absorbs moisture in the range of 2500 PPM, approximately 10 times more than that of mineral oil. As a result it can undergo hydrolysis. The effect of hydrolysis will reverse the reaction of POE oil to its original components of acid and alcohol.
  • journal bearing lubricated compressor In journal bearing lubricated compressor, the incompressibility of water relative to oil can result in loss of hydrodynamic lubricating oil film that in turn leads to excessive wear. As little as 1% of water in oil can reduce the life expectancy of journal bearing by as much as 90%.
  • Lubricant film The primary method of defense against degrading force is the lubricant film.
  • Lubricating oil forms film to fill up the clearance between the bearing and journal.
  • the load on the journal is carried by the layer of oil and transmitted to bearing.
  • the pressurized oil is sent through drilled holes in the crankshaft to supply oil to all bearings. Since journal is supported or floats on the oil layer, there is no metal-to-metal contact. Excessive oil is relieved by the pressure regulating valve, usually to seal chamber to provide lubrication to the shaft seal assembly.
  • solvent refined mineral oil contains chemical impurities such as 40% wax, 38% aromatics, 13400 PPM sulfur, 160 PPM nitrogen, 1.64 PPM polar compounds and 90 PPM moisture. All of these can lead to the formation of sludge and deposit via oxidation and other chemical reaction.
  • cross linkage of the chloroprene polymer with sulfur forms neoprene elastomer.
  • the presence of sulfur in the lubricant will result in additional cross linkage of the chloroprene and subsequent hardening of the elastomer. This will lead to seal leakage in the compressor.
  • One method is to partially de-superheat the discharge gas vapor with liquid refrigerant injection with centrifugal pump known as liquid pressure amplification.
  • This method has many drawbacks. First of all, it increases compressor head pressure and therefore increases power consumption as reported in technical data sheet by US Navy. Secondly, heavier molecular weight refrigerants HCFC and HFC, for example R-22, R-134a and Propane, will result in higher dilution characteristics of 15 % to 20% due to its chemical composition. If discharge gas temperature is further reduced with liquid refrigerant injection, refrigerant dilution becomes extreme and can cause a complete compressor failure.
  • this liquid refrigerant is pumped with the lubricant into the bearings causing a washing effect and decreasing the MTBF (mean time between failures). Also, some of this refrigerant will flash into the rotor sealing screw compressor causing capacity loss. The more refrigerant in the lubricant, the higher the capacity loss and the more other oil related problems.
  • U.S. Patent No. 6,076,367 disclosed a further development. Again, as system pressure increases and refrigerant flow rate increases at higher load, the increased flow rate of refrigerant causes more pressure loss through the condenser. This same increased flow rate causes less pressure to be added to the liquid by the centrifugal pump in the liquid line. Thus, less liquid is bypassed into the compressor discharge line and less superheat is eliminated at the time when more reduction is needed. At some point the pressure loss through the condenser is greater than the pressure added by the centrifugal pump and therefore the effect is lost entirely.
  • compressor manufacturers also found that floating the head pressure can cause oil logging in the evaporator, because the refrigerant mass flow rate in the evaporator will start to decrease. This in turn reduces the refrigerant velocity in the suction riser to the extent that the refrigerant velocity is simply too slow for oil to return to the suction riser and therefore oil will be logged in the evaporator.
  • Another approach to overcome oil logging into condenser and evaporator is to inject chemical additive into the refrigeration system operating with solvent refined mineral oil to produce electromagnetic propagation to push the logged oil out of the condenser and evaporator in order to enhance refrigeration capacity as disclosed, e.g., in U.S. Pat. No. 4,963,280 .
  • solvent refined mineral oil contains chemical contaminants such as 1.64 PPM Polar compounds, 38% aromatics, 40% Wax, 160 PPM Nitrogen, 90 PPM Moisture and 13400 PPM Sulfur. These chemical contaminants in solvent refined mineral oil lead to formation of sludge and deposits via oxidation and chemical reactions.
  • Solvent refined mineral oil has zero or extremely low viscosity index. Moreover, solvent refined mineral oil contains polar molecules which increase the solubility of CFC, HFC and Ammonia refrigerants, and as a result, decrease the effective viscosity of the solvent refined mineral oil. Studies have shown that 3% dilution of CFC, HFC and Ammonia refrigerants in solvent refined mineral oil of ISO 68 grade would result in a loss of viscosity of over 5 cSt at 60 °C oil supply temperatures.
  • Solvent refined mineral oil lacks thermal and chemical stability and will undergo polymerization or de-polymerization.
  • the lack of thermal and chemical stability can build-up or break down of viscosity and also can lead to reaction of mineral oil with refrigerant, metals and contaminants in the system to form sludge and gums as well as carbon deposits on valves.
  • the operating life of solvent refined mineral oil is 3000 hours for air-conditioning application and 1000 hours for refrigeration application.
  • the viscosity of the solvent refined mineral oil at - 30 °C for ISO 68 Grade is 170000 cSt in the evaporator. Therefore, it will be technically and theoretically impossible for a chemical additive to push the 170000 cSt viscous oil logged in evaporator with a help of electromagnetic propagation back to the compressor crankcase.
  • compressor manufacturer Copeland, Hermetic Chemistry and Tribology groups, as a result of internal and external requests, have tested several oil additive products and has not been able to detect any meaningful change in compressor power consumption when measurements were made under controlled laboratory conditions with properly broken-in compressors on laboratory calorimeters at constant condensing and evaporator temperatures and pressures.
  • the present invention relates to oil-free refrigerant (OFR) circulation technology for air-conditioning and refrigeration system. More specifically, the present invention relates to oil-free refrigerant (OFR) circulation technology consisting of frictionless 99.99% oil-vapor free (OVF) refrigeration oil, ultra micron oil-aerosol separator with built-in reservoir, and electronic modulating oil level analyzer to increase energy efficiency and reduce maintenance cost.
  • OVF oil-vapor free
  • the oil-aerosol separator can filter solid contaminant particles down to one micron in size and at the same time can deliver 100% oil-aerosol free refrigerant.
  • the electronic modulating oil level analyzer can maintain compressor crankcase oil level recommended by compressor manufacturers for CFC, HCFC, HFC, ammonia and CO 2 refrigeration compressors at any given variable load.
  • the frictionless 99.99% oil-vapor free (OVF) refrigeration oil provides excellent hydrodynamic and elastohydrodynamic lubrication film for wear protection at high discharge gas temperature and at the same time provides excellent low temperature fluidity for better oil return by maintaining very low viscosity.
  • frictionless 99.99% oil vapor free (OVF) refrigeration oil has zero moisture content, 13/11 oil cleanliness and low friction coefficient. Low friction co-efficient correlates well with thick film formation, even under extreme load and variable condition.
  • the energy efficiency of a compressor is highly affected by lubricant friction loss. Therefore the use of frictionless oil vapor free (OVF) refrigeration oil with extremely low friction coefficient can enhance energy efficiency of a compressor.
  • the compressor 1 drives the contaminated refrigerant to the ultra micron oil-aerosol separator 5 through pipe 51, and then the ultra micron oil-aerosol separator 5 will collect 100% of the oil aerosol to be fed back via pipe 53 to the compressor 1 through the electronic modulating oil level analyzer 6.
  • the 99.99% oil-vapor free (OVF) refrigerant vapor will first be de-superheated and then enter the condenser 2 through pipe 52 for condensation.
  • the liquid refrigerant will then passes through the expansion device 3 and enter the evaporator 4 for evaporation by absorbing surrounding heat.
  • the evaporated refrigerant vapor will then be sucked back into compressor 1.
  • Fig. 3 shows schematically the structure of ultra micron oil-aerosol separator according to the present invention.
  • the compressor 1 will drive the contaminated refrigerant to the ultra micron oil-aerosol separator 5 through pipe 51.
  • An exceptionally pure and extremely fine matrix borosilicate micron fiber filter 54 covers the pipe 51, so that the oil aerosol and 99.99% oil-vapor free refrigerant will go through filter 54.
  • the oil-aerosol will be collected by the filter 54 completely and forms droplets to dropping down to the reservoir 55 on the bottom of the ultra micron oil-aerosol separator 5.
  • the refrigeration oil accumulated in the reservoir of the separator will be fed back to the crankcase though pipe 53 by the electronic modulating oil level analyzer 6 for maintaining proper oil level of the crankcase.
  • the 99.99% oil-vapor free refrigerant will pass through the filter 54 and the de-superheating zone 52 to the condenser 2, then to the expansion device 3 and the evaporator 4 for absorbing surrounding heat for evaporation. Finally the 99.99% oil-vapor free refrigerant will be sucked back to the compressor 1 for recycling.
  • the exceptionally pure and extremely fine borosilicate micro fiber filter 54 can remove 100% of refrigeration oil aerosol mist down to 0.01 micron in size and at the same time will filter solid contaminant particles down to one micron in size trapped in the superheated discharge gas.
  • the ultra micron oil-aerosol separator 5 has an anti-re-entrainment barrier on the downstream side of the separator to prevent refrigeration oil carry over or re-entrainment of the coalesced liquid after passing the borosilicate micro fiber.
  • the anti-re-entrainment barrier is a special barrier which will hold large volume of coalesced lubricant. As the lubricant concentration within the anti-re-entrainment barrier increases, the lubricant gravitates through the re-entrainment barrier to a built-in reservoir at the bottom of the ultra micron oil-aerosol separator 5, where the lubricant will be metered from the built-in reservoir directly into the compressor crankcase through the electronic modulating oil level analyzer 6.
  • the electronic modulating oil level analyzer 6 maintains an oil level in the compressor crankcase for any given variable load condition.
  • the electronic modulating oil level analyzer 6 feeds oil from the reservoir to the compressor crankcase when the oil level falls below recommended level and stops to feed oil from the reservoir back to the compressor crankcase when the oil level is too high.
  • the oil level can therefore be maintained as per compressor manufacturer's recommendation.
  • oil-vapor free (OVF) refrigerant circulation can be achieved, we must first analyze how oil-vapor free (OVF) refrigeration oil, ultra micron oil-aerosol separator and electronic modulating oil level analyzer can overcome the problems in the conventional refrigeration circulation related to oil vapor and oil aerosol carry over, thermal and chemical stability, moisture, oil cleanliness and lubrication.
  • the air-conditioning and refrigeration industry can then utilize the oil free refrigerant circulation technology for CFC, HCFC, HFC, ammonia and CO 2 refrigeration compressors to reduce energy cost, break down cost, maintenance cost and green house gas emission.
  • the present invention uses oil-vapor free (OVF) refrigeration oil which prevents the oil vapor carry over by 99.99% because of its excellent lubricant properties such as very low vapor pressure and very high flash point in the range of 200°C to 450 °C and contains no short-chain molecules.
  • OVF oil-vapor free
  • the oil-vapor free (OVF) refrigeration oil used in present invention has a very high viscosity index in the range of 200 to 450. This high viscosity index ensures adequate bearing oil supply viscosity at a superheated discharge gas temperature and the refrigerant-oil dilution characteristics. Therefore OVF refrigeration oil provides excellent wear protection, prevents further evaporation of oil vapor, and minimizes the generation of oil aerosol carry over.
  • the oil-vapor free (OVF) refrigeration oil used in this invention provides 99.99% evaporation resistance and has 99.99% less oil vapor content at superheated discharge gas temperature leaving the compressor, therefore there will be effectively 99.99% oil-vapor free refrigerant entering the condenser.
  • Screen filter of conventional oil separator can only remove solid contaminants down to 40 microns in size and can easily get blocked permanently in a few hundred hours of operation.
  • Analysis on refrigeration oil samples taken from refrigeration and air-conditioning systems shows that there is a high concentration of 5 to 20 micron solid contaminant particles in general, with the largest percentage of solid contaminant particles in the range around 15 microns.
  • conventional oil separators are hermetically sealed and cannot be accessed for cleaning.
  • the present invention uses a specially designed ultra micron oil-aerosol separator built in with exceptionally pure and extremely fine matrix borosilicate ultra micron fiber filter.
  • This micron fiber filter can remove 100% of oil aerosol mist as low as 0.1 micron trapped in the superheated discharge gas vapor leaving the compressor.
  • This micron fiber filter can also filter solid contaminants as small as 1 micron in size and therefore doubles the compressor bearing life.
  • the ultra micron oil-aerosol separator Based on the principle of coalescing and Brownian motion, the ultra micron oil-aerosol separator provides 100% oil aerosol separation efficiency by continuously exciting oil aerosol molecules to collide with each other to form larger oil aerosol droplets. Therefore oil aerosol carry over or re-entrainment of the coalesced liquid after passing through borosilicate ultra micron fiber filter can be prevented.
  • the present invention has an anti-re-entrainment barrier on the downstream side of the ultra micron oil aerosol separator.
  • the anti re-entrainment barrier is specially designed and provides tough barrier to hold large volume of coalesced lubricant.
  • the separator has a built-in oil reservoir with oil level sight glass. Then the coalesced lubricant from the oil-reservoir is metered directly into the compressor crankcase through electronic modulating oil level analyzer.
  • Refrigeration compressor operating with oil level in the compressor crankcase higher than recommended level can result in running at cylinder temperature 4.4°C to 15°C higher than normal. As a result the heat of compression will be increased and the cool suction gas will expand at a quicker rate. Consequently, the volumetric efficiency of the refrigeration compressor will be reduced.
  • the excess oil in the compressor crankcase can result in valve plate and cylinder head gasket failure. It can also raise discharge gas temperature and condensing temperature, causing higher power consumption and oil equalization problem.
  • the present invention uses 99.99% oil-vapor free (OVF) refrigeration oil and ultra micron oil-aerosol separator in combination with electronic modulating oil level analyzer which continuously monitors the oil level in compressor crankcase and modulates recommended oil level in the compressor crankcase at part load as well as at any variable load by metering the coalesced lubricant drawn from the bottom of oil reservoir directly into the compressor crankcase.
  • OVF oil-vapor free
  • the present invention uses 99.99% oil-vapor free (OVF) refrigeration oil that has less than 0.01% oil mass fraction in refrigerant circulation and has an extremely low viscosity for excellent low temperature fluidity in the evaporator. This is quite different from the case with solvent refined mineral oil or POE oil. At low temperature solvent refined oil or POE oil has very high viscosity and can even lose its fluidity.
  • OVF oil-vapor free refrigeration oil
  • the compressor crankcase oil level does not fluctuate under part load and floating head pressure. This would further enhance the smooth operation of the modulating oil level analyzer to maintain the oil level equilibrium in the refrigeration compressor crankcase under any variable load. As a result energy consumption and maintenance cost will be reduced.
  • oil vapor free (OVF) refrigeration oil that has less than 0.01% oil vapor content and ultra micron oil-aerosol separator that delivers 100% aerosol free refrigerant along with electronic modulating oil level analyzer that maintains oil level equilibrium in the refrigeration compressor crankcase under any variable load are able to accomplish oil free refrigerant circulation.
  • OVF oil vapor free
  • compressor pumps 99.99% pure refrigerant vapor carrying high latent heat capacity to enter the condenser. After condensation the 99.99% pure liquid refrigerant carrying high latent heat capacity circulates through receiver, liquid line, thermostatic expansion valve or electronic expansion valve. The TXV or EEV then feeds the 99.99% pure liquid refrigerant carrying high latent heat capacity to the evaporator with balanced and even distribution flow at the same rate as it evaporates.
  • the oil-free refrigeration circulation technology of present invention allows condenser and evaporator to remain 100% efficient all the time. Therefore with the use of oil free refrigerant circulation technology there is no need to include oil fouling factors in condenser and evaporator design and can save 15% to 20% of initial capital cost on air conditioning and refrigeration equipment.
  • the refrigeration compressor discharges superheated 99.99% oil-vapor free refrigerant vapor with small amount of oil aerosol.
  • the aerosol is filtered out and at the same time the solid contaminant particles down to one micron in size are also filtered. Therefore only 100% oil aerosol free refrigerant with less than 0.01% oil mass fraction enters the condenser.
  • This 99.99% oil-vapor free refrigerant is virtually non-hygroscopic and has 13/11 oil cleanliness standard, free of solid contaminants with particle size below 1 micron.
  • the present invention uses practically 99.99% oil free, 100% oil aerosol free and therefore 99.99% contaminant free superheated refrigerant vapor carrying high latent heat capacity to enter the de-superheating zone, condensing zone and sub-cooling zone of the condenser.
  • Discharge gas temperature is of considerable important in refrigeration system, particularly in the condenser.
  • the rate of chemical reactions approximately doubles when the discharge gas temperature is increased by 10°C.
  • the present invention of oil free refrigerant circulation technology prevents formation of excessive discharge gas temperature and therefore there is less fouling within the water cooled condenser and the amplification of legionella growth rate in the water cooled condenser is also dramatically reduced.
  • the present invention of oil free refrigerant circulation technology achieves maximum condenser heat transfer efficiency, and therefore can increase COP and refrigeration capacity with greater pull down time. All of these factors directly translate into reduction on compressor run time and peak demand charge. Thus energy cost, breakdown cost and maintenance cost are largely reduced.
  • the oil free refrigerant circulation technology of present invention will have 99.99% oil free and 99.99% solid contaminant free liquid refrigerant with high latent heat capacity entering thermostatic expansion valve or electronic expansion valve. Therefore, the thermostatic or electronic expansion valve will be able to maintain accurate superheat control at all the time.
  • the remote bulb of the TXV or EEV sensor at the evaporator outlet will sense a true evaporator outlet temperature due to high quality oil free refrigerant vapor leaving the evaporator outlet. Therefore overfeeding by TXV or EEV to run at a low superheat and flooding or slugging on the compressor with refrigerant can be prevented.
  • erosion of thermostatic expansion valve seat is also prevented due to 99.99% solid contaminant-free liquid refrigerant. All of these factors again directly translate into reduction of compressor run time and peak demand charge. Thus energy cost, break down cost and maintenance cost can be reduced.
  • the oil free refrigerant circulation technology of present invention will further have practically 99.99% oil free and 99.99% solid contaminant free liquid refrigerant carrying high latent heat capacity entering the evaporator with balanced and even distribution flow at the same rate as it evaporates. Therefore the rate of heat transfer and conductance coefficient through the evaporator wall is dramatically increased, that will lead to 100% boiling of the oil free liquid refrigerant to vapor. Consequently the maximum designed heat transfer efficiency of the evaporator is attained.
  • the small amount of oil vapor free (OVF) refrigeration oil circulating with the refrigerant in the evaporator has 0.01% oil mass fraction with extremely low viscosity due to very high viscosity index in the range of 200 to 450 to overcome the short fall of solvent refined mineral oil and POE oil for the given designed mass flow rate. This extremely low viscosity further prevents friction loss and pressure drop due to viscous drag and oil build-up in the evaporator surface area and suction line.
  • OVF oil vapor free
  • the oil vapor free (OVF) refrigeration oil circulation of present invention will have refrigerant in the evaporator with very low pour point in the range of - 60°C to - 90°C to provides excellent fluidity for the 0.01% oil mass fraction across the entire evaporator surface area under very low temperature condition. This will then enhance turbulent transportation of the 0.01% oil mass fraction of the oil vapor free (OVF) refrigeration oil at a very rapid rate of returning to the compressor crankcase to maintain the recommended oil level in the compressor for effective lubrication.
  • the liquid droplets carried over from the evaporator to the compressor crankcase can also be prevented due to even and balanced heat transfer distribution of the oil free liquid refrigerant across the entire evaporator surface area.
  • the p oil vapor free (OVF) refrigeration oil resent of invention has zero moisture and virtually non-hygroscopic by nature.
  • the zero moisture content and non-hygroscopic nature of oil vapor free (OVF) refrigeration oil provides high dielectric strength, therefore prevents compressor motor burn out in hermetic and semi-hermetic compressors and increases the reliability and durability of the compressor, refrigerant, lubricant and associated components such as TXV, moisture indicator sight glass, liquid and suction line filter driers.
  • the frequency of oil change as well as liquid and suction line filter drier replacement can therefore be largely reduced.
  • the moisture removal efficiency of the liquid and suction line drier if present in the system, can further be enhanced.
  • the zero moisture content and non-hygroscopic nature of the oil vapor free refrigeration oil prevents its thermal and chemical degradation as well as formation of hydrochloric and hydrofluoric acid by mineral oil with HCFC and CFC refrigerants and significant amount of organic acids by POE oil with HFC refrigerants.
  • Oil vapor free (OVF) refrigeration oil provides superior corrosion, oxidation and chemical protection, and excellent resistance to long-term oil thickening.
  • Oil vapor free (OVF) refrigeration oil prevents loss of hydrodynamic and elastohydrodynamic lubricating oil film in journal bearing lubrication and in rolling bearing lubrication to prevent erosive wear.
  • Oil vapor free (OVF) refrigeration oil can prevent friction loss, wear and tear of compressor parts, excessive discharge temperature and higher compression ratio with higher power draw.
  • the present invention of oil vapor free (OVF) refrigeration oil can reject water 20 times faster than POE oil and solvent refined mineral oil, and, as a result, can increase latent heat carry capacity of the refrigerant for maintaining maximum heat transfer efficiency for condensation and evaporation. For every 1% of water there will be 2% reduction in refrigeration capacity and 1% increase in energy consumption.
  • OVF oil vapor free
  • the oil-vapor free (OVF) refrigeration oil of present invention is exceptionally pure and clean and exceeds industrial oil cleanliness standard. It has oil cleanliness of ISO 13/11. Therefore it doubles the compressor bearing life and protects the shaft seal face from circulating particle damage and extends seal life dramatically. Oil-vapor free (OVF) refrigeration oil thus can remove heat of compression rapidly, reduce friction and prevent surface wear in journal and roller element bearings. As a result it lowers discharge gas temperature and compression ratio with lower power draw on the refrigeration compressor motor.
  • the exceptionally clean oil-vapor free (OVF) refrigeration oil of present invention has cleanliness of ISO 13/11 that provides excellent oil flow through the drilled holes of crankshaft and other lubricating moving parts. It reduces pressure drop in lubricating oil feed line and also provides tough hydrodynamic and elastohydrodynamic lubrication film between the metal surfaces and prevents friction loss on metal surfaces. Therefore the energy cost and maintenance cost can significantly be reduced.
  • the oil-vapor free (OVF) refrigeration oil of present invention has excellent viscosity to provide tough hydrodynamic and elastohydrodynamic film at the superheated discharge gas temperature to provide excellent wear protection to all moving parts and give satisfactory sealing and lubrication in the compressor.
  • the oil-vapor free (OVF) refrigeration oil of present invention has very high viscosity index. This means that there is a relatively small change in viscosity across the temperature range for the compressor bearing lubrication. Therefore a higher viscosity index provides lower wear. It is worth mentioning that improper lubrication is responsible for 50% to 80% of all mechanical and electromechanical compressor failures.
  • the oil-vapor free (OVF) refrigeration oil of present invention is "resistant to dilution" because of its controlled miscibility and solubility. Resistant to dilution can improve volumetric efficiency in compressor and provide efficient oil return from the system. In addition, test on oil-vapor free (OVF) refrigeration oil of present invention shows that there is no loss of lubricant film under diluted condition with rolling and journal bearing elements at extreme operating condition.
  • High viscosity index of the oil-vapor free (OVF) refrigeration oil of present invention provides a high viscosity for effective lubrication and good sealing wedge on the leading edges of piston rings against the leak back of the discharge gas in reciprocating compressor and compressor rotors in screw compressor.
  • the high viscosity index can retain a low viscosity needed for good oil return from the low temperature side of the refrigeration system.
  • OVF oil-vapor free refrigeration oil of present invention with rotary screw compressor shows 20% improvement in refrigeration capacity over solvent refined mineral oils.
  • the oil-vapor free (OVF) refrigeration oil of present invention has lower friction co-efficient and provides with thick enough film even under extreme load and variable condition. It can therefore prevent friction loss and can greatly reduce friction and viscous drag.
  • oil-vapor free (OVF) refrigeration oil of present invention has the lowest friction coefficient 0.02 at ISO Grade 68 cSt viscosity. That amounts to 300 times less friction loss than mineral oil and 150 times less friction loss than POE oil.
  • oil-vapor free (OVF) refrigeration oil of present invention has high load carrying capacity without causing skidding, dragging or overheating, and has less friction generated by the oil itself while in lubrication, thus results in less power required to overcome friction.
  • Oil-vapor free (OVF) refrigeration oil of present invention causes less frictional heat in contact zone and hence provides thicker lubricating film.
  • the oil-vapor free (OVF) refrigeration oil of present invention has a higher thermal and chemical stability. Therefore oil change interval is significantly extended and temperature of discharge gas and other lubricating parts are lowered. Consequently the oil-vapor free (OVF) refrigeration oil of present invention can provide better wear protection and therefore better reliability on the compressor and other moving components. All of these factors can directly translate into about 50% reduction in maintenance and break down cost.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Power Engineering (AREA)
  • Lubricants (AREA)
  • Compressor (AREA)
EP06020986A 2006-10-06 2006-10-06 Technik für ölfreies Kältemittel in einer Klimaanlage oder in einem Kühlkreislauf Withdrawn EP1909048A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP06020986A EP1909048A1 (de) 2006-10-06 2006-10-06 Technik für ölfreies Kältemittel in einer Klimaanlage oder in einem Kühlkreislauf

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2730862A1 (de) * 2012-11-12 2014-05-14 LG Electronics Inc. Klimaanlage mit einem Ölabscheider
WO2016145208A1 (en) 2015-03-11 2016-09-15 Emerson Climate Technologies, Inc. Compressor having lubricant management system for bearing life
US10598416B2 (en) 2013-11-04 2020-03-24 Carrier Corporation Refrigeration circuit with oil separation
CN117570611A (zh) * 2024-01-16 2024-02-20 山东迈格贝特机械有限公司 一种油分离器以及螺杆式冷水机

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DE202004014254U1 (de) * 2004-09-14 2004-11-25 Kriwan Industrie-Elektronik Gmbh Vorrichtung zur Überwachung des Ölniveaus in einem Kältemittelverdichter
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GB473502A (en) * 1935-10-03 1937-10-14 Standard Oil Dev Co Improvements relating to lubricating compositions
GB1236396A (en) * 1967-08-17 1971-06-23 Norgren Ltd C A Apparatus for the filtration of air or other gaseous media
GB1208789A (en) * 1968-05-09 1970-10-14 Eiichi Uratani Apparatus for separating and removing oil contained in circulating refrigerant
GB2126497A (en) * 1982-09-09 1984-03-28 Domnick Hunter Filters Ltd Coalescing filter element
EP0502808A2 (de) * 1991-03-04 1992-09-09 Carrier Corporation Öl-Abscheider
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EP0852324A1 (de) * 1997-01-06 1998-07-08 Mitsubishi Denki Kabushiki Kaisha Kältemittelumlaufgerät und Zusammenbauverfahren für einen Kältemittelkreislauf
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2730862A1 (de) * 2012-11-12 2014-05-14 LG Electronics Inc. Klimaanlage mit einem Ölabscheider
US9500396B2 (en) 2012-11-12 2016-11-22 Lg Electronics Inc. Oil separator and air conditioner using the same
US10598416B2 (en) 2013-11-04 2020-03-24 Carrier Corporation Refrigeration circuit with oil separation
WO2016145208A1 (en) 2015-03-11 2016-09-15 Emerson Climate Technologies, Inc. Compressor having lubricant management system for bearing life
EP3268611A4 (de) * 2015-03-11 2018-10-31 Emerson Climate Technologies, Inc. Verdichter mit schmiermittelverwaltungssystem für lagerlebensdauer
US10302340B2 (en) 2015-03-11 2019-05-28 Emerson Climate Technologies, Inc. Compressor having lubricant management system for bearing life
CN117570611A (zh) * 2024-01-16 2024-02-20 山东迈格贝特机械有限公司 一种油分离器以及螺杆式冷水机
CN117570611B (zh) * 2024-01-16 2024-03-22 山东迈格贝特机械有限公司 一种油分离器以及螺杆式冷水机

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