1.3 Working fluid 1.3.1General The term "working fluid"means the process medium in heat pump system (for refrigeration process termed medium refrigerant).The discussion here is mostly limited to the processes of absorption and emission of heat at approximately constant temperature,in other words to the usual evaporator- /compressor process("cold-vapor process")with a single component medium. Since the first cold steam plant saw the light (Jacob Perkins'refrigeration from 1834),a series of working fluids have been applied,Perkins even used ether,but in turn was working fluids such as carbon dioxide (CO2),ammonia(NH3),sulfur dioxide(SO2)and methyl(CH3C1).Today,only the ammonia back of these "pioneer fluid",and then primarily used in large refrigeration systems and heat pumps.The rest are replaced with synthetic derived fluid,where the base material is hydrocarbons methane(CH4)and ethane (C2H6).Intentional properties are achieved by a varying number of hydrogen atoms are replaced with mainly chlorine(Cl)or fluorine(F).Other halogens may also occur,such as bromine(Br).The fluid's official designation is "R xyz",where R stands for"Refrigerants"and xyz is the digits of a number that reflects the chemical composition.This symbol covers the rest of the family of the working fluid(see below). Working fluid who have a basis in ethane or methane(hydrocarbon derivatives)and where all Hydrogen atoms are replaced with chlorine and fluorine,termed full-halogenated chlorine-fluorine carbohydrates or just CFC's.Not full-halogenated chlorofluorocarbons containing one or more hydrogen atoms and is designated as HCFCs,If the fluid also are chlorine free and contains only hydrogen,fluorine and carbon, called the llFK,one often uses halocarbons (short for halogenated hydrocarbons)as a generic term for CFCs,HCFCs and HFCs. The pure hydrocarbon derivatives are numbered according to the following key: 1.digit:Number of C atoms-1 2.digit:Number of H atoms +1 3.digit:Number of F atoms If the first digit is zero HP,it will be not printed.This means that all the fluid that have been withdrawn from methane only get two digits.About a bromine atom is substituted,provided the addition B1 to R- number, Example: R-134a C=1+1=2 R-22 H=4-1=3 C=0+1=1 F=3 H=2-1=1 Letter code says that this is an Isomer F=2 That means the refrigerant consist of the same number of atoms,but the CI=1 molecule have a different composition Therefore:CHCIF2 Therefore:C H F 233 In addition to the clean fluid,are also called azeotroper.An azeotrop is a(mixed fluid)mixture of two fluid,which at a given mixture has the same properties as a pure medium,that is evaporation and condensation temperature is constant at a given pressure.Normally,mixtures of fluid that dissolve in each other
1.3 Working fluid 1.3.1General The term "working fluid" means the process medium in heat pump system (for refrigeration process termed medium refrigerant). The discussion here is mostly limited to the processes of absorption and emission of heat at approximately constant temperature, in other words to the usual evaporator- /compressor process ("cold-vapor process") with a single component medium. Since the first cold steam plant saw the light (Jacob Perkins' refrigeration from 1834), a series of working fluids have been applied, Perkins even used ether, but in turn was working fluids such as carbon dioxide (CO2), ammonia (NH3), sulfur dioxide (SO2) and methyl (CH3C1). Today, only the ammonia back of these "pioneer fluid", and then primarily used in large refrigeration systems and heat pumps. The rest are replaced with synthetic derived fluid, where the base material is hydrocarbons methane (CH4) and ethane (C2H6). Intentional properties are achieved by a varying number of hydrogen atoms are replaced with mainly chlorine (Cl) or fluorine (F). Other halogens may also occur, such as bromine (Br). The fluid's official designation is "R xyz", where R stands for "Refrigerants" and xyz is the digits of a number that reflects the chemical composition. This symbol covers the rest of the family of the working fluid (see below). Working fluid who have a basis in ethane or methane (hydrocarbon derivatives) and where all Hydrogen atoms are replaced with chlorine and fluorine, termed full-halogenated chlorine-fluorine carbohydrates or just CFC’s. Not full-halogenated chlorofluorocarbons containing one or more hydrogen atoms and is designated as HCFCs, If the fluid also are chlorine free and contains only hydrogen, fluorine and carbon, called the IIFK, one often uses halocarbons (short for halogenated hydrocarbons) as a generic term for CFCs, HCFCs and HFCs. The pure hydrocarbon derivatives are numbered according to the following key: 1. digit: Number of C atoms - 1 2. digit: Number of H atoms + 1 3. digit: Number of F atoms If the first digit is zero HP, it will be not printed. This means that all the fluid that have been withdrawn from methane only get two digits. About a bromine atom is substituted, provided the addition B1 to R - number, Example: R-134a C = 1 + 1 = 2 H = 4 – 1 = 3 F = 3 Letter code says that this is an Isomer. That means the refrigerant consist of the same number of atoms, but the molecule have a different composition Therefore: C 2 H 3 F 3 R -22 C=0+1=1 H=2-1=1 F=2 Cl=1 Therefore: CHClF2 In addition to the clean fluid, are also called azeotroper. An azeotrop is a (mixed fluid) mixture of two fluid, which at a given mixture has the same properties as a pure medium, that is evaporation and condensation temperature is constant at a given pressure. Normally, mixtures of fluid that dissolve in each other
zeotrope,that is,they evaporate and condense over a temperature interval(sliding temperature).In R- sisters are the azeotrope fluid numbered 500 and upwards,for example.R-500(73.8%R12,R152a 26.2%) andR502(48.8%R-22,51.2%R-115). Hydrocarbons are referred to in the same way as halocarbons.Examples of this are propane(C3H8)and propylene which respectively have the designation R-290 and R-1270. Inorganic fluid are collected in a separate group with 7 as the first digit and Molecular weight as sequential digits.Examples include ammonia,which,with Molecular weight equal to 17 have the designation R-717,water is designated as R-718 and R-744 carbon dioxide(CO2). 1.3.2 What determines the medium's versatility as a working medium? There are many factors that come in,partly due to deviations from the idealism of the basic process,and partly of more practical nature.To simplify the overview,the elements are grouped according to the following pattern: 1)Features that determine the theoretical process in terms of goodness energy and volume needs.That is to say: power factor [- volumetric thermal performance [kj/m3] 2)Properties of importance for the practical implementation of the process, such as: resulting system pressure [bar] possible operating range of one-step compression -Volume and energy in the compressor heat exchanger effectiveness Dimensions of pipes,valves,etc. compared to oil relation to water conditions for construction materials 3)Properties of the significance of the leak to the environment toxicity flammability -panic creative ability -warning properties(odor,color,etc.) -dilution properties ozone-depleting ability("ozone depletion potential,ODP) -contribution to global warming("global warming potential,GWP) -contribution to environmental damage at the soil surface(smog,acid rain,etc.) -Other possible environmental disturbances 4)Pricing and Availability
zeotrope, that is, they evaporate and condense over a temperature interval (sliding temperature). In Rsisters are the azeotrope fluid numbered 500 and upwards, for example. R-500 (73.8% R12, R152a 26.2%) and R502 (48.8% R-22, 51.2% R-115). Hydrocarbons are referred to in the same way as halocarbons. Examples of this are propane (C3H8) and propylene which respectively have the designation R-290 and R-1270. Inorganic fluid are collected in a separate group with 7 as the first digit and Molecular weight as sequential digits. Examples include ammonia, which, with Molecular weight equal to 17 have the designation R-717, water is designated as R-718 and R-744 carbon dioxide (CO2). 1.3.2 What determines the medium's versatility as a working medium? There are many factors that come in, partly due to deviations from the idealism of the basic process, and partly of more practical nature. To simplify the overview, the elements are grouped according to the following pattern: 1) Features that determine the theoretical process in terms of goodness energy and volume needs. That is to say: - power factor [-] - volumetric thermal performance [kj/m3] 2) Properties of importance for the practical implementation of the process, such as: - resulting system pressure [bar] - possible operating range of one-step compression - Volume and energy in the compressor - heat exchanger effectiveness - Dimensions of pipes, valves, etc. - compared to oil - relation to water - conditions for construction materials 3) Properties of the significance of the leak to the environment - toxicity - flammability - panic creative ability - warning properties (odor, color, etc.) - dilution properties - ozone-depleting ability ("ozone depletion potential, ODP) - contribution to global warming ("global warming potential, GWP) - contribution to environmental damage at the soil surface (smog, acid rain, etc.) - Other possible environmental disturbances 4) Pricing and Availability
1.3.3 Actual working fluid 1.3.3.1 General Until 1990,heat pumps,mainly used R-12(CFC-12;CF2Cl2)and R-22(HCFC-22;CHF2Cl)as a medium, with maximum temperature of heat supply,respectively,ca.83C and 61C with standard construction equipment(25 bar pressure rating).Azeotropic R-500(CFC-500)and R-502(CFC-502)has also been used to a certain extent.In high-temperature heat(80-120C)for industrial purposes,R-114(CFC-114; CF2CICF2Cl)has been the dominant medium of work.A common feature of the mentioned fluids is that they are neither flammable/explosive or toxic and moreover,not aggressive towards copper or copper alloys. 1st of January 1989 came the so-called Montreal Protocol in force,with demands for substantial reduction of the consumption of certain ozone-depleting substances including CFC substances R-12 R-114,R-115. Reduction Plans also included azeotropic fluids containing the regulated CFCs fluid,including R-500 and R- 502.In Norway,from July 1,1991 is prohibited to manufacture,import,make,install and sell refrigeration and heat pumps with CFCs as heat transfer medium.From 1995 it was fully implemented import bans,but it will still be a time permitted to use CFCs used for replenishment of existing facilities.From 1992,HCFC- fluid including R-22 incorporated into the Montreal Protocol's reduction plans.Although full phase-out is set to approx.2020,many European countries prohibit new installations of R-22 from approx.2000. It's over the years carried out extensive research to identify alter-native working fluids to CFCs and HCFCs fluid.Table 1.2 provides an overview of today's most current synthetic and natural working fluids. Working fluid for high temperature industrial applications are described in(5,11). Table 1.2 Recent alternatives to CFC-12(R-12)and HCFC-22(R-22) Fluid Formula Boiling Critical Critical Saturation Flammable Toxic Ozone Greenhouse point C temperature, pressure, temperature, depletion warming (1 bar) C bar C,25 bar potential potential CFC-12 CCL2F2 -298 118,8 41,1 84,2 No No 1,0 7300 HCFC- CHCIF2 -40,8 96,2 49,9 61,4 No No 0,055 1500 22 HFC- HFC-mix -26,1 101,1 40,6 77,6 No No 0 1300 134a R-404a HFC-mix -46,5 72,1 373 55 No No 0 3750 R-407c HFC-mix -43,6 86,1 46,2 60 No No 0 1610 R-410a HFC-mix -505 72,5 49,6 43 No No 0 1890 R-717 NH3 -33,3 133,0 114,2 58,2 No Yes 0 0 Propane CaHio -42,1 96,8 425 68,1 Yes No 0 0 C02 C02 -78,4 31,1 73,7 No No 0 1
1.3.3 Actual working fluid 1.3.3.1 General Until 1990, heat pumps, mainly used R-12 (CFC - 12; CF2Cl2 ) and R-22 (HCFC-22; CHF2Cl) as a medium, with maximum temperature of heat supply, respectively, ca. 83 ° C and 61 ° C with standard construction equipment (25 bar pressure rating). Azeotropic R-500 (CFC-500) and R-502 (CFC-502) has also been used to a certain extent. In high-temperature heat (80-120 ° C) for industrial purposes, R-114 (CFC-114; CF2ClCF2Cl) has been the dominant medium of work. A common feature of the mentioned fluids is that they are neither flammable / explosive or toxic and moreover, not aggressive towards copper or copper alloys. 1 st of January 1989 came the so-called Montreal Protocol in force, with demands for substantial reduction of the consumption of certain ozone-depleting substances including CFC substances R-12 R-114, R-115. Reduction Plans also included azeotropic fluids containing the regulated CFCs fluid, including R-500 and R- 502. In Norway, from July 1, 1991 is prohibited to manufacture, import, make, install and sell refrigeration and heat pumps with CFCs as heat transfer medium. From 1995 it was fully implemented import bans, but it will still be a time permitted to use CFCs used for replenishment of existing facilities. From 1992, HCFCfluid including R-22 incorporated into the Montreal Protocol's reduction plans. Although full phase-out is set to approx. 2020, many European countries prohibit new installations of R-22 from approx. 2000. It's over the years carried out extensive research to identify alter-native working fluids to CFCs and HCFCs fluid. Table 1.2 provides an overview of today's most current synthetic and natural working fluids. Working fluid for high temperature industrial applications are described in (5, 11). Table 1.2 Recent alternatives to CFC-12 (R-12) and HCFC-22 (R-22) Fluid Formula Boiling point C (1 bar) Critical temperature, C Critical pressure, bar Saturation temperature, C, 25 bar Flammable Toxic Ozone depletion potential Greenhouse warming potential CFC-12 CCL2F2 -29,8 118,8 41,1 84,2 No No 1,0 7300 HCFC- 22 CHCIF2 -40,8 96,2 49,9 61,4 No No 0,055 1500 HFC- 134a HFC-mix -26,1 101,1 40,6 77,6 No No 0 1300 R-404a HFC-mix -46,5 72,1 37,3 55 No No 0 3750 R-407c HFC-mix -43,6 86,1 46,2 60 No No 0 1610 R-410a HFC-mix -50,5 72,5 49,6 43 No No 0 1890 R-717 NH3 -33,3 133,0 114,2 58,2 No Yes 0 0 Propane C4H10 -42,1 96,8 42,5 68,1 Yes No 0 0 CO2 C02 -78,4 31,1 73,7 - No No 0 1
1.3.3.2 Presentation of the most appropriate working fluid a)R-22(HCFC 22) R-22 has been almost supreme as working fluid in heat pumps with moderate temperature requirements (<61C).This is partly because the fluid has a high volumetric heat output,so that the necessary compressor volume is in the range of 35-40%less than the use of R-12 and R-500.A significant drawback of R-22 is that the gas temperature from the compressor is relatively high compared with other halocarbons.In some systems that have worked with a relatively high temperature lift,this has led to the decomposition of the oil with subsequent acid formation,flat copper ring and compressor failure.This has to some extent,given the heat a bad reputation. Although R-22 is regulated by the Montreal Protocol,the medium is still in use in a variety of applications, including small reversible air conditioning units for combined cooling and heating(so-called comfort heat pumps)and larger number of climate coolers. b)R 134a(HFC 134a HFC-134a is a chlorine-free medium without ozone-depleting effect.The medium was early identified as a promising substitute medium for R-12 in refrigeration and heat pumps,since the medium is non-toxic, non flammable and also closest to the R-12 with respect to important thermodynamic properties.A drawback of R-134a is the medium's relatively high GWP(Global worming potential)value.Increased focus on the harmful effects of the greenhouse effect has led to R-134a and other HFCs now been incorporated into the international environmental agreements(Kyoto Protocol). R-134a is currently available in desired quantities,but the price is relatively high because of the complicated manufacturing process.It is designed compressors,heat exchangers,valves,etc.especially for R-134a,and the medium is well suited for turbo compressors(high performance)because of high molecular weight(102.03).R-134a has approx.2-3%lower volumetric heat performance than R-12 at 0 C evaporation temperature so compressor volume must be increased accordingly to achieve the same performance.Impact factor for a heat pump system with R-134a is approximately the same as using R-12. Because of the medium sized throttling recommended however to use the remote during cooling,such as water-cooled in subcooling heat exchangers. R-134a has minimal solubility in mineral oil,and it must be used only ester based lubricating agents(fully synthetic).It should be noticed that moisture in the plant in combination with high temperatures will quickly lead to acid formation and subsequent operational problems.It is therefore very important to keep the humidity level in the plant at a minimum through proper handling of ester oil(hygroscopic),and best practices for installation and vacuum ring of the plant. Heat pump system with R-12 and R-500 can be converted to R-134a if the system is in good technical condition.To avoid future operational problems as a result of mineral residue,high moisture levels, residual chlorine,etc.The facilities must be cleaned very thoroughly before adding R-134a(the default flush method has been developed)
1.3.3.2 Presentation of the most appropriate working fluid a) R-22 (HCFC 22) R-22 has been almost supreme as working fluid in heat pumps with moderate temperature requirements (<61 ° C). This is partly because the fluid has a high volumetric heat output, so that the necessary compressor volume is in the range of 35-40% less than the use of R-12 and R-500. A significant drawback of R-22 is that the gas temperature from the compressor is relatively high compared with other halocarbons. In some systems that have worked with a relatively high temperature lift, this has led to the decomposition of the oil with subsequent acid formation, flat copper ring and compressor failure. This has to some extent, given the heat a bad reputation. Although R-22 is regulated by the Montreal Protocol, the medium is still in use in a variety of applications, including small reversible air conditioning units for combined cooling and heating (so-called comfort heat pumps) and larger number of climate coolers. b) R 134a (HFC 134a ) HFC-134a is a chlorine-free medium without ozone-depleting effect. The medium was early identified as a promising substitute medium for R-12 in refrigeration and heat pumps, since the medium is non-toxic, non flammable and also closest to the R-12 with respect to important thermodynamic properties. A drawback of R-134a is the medium's relatively high GWP (Global worming potential) value. Increased focus on the harmful effects of the greenhouse effect has led to R-134a and other HFCs now been incorporated into the international environmental agreements (Kyoto Protocol). R-134a is currently available in desired quantities, but the price is relatively high because of the complicated manufacturing process. It is designed compressors, heat exchangers, valves, etc. especially for R-134a, and the medium is well suited for turbo compressors (high performance) because of high molecular weight (102.03). R-134a has approx. 2-3% lower volumetric heat performance than R-12 at 0 ° C evaporation temperature so compressor volume must be increased accordingly to achieve the same performance. Impact factor for a heat pump system with R-134a is approximately the same as using R-12. Because of the medium sized throttling recommended however to use the remote during cooling, such as water-cooled in subcooling heat exchangers. R-134a has minimal solubility in mineral oil, and it must be used only ester based lubricating agents (fully synthetic). It should be noticed that moisture in the plant in combination with high temperatures will quickly lead to acid formation and subsequent operational problems. It is therefore very important to keep the humidity level in the plant at a minimum through proper handling of ester oil (hygroscopic), and best practices for installation and vacuum ring of the plant. Heat pump system with R-12 and R-500 can be converted to R-134a if the system is in good technical condition. To avoid future operational problems as a result of mineral residue, high moisture levels, residual chlorine, etc. The facilities must be cleaned very thoroughly before adding R-134a (the default flush method has been developed)
c)HFC-mixtures It has in recent years been developing a series of synthetic mixtures of HFC R-22.The fluid has no ozone- depleting effect,and the basic components are HFC-32(flammable),HFC-143a(flammable),HFC-125 and HFC-134a.All blends contain a flammable component,but the composition is always the case that the mixture is not flammable.The most relevant fluid to R-404A,R-407C and R-410a. R-404a is a three-component mixture(HFK-125/143a/134a,44%/52%/4%)with low temperature drift (0.1C),which was originally designed to replace R-502 in the freezer-and cooling systems.The medium used also in small heat pump systems.Volumetric thermal performance is that of R-502,while energy consumption is slightly in excess.R-404a can be used in both new projects and by conversions. R-407c is a three-component mixture (HFK-125/32/134a,25%/23%/52%)developed for air conditioning,condensing temperature is approx.60C at 26 bar.The fluid provides almost the same volume compressor needs and energy efficiency through the use of R-22.R-407C has a very high temperature drift through evaporation and condensation (about 7C),and this means that the medium is primarily suited for new installations where one can design the heat exchangers for countercurrent heat exchange. R-410A is a blend two-component(HFK-125/32,50%/50%)with minimal temperature drift(<0.2 C).The fluid is about.50%higher saturation pressure than R-22,and the necessary compression volume is reduced in the same scale.The high pressure,however,that the fluid can only be used in new systems without any possibility of old models conversion. d)Ammonia(NH3) From a thermodynamic and technical point of view,the ammonia in most respects superior to halocarbons (see also Section 1.3.4,"Criteria for the choice of working fluid").These are the main reasons why the fluid has been almost supreme in large industrial refrigeration plants for decades.With increased focus on energy efficiency and environmental ammonia is now increasingly considered as the best work the fluid in greater heat pump systems(>100 kW)ice water coolers,etc. Ammonia has the disadvantage that when moisture is present attack copper and copper alloys,ammonia plant must be built without any hints of such materials.This has long ruled out the use of ammonia in the (semi)hermetic compressors windings when consumed.Some manufacturers have developed semi- hermetic compressors for ammonia,where the medium is separated from the motor windings,as well as hermetic compressors with aluminum windings. The main complaint against ammonia used as the working fluid in heat pump systems is that the medium is toxic,has a sharp pungent odor(panic-creating)and also is flammable/explosive in certain proportions with air. The danger of poisoning with ammonia plants are very small,as the medium by its distinctive odor is easily recognized even at a concentration of about 10 ppm(parts per million).Lethal concentration at 30- 60 min
c) HFC-mixtures It has in recent years been developing a series of synthetic mixtures of HFC R-22. The fluid has no ozonedepleting effect, and the basic components are HFC-32 (flammable), HFC-143a (flammable), HFC-125 and HFC-134a. All blends contain a flammable component, but the composition is always the case that the mixture is not flammable. The most relevant fluid to R-404A, R-407C and R-410a. R-404a is a three-component mixture (HFK-125/143a/134a, 44% / 52% / 4%) with low temperature drift (0.1 ° C), which was originally designed to replace R-502 in the freezer - and cooling systems. The medium used also in small heat pump systems. Volumetric thermal performance is that of R-502, while energy consumption is slightly in excess. R-404a can be used in both new projects and by conversions. R-407c is a three-component mixture (HFK-125/32/134a, 25% / 23% / 52%) developed for air conditioning, condensing temperature is approx. 60 ° C at 26 bar. The fluid provides almost the same volume compressor needs and energy efficiency through the use of R-22. R-407C has a very high temperature drift through evaporation and condensation (about 7 ° C), and this means that the medium is primarily suited for new installations where one can design the heat exchangers for countercurrent heat exchange. R-410A is a blend two-component (HFK-125/32, 50% / 50%) with minimal temperature drift (<0.2 ° C). The fluid is about. 50% higher saturation pressure than R-22, and the necessary compression volume is reduced in the same scale. The high pressure, however, that the fluid can only be used in new systems without any possibility of old models conversion. d) Ammonia (NH3) From a thermodynamic and technical point of view, the ammonia in most respects superior to halocarbons (see also Section 1.3.4, "Criteria for the choice of working fluid"). These are the main reasons why the fluid has been almost supreme in large industrial refrigeration plants for decades. With increased focus on energy efficiency and environmental ammonia is now increasingly considered as the best work the fluid in greater heat pump systems (> 100 kW) ice water coolers, etc. Ammonia has the disadvantage that when moisture is present attack copper and copper alloys, ammonia plant must be built without any hints of such materials. This has long ruled out the use of ammonia in the (semi) hermetic compressors windings when consumed. Some manufacturers have developed semihermetic compressors for ammonia, where the medium is separated from the motor windings, as well as hermetic compressors with aluminum windings. The main complaint against ammonia used as the working fluid in heat pump systems is that the medium is toxic, has a sharp pungent odor (panic-creating) and also is flammable / explosive in certain proportions with air. The danger of poisoning with ammonia plants are very small, as the medium by its distinctive odor is easily recognized even at a concentration of about 10 ppm (parts per million). Lethal concentration at 30- 60 min