13.12. a) It should not be Poisonous or injurious. Easy to liquefy at moderate pressure and temperature. It is used in ice plant and in big installation. Secondary refrigerants are water, brine, glycol, etc. Mixes well with oil, 15. Refrigerants are used to cool process fluids to temperatures lower than those achievable using cooling water. The refrigerants are internationally designated as ‘R’ followed by certain numbers, such as R-11, R-12, R-114, etc. The suction line should contain low-pressure superheated suction vapor. They are safer and generally suitable for refrigeration systems. Refrigerant Lines Suction Line = Line Between the Evaporator and the Compressor. (1) The main function of the refrigerant is to absorb the heat from the indoor air, it transitions from a low-pressure gas to high-pressure liquid and transfer it to the atmosphere. A refrigerant should have _____? b) It should be readily available at a low cost. High thermal conductivity, 7. ): satisfactory thermal and physical properties, In Lees' Loss Prevention in the Process Industries (Fourth Edition), 2012. Safety features include flammability and toxicity, in conjunction with the inventory required. Use is sometimes made in the process industries of systems in which a refrigerated heat transfer fluid is circulated between a refrigeration set and the process. - It must have low specific heat and high latent heat. – It has a somewhat high affinity for moisture. EU and US regulations set maximum charges of 57 or 150 grams of refrigerant, keeping the concentration in a standard kitchen below 20% of the lower explosive limit. The refrigerants which are first cooled by primary refrigerant and then used for cooling purpose are called as secondary refrigerant. In 2010, about one-third of all household refrigerators … A good refrigerant must be nonflammable and non-explosive. This means that owners and administrators need to take the long view when making decisions about their capital investments. When reusing the existing base building HVAC, a comprehensive CFC phase-out conversion must be conducted prior to project completion. Table 17-1. Miscellaneous organic compounds are in the 600 series; numbers are given in numerical order, for example R600a, isobutane. The halogenated hydrocarbons are considered to be nonflammable. Hissing or bubbling noise. Relevant general properties are the normal boiling point and refrigerant service temperature, the latent heat and the coefficient of performance (COP). Reference : https://nptel.ac.in/courses/112105129/, RAC / HVAC - Articles , Notes , Que and Answers, Mechanical Subjectwise Basic Concept Notes ,Articles, Thermal Engineering - Articles , Notes , Interview Q & A, New Mechanical Projects 2020 ( All Projects Post Index List ). In the refrigeration system, to avoid the danger of explosion or fire hazard during high compression, the refrigerants should not be flammable or explosive even when mixed with air/oil. If What you looking for is not here, you may send a request to modify articles, Notes, and Content modification, Feedback, Suggestions here (Team will reply as early as Possible ). Refrigerants are classified by ASHRAE, and their familiar ‘R’ numbers are assigned according to certain rules. iii) Hydrocarbons:- Methane, Ethane, Propane, etc. The machine operates... LearnMech.Com is a Mechanical Project-oriented platform run by Sachin Thorat who is a B-Tech Graduate in Mechanical Engineering. (c) Evaporator and Condenser pressure: Both Evaporator and Condenser pressure should be above slightly above the atmospheric level. Non-toxic 10. Halogenated hydrocarbon refrigerants are odorless, so the leakage of such refrigerants cannot be easily detected. A refrigerant should have a critical temperature and pressure well above the operating temperature and pressure of the system. Uses – It is used in an aircraft air-conditioning system. This is essential information for a service call, so it should be prominently displayed on the label. and low freezing point. In case of centrifugal compressors, a high suction value of the volume is desired, where the efficiency of the compressor can be increased. This leakage of... Slotter Machine - Types, Parts, Operations, Diagram, Specification. Super High Performance Compression Heat Pump, High-Efficiency Type for Heating Only, Refrigerant maldistribution in an evaporator of automotive air conditioning system: investigation and a design improvement by numerical simulations, Vehicle Thermal Management Systems Conference Proceedings (VTMS11), International Journal of Heat and Mass Transfer. Available refrigerants for various levels or conditions of operation may be toxic, flammable, irritating on exposure, hydroscopic and expensive. f) It should be above the condensing temperature & pressure. If you are low on refrigerant, you have a leak in your AC system. Thus, the latent heat of refrigerant should be as large as possible. Table 17-4. Your email address will not be published. 6. link to Hydraulic seals - Definition, Types, Diagram , Function, Failure, Application, link to Slotter Machine - Types, Parts, Operations, Diagram, Specification. Hydraulic seals - Definition, Types, Diagram , Function, Failure, Application. 3.4. i) Air Conditioner – R-22, R-114 ii) Domestic Refrigerator – R-12, R-143a iii) Ice Plant – In primary circuit Ammonia and secondary circuit Brine solution. Other relevant ASHRAE publications are the ASHRAE Thermodynamic Properties of Refrigerants (ASHRAE/2) and the ASHRAE Handbook of Fundamentals (ASHRAE, 1993/7). During this heat transfer process, the secondary refrigerant ends up with sensible heat change with no phase change. General affirmation covers Types I through III. 6. The refrigerants which directly take part in the refrigeration system are called primary refrigerant. A good refrigerant should have no ozone depletion potential. The age of your system needs to first be considered. B. Sam Kubba Ph.D., LEED AP, in LEED v4 Practices, Certification, and Accreditation Handbook (Second Edition), 2016. This is an index that indicates the ability of a gas to absorb infrared rays. – R134a is the nonflammable and non-explosive, has toxicity within limits and good. The LEL can be exceeded inside the appliance, so no potential ignition sources can be present. It may be considered as a vertical shaper. It should have low viscosity. v) Unsaturated organic compounds:– Refrigerant with ethylene and propylene base. In 1834, edger, ammonia, sulphur dioxide, methyl chloride, and carbon dioxide came into use as refrigerants in, compression cycle refrigeration machines. A refrigerant is chemical compound that is used as the heat carrier, which changes from gas to liquid and then back to gas in the refrigeration cycle. (d) Compression ratio: It should be as small as possible. The numerical simulations of refrigerant two-phase flow show that the new header design improves the uniformity of the liquid and vapour phase distribution from the header towards the evaporating channels. b) It should be readily available at a low cost. The same holds for the corresponding refrigerant velocity at the inlet of the evaporators’ headers. Coefficient of Performance of Refrigerants. Refrigerants Example – Applications Of Refrigerants. If this applies to your system, investing in repairing or replacing parts is not the best option as it could be more expensive over time. Since oil is a liquid it has the tendency to 'leak' through every gas/slot it finds during movement. It’s a common misconception that the refrigerant level in your air conditioner will naturally diminish over time, but it’s simply not true. The halogenated refrigerants have ozone depletion potential, whereas the natural refrigerants (hydrocarbon, air, CO2, NH3 and water) do not. The specific volume of the refrigerant vapor that a compressor is required to pump roughly determines the size of the compressor. 4. Various ways of substituting the atom or group on the carbons can exist and this is denoted by two lower-case letters (see Figure 3.5). Uses – It is used in the marine refrigeration system. Thus the chemical formula for Dichloro-tetrafluoro-ethane becomes C2Cl2F4 and the numbers of Refrigerant becomes R(2-1) (0+1) (4) or R-114. Refrigerants with higher boiling points tend to be more efficient and may work well in a smaller machine. ii) Azeotropes:- Mixture of different refrigerant. Refrigerant is chemical used in a cooling mechanism, such as an air conditioner or refrigerator, as. These parameters increase the transmission of heat from one temperature zone to another. The leakage and detectability of a refrigerant are an important factor to be considered, as leakage should be easily detectable to avoid the loss of refrigerant from the system. These pressures cannot be obtained with a conventional compressor and also water creates such a volume of vapor that the compressor needed would be huge. In most process systems, the evaporation of the refrigerant is carried out in shell and tube heat exchange equipment, and allowances must be made for a reasonable temperature approach between the process fluid which always leaves the evaporator at a higher temperature (by 3°–15°F) [−16° to −9°C] than the refrigerant. The slotter or slotting machine is also a reciprocating type of machine tool similar to a shaper. Introduction to Slotting Machine : 2. The label should also show a refrigerant type. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be. This factor is very important while selecting a refrigerant. Additionally, he has interested in Product Design, Animation, and Project design. If your system springs a leak, the leak will need to be patched and your refrigerant will need to be recharged. Refrigerant is chemical used in a cooling mechanism, such as an air conditioner or refrigerator, as the heat carrier which changes from gas to liquid and then back to gas in the refrigeration cycle. Pick up the wrong statement ? (a) Boiling Temperature: The boiling temperature of the refrigerant should be low to reduce the capacity of the compressor. A variety of refrigerants are available, including: ammonia (R717); carbon dioxide; ethylene (R170), ethane (R1150), propylene (R1270) and propane (R290); and chlorofluorohydrocarbons (CFCs) such as dichlorodifluoromethane (R12) and chlordifluoromethane (R22). If it is, the materials used in the construction of evaporators and condensers should be good enough to withstand pressure, which in turn will result in high initial cost of the system. According to Mike Opitz, Certification Manager, LEED™ for Existing Buildings (USGBC). consider the following refrigerants to find its chemical formula and the number. The older your system is, the more cost effective it will be to repair it. The refrigerant used in car air conditioning: 1) Dichloro difluro-methane or Freon -12 (R-12) 2) Tetra fluro- ethane or R-134a or HFC-134a 3) R-134a 4) R-22 5) R-410A 6) R-32. In the outer atmosphere of earth up to 50 Km, there is a layer called Stratosphere. Chemical refrigerants are the heart of a large majority of building HVAC and refrigeration equipment. Question is ⇒ Pick up the wrong statement. The maintenance requirements for operation of the different types of refrigeration systems vary somewhat and should be evaluated along with the particular performance. The refrigerant in your AC system is kept under high pressure as it circulates through your home. c) It should have a high COP & low power requirements. If refrigerant is low, they should tell you about the leak Rather than just saying, “You need more refrigerant; here’s the cost,” your AC technician should let you know that you are low on refrigerant and explain to you that means you have a leak. 2. ODP is defined as “the integrated change in total ozone per unit mass emission of a specific ozone-depleting substance relative to the integrated change in total ozone per. Hydrocarbons such as propane, ethane and butane are highly flammable and explosive. Certain metals are attacked by refrigerants. Uploaded by: keysersoze18. 1. This is impossible for some systems; however, the issue is important and must be recognized, as explosive mixtures can be formed with some refrigerants. Fig. Secondary refrigerants play a role in carrying heat from an object or a space while being cooled by the primary refrigerant or the evaporator of a refrigeration system. Get Answer . Freon, Carbon Dioxide, SO 2 are non flammable. Water: Used in Air conditioning systems for cooling, Dehumidification, etc. Secondary refrigerants allow the amounts of environmentally harmful primary refrigerants to be minimized and contained in a restricted area. Generally speaking, it is less expensive to operate at as low a pressure level on the discharge as is consistent with the suction pressure and with the physical characteristics of the refrigerant. Most of the early refrigerant materials have been. Introduction to Seals : d) It should not be Inflammable. i) Halocarbon compounds e.g R -11 – Trichloromonofluromethane R – 12 R – 13 R -21 etc. Adding refrigerant could cost you more money in the long run because if there is a leak, the refrigerant will leak out again and have to be continually refilled. A refrigerant followed by a two-digit number indicates that a. refrigerant is derived from methane base while a three-digit number represents ethane bases. The refrigerant flow rate in the automotive air conditioning system decreases at low loads. b) It should not be corrosive & should not have any effect on materials used in equipment. But while (HFCs) may be suitable as short to medium-term replacements, they may not be suitable for long-term use because of their high global warming potential (GWP). 3 will be achieved. discarded for safety reasons or for lack of chemical or thermal stability. and low freezing point, … In order to overcome this problem the installation of the fins over the inlet of evaporating channels is considered. In the present day, many new refrigerants including halo-carbon compounds, hydrocarbon compounds are used for air-conditioning, The suitability of a refrigerant for a certain application is determined by its physical, thermodynamic, chemical properties, and by various practical factors. In the Stratosphere layer there is more concentration of Ozone gas. Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Filter material is usually packed in at both ends; in the example shown Fig. c) It should have fewer tendencies to leak & if it is leaking it should be easily detectable. -The refrigerant should have low boiling point and low freezing point. depletion of the ozone layer and very little greenhouse effect. c) It should have a high COP & low power requirements. C. High specific volume and high latent heat of vaporisation. Evaporation of the liquid is an important step in the refrigeration cycle, which produces cooling. A substance used as a refrigerant should have a boiling point in a particular range that fits the machine in which it is used. e) It should have a high latent heat of vaporization. Let us consider the following refrigerants to find its chemical formula and the number. Azeotropic mixtures are in the 500 series. Brines are often chosen as secondary refrigerants for large refrigeration systems, such as those supplying supermarkets, the most common brine being water-glycol solutions, water-ethanol solutions, and acetate solutions. Halogenated hydrocarbons may react with zinc but not with copper, aluminum, iron and steel. A good refrigerant should have: (a) High latent heat of vaporization and low freezing point [IES-1992] (b) High operating pressure and low freezing point (c) High specific volume and high latent heat of vaporization. Non-corrosive to metal, 8. Refrigerant poisoning can occur if a person inhales or consumes the chemicals — also known by the brand name of Freon — from cooling appliances, such as refrigerators and air conditioners. Properties – Non-toxic, Non-flammable, Non-explosive Required less compressor displacement. In the rare event that you have a problem with your item please contact us first and we'll be happy to help. It gives a low refrigeration effect. Low specific volume of vapor, 6. This is called as global warming. – Due to all the above factors, R134a is considered to be an excellent replacement for R12 refrigerant. We see that in this refrigerant Number of chlorine atoms, p = 2 Number of fluorine atoms q = 2 And the number of hydrogen atoms, n= 0 We know that n + p + q = 2m +2 0 + 2 + 2 = 2m +2 or m = 1 i.e Number of carbon atoms = 1. Also, the weight of the refrigerant to be circulated in the system will be less if its latent heat is high, thereby reducing the initial cost of the refrigerant. For example, in the EA Credit 4 (Enhanced Refrigerant Management) for NC, Schools, and CS, points can be earned by either not using refrigerants (Option 1) or by selecting environmentally friendly refrigerants and HVAC&R that minimize or eliminate the emission of compounds that contribute to ozone depletion and global warming (Option 2). High latent heat of vaporisation and low freezing point. Table 17-3 shows the approximate COP of some refrigerants. High coefficient of performance, end 16. Switches must be placed outside the refrigerated compartment or replaced by sealed versions, and only spark-free fans can be used. The quantity of refrigerant needed for a particular level of evaporation is a function of its latent heat, except when using steam jet refrigeration, because the use of its chilled water involves only sensible heat transfer to process fluids. It should not be non-irritating to eyes. 4. Ammonia leakage can be easily detected by its odor. a) It should be easy & safe to handle. The numbers are in chronological order of the refrigerant’s approval by ASHRAE.
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