Therefore cost of the refrigerants is normally high when compared to other chemicals. A denser refrigerant will have fewer tendencies to leak as compared to higher density refrigerant. Each refrigerant has different material compatibility. Viscosity; It should be as small as possible to ensure that the pressure drop in the system is as small as possible. Under ideal conditions, the mass flow rate of refrigerant in the system should be proportional to the cooling load. Therefore, it is important that the oil and the refrigerant are miscible with each other so that oil following the refrigerant out in the system is Chemical Engineers spend their life in making the world a […]. The quantity of refrigerant used in industries is very less. The lubricating oils must be soluble in Refrigerants. However, its use has been restricted nowadays because of its many inherent disadvantages. In a negative pressure evaporator Atmospheric air or Moisture will Leak into the system. This is a hydrofluorocarbon (HFC) and haloalkane refrigerant commonly known as norflurane or Freon 134A. To have the minimum change in entropy during the throttling process, the specific heat should be minimum. Long answer: This is a very bad idea for multiple reasons: * R22 & R404A have different pressure temperature characteristics. It must be sourced and procured within a short span of time to enable the user in case of leaks, maintenance schedules etc. ODP of R11 is fixed as the maximum value of 1.0. Sorry, you have Javascript Disabled! Toxicity is the important properties of refrigerants. The vacancies include those in Johnson Matthey, Phillips 66, HUNTSMAN, GSK, Cipla, DSM, Bayer, Deepak Fertilisers and Petrochemicals Corporation Ltd, SANOFI, etc.. SO2 can be detected with NH3 H2O Solution. 386 In hermetic arrangements, the motor windings are cooled by refrigerants vapor on its way to the suction valve of the compressor. A hot crankcase and cylinder head accompanied by a low suction pressure would be caused by A. Unprecedented pandemic has taught many lessons to everyone of us. Therefore, the dielectric strength of refrigerant is an important property in hermetically sealed compressor units. The capacity of the system depends on how often a pound of refrigerant evaporates and this depends on compressor size and on properties of the refrigerant at refrigerant cycle temperatures. Enthalpy of vaporization:. In hermetically sealed compressors refrigerant vapor contacts with motor windings and may cause short circuits. It is highly toxic, non-flammable, non-explosive, non-corrosive and works at low pressures. Name 3 types of refrigerant compounds and the element components of each. a) Boiling point at atmospheric pressure should be low. Choose from 71 different sets of epa refrigerant flashcards on Quizlet. The liquid has to vapourise at the evaporator coil to cause cooling. Tag Index c) Latent heat of vaporization of refrigerant must be … Freon-11 (Trichlorofluoromethane) is used under low operating pressures; it is non-toxic, non-corrosive and non-flammable. In the case of leakage of the refrigerant from the system, the refrigerant will be contaminated with the refrigerated products. All Rights Reserved. In today's world, other properties of the refrigerant are more important. About Us Economic considerations: The refrigerant used in the vapor compression cycle of the refrigeration or air-conditioning system should produce maximum refrigerating effect. Therefore ammonia cannot be used for small refrigeration systems. While able to follow the load better than fixed restrictors or capillary tubes, their operating characteristics are The refrigerants should be non poisonous to humans and food stuff. Refrigerants with low boiling points will have high condenser pressure and high vapor density. HFO-1234yf (or YF) has been shown to be a desirable, lowenvironmental-impact alternative to the more common HFC-134a as a refrigerant [1][2][3][4] [5]. CCl2F2, CH4Cl can form HCL with water which dissolves the copper from condenser tubes and deposits them on compressor pistons and deteriorates the life of the machinery. Refrigerants with High vapor density/ Low specific volume will require a smaller compressors and velocity can be kept small and so the condenser tubes used will also be in smaller diameter. This is the most important property of refrigerant. This site uses Akismet to reduce spam. Most of the refrigerants form acids or bases in the presence of water. However, the oil in the refrigeration system is a contaminant that lowers the efficiency of the refrigeration system. Presence of air will reduce the partial pressure of refrigerant and the condensation temperature will rise. Thermal conductivity of the refrigerant should be high for faster heat transfer during condensation and evaporation. Environmentalfactors. Privacy Policy Refrigerants should have low freezing point than the normal operating conditions. The characteristics of some refrigerants make them desirable for use with reciprocating compressors. Distinction between Work and Internal Energy, https://me-mechanicalengineering.com/about/. What is Chemical Engineering all about? It is odorless, non-toxic, non-flammable, non-explosive and non-corrosive. Therefore, epoxy resin is not desirable for the use with those refrigerants. Critical pressure of the refrigerant should be higher than the condenser pressures. 2. Therefore oil separators are to be employed. Electronic detectors, Ultrosonic leak detectors may also be used to detect the leaks. Global Warming Potential (GWP) is a relative measure of how much heat a refrigerant  traps in the atmosphere. Get unlimited access to 5,000+ magazines, newspapers and curated premium stories at flat 55% off, Cooling Tower Efficiency Calculations – 75,000+ Views, Chemical Engineering Jobs Digest January 2021. It may accumulate in evaporator. Q2. A good refrigerant should have low viscosity and high thermal conductivity. What is the desirable characteristic of a refrigerant? Contact. The ozone depletion potential (ODP) of a refrigerant is the relative amount of depletion to the ozone layer it can cause. Ammonia will form explosive mixture when the concentration in air is between 16 to 25 %. This phenomenon is called Oil logging. But, I really wants to download it. The year which will be remembered in the history has come to an end. If it is brought into contact with open flame or heater elements, it decomposes into highly toxic constituents. In order to have a broad range of isothermal energy transfer, the refrigerant should have a critical temperature above the condensing temperature. The high specific heat of vaporization High suction gas density Positively, but not excessive pressure, the boiling point and condensation conditions The critical temperature and the triple point are far beyond the operating range 'ME Mechanical' is an online portal for mechanical engineers and engineering students. - Thermodynamics. It makes white fumes of ammonium sulfide. For Methane GWP is 72, it means that if the same mass of CH4 and CO2 were introduced into the atmosphere, that methane will trap 72 times more heat than the carbon dioxide. © Copyright 2020 ME Mechanical. Lack of Toxicity. Insufficient refrigerant C. Air in the system D. Stuck discharge valve ANS: B 240. Topic Index What is the desirable characteristics of a refrigerant? Some of the widely used cryogenic refrigerants are Helium, Nitrogen, Oxygen, Hydrogen. Characteristics of a Good Refrigerant Boiling Point. In some applications, toxicity is of negligible importance whereas in others, such as comfort cooling, a non-toxic and non-flammable refrigerant is essential. Moderately high evaporator pressure boosts the compressor suction pressure thus reduces the power costs. Due to the above disadvantages, Positive evaporator pressure is preferred. Advances in mechanical valves led toautomatic expansion valves. The detection of leaks should be easy to loss of refrigerant. R-22 for example, has an ODP of 0.055. If the refrigerant velocity is not sufficient, then it cannot carry all oil back into the compressor. Curiously enough the use of air as a refrigerant is both older and more recent than the other vapour refrigerants. Higher latent heat of vaporization of the refrigerant will result in lower mass flow rates according to the Heat transfer equation. Although no perfect refrigerant is known, there are certain factors which determine a refrigerant's desirability for a particular duty and the one selected should possess as many as possible of the following characteristics: Here are some of the desirable properties of refrigerant explained in detail. Freon-12 (Dichloro difluoromethane) is non-flammable, non-toxic and non-explosive. The price of the refrigerants is generally high when compared to other chemicals in the industry. Ammonium Hydroxide Solution turns the red litmus paper into blue; thereby condenser tube leaks can be identified. (adsbygoogle=window.adsbygoogle||[]).push({}); Home CH3Cl reacts with Aluminium. Critical pressure of the refrigerant should be higher than the condenser pressures. The toxicity depends upon the concentration and exposure limits. It must be sourced and procured within a short period to enable the user in case of leaks, maintenance schedules, etc. It is used for air-conditioning applications. Figures 5-11 shows the test results. GWP of Carbon Dioxide is 1.0. Miscibility with Oil; The refrigerant should not be miscible with the oil else the lubricating strength will be reduced. Let us look back on the journey so far for […], Copyright © 2016-2020 - Chemical Engineering Site, Advertise | Testimonials |Sitemap | Privacy Policy | Disclaimer. Similarly if it is very low industry professional will not take necessary action to control the leaks. Leak outside the system results in refrigerant loss and it can be identified easily and refrigerant loss can be topped up. When can you say a System is in Thermodynamic Equilibrium ? Submit Guest Post Freon leak can be detected by a halide torch. Thermodynamic Properties Of Refrigerant Boiling and condensing temperature and pressures The boiling temp of refrigerant at atmospheric pressure should be low. The desirable characteristics of “ideal” refrigerants are considered to be as follows: Normal boiling point below 0 °C; Non-flammable; Non-toxic; Easily detectable in case of leakage; Stable under operating conditions; Easy to recycle after use; Relatively large area for … The free water apart from the dissolved water in refrigerant freezes below 0 Deg C and chokes the narrow orifice of expansion valve. These characteristics could include vapor pressure, transport properties, lubricant and material compatibility, thermodynamic performance, cost, flammability, toxicity, stability, and environmental properties. a. it should not be toxic b. it should not be non-corrosive c. it should have minimum enthalpy of vaporization d. all of the above View Answer / … Sulfur dioxide was widely used as refrigerant during the early 20th century. Most of the refrigerants form acids with water. Theoretically, almost any liquid can be used as a refrigerant if its pressure/temperature relationship is suitable for the conditions. The refrigerant may leak out of the system. Eg: Ammonia, R22, R12 etc, If Boiling Point is High, Low Condenser Pressure – Centrifugal Compressor is used. What type of refrigerant are R-11 and R-12. To enable the use of smaller compressors and other equipment the refrigerant should have smaller vapor density. 3. Excess refrigerant B. Higher heat transfer coefficient requires smaller area and lower pressure drop. Time weighted Average is the concentration to which repeated eight hour exposures for five days in a week which is considered to be safe. There is no rule of thumb governing the selection of refrigerants. In addition, if the volume of charge is large, there should be no danger to health and property in case of its escape. Other desirable characteristics of a refrigerant include being nontoxic, noncorrosive, nonflammable, and chemically stable; having a high enthalpy of vaporization (minimizes the mass flow rate); and, of course, being avail-able at low cost. To ensure the maximum heat absorption during refrigeration, a refrigerant should have a high enthalpy of vaporization. DESIRABLE PROPERTIES OF REFRIGERANT OR SELECTION OF A REFRIGERANT. However, there are five criteria should be taken into account: 1. Learn epa refrigerant with free interactive flashcards. Ammonia is one of the earliest types of refrigerants which is still widely used in many applications due to its inheritance excellent thermal properties, It is toxic in nature, flammable explosive under certain conditions, it has low specific volume¸ high refrigerating effect, low piston displacement in case of reciprocating compressors make it an ideal refrigerant for cold storage’s, ice plants, packing plants, skating rinks breweries, etc. If Boiling Point is Low, High Condenser Pressure – Reciprocating Compressor is used. The problems with a leakage are wearing out of joint or the material used for the fabrication of the system. This will cause corrosion and deteriorates valves, Seals and Metallic parts. Otherwise the zone of condensation decreases and the heat rejection occurs. So, please make it downloadble format. Halocarbons. Learn how your comment data is processed. The cryogenic refrigerants have a shallow boiling point at atmospheric pressure. For this, the liquid saturation line should be almost vertical. Desirable properties The ideal working fluid or often called refrigerant would have favorable thermodynamic properties, be noncorrosive to mechanical components, and be safe, including freedom from toxicity and flammability. Refrigerants should be readily available near the usage point. Otherwise the zone of condensation decreases and the heat rejection occurs. This makes the equipments compact and reduced the operating cost. It is highly chemically stable. Freon, Carbon Dioxide, SO2 are non flammable. should not be toxic as they will come into contact with human beings. Most of the halogenated refrigerants meet these requirements. refrigerant mixture, and the refrigerant concentration can be up to 40 wt%. The condenser tubes have to be designed for higher pressures which also give raise to capital cost of the equipment. These parameters increase the transmission of heat from one temperature zone to another. Which of the following characteristics that is not desirable in a refrigerant? What is the desirable characteristic of a refrigerant? It increasers the condenser pressures and thereby the power consumption for the compressor will also rise. High Vapor Density As a refrigerant, it possesses completely stable thermal characteristics, has low toxicity, and is non-corrosive and non-combustible. Whenever we choose them for particular use Properties of Refrigerants also plays a vital role in economic and environmental friendly application. A boiling-point temperature low enough that air … It consists of an alcohol lamp that emits a blue flame. - Published on 20 Aug 15. a. it should not be toxic. Visit our about section to know more. Methane, butane and other hydrocarbons are flammable. High Pressure Boilers: Features and Advantages, Merits and Demerits of Water Tube Boiler over Fire Tube Boiler. due to its excellent safety properties. Technological issues. 4. Insulation of windings in hermatic compressors will also get damaged. It is widely used in … Refrigerants will affect human health if they are poisonous. The liquid at the evaporator coil … Water for example cannot be used below 0 Deg C. The lower the condenser pressure the power required for compression will be lower. Thermophysical properties. Explore 150+ Jobs for Chemical Engineers at various locations for Freshers as well as Experienced. The desirable characteristics of ‘ideal’ re… The refrigerants should not react with the materials used in refrigeration cycle like evaporators, condenser tubes, compressors, control valves etc. b) Freezing point at atmospheric pressure should be low. This may also cause bursting of the tubes. The most reliable way to be safe is to choose a refrigerant that is neither toxic nor flammable. Strong smelling chemicals like acrolein may be added to refrigerant for easy leak detection. A. If the oil is not miscible in the refrigerant used and it is heavier it will settle down in the evaporator and reduces the heat transfer. Name a Chlorine-free refrigerant. The proportions of the components are chosen based on the exact characteristics desired in the final product. Safety is perhaps the most important single factor in the selection of a refrigerant. In addition to these criteria, other considerations such as; local regulations and standards, maintainability and capability (such as having staff with skills to support the units). Other refrigerants are best adapted to centrifugal or rotary compressors. Refrigerants are widely used in Refrigeration cycle where cooling effect below the atmospheric temperatures are needed. We continue to change in order to grow and really do shine. Cryogenic refrigerants are those refrigerants which produce minus temperature in between range -157°C to -273°C in the refrigerated space. That’s means it should have high coefficient of performance and consume less power for producing certain refrigerating effect. 1 Answer. This test is based on Beilstein Test for Chlorine. List 6 desirable characteristics of a refrigerant. Shallow industry professional will not take necessary action to control the leaks. Since a refrigerant absorbs and releases heat primarily through evaporation and condensation, a high latent heat of vaporization might seem to be desirable. Therefore dielectric strength should be high to avoid short circuits. If Freon is present blue flame turns into green. To see this page as it is meant to appear, please enable your Javascript! Due to low operating pressure and high displacement, it is used in systems employing centrifugal compressors. Refrigerants should be available near the usage point. Safety. Hence, it is desirable that the refrigerant has a pungent smell so that its leakage can be detected immediately. Dear Sir, All the contents are very usefull for mechanical engineering students like me. having the most desirable characteristics, thus introducing the first chlorofluorocarbons (Lawrence 2003). It should not freeze during application. Short answer: NO. HFCs. If the oil density is less than the refrigerant used and it if it is immiscible, the oil will float on the surface of the refrigerant. Change is the only option to survive and grow! Ammonia and SO2 can be detected by their characteristic smell. Desirable refrigerants are those which possess chemical, physical, and thermodynamic properties that permit their efficient application and service, in practical designs of refrigerating equipment. Sometimes, the product to be cooled is such that a constant evaporator temperature has to be maintained. Ammonia reacts with Copper and Cuprous alloys and forms copper complexes. 16 Viscosity and Thermal Conductivity. In an example with R-12, assume the compressor is of the right size to deliver one ton of refrigeration when refrigerant evaporates at 0 deg. The quantity of refrigerant used in any industry is very small. According to Wikipedia, Chemical engineering is a branch of engineering that applies physical sciences (physics and chemistry), life sciences (microbiology and biochemistry), together with applied mathematics and economics to produce, transform, transport, and properly use chemicals, materials and energy. Atmospheric air ingression inside the system may sometime results in explosions if the flammability values of the refrigerants are in wide range. The refrigerant should not make combustion mixture in Air. Detect the leaks wearing out of joint or the material used for small refrigeration systems contents are usefull. In thermodynamic Equilibrium and non-flammable in order to have a broad range of isothermal energy transfer the. 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Be low be low Jobs for chemical Engineers spend their life in making the world a [ ….. Liquid at the evaporator, and is non-corrosive and works at low temperature zones and and. Atmospheric temperatures are needed with the oil else the lubricating strength will be reduced moderately high evaporator pressure is.. Carbon dioxide, SO2 are Non flammable test results during the throttling process, the dielectric of... Pungent smell so that its leakage can be topped up Guest Post Privacy contact!