R4a is capable to be at temperatures of 28c at room temperatures of 38c, its performance being very similar to that of an r12. To enable the use of smaller compressors and other equipment the refrigerant should have smaller vapor density. Compressor has to be operated at high vacuum if the boiling point of the refrigerant is high at atmospheric pressure. Jul 17, 2017 a good refrigerant has no odor when it is in a low concentration so that the appliance does not have a chemical smell at all times. In refrigeration and air conditioning applications there are wide range of conditions in which the refrigerants have to work, hence different refrigerants possessing suitable properties are used for different applications. Technical information at22 thermodynamic properties of dupontz freon. Guidelines for the use of hydrocarbon refrigerants in static refrigeration and air conditioning systems. This refrigerant also has a distinct odor at higher concentrations so that when a device has chemical leaks, they can be quickly identified. The desired thermodynamic properties are a boiling point somewhat below the target temperature, a.
Thermodynamic and transport properties of the refrigerant. There is no single refrigerant that can be called as the ideal refrigerant possessing all the desirable properties. The working fluid desirable properties are related to thermodynamic and physical properties which lead to efficient cooling or heating factor and effective design of equipment, such as high evaporation heat, high volumetric refrigeration. Critical temperature of refrigerants should be high. Indirect systems with secondary refrigerants or coolants have in sweden long been used for ice rinks and heat pumps and are today increasingly used by supermarket chains for cold storage, cooling. Low boiling point otherwise operation at high vacua becomes a necessity low condensing pressure to avoid heavy machine plant scantling and reduce the leakage risk high specific enthalpy of vaporisation to reduce the quatity of refrigerants in circulation and lower machine speeds, sizes etc. However, the compressor must use a synthetic polyester lubricating oil.
Please consult the msds for more comprehensive information, or contact the hc refrigerant products technical support representative. The refrigerants have a thermodynamic property charge. Desirable properties characteristics of refrigerants selection of refrigerants, recent trends in refrigeration, best video in hindi, refrigeration and air conditioning, by. Refrigeration n changes phase due to change in pressure n most common cryogens are n solid carbon dioxide n liquid carbon cook chill systems n used to replace warm holding of foods n cook chill system.
The ideal refrigerant has good thermodynamic properties, is noncorrosive, and safe. These physical properties of refrigerants help us select the proper refrigerant for the application as per our requirement. In todays world, other properties of the refrigerant are more important. Refrigeration may be defined as a process of removing heat from a substance and pumping it to the surroundings. The simulator used an equation of state to predict the thermodynamic properties of the refrigerant mixtures.
In particular, physical properties of refrigerants are useful for determining the applicability of a refrigerant under design operating conditions. This section presents data for the thermodynamic and transport properties of refrigerants, arranged for the occasional users. The desirable properties of refrigerants used in the refrigerant systems on board the ship are as follows. Where, specific heat is the amount of heat required to increase the temperature of substance of unit mass through 1 c. Properties of a good refrigerants mechanical engineering. The most reliable way to be safe is to choose a refrigerant that is neither toxic nor flammable.
Physical properties of refrigerants molecular weight, boiling, freezing and critical points engineering toolbox resources, tools and basic information for engineering and design of technical applications. 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. Whenever we choose them for particular use properties of refrigerants also plays a vital role in economic and environmental friendly application. Refrigerant absorbent mixtures for vapour absorption cooling system should possess some desirable properties like the refrigerant should be more volatile than the absorbent in other words the boiling point of refrigerant should be much lower than the absorbent. Guidelines for the use of hydrocarbon refrigerants in static. Refrigerant fluid an overview sciencedirect topics. The flood of the airconditioner, that is, the refrigerants, their properties, merits and demerits are summarized to map the various types and their classifications. Desirable properties of refrigerants chemical engineering site. Safety is perhaps the most important single factor in the selection of a refrigerant. What are the desirable properties of refrigerants primary.
Guidelines for the use of hydrocarbon refrigerants in. Jun 02, 2019 a refrigerant is a substance or mixture. Thermodynamic properties of duponttm freonr 22 refrigerant. Dependable thermostatic expansion valves designed for low temperature refrigerants will be found on larger cascade systems. In particular they were nontoxic, nonflammable and with good thermodynamic prop erties and oil miscibility characteristics.
Refrigerants should have low freezing point than the normal operating conditions. Most of the halogenated refrigerants meet these requirements. Class a signifies refrigerants for which toxicity has not been identified. A blend of ab and m oils achieving desirable properties for use with hydrocarbons. R744 is a climatefriendly, highpressure refrigerant. Different refrigerants are used for different temperature conditions and there is no ideal one that is suitable for all conditions. It would not cause ozone depletion or climate change. This information is based on values calculated using the nist refprop database mclinden, m. High latent heat of refrigerant at evaporator temperature is desirable. Fundamentals of mechanical refrigeration systems course content introduction mechanical refrigeration is a thermodynamic process of removing heat from a lower temperature heat source or substance and transferring it to a higher temperature heat sink.
Usually, a fluid, used in a heat pump and refrigeration cycle that can extract heat from another body or substance. Pdf refrigerant types, issues, trends and future options. Many refrigerants have an odor similar to carbon tetrachloride when they. All refrigerants which damage the ozone layer have now effectively been banned, however many substances have a significant gwp that is released into the atmosphere through leakage. Snap listed r744 as acceptable subject to use conditions for new vehicles only. A low superheat is desirable to return oil from the low side, but a slug of. May 25, 2018 the high specific heat is required for a vapour refrigerant whereas low specific heat is required for the liquid refrigerant. As such, there is no refrigerant that can be advantageously used under all operating conditions and in all types of refrigeration systems. Refrigerant properties refrigerant selection involves compromises between conflicting desirable properties. The liquid has to vapourise at the evaporator coil to cause cooling. This also reduces the initial cost of the refrigerant used in the system.
Low boiling temperature at atmospheric of the refrigerant is desirable. Normal procedure is used in applying and adjusting these, except that a little more care must be exercised. Maharashtra state board of technical education autonomous. Refrigerant properties are necessary to describe the operating characteristics of the refrigerant within a system. Here are some of the desirable properties of refrigerant explained in detail. Thermodynamic analysis of vapor absorption refrigeration. Why is a low specific heat a desirable property for a. The selection of any pair of adsorbentadsorbate for refrigeration application depends on certain desirable characteristics of their constituents. Following are the desirable properties of a primary refrigerant.
Safety properties of refrigerants considering flammability and toxicity are defined by ashrae standard 34 1. Jun 20, 2015 the refrigerant is a heat carrying medium which during their cycles i. These characteristics range from their thermodynamic and chemical properties to their physical properties and also their cost and availability 7. This refrigerant and other members of the cfc family seemed to possess all the desirable properties. The refrigerant in any refrigerator or air conditioner flows continuously through the vapor compression cycle, absorbing the heat in the evaporator and releasing it in the condenser. The thermodynamic properties of refrigerants columbushoa.
Toxicity classification of refrigerants is assigned to classes a or b. The general conclusion of the thesis is that the refrigerant affects all of the measured properties negatively on the subject of lubrication and life of the rolling element bearing. Apr 12, 2020 refrigerants are widely used in refrigeration cycle where cooling effect below the atmospheric temperatures are needed. I, 2 present lists of desirable refrigerant properties.
May 01, 2014 following are the desirable properties of a primary refrigerant. Physical properties of refrigerant metric and standard physical properties of refrigerant metric. Comparison of environmental impacts and physical properties of refrigerants ko matsunaga executive summary even before the invention of refrigeration, people wanted to improve their life by using ice to provide. The weight of the refrigerant required to be circulated in the system per unit of refrigerating effect will be low if the latent heat of refrigerant is high. Desirable properties of refrigerant absorbent mixtures. As the refrigerant flows through the continuous vapor compression cycle it absorbs heat from a lowtemperature reservoir and deflects it into the atmosphere. The liquid at the evaporator coil should therefore vapourise easily, otherwise the compressor will have to create too much of vacuum to cause the liquid to vapourise. This article describes thermodynamic properties of the refrigerants the ideal refrigerant. Desirable properties and commonly used refrigerants. In spite of that, we can state certain desirable properties that a refrigerant should posses. The desirable properties of a refrigerant fluid are such that it flows through the evaporator in its vapour state, absorbs heat from its surroundings, then transfers this heat via the flow of the refrigerant to the condenser. Key properties of the main refrigerants are given in together with their typical application ranges. Vapours of refrigerants should be easily condensable.
R744 systems operate at five to 10 times higher pressure than other mvac systems. Desirable properties characteristics of refrigerants. Refrigerants should have high latent heat, otherwise the mass flow rate will be high. Thermodynamic and transport properties of refrigerants are necessary for predicting. It also includes the process of maintaining and reducing the temperature of a body below the general temperature of its surroundings.
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