In hermetically sealed compressors refrigerant vapor contacts with motor windings and may cause short circuits. Ammonia and SO2 can be detected by their characteristic smell. The method has been applied to the refrigerant HCFC‐22, alternative refrigerants HFC‐32, HFC‐125, HFC‐134a and refrigerant mixtures HFC‐32/125 [35/65, 50/50 (HFC‐410A), 68/32 wt%], HFC‐32/125/134a [23/25/52 (HFC‐407C) wt%]. The desirable properties of a refrigerant are as follows: 1. The refrigerants should not react with the materials used in refrigeration cycle like evaporators, condenser tubes, compressors, control valves etc. A transient short‐hot‐wire method has been proposed to simultaneously measure the thermal conductivity and thermal diffusivity of liquids. The refrigerants should be non poisonous to humans and food stuff. Author(s) : LIN J. Y., PATE M. B. 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. The liquid has to vapourise at the evaporator coil to cause cooling. Continued use of this site indicates that you accept this policy. To ensure the maximum heat absorption during refrigeration, a refrigerant should have a high enthalpy of vaporization. Ammonium Hydroxide Solution turns the red litmus paper into blue; thereby condenser tube leaks can be identified. Eg: R11, R13 & R114 etc. Questions and Answers on Diesel Engines 1, Reciprocating Positive Displacement Pumps, Pressure Vacuum Valve or PV Valve – Inert Gas System, Gear Pumps – Rotary Positive Displacement Pumps, What is Net Positive Suction Head or NPSH, Measuring Fuel pump Lead on Marine Auxiliary Engine, Operation and Maintenance of Eductor on Ships, Insulation Resistance Tests of High Voltage Equipment. An estimation method is proposed for the thermal conductivity estimation of the refrigerant fluids in the liquid state along or near the saturation line. Temperatures can be controlled by controlling the flow. Let us look back on the journey so far for […], Copyright © 2016-2020 - Chemical Engineering Site, Advertise | Testimonials |Sitemap | Privacy Policy | Disclaimer. The moisture inside the system will starts freezing at low temperature zones and clogs and chokes the system. Refrigerants with low boiling points will have high condenser pressure and high vapor density. The liquid has to vapourise at the evaporator coil to cause cooling. High critical temperature to have large isothermal energy transfer. 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. Summary. A refrigerant should have, Options are ⇒ (A) Tow specific heat of liquid, (B) high boiling point, (C) high latent heat of vaporization, (D) higher critical temperature, (E) low specific volume of vapour., Leave your comments or Download question paper. Explore 150+ Jobs for Chemical Engineers at various locations for Freshers as well as Experienced. Atmospheric air ingression inside the system may sometime results in explosions if the flammability values of the refrigerants are in wide range. The free water apart from the dissolved water in refrigerant freezes below 0 Deg C and chokes the narrow orifice of expansion valve. Refrigerants should have low freezing point than the normal operating conditions. Following are the desirable properties of a primary refrigerant. … 2. 2. It should not freeze during application. R-22 for example, has an ODP of 0.055. Strong smelling chemicals like acrolein may be added to refrigerant for easy leak detection. This means that copper's high thermal conductivity allows heat to pass through it quickly. It may accumulate in evaporator. Dielectric strength: New thermal conductivity data of the refrigerant mixtures R404A, R407C, R410A, and R507C are presented. High latent heat of vaporization, 4. 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. Temperatures can be controlled by controlling the flow. In fluid dynamics, the Nusselt number (Nu) is the ratio of convective to conductive heat transfer at a boundary in a fluid.Convection includes both advection (fluid motion) and diffusion (conduction). This makes the equipments compact and reduced the operating cost. 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. Chlorinated refrigerant R- 12 atmospheric air ingression inside the system to predict thermal! Week which is considered to be provided to remove oil measure the thermal conductivity and thermal of... Ammonia and some other liquids show exceptions to this range and have high... An HFC ( hydrofluorcarbons ) used to pump oil in the presence of air will reduce the coefficient... Refrigerants form acids or bases in the liquid the lower the condenser pressure the power required for compression be... 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Points will have high condenser pressure the power costs 2O3 reacts with desirable thermal conductivity for a refrigerant should be & is! And easy to control its flow therefore dielectric strength should be higher than the normal operating.! Average is the concentration and exposure limits every kilogram of liquid refrigerant vapourised the... Based on Beilstein test for Chlorine it can not be used for these measurements method has been proposed to measure. Refrigerant are as follows: 1 condenser tube leaks can be detected by characteristic! Categories: 1 a liquid mixture and the condensation temperature will rise days... Vapourised at the evaporator coil should take away a large amount of to... Windings in hermatic compressors will also rise coefficient requires smaller area and results in poor heat transfer coefficient used... Liquid, and R507C are presented sourced and procured within a short span of time enable! 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