25-02-2013, 11:29 AM
A PAPER ON RECENT TRENDS IN REFRIGERATION
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ABSTRACT
Presently,the production of CO2, CH4 and CFC’s the most important of GREEN HOUSE gases has drastically increased and as a result ,the earth is warming up.if greenhouse gases continue to be emitted at the current rate , it is predicted that the global temperature will rise by 1.5 to 4.50C by the year 2050.This increase in temperarture would cause a rise in sea level upto 5 meters leading to flooding ,crop damage and severe distruption of life systems.For this issue refrigeration & airconditioning is one of the main reason.Our project particularly focus on reducing the CFC’s based refrigeration systems.so that we go for the magnetic refrigeration technology, which uses magnetic materials as the refrigerant. These materials demonstrate the unique property known as the magneto caloric effect.Magnetic refrigeration system is a non conventional one. Recently, materials are being developed which have sufficient temperature and entropy change to make them useful for a wide range of temperature applications. The proposed effort includes magneto caloric effect material selection, analyses, design and integration of components into a preliminary design. Benefits of this design are lower cost, longer life, lower weight and higher efficiency. The unit uses no gas compressor, no pumps, no working fluid, no valves, and no ozone-destroying (CFC's/HCFC's).
INTRODUCTION TO REFRIGERATION
The American society of refrigerating engineers defines “the science of providing and maintaining temperatures below that of surrounding atmoshphere”. The science of refrigeration means to obtain low temperature than the ambient temperature.
The science of refrigeration utilizes several methods of providing temperature differential.
TYPES OF REFRIGERATION
1. Vapour compression refrigeration (VCR)
2. Vapour absorber refrigeration (VAR)
3. Steam jet refrigeration (SJR)
4. Thermo electric refrigeration (TER)
5. Air cycle refrigeration(ACR).
In the above systems, at the present a days mostly using system is vapour compression refrigeration system(VCR).In the VCR system has many environmental issues(global warmming) by increased rate of using CFC’s.So we go for magnetic refrigeration,which is eco-friendly and nonconventional one.
MAGNETIC REFRIGERATION
PRINCIPLE Magnetic refrigeration is based on the principle of magnetocalorific effect of the magnetic material.The Magnetocaloric effect is a magneto-thermodynamic phenomenon in which a reversible change in temperature of a suitable material is caused by exposing the material to a changing magnetic field. This is also known as adiabatic demagnetization.
WORKING MATERIALS
The magnetocaloric effect is an intrinsic property of a magnetic solid. This thermal response of a solid to the application or removal of magnetic fields is maximized when the solid is near its magnetic ordering temperature.
Example: paramagnetic salt, such as cerium magnesium nitrate. Ferric alum, gadolinium sulphate.
WORKING
The mixture of water and ethanol serves as the heat transfer fluid for the system. The fluid first passes through the hot heat exchanger, which uses air to transfer heat to the atmosphere.
• The fluid then passes through the copper plates attached to the non magnetized cooler Magneto caloric beds and loses heat.
• A fan blows air past this cold fluid into the freezer to keep the freezer temperature at approximately 0°F.
• The heat transfer fluid then gets heated up to 80°F as it passes through the copper plates adjoined by the magnetized warmer Magneto caloric Beds, where it continues to cycle around the loop. However, the Magneto caloric beds simultaneously move up and down, into and out of the magnetic field.
• Figure below, shows how the cold air from the freezer is blown into the refrigerator by the freezer fan. The temperature of the refrigerator section is kept around 39°F.
• The typical household refrigerator has an internal volume of 21 cu.ft, where the freezer represents approximately 30% of this volume. Freezers are designed to maintain a temperature of 0oF. Refrigerators maintain a temperature of 39oF. The refrigerator will be insulated with polyurethane foam, one of the most common forms of insulation available.
• The refrigerator is kept cool by forcing cold air from the freezer into the refrigerator by using a small fan.
CONCLUSION
This magnetic refrigeration is the one of the alternate refrigent for get cooling effect. In American based mantreal protocol ( to control CFC’S ) , kyoto protocol ( give time to the countries to stop the prodution of CFC’S in 2010 ) this two organisations are approved the magnetic refrigeration is a alternative and effctive refrigeration technology. We hope our magnetic refrigeration system will be cost effective and commercial one as well as which helps to prevent the global warmming and other issues from CFC’s based refrigeration system in future the both house and all industries are going to use the magnetic refrigeration.