19-10-2012, 02:10 PM
HISTORY OF REFRIGERATION AND AIR-CONDITIONING
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REFRIGERATION AND AIR CONDITIONING:
Mechanical refrigeration, whether for refrigeration itself or for air conditioning, relies on a closed system in which a refrigerant—basically a compound of elements with a low boiling point—circulates through sets of coils that absorb and dissipate heat as the refrigerant is alternately compressed and allowed to expand. In a refrigerator the circulating refrigerant draws heat from the interior of the refrigerator, leaving it cool. In an air conditioner, coils containing refrigerant perform a similar function by drawing heat and moisture from room air.
This may sound simple, but it took the pioneering genius of a number of engineers and inventors to work out the basic principles of cooling and humidity control. Their efforts resulted in air conditioning systems that not only were a real benefit to the average person by the middle of the 20th century but also made possible technologies in fields ranging from medical and scientific research to space travel.
The development of machines after 1850 to control the temperature and moisture content of air profoundly affected the way Americans lived and worked. Although refrigeration and air conditioning are historically and technologically entwined, their purposes differ. Refrigeration preserves food and other perishables; air conditioning—a term coined in 1906 by textile engineer Stuart Cramer—controls temperature and humidity in spaces generally occupied by human beings.
INTRODUCTION
This section briefly describes the main features of the Refrigeration and Air conditioning System.
AIR-CONDITIONING:
Control of temperature, humidity, purity, and motion of air in an enclosed space, independent of outside conditions is called air-conditioning. In a self-contained air-conditioning unit, air is heated in a boiler unit or cooled by being blown across a refrigerant-filled coil and then distributed to a controlled indoor environment.
Refrigeration air conditioning equipment usually reduces the humidity of the air processed by the system. The relatively cold (below the dew point) evaporator coil condenses water vapor from the processed air, (much like an ice-cold drink will condense water on the outside of a glass), sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity. Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space. In food retailing establishment’s large open chiller cabinets act as highly effective air dehumidifying units.
REFRIGERATION:
Refrigeration is the process of removing heat from an enclosed space, or from a substance, and moving it to a place where it is unobjectionable. If we remove a bucket of water from a tank, the surrounding water rushes in to fill the cavity. Similarly heat rushes in to replace the heat when the heat is removed from refrigerated space. Whatever heat enters through insulation into the refrigerated space has to be removed with the help of refrigerating machine.
OBJECTIVE OF THE PROJECT:
In day-to-day world every one concentrates on the compactness and efficiency of every product. “HUMAN COMFORT” will mostly depend on conductive environment which deals with the conditions of environment around us, mostly they are HOT & COLD, present days everyone is utilizing the modern gadgets which provide them comfort. Air conditioner is one of the gadgets which provide them required Humidity and Temperature at the required place. But most of the people are not able to afford for a air conditioner due to its initial cost and maintenance cost but if one fabricates such a product that which will survive multiple purpose then it will be afforded by many, so keeping this in our thought we have fabricated an economical and reliable unit known as “water heater, water cooler and air conditioner”.
Working of Reciprocating Compressor
SUCTION STROKE:
Let us suppose that initially the piston is at the top position inside the cylinder; this is called as the top dead center (TDC) position of the piston. At this position the refrigerant that has already been compressed is delivered from the discharge valve. From the top dead center position the piston starts moving towards the downward direction. At this instance the discharge valve is already closed, while the suction valve opens due to suction pressure of the refrigerant from the suction pipeline. The refrigerant from the suction pipeline is taken inside the cylinder of the compressor via the suction valve. As the piston moves downwards, the amount of the refrigerant taken inside the cylinder increases. When the piston reaches bottom most position it is said to be in bottom dead center position (BDC). At this position the maximum amount of the refrigerant is sucked by the cylinder or compressor.
Inside the cylinder and it finally reaches the TDC position, where the entire compressed refrigerant inside the cylinder is delivered to the discharge line and the discharge valve closes. From here on the piston starts moving again to the BDC position and the operation of the compressor continues.