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Refrigeration and air conditioning by rk rajput pdf free download. Refrigeration and air conditioning is the process of removing heat from an area to make it cool or cold enough to meet human needs. This includes cooling food and drink, preserving their safety, extending the life of surgical instruments, maintaining certain pharmaceuticals in a stable condition for use, providing energy for heating or producing power, controlling fermentation temperatures in breweries. When people talk about "cooling off" they are often referring to the act of bringing down someone's body temperature by exposing them to cold water or snow. The history of air conditioning begins in the 19th century, when people first tried using ice and seawater in large ducts in order to cool air. The first air conditioning system was built by William Lenz in 1881. Air conditioning became more practical with the invention of vapor-compression refrigeration by Carl von Linde in 1902, allowing more efficient cooling of larger spaces. In 1911, an American engineer named Willis Carrier adapted a fan used for ventilating hot factories to create the modern air conditioner. The key component that made this new invention practical was his decision to use liquefied gas as the refrigeration agent instead of an only refrigerant, which he patented two years later. He initially experimented with using ammonia, but it proved to be far too toxic. Carrier turned to hydrocarbon refrigerants as they were non-toxic, but they too were not very efficient. However, the first truly successful system was developed by Frank Gilbreth in 1925. Gilbreth's invention used the simple stages of cooling water through a coil inside a refrigerator, followed by chilling that water with ammonia-filled tubes outside the fridge. One of the earliest AC units that has been restored is now on display in the Museum of Science & Industry in Chicago. In the early 1930s, Willis Carrier began designing a more complex system with a single central air handler served by ducts, and multiple zones cooled by localized coils. In 1939 he described a multi-zone air conditioning system in an article called "Air Conditioning for Armies" in the magazine Industrial Engineering. In the 1940s his company purchased land near Albany, NY and built a full-scale research facility to develop new concepts for air conditioning systems. The unique design of the building that resulted from this effort became known as a "Carrier Dome". In 1945 Carrier's company purchased all rights to his invention from him and he was paid $20 million ($198 million in 2018 dollars). Carrier was allowed to continue experimenting but any future patents would be his alone. As companies with large commercial buildings built their own air conditioning systems, an industry grew around servicing and maintaining them. The largest user of air conditioning is in the United States, particularly in urban areas. The most common use of air conditioning is in large office buildings, shopping malls, hotels and schools where it keeps the temperature comfortable for people to work during the day. This is particularly important when compared with other options such as central heating systems that can be used when not busy or when they are not needed at all. cfa1e77820
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