Q.1 What is the basic principal of refrigeration and what do you understand by refrigeration cycle?Ans.1Refrigeration is a process in which work is done to move heat from one location to another. In other words it is a process in which heat is absorbed from lower temperature region and resentor transfer it to the high temperature region. asic principle of refrigeration isto pass a colder li!uid known as the refrigerant" continuously around the ob#ect which is to be cooled. $his will take heat out from the ob#ect which is to be cooled. %ue to the temperature di&erence ob#ect e#ects heat to the refrigerant li!uid. $he refrigerant is in turn gets heated up due to heat absorption.A refrigerant is a substance or mi'ture" usually a (uid" used in a heat pump and refrigeration cycle. A refrigerant is a (uid used for heat transfer in a refrigeration system. )ost refrigerants absorb heat during evaporation at low temperature and low pressure and re#ect heat during condensation at a higher temperature and higher pressure In most cycles it undergoes phase transitions from a li!uid togas and back again.$here are two $ypes of refrigerants* primary and secondary. +rimary refrigerants, it undergoes phase transition from a li!uid to a vapor and back again.-econdary refrigerants, itdoesn.t undergoes any phase transitions and always remains in li!uid form. Application of refrigeration * +robably the most widely used current applications of refrigeration are for air conditioning of private homes and public buildings" and refrigerating foodstu&s in homes" restaurants and large storage warehouses. $he use of refrigerators in kitchens for storing fruits and vegetables. It is also used in medicine and sterili/ation. )etal workers use refrigeration to temper steel and cutlery. In transporting temperature,sensitive foodstu&s and other materials by trucks" trains" airplanes and seagoing vessels" refrigeration is a necessity.)ethods of refrigeration can be classi0ed as non,cyclic" cyclic" thermoelectric and magnetic. 11 2yclic method * $his consists of a refrigeration cycle" where heat is removed from a low,temperature space or source and re#ected to a high,temperature sink.2yclic refrigeration can be classi0ed as*) 3apor cycle 4a1 3apour,compression refrigeration4b1 3apour,absorption refrigeration) 5as cycle * 5as is used instead of refrigerant. 5as has been moved from higher pressure to lower pressure which reduces the temperature. Its process is same as the other methods. When the working (uid is a gas that is compressed and e'panded but doesn6t change phase" the refrigeration cycle is called a gas cycle. Air is most often this working (uid. As there is no condensation and evaporation intended in a gas cycle" components corresponding to the condenser and evaporator in a vapor compression cycle are the hotand cold gas,to,gas heat e'changers in gas cycles. $he gas cycle is less e7cient than the vapor compression cycle because the gas cycle works on the reverse rayton cycle instead of the reverse Rankine cycle. As such the working (uid does not receive and re#ect heat at constant temperature. In the gas cycle" the refrigeration e&ect is e!ual to the product of the speci0c heat of the gas and the rise in temperature of the gas in the low temperature side. $herefore" for the same cooling load" a gas refrigeration cycle needs a large mass (ow rate and is bulky. Vapour compression refrigeration method * it is the most common method of transferring heat from a low temperature to a high temperature. It is used in general refrigerators" compressors" etc. in this method both the temperature and pressure increases. 0rstly compression is done where vapor is compressed" than vapor are cooled and converted into li!uid state and hence condensation occurs" than further e'pansion is carried out wherevapor become partially li!uid and partially gaseous. 8astly" evaporation is carried out. 9ere electricity is less consumed and e'ternal heat is not re!uired. Vapour absorption refrigeration method * it is !uite similar as that of the vapour compression method e'cept vapour instead of compression undergoes absorption. 9igh temperature and pressure is released. :lectricity consumed is more and e'ternal heat is re!uired.;1