Simple aircraft refrigeration cycle • The outside low pressure and low temperature air (state 1) is compressed due to ram effect to ram pressure (state 2). • The cold air at state 5 is supplied to the cabin. It picks up heat as it flows through the cabin providing useful cooling effect. 6 Refrigeration and Air Conditioning It is a well-known fact that the spoilage of food and many other items reduces at a lower temperature. At a lower temperature, molecular motion slows down and the growth of bacteria that causes food spoilage also retards. Efficiency of the Otto Cycle vs. Carnot Cycle • There are only two temperatures in the Carnot cycle • Heat is added at T H • Heat is rejected at T L • There are four temperatures in the Otto cycle!! • Heat is added over a range of temperatures • Heat is rejected over a range of temperatures.
5 Refrigeration without a Refrigerant 72 Evaporative cooling 72 Peltier-Seebeck effect (thermoelectric devices) 73 Magneto-Calorific Effect (Magnetic Refrigeration) 75 Thermo-acoustic effect (acoustic refrigeration) 76 Summary of Chapter 5 78 Further Reading 78 Download free eBooks at bltadwin.ru Efficiency of the Otto Cycle vs. Carnot Cycle • There are only two temperatures in the Carnot cycle • Heat is added at T H • Heat is rejected at T L • There are four temperatures in the Otto cycle!! • Heat is added over a range of temperatures • Heat is rejected over a range of temperatures. • Mechanical refrigeration using compressors, condensers and evaporators • Vapour absorption蒸氣吸收 • Produce refrigeration effect by thermal energy input • Liquid refrigerant produce refrigeration during evaporation; the vapour is absorbed by an aqueous absorbent • Air or gas expansion (air or gas cycle)空氣膨脹.
Carnot cycle, here the enclosed area is a rectangle. This cycle is often used as a comparison cycle to describe the quality of the cyclic process. The direction of the cyclic process in theT-s diagram determines w hether this is a heat pump cycle (refrigeration cycle) or a work machine cycle (steam power cycle). Refrigeration cycles are anti-. Mechanical refrigeration works by changing the The majority of heat is removed from the The majority of the works by removedchanging the absorbed heat is state of the refrigerant. from the temperature controlled space as the refrigerant absorbs heat when it changes state from a absorbed heat is removed from the refrigeration system in. Chapter Refrigeration Cycles The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. The above figure shows the objectives of refrigerators and heat pumps. The purpose of a refrigerator is the removal of heat, called the cooling load, from a low-temperature medium.
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