aircondition

aircondition - University of Texas at Arlington MAE 3183,...

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University of Texas at Arlington MAE 3183, Measurements II Laboratory Air Conditioning 1 Experiment #7 Air Conditioning
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University of Texas at Arlington MAE 3183, Measurements II Laboratory Air Conditioning 2 Introduction Most Americans take pleasant living conditions for granted. In the winter, homes stay just below 68 ° F while the outside temperature remains below freezing. In the summer the outside temperature may exceed 100 ° F while most people work inside offices that stay around a comfortable 72 ° F. These living conditions are made possible through the Air Conditioning Cycle (Dry Vapor Compression Cycle). This cycle transfers heat energy from one environment into another through the use of mechanical energy. The AC cycle needs energy to operate. Due to the fact that energy is not a self-creating entity in nature, we have to produce it ourselves. With the economic nature of humans, this soon gets expensive. The best idea would be to use as little energy (money) in the AC cycle as possible while still offering a nice level of comfort. What can be done to offer more efficiency from the AC cycle? Does the biggest motor produce the best efficiency? Does using bigger heat exchangers to transfer heat from environments help? Does the fluid being used affect the performance of the system? These are all questions that have to be answered in the quest for the optimum AC cycle. The “efficiency” of a refrigeration system can be expressed by two parameters. The first parameter is the coefficient of performance, β . This value is the ratio of the energy sought (heat transferred from the refrigerated space to the working fluid) to the energy that costs (work input to the working fluid). This quantity tells the level of efficiency in the cycle itself without the characteristics of the compression device. This is useful when considering different types of expansion configurations, fluids, flow rates, heat exchanger types, etc. The second parameter is the compressor efficiency , η . This value is the ratio of the energy imparted to the fluid to the energy input to the compressor. This quantity tells how effective the compressor is at transferring work energy into the fluid. This is useful when considering different types of compressors. In this experiment, the student examines an experimental AC system. The system is operated at various flow rates with two different types of flow control. The resulting performance can be determined and a pattern of performance can be generated. These results have real world significance, say when an engineer has made a change to an existing system and wishes to document the change in performance of the system. Theory The vapor-compression refrigeration cycle is fundamentally a four stage process. For examination purposes, the process will be considered with the starting point as the working fluid goes into the condenser. In the discussion terms such as “low “ and “high” will only have relevance to other states elsewhere in the system. Examine Figure 1 and consider the following discussion.
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This note was uploaded on 06/15/2009 for the course MAE 3183 taught by Professor Staff during the Spring '08 term at UT Arlington.

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aircondition - University of Texas at Arlington MAE 3183,...

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