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Development of Empirical Temperature and Humidity-Based Degraded-Condition Indicators for Low-Tonnage Air Conditioners

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dc.creator Watt, J. B.
dc.date.accessioned 2011-06-03T14:26:11Z
dc.date.available 2011-06-03T14:26:11Z
dc.date.issued 1997-12
dc.identifier.other ESL-TH-97-12-03
dc.identifier.uri http://hdl.handle.net/1969.1/94784
dc.description.abstract A split-system direct-expansion air conditioner was used to empirically determine temperature and return-air humidity indicators that could detect performance degradation resulting from degraded conditions. The air conditioner test bench was equipped with the ability to use either a short-tube orifice (STO) or a thermal expansion valve (TXV). The degraded conditions studied include low evaporator airflow, highand low-charge, and a blocked condenser coil. The work presented in this thesis is experimentally based which could identify degraded effects that fall outside of a simulation-based approach. It sought to utilize only low-cost temperature sensing means, although return-air humidity was an important factor for obtaining early detection over a wide range of operating conditions. It was empirically based rather than model based to reduce computation time with a real-time processor. Further, the current work differentiated between a system that uses a shorttube orifice (STO), or fixed-orifice expansion, and a system that uses a thermal expansion valve (TXV), or variable-orifice expansion. This thesis shows that low-cost temperature sensors could be used to detect the degraded conditions studied. However, it is also shown that indicators of low evaporator airflow depend on three loading factors; outdoor-air temperature, return-air temperature, and return-air humidity. In the literature, the humidity sensing point has been neglected by automated detection systems for failures and degraded conditions of low-tonnage air conditioners. The effects of the loading factors on the indicators relative to improper charge and a blocked condenser coil were not studied. Finally, while there were differences in the performance of a STO system and a TXV system relative to the degradations studied, a common set of indicators was identified that could detect degraded conditions without regard to the expansion device. en_US
dc.language.iso en_US en_US
dc.publisher Energy Systems Laboratory (http://esl.tamu.edu) en_US
dc.subject Mechanical Engineering en_US
dc.subject HVAC en_US
dc.title Development of Empirical Temperature and Humidity-Based Degraded-Condition Indicators for Low-Tonnage Air Conditioners en_US
dc.type Thesis en_US

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