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Desenvolvimento de um novo conceito de calorímetro para medição do desempenho de compressores em transientes periódicos de sistemas de refrigeração

  • Balvedi, Daniel Faitão
Publication Date
Sep 22, 2018
Repositório Institucional da UFSC
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Abstract : Reciprocating compressor are designed and tested in calorimeters under steady-state operating conditions defined by standards. However, most household refrigerators operate under transient and periodic regimes, characterized by alternate periods in which the compressor is either operating (on) or idle (off). The result is a decoupled design approach since steady-state conditions not necessarily represent the operating conditions found in refrigerators. The present work considers the development of an experimental facility to test compressors under actual transient operating conditions of refrigerators. Initially, curves of evaporating and condensing pressures measured in a household refrigerator operating under on/off cycling conditions were prescribed as input data for the new calorimeter facility. The main parameters of compressor performance were measured in such transient conditions and found in good agreement with the experimental data obtained for the same compressor working in the refrigerator, hence validating the new calorimeter test facility. A virtual refrigeration system was then developed using the Modelica modeling language in order to simulate the components of a household refrigerator, except for the compressor. The virtual system was then coupled to the new calorimeter so to provide the instantaneous operating condition resulting from the interaction between the compressor under test and the virtual system. The virtual system model is also used to set when the compressor is on or off based on predictions for the freezer temperature. The strategy used for the coupling between the virtual model and the experimental facility proved to be reliable. The coupled procedure was used to emulate a compressor working in a household refrigerator under different ambient temperatures (16 °C, 25 °C and 32 °C). Results for the compressor performance were found in good agreement with experimental data obtained in the refrigerator at the reference ambient temperature (32 °C) while some deviations were verified in the other conditions (16 °C and 25 °C) due to differences in the prediction of the suction pressure. Although improvements are still required in the modeling of the refrigeration system, the new calorimeter facility was validated as a viable method to assess the effect of different compressor designs in a coupled manner with the refrigeration system.

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