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Metastable flow in capillary tubes: An experimental evaluation |
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| Authors: | Alex Alberto Silva Huerta Flvio Augusto Sanzovo Fiorelli Otvio de Mattos Silvares |
| Institution: | aMauá Institute of Technology, Praça Mauá no. 1, 09580-900 – São Caetano do Sul (SP), Brazil bIMENSU – Mairiporã Institute of Technology, Rodovia Fernão Dias Km 67, 076000-000 – Mairiporã (SP), Brazil cUniversity of São Paulo, Mechanical Engineering Department, Av. Prof. Mello Moraes, 2231 – Cidade Universitária, 05508-900 – São Paulo (SP), Brazil |
| Abstract: | This work presents the results of an experimental study with pure refrigerants R-134a and R-600a and refrigerant–oil mixtures flowing through capillary tubes in order to analyse the metastable flow. A large number of experiments were carried out to verify the influence of several variables on the underpressure of vaporization, mainly the inlet subcooling, internal diameter and inlet pressure. Capillary tubes with internal diameter of 0.69 mm and 0.82 mm were tested for condensation temperatures between 40 °C and 50 °C and subcooling degrees between 3 °C and 12 °C. Measurements for oil concentrations of 1% and 3% were conducted and compared with those for pure refrigerant R-134a. The oil influence on the metastable flow was tested and the effect on the underpressure of vaporization is addressed for lower oil concentrations. |
| Keywords: | Refrigeration Metastable flow Capillary tubes Experimental analysis |
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