Convective boiling pressure drop of refrigerant R-134a in horizontal smooth and microfin tubes

• Published in: International journal of refrigeration Vol. 27; no. 8; pp. 895 - 903
• Main Authors: Filho, Enio P.Bandarra, Jabardo, José M.Saiz, Barbieri, Paulo E.L.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2004; Elsevier Science
• Subjects: Applied sciences; Boiling; Chute de pression; Ebullition; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Experiment; Expérimentation; Finned tube; Horizontal tube; Measurement; Mesure; Pressure drop; R-134a; Refrigerants; Refrigerating engineering; Refrigerating engineering. Cryogenics. Food conservation; Tube aileté; Tube horizontal; Measurement; Experiment; Finned tube; Tube horizontal; Mesure; Chute de pression; Boiling; Expérimentation; R-134a; Ebullition; Pressure drop; Horizontal tube; Tube aileté; Refrigeration installation; Correlation; Two phase flow; Phase change; Quality; Liquid phase; Smooth tube; Copper; Annular flow; Refrigerant fluid
• ISSN: 0140-7007; 1879-2081
• DOI: 10.1016/j.ijrefrig.2004.04.014

Present study deals with the pressure drop of refrigerant R-134a under convective boiling conditions in horizontal smooth and microfinned (‘grooved’) copper tubes. Experiments have been carried out in an experimental set up developed for change of phase studies with a test section made out of 7.0, 7.93, and 9.52 mm external diameter, 1.5 m long copper tubes, electrically heated by tape resistors wrapped on the external surface. Mass velocities and refrigerant qualities varied in the following ranges: 70–1100 kg s −1 m −2 and 5–95%. The annular flow pattern has been observed to occur over most of the operational conditions. For smooth tubes, the Jung and Radermacher correlation for the liquid two phase flow multiplier fits with reasonable precision the experimental data. As for grooved tubes, a correlation of the two phase flow multiplier in terms of the Martinelli's parameter has been developed which fits the data with an average absolute deviation of the order of 6.3%. The proposed correlation fits with good precision data obtained elsewhere for grooved tubes of different diameter and microfin geometry.