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Title:Investigation of oil retention and pressure drop in suction lines using R134a with AB ISO 32
Author(s):Budhiraja, Bharat
Advisor(s):Hrnjak, Predrag S.
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Oil return
Pressure drop
Horizontal tube
Vertical tube
Abstract:In refrigeration systems, a small quantity of oil, meant for compressor lubrication, is removed from the compressor during operation, by the high velocity refrigerant vapor exiting it, which forms a mixture with the oil. This circulating refrigerant/lubricant mixture affects the system performance in terms of heat transfer coefficient and pressure drop. The circulating liquid mixture possesses the maximum viscosity in the suction line to compressor, due to the superheated vapor, and it is for this reason that studies are performed to evaluate oil retention and pressure drop in suction lines. The aim of the current work is to study the oil retention and pressure drop in suction lines for a mixture of R134a as refrigerant and AB ISO 32 as the lubricating oil. The oil retention and pressure drop were evaluated in horizontal and vertical suction lines with an internal diameter of 10.2 mm and length approximately 2 m. The system operating conditions were kept fixed at a saturation temperature of 13˚C and a superheat of 15˚C. The mass flux was varied from 30 kg/m2-s – 140 kg/m2-s, and three OCRs of 1%, 3% and 5% were tested. The experimental results of the current work were compared to results of R134a/POE100 by Ramakrishnan and Hrnjak (2012) and R134a/POE32 by Sethi and Hrnjak (2011). Results showed that AB32 yields a higher oil retention than POE100 and POE32. An analytical model was also proposed to predict the experimental results. Based on the prediction of the results by the model and also the observations made during experimentation it was concluded that vapor R134a was miscible in AB32 oil. Flow visualizations in the liquid line before the evaporator and the horizontal and vertical suction lines were also carried out to study the different flow regimes.
Issue Date:2012-09-18
Rights Information:Copyright 2012 Bharat Budhiraja
Date Available in IDEALS:2012-09-18
Date Deposited:2012-08

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