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ACRC Technical Report 226PDF


Title:Experimental Measurement and Modeling of Oil Holdup
Author(s):Crompton, J.A.; Newell, T.A.; Chato, J.C.
Subject(s):oil holdup
Abstract:Often in air conditioning and refrigeration vapor compression systems the working fluid is mixed with lubricating oil, which flows through the system as it operates. The effects of this oil in the system include the possible degradation of heat transfer, increased pressure drop, insufficient lubrication for the compressor and the possibility of flooding the compressor suction ports with oil should the compressor valve fail. In order to quantitatively evaluate these effects on the system, a better understanding of the flow of oil through various operating conditions is required. The purpose of this investigation is the measurement of oil retention in small diameter round copper tubes with various internal geometries. Test sections include an internally smooth, an axially microfinned and a helically microfinned tube, all with an outer diameter of 9.53 mm (3/8”). Mass fluxes of 75 to 300 kg/m2s are tested, with an emphasis on 75 and 150 kg/m2s, and qualities of 0% to 100% are reached. The refrigerant/oil mixtures examined include R134a with a polyol ester, R134a with a polyalkylene glycol, R134a with an alkylbenzene, R22 with an alkylbenzene and R410A with a polyol ester. Additionally, it is important to examine the void fraction and flow visualization of the mixtures to determine if the oil has an effect in these areas. Finally, two models have been developed for oil holdup prediction. The first is based on the test section’s liquid volume fraction and is used at mid to low-range qualities, while the second, with the Blasius turbulent flow formula as a basis, is used to predict holdup at high qualities.
Issue Date:2004-05
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-226
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Project 150
Date Available in IDEALS:2009-06-19

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