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ACRC Technical Report 128PDF


Title:Experimental Investigation of Mobile Air Conditioning System Control for Improved Compressor Reliability
Author(s):Wandell, E.W.
Contributor(s):Dunn, W.E.; Miller, N.R.
Subject(s):mobile air conditioning systems
Abstract:Mobile air conditioning circulating oil concentration and compressor start-up torque were experimentally investigated to develop a control strategy to improve compressor reliability. An installed electronic expansion valve provided the control actuation. Realtime circulating oil concentration data were obtained for steady-state, quasi-steady, and start-up operating regimes with an installed optical concentration sensor. A two-phase refrigerant-oil model was developed for R134a and polyalkylene glycol (PAG) oil to predict oil film thickness, average film velocity, and interfacial shear between the refrigerant vapor and the refrigerant-oil liquid film. Experimental and model results were analyzed and compared. Evaporator superheat reduced the circulating oil concentration due to an increase in the oil film thickness on the walls of the evaporator and suction line. The model predicted oil film thickness to increase by a factor of four as refrigerant quality approaches one. Increasing the refrigerant-mass flow rate only exhibited secondary effects due to slightly thinner oil films and a correspondingly higher circulating oil concentration. The influences of charge distribution, expansion valve position, compressor head pressure, and refrigerant charge level on start-up torque and initial capacity were investigated. Closing the expansion valve while the compressor clutch is disengaged was found to reduce the start-up torque by retaining the refrigerant in the system high side and preserving a pressure gradient across the expansion valve.
Issue Date:1997-08
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-128
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Project 78
Date Available in IDEALS:2009-04-29
Identifier in Online Catalog:4170089

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