University of Illinois Urbana-Champaign

Oil migration and property change at compressor suction and discharge

Wang, Xin

Content Files
WANG-THESIS-2022.pdf

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https://hdl.handle.net/2142/115617

Description

Title
Oil migration and property change at compressor suction and discharge
Author(s)
Wang, Xin
Issue Date
2022-04-28
Director of Research (if dissertation) or Advisor (if thesis)
Elbel, Stefan
Department of Study
Mechanical Sci & Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
  • Oil migration
  • Oil property
  • Compressor
  • Oil-refrigerant mixture
Abstract
The oil migration has great impact on the vapor compression systems, especially for systems that require frequent on-off cycling. Excessive amount of oil retained in the system and lack of oil return to the compressor can cause low system efficiency and potential compressor failure. This thesis aims at exploring oil-refrigerant mixture properties during startup and shutdown period at different locations in the system. The variation of temperature and pressure would result in different mixture concentrations and properties. Oil properties like solubility, viscosity, density, surface tension and contact angle can be influenced and will affect system performance. Warm and cold startup conditions are recorded and compared. Oil flow during startup is different from the annular mist flow in steady-state conditions. Oil flow is composed of oil droplets traveling with refrigerant vapor flow and oil film attached to the inner wall of discharge tube. During startup, small oil droplets are carried by vapor refrigerant to the discharge where some of droplets are attached to the tube wall and form film flow in low velocity, others coalesce into larger droplets. During the compressor shutdown, the oil flow in contact with the inner wall of discharge stops immediately with while oil droplets in the vapor core flow slower and stop gradually. In the end, oil droplets flow down and coalesce with oil film to accumulate at the bottom of the tube. The high-speed camera and video analysis method are used to analysis oil migration and show variation of surface tension, viscosity, and wettability. Properties of mixture like solubility, density, saturation pressure and viscosity are predicted by existing models.
Graduation Semester
2022-05
Type of Resource
Thesis
Handle URL
https://hdl.handle.net/2142/115617
Copyright and License Information
Copyright 2022 Xin Wang

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