Oil migration and property change at compressor suction and discharge

Wang, Xin

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

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

Copyright and License Information

Copyright 2022 Xin Wang

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