Commissioning of experimental facility for oil circulation rate measurements in a vapor compression system

Haider, Syed Angkan

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https://hdl.handle.net/2142/122060 Copy

Description

Title

Commissioning of experimental facility for oil circulation rate measurements in a vapor compression system

Author(s)

Haider, Syed Angkan

Issue Date

2023-12-07

Director of Research (if dissertation) or Advisor (if thesis)

Miljkovic, Nenad

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 circulation
• oil circulation rate
• oil retention
• vapor compression system
• swash plate compressor
• refrigerant-oil mixture
• ASHRAE standard 41.4
• annular-mist flow

Abstract

Lubricant oil is essential in typical vapor compression refrigeration and air conditioning systems, where the oil is primarily used to lubricate the moving parts inside the compressor. The relative motion between the moving parts can cause them to wear out and eventually lead to the failure of the compressor. So, the oil helps to extend the useful life of the compressor. In addition to that, the oil has other benefits such as dissipating heat away from the compressor and ensuring better sealing and hence good volumetric efficiency. Outside the compressor, the oil is a contaminant and has little use, and mostly causes problems at both the system and component levels. Oil is known to generally reduce heat transfer coefficient and increase pressure drop. It can coat the tube inner walls and act as a barrier to heat transfer by reducing the area available for heat transfer and presenting itself as an additional thermal resistance. As a result, both the system capacity and coefficient of performance drop (COP), and energy efficiency takes a hit. The movement of oil from the compressor to the rest of the system and back to the compressor is known as oil circulation. However, not all the oil returns to the compressor and some gets stuck at different locations around the system in a process called oil retention. To understand the oil effects better, a better knowledge of the degree of oil circulation is necessary. The oil motion around the system is quantified by the oil circulation rate (OCR) which is the ratio of the oil flow rate to the total flow rate of the oil-refrigerant mixture. In real systems, the ASHRAE standard 41.4 is used to measure OCR in steady state. This method involves taking a sample of refrigerant-oil mixture from a system running in steady state. Once the sample is taken, mass analysis of the sample is done to determine the oil concentration at the outlet of the condenser. The oil concentration is the same as the oil circulation rate since the mixture is miscible and is a homogeneous liquid. The present work was aimed at building and commissioning an experimental facility that could be used to run such tests. The whole facility was not built from scratch, a lot of the components were present in the lab, and our job was to build and modify the facility for the tests we wanted to perform. This included finding the current components, connecting everything, calibrating all the sensors, fixing the data logging unit, and all the other crucial tasks needed to have an experimental facility that would cater to all our needs. The next goal was to learn how to run the experimental facility at specified standard indoor and outdoor conditions to provide us with comparable test results. Finally, once steady state system conditions were achieved, oil circulation rate was measured for different compressor speeds to see the variation in oil circulation around the system.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Syed Angkan Haider

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