Detection of refrigerant leaks with focus on low-GWP mixtures

In the context of global climate goals and tightening environmental regulations, the use of low-global-warming-potential (low-GWP) refrigerants, particularly flammable A2L-class and zeotropic blends, is rapidly increasing across refrigeration and air-conditioning systems. This is a comprehensive study of zeotropic refrigerant leakage under different scenarios. The study begins with a detailed literature review on refrigerant leakage effects, detection principles, and physical leakage modeling, establishing the background for subsequent research. Experimental facilities were designed to test thermal conductivity-based sensing, including both steady-state and gas-flow leakage scenarios, as well as a pipeline leakage test platform simulating realistic HVAC system conditions. Methods for calibrating flowmeters and estimating key parameters were developed to ensure measurement accuracy. The experiment on refrigerant leakage in gas flow and in a sealed chamber were conducted, and another experiment of refrigerant leakage from pipeline is underway. The experimental results demonstrate that modern thermal conductivity sensors provide more reliable responses to preset refrigerant concentrations, though actual readings tend to slightly underestimate the expected LFL percentages. In contrast, Pellistor-like sensors (e.g., VQ31MB) showed selective responsiveness, detecting R1234yf but failing to respond reliably to blended refrigerants, suggesting limited applicability in complex leak scenarios. Additionally, by analyzing diffusion dynamics across refrigerants, the work highlights the influence of molecular weight, structure, and density on dispersion rates, offering critical insights for sensor placement and calibration strategies. Leakage modeling and preliminary simulation efforts complement the experimental work, paving the way for future studies to optimize system-level detection strategies. Looking ahead, the research identifies key areas for further exploration, including real-world leakage validation, localization of leak sources, system failure time assessments, and multi-fault scenario analysis. Collectively, this thesis advances the understanding of refrigerant leakage detection, providing both practical insights and a methodological foundation for improving the safety and sustainability of next-generation refrigeration systems....

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Xu, Yile

Contributors dc:contributor

• Wang, Sophie

• Zeotropic Refrigerants
• Leakage Detection
• Thermal Conductivity Sensor
• Hvac System Safety

Statement dc:rights

• Copyright 2025 Yile Xu.

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129952

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129952