Physics

Title of thesis: Modeling and Control System Design of a Cascade Vapor Compression System
Abstract: This thesis investigates the modeling, simulation, and analysis of a cascade vapor compression system designed for aerospace thermal management, delivering a 25 kW cooling capacity. Control design focuses on maintaining a liquid coolant at 20 °C, ensuring 5 °C superheat at the evaporator outlets, and an intermediate temperature optimized at the geometric mean of the low-stage evaporator and high-stage condenser to enhance system efficiency. PI controllers are incorporated to regulate performance under varying operating conditions. A MATLAB Simscape model was developed using R134a for the low stage and R1233zd(E) for the high stage, enabling performance evaluation across a range of ambient temperatures and heat loads. Simulations demonstrate robust operation at high ambient conditions, maintaining stable superheat and coolant temperatures. However, at lower temperatures, the system exhibits oscillations and two-phase region entry, indicating limitations in colder regimes. The high-stage compressor’s control of the intermediate temperature contributes to improved efficiency, although slower dynamics suggest further tuning is needed. These findings confirm the system’s suitability for aerospace applications, particularly under high-temperature conditions, while highlighting the need for advanced control strategies and further investigation of low-temperature performance to enhance overall reliability and efficiency. 
Examiner: Magnus Karlsteen Supervisor: Magnus Karlsteen Industrial Supervisor: Olof Hannius Opponent: Quentin Tristan Moulet
Location of presentation:&nbsp;<a rel="noopener" href="https://maps.chalmers.se/#24d8b7be-1f59-4388-be28-a07861b429b2" target="_blank" title="Chalmers maps" data-anchor="#24d8b7be-1f59-4388-be28-a07861b429b2">PJ-salen</a>

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Presentation of master thesis

Master thesis presentations at Physics

September 15, 2025

11:00- 12:00 Casper Jarhult, MPCAS