Design and thermodynamic analysis of a magnetic refrigeration system onboard ship for near-room temperature applications

This thesis investigates the design and thermodynamic performance of a magnetic refrigeration system intended for near-room temperature applications on board ships. Unlike conventional vapor compression systems, magnetic refrigeration employs the magnetocaloric effect (MCE) and environmentally benign solid refrigerants, such as gadolinium, which exhibit temperature changes when subjected to changing magnetic fields. The study begins with a detailed literature review covering the fundamental principles of magnetic refrigeration, magnetocaloric materials, and the working cycle known as the Active Magnetic Regenerator (AMR). A bench-scale experimental system using gadolinium as the magnetocaloric material was designed and developed in the laboratory. The system includes a mechanically controlled magnetic field source, a heat transfer loop, and instrumentation to monitor temperature variation under different field strengths. Thermodynamic performance indicators such as the coefficient of performance (COP), cooling capacity, and entropy variation were calculated under varying cycle conditions. The results demonstrate that magnetic refrigeration has significant potential in marine environments, particularly in terms of compactness, energy efficiency, and ecological impact, provided that system optimization and integration challenges are addressed. Under experimental conditions with magnetic field strengths varying from 50 to 80 mG, the system achieved a maximum temperature span (ΔT) of 2.20°C. The coefficient of performance (COP) ranged between 0.28 and 2.16, and the peak cooling capacity reached approximately 1338 W during optimal operation. Entropy change across the regenerator cycle was measured at 90.35 J/kg·K. The working fluid maintained a flow rate of 5 to 20 L/min under stable operation, and the system responded to field switching in less than 300 seconds. The results of this research contribute to the growing body of research on sustainable onboard refrigeration technologies and offer insights into the practical viability of implementing magnetic cooling systems in maritime applications. Keywords: Magnetic refrigeration, Gadolinium, Active Magnetic Regenerator (AMR), Thermodynamic analysis