University of Twente Student Theses


Modeling of magnetocaloric refrigeration with packed bed regenerator

Budiman, A.H.S. (2016) Modeling of magnetocaloric refrigeration with packed bed regenerator.

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Abstract:Cooling by vapor compression is currently the most widely used technology for refrigeration or heat pump systems. Vapor compression itself is a 100-year-old technology that uses refrigerants which potentially cause problems to the environment especially related to ozone depletion and global warming. The system also requires a compressor that is a weakness as it dissipates noise and vibrations. One of the alternative technologies to vapor compression cooling is magnetic refrigeration that works based on the magnetocaloric effect (MCE) which no longer utilizes the refrigerants. Currently, the magnetocaloric refrigeration system with an active magnetic regenerator (AMR) is considered as the best one to create sufficient temperature span between the cold and hot region for a practical cooling device. However, the active magnetic regenerative refrigerator (AMRR) cannot break the vapor compression cooling dominance yet since it has an inferior overall performance. The performance can be upgraded with a better heat transfer between the MCM and the working fluid. Compared to a straight channel configuration, a spherical packed-bed regenerator has better heat transfer characteristics since it has a larger heat transfer area over the same volume. At room temperature, the system should utilize a suitable MCM. Gadolinium (Gd) is one of the MCMs with the Curie point near room temperature (around 293 K). Since Gd is a rare-earth material, it is necessary to search for a replacement for the material. The cheap and non-toxic MnFe(P,Si) compound is a promising candidate for Gd alternative. This study investigates and compares the performance of an AMRR with spherical packed- bed regenerator made from Gd and four layers of MnFe(P,Si) compound with different (P,Si) compositions, by numerical simulations using commercial software COMSOL Multiphysics. The compound itself is developed by the Fundamental Aspects of Materials and Energy group of the TU Delft, as reported by their publications. Some interpolations and assumptions of the required magnetocaloric properties are taken to complete the input data. The model geometry is based on a Gd AMRR experimental device of the University of Ljubljana, Slovenia. The experimental result used to verify the simulation outcome. The study predicts that the AMRR with layered compound has a nearly equal performance to the one with Gd in temperature span wise. On the other hand, the predicted maximum cooling capacity of the system with layered AMR is higher than the system with Gd AMR.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Sustainable Energy Technology MSc (60443)
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