Exergy Analysis of a Parallel-Plate Active Magnetic Regenerator with Nanofluids

Ibai Mugica,Steven Roy,Jonathan Bouchard,Hakim Nesreddine,Sébastien Poncet

doi:10.3390/e19090464

Abstract

This paper analyzes the energetic and exergy performance of an active magnetic regenerative refrigerator using water-based Al2O3 nanofluids as heat transfer fluids. A 1D numerical model has been extensively used to quantify the exergy performance of a system composed of a parallel-plate regenerator, magnetic source, pump, heat exchangers and control valves. Al2O3-water based nanofluids are tested thanks to CoolProp library, accounting for temperature-dependent properties, and appropriate correlations. The results are discussed in terms of the coefficient of performance, the exergy efficiency, and the cooling power as a function of the nanoparticle volume fraction and blowing time for a given geometrical configuration. It is shown that while the heat transfer between the fluid and solid is enhanced, it is accompanied by smaller temperature gradients within the fluid and larger pressure drops when increasing the nanoparticle concentration. It leads in all configurations to lower performance compared to the base case with pure liquid water.

Highlights

Refrigeration and air conditioning demand has continuously grown during the last decades.Environmental requirements and current ecological standards limit conventional technologies, such as vapor compression cycles
The operating principle is based on the magnetocaloric effect (MCE), which is related to a change of entropy in the magnetocaloric material (MCM) due to a variation of the applied magnetic field
To better understand how the nanofluids affect the efficiency of the system, one needs to look at the heat transfer mechanisms responsible for the entropy generation within the regenerator

Summary

Introduction

Refrigeration and air conditioning demand has continuously grown during the last decades.Environmental requirements and current ecological standards limit conventional technologies, such as vapor compression cycles. Magnetic refrigeration suggests many industrial applications: domestic or industrial cold production for food storage or air conditioning of buildings as few examples. It offers economic, ecological and environmental benefits and a high potential to develop higher efficiencies and lower noise production than current refrigeration systems. The operating principle is based on the magnetocaloric effect (MCE), which is related to a change of entropy in the magnetocaloric material (MCM) due to a variation of the applied magnetic field This generates a quasi-instantaneous temperature change, typically about 2 K·T−1 for gadolinium at room temperature [1]. This process (Brayton cycle) produces cold and reaches steady-state conditions after a number of repeated cycles

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Conclusion