Local Entropy Generation Analysis of a Rotary Magnetic Heat Pump Regenerator

The rotary magnetic heat pump has attractive thermodynamic performance, but it is strongly influenced by the effectiveness of the regenerator. This study uses local entropy generation analysis to evaluate the regenerator design and to suggest design improvements. The results show that performance of the proposed design is dominated by heat-transfer-related entropy generation. This suggests that enhancement concepts that improve heat transfer should be considered, even if the enhancement causes a significant increase in viscous losses (pressure drop). One enhancement technique, the use of flow disruptors, was evaluated and the results showed that flow disruptors can significantly reduce thermodynamic losses. The results of this study also suggest that, in this case, the widely used efficiency index is an inappropriate thermodynamic measure of the performance of a heat transfer enhancement technique and that a figure-of-merit based on second law considerations should be used.