Investigation of bypass fluid flow in an active magnetic regenerative liquefier

Abstract

Active magnetic regenerators (AMR) with second order magnetocaloric materials operating below the Curie temperature have a unique property where the magnetized specific heat is lower than the demagnetized specific heat. The associated thermal mass imbalance allows a fraction of heat transfer fluid in the cold heat exchanger to bypass the magnetized regenerator. This cold bypassed fluid can precool a process stream as it returns to the hot side, thereby increasing the efficiency of liquefaction and reducing the cost of liquid cryogens. In the present work, the net cooling power of an active magnetic regenerative liquefier is investigated as a function of the bypass flow fraction. Experiments are performed at a fixed temperature span yielding a 30% improvement in net cooling power, affirming the potential of bypass flow in active magnetic regenerative liquefiers.