Propane liquefaction with an active magnetic regenerative liquefier

Abstract

Magnetic refrigeration is a well-known cooling technique based on the magnetocaloric effect (MCE) of certain solids as they enter or leave a high magnetic field. An active magnetic regenerator (AMR) uses certain ferromagnetic materials simultaneously as MCE refrigerants and as a regenerator. An effective active magnetic regenerative refrigeration cycle consists of four steps: adiabatic magnetization with no heat transfer gas flow; heat transfer gas flow at constant high field; demagnetization with no heat transfer gas flow; and heat transfer gas flow at constant low field. The first heat transfer gas flow step from a cold-to-hot temperature in this cycle rejects heat from the magnetized regenerator to a hot sink and the second reverse heat transfer gas flow step from a hot-to-cold temperature absorbs heat from a cold source. Our primary objectives of the present work were to demonstrate an AMR-cycle liquefier, determine the cooling power of a magnetic refrigerant executing an AMR cycle, and understand the impact of intermittent cooling of the AMR cycle of a reciprocating, dual regenerator design with continuous liquefaction and parasitic heat leaks. This article describes how an AMR-cycle refrigerator using Gd regenerators moving through ∼2.7 T changes at 0.25 Hz was used to liquefy pure propane at two different supply pressures. The measured rates of liquefaction and elapsed times were measured and used to determine the volume collected and derive cooling power at liquefaction conditions for both runs. These results were compared to those obtained from cool-down temperature vs. time data during the same run. The agreement between the two, independent cooling-power results was excellent after the duty cycle of the AMR cycle cooling was properly treated. No direct measurements of the efficiency were made.