Design and development of rotary magnetic refrigeration prototype with active magnetic regeneration system

Abstract

In the field of cooling system, a traditional vapor compression (VC) technology has been used over long time. The VC cooling is simple and cost effective, however, it raises global warming concern due to its relatively low energy efficiency and usage of ozone depletion substances. Magnetic refrigeration (MR) has been proposed as a potential cooling technology that can replace the VC cooling. MR can potentially be operated with efficiency closer to the theoretical efficiency, without using environmentally-harmful refrigerants. In the MR system, a magnetocaloric material (MCM) with magnetocaloric effect (MCE) is used as a refrigerant. The temperature of MCM can be increased and decreased under adiabatic magnetization and demagnetization, respectively. Water/ethylene glycol can be used as heat-exchanging fluid. In this work, a rotary MR prototype was designed and built. The prototype consists of the following main systems: 1. Flow distribution system, 2. Rotary magnetic field generator 3. Mechanic system, and 4. Temperature and pressure sensor system. Four beds of magnetocaloric gadolinium (Gd) particulates were used as an active magnetic regenerative cooling media. Fluid flow was controlled by pneumatic pump and solenoid valves. Rotary magnetic field generator was designed and built with maximum and minimum fields of 0.65 and 0 T, respectively. The overall setup and preliminary study showed that the pressure drop across the system was 2 bar when the flow rate was only 0.5 L/min. Increasing flow rate further resulted in too high pressure drop causing the MCM bed to swell. Therefore, the flow rate was limited to 0.5 L/min resulting in insufficient heat transfer rate by the slow heat exchange fluid flow. Consequently, the maximum temperature span was measured to be 0.5 K. The prototype must be improved to drive flow rate higher and to reduce the pressure drop of the system.