## 2 Experimental Setup
### Metal Hydride Hydrogen Storage System Setup  
The experimental device and its schematic is shown in Figure 4. The experimental setup consists of an argon cylinder and a hydrogen cylinder with a vacuum pump and hydrogen storing section. Argon is implemented to provide the required inert atmosphere for LaNi\({}_{5}\) when there are no experiments running. Hydrogen cylinder provides Ultra High Purity (UHP hydrogen of 99.999% purity) level for experiments. Both argon and hydrogen cylinders are connected to the rest of setup through a single pipe. Also, a vacuum pump provides a vacuum in connecting lines and a hydrogen storage section. The reactor is made of Stainless Steel containing 171 g of a LaNi\({}_{5}\) powder activated by successive absorption/desorption cycles. The particle size is about 60 \(\upmu\)m and the porosity is about 0.5.  
The whole hydrogen storage unit is submerged in water in a thermostatic bath. The bath heats and cools the hydrogen reservoir and Metal Hydride (MH) reactor during hydrogen desorption and absorption, respectively. During experiments, two different magnets (as shown in Table 1) are used to analyze the effect of change in magnetic field intensity on the heat transfer in the MH bed. In experiments with magnets, the magnet was placed at the bottom of the reactor and the temperature at the center of the reactor and on its wall, respectively, is measured. The reactor is connected to the reservoir using connecting tubes. The thermostatic bath is heated by a 1000 W heater with a build-in circulation pump. Deploying a thermostatic bath ensures consistency of boundary conditions throughout the experiments. It also ensures that adding the thermal mass of a magnet when the magnetic field is required does not impact the consistency of boundary conditions in the setup.  
The pressure within the hydride bed is measured by installing a sensor between the hydrogen tank and the hydride bed. To measure the temperature at different locations, five thermocouples and thermal probes are utilized. Two thermal probes are inserted into the reservoir and reactor. Three thermocouples are measuring the temperature at the reactor wall, inside the thermostatic bath, and the room (ambient) temperature. Measured data from transducers and thermocouples is transferred to a computer by LabView through a data acquisition unit (DAQ). Thermocouple positions are presented in Table 2.  
For the absorption test, initially, the hydrogen tank is charged at the desired pressure and was kept in contact with the metal hydride reactor. The hydrogen pressure inside the tank decreases until it reaches a stable value. Because the absorption reaction is exothermic, the hydride bed is cooled by using water coming from a thermostatic bath.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Magnet Number** & **Thickness (cm)** & **Nominal Intensity (Gauss)** \\ \hline
1 & 1.27 & 2952 \\
2 & 2.54 & 4667 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Magnetic intensities of selected magnets.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Thermocouple** & **Position** \\ \hline T1 & Metal hydride reactor \\ T2 & Hydrogen reservoir \\ T3 & Thermostatic bath \\ T4 & Room temperature \\ T5 & Reactor wall \\ \hline \hline \end{tabular}
\end{table}
Table 2: Thermocouple positions in hydrogen storage setup.