## 3 Results and Discussion
### Effect of Inlet Velocity  
The variation in outlet velocity generated in the cooling channel for both water and ferrofluid cooling under the influence of inlet velocity and voltage is depicted in Figure 6. The outlet velocity is the total velocity generated as a combination of constant velocity of the inlet coolant path and the MHD pump inlet coolant path. Water velocity is only dominated by the constant velocity inlet coolant path because water has no self-circulation characteristics in the presence of the MHD pump. Therefore, the outlet velocity remains constant with changes in voltage for each inlet velocity in the case of water cooling. However, with the increase in inlet velocity, the outlet velocity of water increases owing to the rise in driving force. For water cooling, the outlet velocities of 0.81 mm/s, 1.21 mm/s, 1.61 mm/s, 2.02 mm/s, and 4.03 mm/s are evaluated for inlet velocities of 2 mm/s, 3 mm/s, 4 mm/s, 5 mm/s, and 10 mm/s, respectively. The ferrofluid depicts self-circulation characteristics in the presence of the MHD pump under the influence of electromagnetic parameters, hence, the outlet velocity in the case of ferrofluid cooling is contributed to by both constant velocity coolant path as well as the MHD pump coolant path. In water cooling, the velocity is generated only by the constant velocity coolant path, whereas in ferrofluid cooling, the velocity is generated by the constant velocity coolant path as well as the MHD pump. Therefore, the outlet velocity in the case of ferrofluid cooling is superior compared to that of water cooling under the same conditions. Furthermore, the outlet velocity of ferrofluid increases linearly with increase in voltage for each inlet velocity because the Lorentz force  
Figure 5: Comparison of simulated data from the present study with reference studies [43; 44; 45] for (**a**) velocity and (**b**) temperature. in the MHD pump, which drives the ferrofluid, increases with an increase in voltage. The maximum outlet velocity is found at a higher voltage where the Lorentz force is at its maximum. In the case of ferrofluid cooling, the outlet velocity increases from 1.7 mm/s to 6.56 mm/s for inlet velocity of 2 mm/s, 1.78 mm/s to 6.62 mm/s for inlet velocity of 3 mm/s, 1.87 mm/s to 6.86 mm/s for inlet velocity of 4 mm/s, 1.97 mm/s to 6.63 mm/s for inlet velocity of 5 mm/s and 2.65 mm/s to 7.02 mm/s for inlet velocity of 10 mm/s with increase in voltage from 0.1 V to 0.5 V.  
The Lorentz force generated using the MHD pump is low at a lower voltage or lower value of magnetic field intensity. The Lorentz force with lower magnitude is not sufficient enough to drive the ferrofluid in a perpendicular flow direction, which results in ferrofluid flow in the reverse direction in terms of backflow. Therefore, the critical values of magnetic field intensity and voltage are needed to avoid the backflow of ferrofluid from one coolant path to another coolant path. To understand this phenomena, the flow streamlines of ferrofluid in cooling channel in the case of with backflow at 10 mm/s inlet velocity and 0.1 V and that of without backflow at 10 mm/s inlet velocity and 0.5 V are depicted in Figure 7. As shown in Figure 7, in the case of higher voltage of 0.5 V, the generated Lorentz force using the MHD pump is significant enough to drive the ferrofluid flow in a perpendicular direction without any backflow. The backflow reduces the amount of coolant that should be passed through the channel for inverter cooling, owing to the reversal of ferrofluid flow. Furthermore, the backflow disturbs the uniformity of ferrofluid flow in the cooling channel beneath the inverter. Therefore, the amount of heat that should be carried by ferrofluid from the inverter is affected by backflow. The temperature contours of the  
Figure 6: Outlet velocity comparison for water and ferrofluid cooling under the influence of inlet velocity and voltage.