# Thermal-Hydraulic Modeling of Oil-Inmersed Motor Pump
## 4 Discussion  
Considering the negligible discrepancy observed between the calculated leakage temperature and the corresponding actual temperature, the thermodynamic model utilized in this study is demonstrated to possess high accuracy. Therefore, the investigation is further expanded to incorporate a more comprehensive range of operating conditions. Figure 14 depicts the temporal evolution of individual nodes in the context of a motor pump operating at a speed of 1450 rpm and an outlet pressure of 6 MPa. To be specific, the temperature of the inlet, outlet, leakage port, and connector node all exhibit an upward trajectory, beginning simultaneously from their respective initial values. After approximately 20,000 s of operation, the temperature of each node ultimately attains a steady-state condition. The temperature attained at the leakage port, connector, pump chamber, and shell were recorded as 26.5, 27.1, 32.9, and 27.6 \({}^{\circ}\)C, respectively. It is noteworthy that the temperature of the inlet and outlet nodes is observed to be nearly identical, with the outlet temperature being only 0.05 \({}^{\circ}\)C higher than that of the inlet. Furthermore, owing to the distinctive radiative heat transfer process that occurs through the surrounding air, the temperature of the shell undergoes a relatively slow and gradual stabilization process. Figure 14: Temperature change curves of each node at 1450 rpm and 6 MPa. Figure 13: Calculated loss under 6 MPa outlet pressure. The temperature readings in Figure 15 reveal that the inlet, outlet, leakage outlet, shell, pump chamber and connector experienced, respectively, temperature increments of 0.04, 0.2, 0.4, 2.2, 5.1 and 3.7 \({}^{\circ}\)C. The rise in outlet temperature corresponds to an increase in outlet pressure, which induces a higher input torque, thus augmenting the external input power to the pump and elevating the outlet temperature. Meanwhile, the inlet temperature elevation arises from heightened heat leakage from the outlet into the inlet, raising the temperature of the inlet oil. Furthermore, the increase in motor power and the change in oil viscosity cause the temperature of the leakage port to change. Lastly, as the oil temperature within the motor pump escalates, the temperature of the shell increases, given that the contact area and heat transfer coefficient between the shell and the oil remain constant. As the outlet pressure is increased, there is a trend towards temperature equalization observed between the pump chamber, connector, and leakage port. The rise in outlet pressure results in an elevation of the pump oil leakage rate, which in turn increases the influx of oil into the pump chamber, connector, and leakage port, ultimately leading to an accelerated rate of heat exchange between the motor pump and its internal components. Consequently, this dynamic process causes the temperature distribution within the motor pump to become more uniform. As the outlet pressure is raised, there is a more linear and progressive increase observed in the temperature of each connector. Figure 16 illustrates that the temperatures of the inlet and outlet nodes remain stable, exhibiting minimal fluctuations over time. The temperature change follows a specific order, with the highest temperature change occurring at the leakage port, followed by the connector, pump chamber, shell, oil outlet, and oil inlet nodes. The temperature change values of each node are 9.7, 2.7, 2.3 and 1.6 \({}^{\circ}\)C, respectively. As the rotational speed increases, the temperature demonstrates a non-linear variation characterized by an initial rise, followed by a decline, and then a subsequent rise. This behavior primarily arises from the consequential impact of temperature fluctuations on the viscosity of the oil fluid. The similarity observed in temperature changes between the pump chamber and the connector can be attributed to the influence of throttling losses on the pump chamber and the heat generated through viscous friction between the oil fluids.