# Thermal-Hydraulic Modeling of Oil-Inmersed Motor Pump
## 4 Discussion
The small temperature difference between the connector and the pump chamber indicates that the effect of connector throttling loss is negligible. The observed elevation in oil temperature can be predominantly ascribed to churning losses resulting from high-velocity lubricating oil at the leakage end, accompanied by a subsequent escalation in motor power losses. This underscores the notable significance of temperature increment induced by the electric motor, warranting careful consideration. Figure 15: The temperature curve of each node varies with the outlet pressure at 1450 rpm. As shown in Figure 17, the leakage port oil temperature across different operational scenarios is calculated. At low pressure conditions, the oil temperature remains within an acceptable range. However, as the pressure and rotational speeds increase, limitations become evident. This is primarily due to the fact that under high-pressure and high-speed conditions, the oil fluid temperature is more prone to reaching elevated levels. Consequently, this leads to a deterioration in the overall performance of the motor pump system. At a pressure of 9 MPa, the temperature is relatively elevated. However, it is important to highlight that a critical threshold is observed at a pressure of 15 MPa. At this critical point, a transition occurs in the oil temperature regime, shifting from higher temperatures to lower temperatures. As shown in Figure 17, the calculated values of oil temperature at the leakage point under various operating conditions are shown in the diagram. At low pressure, the oil temperature remains within a reasonable range, with a maximum temperature of 57.5 \({}^{\circ}\)C. However, at 8-12 MPa, the temperature shows an increasing trend with higher rotational speeds, while at other pressures, it exhibits a decreasing trend followed by an increase. This is mainly because the leakage of oil at 3-8 MPa gradually increases, leading to an increase in the temperature. This is because the leakage of oil at 3-8 MPa gradually increases, leading to an increase in the temperature. increase in heat exchange efficiency between the oil, resulting in temperature reduction. However, as the rotational speed increases, motor losses such as churning losses also increase, causing the temperature to rise. At 12-18 MPa, the continuous temperature increase causes a decrease in oil viscosity, which in turn leads to temperature reduction. However, with the continuous increase in motor losses, the temperature variation caused by viscosity no longer suppresses the temperature rise caused by the motor. At a constant rotational speed, the temperature exhibits a trend of initially increasing and then decreasing. At a pressure of 9 MPa, the temperature is relatively high. However, it is worth noting that at a pressure of 15 MPa, it is the critical value where the oil temperature begins to transition from high to low. In conclusion, the variation in oil temperature is influenced by the leakage amount of oil flowing inward, oil viscosity, and motor losses, which all contribute to these changes. As shown in Figure 18a, when the outlet pressure condition is changed, it is observed that the temperature change with motor power loss is more than 2.8 \({}^{\circ}\)C than that without motor power loss. This observation highlights the significant impact of motor power loss on the resultant changes in oil viscosity. In low-pressure conditions, a distinct temperature disparity is observed between scenarios with motor power loss and without motor power loss. However, as the pressure rises, the temperature gap between the two scenarios diminishes, and the temperature response tends towards linearity. This phenomenon can be ascribed to the similarity in oil viscosity corresponding to these temperature levels. Additionally, under higher pressures, the oil leakage rate experiences a substantial increase, leading to accelerated heat exchange at the leakage port. Consequently, the temperature tends to converge towards a state resembling that of no motor power loss.