Parametric Study of Motor/Shroud Heat Transfer Performance in an Electrical Submersible Pump (ESP)

A shroud is commonly used around the motor of an electrical submersible pump (ESP) to accelerate reservoir fluids past the motor for cooling. Standard practice has been to design the shroud/motor configuration relative to the casing using a minimum fluid velocity of 0.3048 m/s (1 ft/s) rule of thumb as a production strategy. The increase in the use of ESPs to exploit heavy oil reservoirs has brought up the necessity of revising this rule in order to prevent motor burnouts. A parametric study has been conducted using the computational fluid dynamics software CFX4.2 to examine the heat transfer behavior of the shroud motor configuration as a function of motor/shroud standoff. The objective of this effort is to examine the validity of the historical rule of thumb for heavy oils. Results for a case study on an oil with a viscosity of 78 cp @ 320 K are presented. Further, to explore the possibility of enhancing the heat transfer characteristics, the flow configuration was modified by incorporating several openings on the shroud. Based on the obtained results, it can be concluded that fluid velocity should be kept around 0.85 m/s (2.8 ft/s) as opposed to 1 ft/s to assure proper cooling of the motor. Also, flow redistribution by proper placement of the slots on the shroud may produce better heat transfer between the oil and the motor wall. [S0195-0738(00)00703-2]