motor_cooling.py

class openconcept.thermal.motor_cooling.LiquidCooledMotor(**kwargs)

Bases: Group

A component (heat producing) with thermal mass cooled by a cold plate.

Inputs:

  • q_in (float) – Heat produced by the operating component (vector, W)

  • mdot_coolant (float) – Coolant mass flow rate (vector, kg/s)

  • T_in (float) – Instantaneous coolant inflow temperature (vector, K)

  • motor_weight (float) – Object mass (only required in thermal mass mode) (scalar, kg)

  • T_initial (float) – Initial temperature of the cold plate (only required in thermal mass mode) / object (scalar, K)

  • duration (float) – Duration of mission segment, only required in unsteady mode

  • power_rating (float) – Rated power of the motor (scalar, kW)

Outputs:

  • T_out (float) – Instantaneous coolant outlet temperature (vector, K)

  • T (float) – Windings temperature (vector, K)

Options:

  • motor_specific_heat (float) – Specific heat capacity of the object in J / kg / K (default 921 = aluminum)

  • coolant_specific_heat (float) – Specific heat capacity of the coolant in J / kg / K (default 3801, glycol/water)

  • num_nodes (int) – Number of analysis points to run

  • quasi_steady (bool) – Whether or not to treat the component as having thermal mass

  • case_cooling_coefficient (float) – Watts of heat transfer per square meter of case surface area per K temperature differential (default 1100 W/m^2/K)

class openconcept.thermal.motor_cooling.MotorCoolingJacket(**kwargs)

Bases: ExplicitComponent

Computes motor winding temperature assuming well-designed, high-power-density aerospace motor. This component is based on the following assumptions: - 2020 technology level - 200kW-1MW class inrunner PM motor - Liquid cooling of the stators - “Reasonable” coolant flow rates (component will validate this) - Thermal performance similiar to the Siemens SP200D motor

The component assumes a constant heat transfer coefficient based on the surface area of the motor casing (not counting front and rear faces) The MagniX Magni 250/500 and Siemens SP200D motors were measured using rough photogrammetry.

Magni250: 280kW rated power, ~0.559m OD, 0.2m case “depth” (along thrust axis) Magni500: 560kW rated power, ~0.652m OD, 0.4m case “depth” Siemens SP200D: 200kW rated power, ~0.63m OD, ~0.16 case “depth”

Based on these dimensions I assume 650kW per square meter of casing surface area. This includes only the cylindrical portion, not the front and rear motor faces.

Using a thermal FEM image of the SP200D, I estimate a temperature rise of 23K from coolant inlet temperature (~85C) to winding max temp (~108C) at the steady state operating point. With 95% efficiency at 200kW, this is about 1373 W / m^2 casing area / K. We’ll reduce that somewhat since this is a direct oil cooling system, and assume 1100 W/m^2/K instead.

Dividing 1.1 kW/m^2/K by 650kWrated/m^2 gives: 1.69e-3 kW / kWrated / K At full rated power and 95% efficiency, this is 29.5C steady state temp rise which the right order of magnitude.

Note

See the LiquidCooledMotor for a group that already integrates this component with an electric motor.

Inputs:

  • q_in (float) – Heat production rate in the motor (vector, W)

  • T_in (float) – Coolant inlet temperature (vector, K)

  • T (float) – Temperature of the motor windings (vector, K)

  • mdot_coolant (float) – Mass flow rate of the coolant (vector, kg/s)

  • power_rating (float) – Rated steady state power of the motor (scalar, W)

  • motor_weight (float) – Weight of electric motor (scalar, kg)

Outputs:

  • dTdt (float) – Time derivative dT/dt (vector, K/s)

  • q (float) – Heat transfer rate from the motor to the fluid (vector, W)

  • T_out (float) – Outlet fluid temperature (vector, K)

Options:

  • num_nodes (float) – The number of analysis points to run

  • coolant_specific_heat (float) – Specific heat of the coolant (J/kg/K) (default 3801, glycol/water)

  • case_cooling_coefficient (float) – Watts of heat transfer per square meter of case surface area per K temperature differential (default 1100 W/m^2/K)

  • case_area_coefficient (float) – rated motor power per square meter of case surface area (default 650,000 W / m^2)

  • motor_specific_heat (float) – Specific heat of the motor casing (J/kg/K) (default 921, alu)