Directly Cooled Windings Using Turbulent Coolant Gaps
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Solution Overview
Problem
Existing electric machines face limitations in heat dissipation due to laminar coolant flow and limited material thickness of wires, leading to increased electric losses and low Nusselt numbers, which restricts current density and power density.
Innovation Solution
The electric machine design features fluid-tight internal housings with coolant inlets and outlets, allowing continuous coolant flow that absorbs heat from windings, and incorporates gaps between windings to promote turbulent flow, enhancing convective heat transfer and independent design of wire and coolant flow for improved cooling capacity and current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hollow windings with small diameter flow channels are used for direct cooling, then the coolant is in direct contact with windings improving cooling capacity, but the laminar flow results in low Nusselt number and reduced heat transfer efficiency
Solution Approach 1:
The patent changes the flow regime parameter from laminar to turbulent flow by increasing mass flow rate and designing appropriate flow channel geometries. This transitions the Nusselt number from low (laminar) to high (turbulent) values, dramatically improving convective heat transfer while maintaining direct contact cooling benefits
Solution Approach 2:
The patent introduces dynamic flow characteristics by creating turbulent flow conditions rather than steady laminar flow. The turbulent flow regime with its chaotic eddies and mixing enhances heat transfer coefficients, making the cooling system adaptive and highly efficient at removing heat from windings
2Loss of energy
If high mass flow rate is used to achieve turbulent flow for improved heat transfer, then heat transfer coefficient increases, but the required pump power and system complexity increase significantly
Solution Approach 1:
The patent optimizes the balance between mass flow rate and flow channel geometry to achieve turbulent flow at moderate pump powers. By adjusting parameters such as channel diameter, length, and roughness, the system achieves high Nusselt numbers without requiring excessively high mass flow rates that would demand oversized pumps
Solution Approach 2:
The patent employs flow channel designs that utilize porous structures or surface roughness features to promote turbulence and enhance heat transfer. These porous or textured surfaces create flow disturbances that increase the Nusselt number while requiring minimal additional pump power to maintain the enhanced flow regime
3Reliability
If limited material thickness of wires is used, then electrical insulation is maintained, but electric losses increase due to increased current density
Solution Approach 1:
The patent changes the thermal management parameters to enable higher current densities in thin-wire windings. By implementing effective direct cooling with turbulent flow, the system can sustain higher current loads without thermal degradation, allowing thin wires to carry higher currents with acceptable loss levels while maintaining insulation integrity
4Device complexity
If conventional cooling systems with cooling jackets and fins are used, then structural simplicity is maintained, but heat dissipation capacity is insufficient for high current density applications
Solution Approach 1:
The patent extracts the cooling function from the structural components (separating cooling channels from housing fins and jackets) and integrates it directly into the winding structure itself. This allows the windings to be self-cooled through internal turbulent flow, achieving high heat dissipation capacity without adding external cooling complexity
Solution Approach 2:
The patent merges the electrical conductor function with the heat transfer medium function by using the same winding structure for both current conduction and coolant flow. This integration enables direct thermal coupling between heat generation and heat removal, achieving superior heat dissipation while maintaining structural simplicity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly increases the convective heat transfer coefficient, reduces power losses, and allows for higher current and power densities without increasing wire diameter, enabling more efficient heat dissipation and compact, lightweight electric machines.
Implementation Method 1
the windings of the electric machine are hollow, and are cooled by an internal flow of a dielectric fluid
Implementation Method 2
bypassing the thermal resistances of a cooling jacket, a stator, or other components
Implementation Method 3
In order to reach a turbulent flow for improved heat transfer, the mass flow rate needs to be extremely high when maintaining the small diameters of the wires
Implementation Method 4
the at least one internal housing comprises at least one internal wall that creates at least one flow channel inside the respective internal housing
Data Source
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AI summary
An electric machine is proposed, comprising a plurality of windings for creating electromagnetic fields, and at least one fluid-tight internal housing, wherein at least one group of the windings is arranged in an interior space of one of the at least one internal housing, wherein each of the at least one group of the windings comprises at least two electric connecting sections for connecting the respective group of the windings to an external electrical circuit, and wherein the at least two electric connecting sections reach from the interior space through a wall of the respective internal housing to outside the respective internal housing, wherein the at least one internal housing comprises a coolant inlet and a coolant outlet, and wherein neighboring windings of the at least one group of the windings enclose gaps between each other, wherein the gaps are in fluid communication with the respective coolant inlet and the coolant outlet to be flown through by a coolant.