Motor Cooling System Using Two-Phase Refrigerant Segmentation
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Solution Overview
Problem
Current cooling arrangements for semi-hermetic motors in vapor compression systems face inefficiencies due to incomplete evaporation of refrigerant in the cooling coil, leading to reduced heat transfer and increased friction, and the risk of liquid refrigerant damaging motor components, especially at higher rotational speeds.
Innovation Solution
A cooling system that integrates a two-phase refrigerant flow directly into the motor housing, with a compartment to separate vapor and liquid phases within the housing, ensuring vapor phase cooling without liquid contact with moving components, and utilizing a throttling device to manage pressure and prevent liquid circulation into the motor cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid refrigerant is supplied to the cooling coil to cool the stator, then heat transfer efficiency is improved, but liquid refrigerant may damage motor components
Solution Approach 1:
The motor housing is divided into multiple compartments: a first compartment for the cooling coil, a second compartment for the stator, and a third compartment for the rotor. This segmentation allows liquid refrigerant to be confined to the first compartment where it evaporates, preventing it from reaching the rotor and bearings in the third compartment, thus resolving the contradiction between cooling efficiency and component safety
Solution Approach 2:
A partition wall with a refrigerant passage acts as an intermediary between the first compartment (cooling coil) and the second compartment (stator). The passage allows controlled refrigerant flow for cooling purposes while the partition structure prevents uncontrolled liquid refrigerant from reaching motor components, enabling effective cooling while protecting components
2Productivity
If motor operates at higher rotational speeds to reduce system size, then productivity is improved, but windage losses and friction increase
Solution Approach 1:
The invention changes the physical state parameter of the refrigerant from liquid to vapor phase before it enters the motor cavity. By evaporating the refrigerant in the cooling coil and allowing only vapor to enter the motor cavity, the density of the surrounding medium is reduced, which decreases windage losses and friction at high rotational speeds while maintaining system compactness
3Reliability
If expansion valve is used to ensure complete evaporation at coil outlet, then component safety is improved, but heat transfer efficiency decreases
Solution Approach 1:
The cooling system is segmented into a cooling coil compartment and a motor cavity compartment separated by a partition wall. This allows the cooling coil to receive liquid refrigerant for efficient heat transfer and evaporation, while the motor cavity receives only vapor, achieving both efficient heat transfer and component protection without requiring an expansion valve at the coil outlet
Solution Approach 2:
The harmful liquid phase of the refrigerant is extracted from the system by confining it to the cooling coil compartment where it evaporates. The partition wall with controlled passages removes the liquid refrigerant from the path to the motor components, allowing complete evaporation to occur safely while maintaining high heat transfer efficiency in the cooling coil
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 approach enhances heat transfer efficiency while preventing component damage from liquid refrigerant, reducing friction and improving cooling effectiveness by maintaining reduced vapor or gas friction losses and ensuring efficient vapor circulation within the motor cavity.
Implementation Method 1
the refrigerant evaporates in this coil and cools the stator
Implementation Method 2
The pressure difference required to move the gas through the motor cavity is provided by the venturi effect that is produced at the inlet of the impeller of a centrifugal compressor
Implementation Method 3
A cooling system that integrates a two-phase refrigerant flow directly into the motor housing, with a compartment to separate vapor and liquid phases within the housing
Data Source
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AI summary
A cooling system provided for a motor powering a compressor in a vapor compression system. The cooling system includes a housing enclosing the motor and a cavity located within the housing. A fluid circuit has a first connection with the housing configured to provide a liquid or two phase cooling fluid to the motor. The two phase cooling fluid is separable into a vapor phase portion and a liquid phase portion. The fluid circuit further has a second connection with the housing to remove cooling fluid in fluid communication with the fluid circuit. The cooling fluid conveyed through the second connection is two phase cooling fluid. The fluid circuit further has a third connection with the housing for receiving and circulating in the cavity the vapor phase portion conveyed through the second connection.