Compressor Motor Cavity Cooling With Intermediate Pressure Refrigerant
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Solution Overview
Problem
High-speed hermetic motors experience substantial windage losses due to gas density in the motor cavity, which conventional cooling methods fail to adequately address while maintaining efficient motor operation and minimizing seal leakage.
Innovation Solution
A vapor compression system with a motor coolant system that maintains refrigerant at an intermediate pressure between evaporator and condenser operating pressures within the motor cavity, using connections to the condenser and evaporator to manage refrigerant flow and pressure, thereby reducing gas density and optimizing motor efficiency while minimizing seal leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If evaporator gas is directed through the rotor to minimize windage losses, then motor efficiency is improved, but seal leakage is maximized due to large differential pressure across seals
Solution Approach 1:
The patent introduces an intermediary pressure chamber between the evaporator and motor cavity, using intermediate pressure refrigerant as a mediator to cool the motor while reducing the pressure differential across seals, thereby minimizing both windage losses and seal leakage simultaneously
Solution Approach 2:
The patent changes the pressure parameter of the refrigerant used for motor cooling from evaporator pressure to intermediate pressure, which reduces the density differential and pressure gradient across seals while still providing adequate cooling to minimize windage losses
2Loss of energy
If vacuum pumps are used to lower gas density in motor cavity, then windage losses are reduced, but motor cooling capability is compromised
Solution Approach 1:
The patent changes the pressure parameter of the refrigerant from evaporator pressure to intermediate pressure, optimizing the balance between windage loss reduction and motor cooling effectiveness
Solution Approach 2:
The patent applies different refrigerant conditions to different locations: intermediate pressure refrigerant for motor cooling and evaporator pressure refrigerant for system operation, optimizing local conditions for each function
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 reduces windage losses and seal leakage, achieving better motor efficiency and minimizing combined power losses by maintaining optimal refrigerant pressure and flow within the motor cavity.
Implementation Method 1
A vapor compression system with a motor coolant system that maintains refrigerant at an intermediate pressure between evaporator and condenser operating pressures within the motor cavity
Implementation Method 2
Windage losses decrease as the density of the gas in the motor cavity decreases resulting in better motor efficiency
Data Source
AI summary
A motor coolant method and system is used to cool a compressor motor (36) in a refrigeration system having a multi-stage compressor (38). The compressor includes a first compressor stage (42) and a second compressor stage (44), the first compressor stage providing compressed refrigerant to an input of the second compressor stage. The motor coolant system has a first connection with the refrigerant loop to receive refrigerant into the motor cavity for cooling, the received refrigerant provided from a system component having a high pressure, and a second connection with the refrigerant loop to return refrigerant to an intermediate pressure greater than an evaporator operating pressure. The pressure inside the motor cavity may be approximately the pressure within the first stage discharge and second stage suction to minimized seal leakage between the motor cavity and the internal pressures of the first and second stage compressors.