System for rotor cooling
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Solution Overview
Problem
Hermetic motors in vapor compression systems face significant windage losses due to friction, which are not adequately addressed by existing methods, especially at high speeds, and these methods often compromise motor efficiency and seal leakage.
Innovation Solution
A vapor compression system with a motor coolant system that maintains refrigerant at an intermediate pressure within the motor cavity, greater than evaporator pressure and less than condenser pressure, using connections from the condenser and evaporator to manage refrigerant flow and minimize gas density and pressure differentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If refrigerant is suctioned across motor windings to cool the motor, then motor temperature is reduced and motor efficiency increases, but windage losses due to friction are not adequately addressed
Solution Approach 1:
The patent changes the pressure parameter of the refrigerant in the motor cavity from suction pressure to intermediate pressure (between suction and discharge pressure). This parameter change reduces the density differential between motor cavity gas and suction gas, thereby reducing windage losses while still providing adequate cooling through the refrigerant circulation system
Solution Approach 2:
The patent converts the previously harmful high-density suction gas (which caused high windage losses) into a beneficial intermediate-pressure gas that provides both adequate cooling and reduced windage losses. The refrigerant circulation system transforms the cooling function into a dual-purpose system that also manages pressure and density
2Loss of energy
If pressure valve is placed in motor cavity to maintain constant pressure, then motor efficiency increases, but seal leakage is not adequately addressed and mechanical equipment complexity increases
Solution Approach 1:
The patent extracts the mechanical pressure valve from the motor cavity and replaces it with a refrigerant circulation system that maintains intermediate pressure through fluid dynamics. This removes the mechanical moving part while achieving the same pressure control function through the refrigerant flow management system
Solution Approach 2:
The patent replaces the mechanical pressure valve system with a refrigerant circulation system that uses fluid flow and pressure differential to maintain intermediate pressure in the motor cavity. This substitution eliminates mechanical wear and seal leakage issues associated with moving parts
3Temperature
If refrigerant at suction pressure is used for motor cooling, then motor cooling is achieved, but windage losses are substantial due to high gas density in motor cavity
Solution Approach 1:
The patent changes the pressure parameter of the motor cavity refrigerant from suction pressure to intermediate pressure (between suction and discharge pressure). This parameter change reduces gas density in the motor cavity, thereby reducing windage losses while maintaining adequate cooling through the refrigerant circulation system
Solution Approach 2:
The patent applies different pressure conditions to different parts of the refrigeration system: suction pressure in the evaporator, intermediate pressure in the motor cavity, and discharge pressure in the condenser. This local differentiation of pressure quality optimizes both cooling performance and windage loss reduction
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, optimizing motor efficiency and minimizing combined power losses by balancing refrigerant pressure and flow within the motor cavity.
Implementation Method 1
A motor coolant system is configured to cool the compressor motor
Implementation Method 2
maintains refrigerant at an intermediate pressure within the motor cavity, greater than evaporator pressure and less than condenser pressure
Implementation Method 3
minimize gas density and pressure differentials
Data Source
Figure 1
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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.