Heat Pump Compressor Oil Sump Depressurization for Viscosity Retention
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Solution Overview
Problem
In refrigeration systems, particularly in heat pumps and organic Rankine cycle systems, the absorption of refrigerant by lubricating oil leads to reduced oil viscosity and lubricity, causing mechanical issues such as oil foaming and potential compressor failures, especially at elevated temperatures.
Innovation Solution
A pressure reducing device is introduced between the oil sump and the low-pressure side of the refrigerant system to lower the refrigerant pressure in the oil sump, reducing refrigerant dilution in the oil and maintaining higher oil viscosity and lubricity, while also applying a similar pressure reduction in the motor housing to enhance cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refrigerant pressure in the oil sump is reduced, then the refrigerant dilution in the oil is reduced and oil viscosity is maintained, but the cooling efficiency of the motor may be compromised
Solution Approach 1:
The system divides the refrigerant pressure control into two separate zones: the oil sump is maintained at a lower pressure to reduce refrigerant dilution and maintain oil viscosity, while the motor housing is maintained at a higher pressure to ensure adequate motor cooling. This segmentation allows each component to operate under optimal pressure conditions independently.
Solution Approach 2:
Different pressure conditions are applied to different parts of the system: the oil sump operates at reduced pressure to protect lubrication quality, while the motor housing operates at elevated pressure to enhance cooling efficiency. This local differentiation of operating conditions resolves the contradiction between lubrication and cooling requirements.
2Temperature
If the refrigerant pressure in the motor housing is increased, then the motor cooling efficiency is improved, but the refrigerant absorption by the oil increases leading to reduced oil viscosity
Solution Approach 1:
The system separates the motor housing and oil sump into distinct pressure zones, allowing the motor housing to be pressurized for improved cooling while the oil sump maintains reduced pressure to prevent refrigerant absorption and maintain oil viscosity.
Solution Approach 2:
A pressure control mechanism acts as an intermediary between the motor housing and oil sump, regulating the refrigerant pressure in each zone independently to achieve both effective motor cooling and oil viscosity maintenance.
3Device complexity
If standard water chiller technology is used for heat pump applications with high evaporation temperatures, then the design is simple, but the system cannot operate reliably at elevated temperatures
Solution Approach 1:
The system modifies the operating parameters of the compressor by implementing variable pressure control in the oil sump and motor housing, enabling standard water chiller technology to operate reliably at high evaporation temperatures up to 70°C that were previously unsuitable for such systems.
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 solution effectively reduces the risk of mechanical failures by maintaining optimal oil viscosity and lubricity, and improves motor cooling by lowering refrigerant pressure, allowing for extended operation at higher temperatures and extending the application range of standard compressor systems to heat pump conditions.
Implementation Method 1
A pressure reducing device is introduced between the oil sump and the low-pressure side of the refrigerant system to lower the refrigerant pressure in the oil sump
Implementation Method 2
the absorption of refrigerant by lubricating oil leads to reduced oil viscosity and lubricity
Implementation Method 3
The motor operates in an atmosphere of refrigerant, the refrigerant surrounding and cooling the motor
Implementation Method 4
the refrigerant surrounding and cooling the motor
Data Source
AI summary
A system for reducing the refrigerant pressure in an oil sump or in a cavity of a housing. The invention is particularly useful for reducing pressure in a compressor for heat pump applications that has been validated for water chiller operations or in turbine and generator systems in ORC systems generating electricity using refrigerant, the ORC systems essentially being a heat pump application operating in reverse. An auxiliary compressor, an auxiliary condenser or an ejector pump may be used to reduce pressure in the oil sump, to separate refrigerant from oil. The auxiliary compressor, the auxiliary condenser or the ejector pump may also be used to reduce the pressure of refrigerant in the housing of a compressor in heat pump applications at temperatures and pressures at which the compressor was validated for water chiller applications and of the turbine and generator in ORC applications.