Air-Cooled Helium Compressor With Split Oil and Helium Cooling
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Solution Overview
Problem
Helium compressors in cryogenic refrigeration systems face challenges in air cooling, especially when operating outdoors, where temperatures can range from −30° C. to +45° C., leading to increased oil viscosity, difficulty in starting the compressor, and frequent adsorber replacement due to contaminant outgassing, and inefficiencies in heat rejection.
Innovation Solution
The solution involves circulating hot oil to an outdoor air-cooled heat exchanger while cooling high-pressure helium in an indoor air-cooled heat exchanger, allowing for at least 65% of the compressor's heat to be rejected outdoors during summer, with the option to reject heat to indoor space during winter, thus maintaining the oil separator and adsorber indoors and optimizing heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the compressor is mounted outdoors and cooled by outdoor air, then heat rejection is improved, but oil viscosity increases and compressor start-up becomes difficult at low temperatures
Solution Approach 1:
The cooling system is segmented into two separate heat exchangers: one for oil cooling and one for helium cooling. This allows independent temperature control for each fluid, enabling the oil to be kept at operational temperatures for easy start-up while the helium is cooled for efficient heat rejection outdoors.
Solution Approach 2:
Different thermal conditions are applied to different components: the oil is maintained at higher temperatures (−10° C. to +50° C.) to reduce viscosity and enable easy start-up, while the helium is cooled to lower temperatures for efficient heat rejection. Each component receives the thermal quality it needs for optimal performance.
2Temperature
If the compressor operates at high outdoor temperatures, then heat rejection is improved, but contaminant outgassing from oil increases and adsorber replacement frequency increases
Solution Approach 1:
The system separates oil cooling and helium cooling into distinct heat exchangers, allowing the oil to be cooled to controlled temperatures that minimize contaminant outgassing while still enabling effective heat rejection of the compressor heat load through the helium cooling path.
3Temperature
If water cooling is used, then heat rejection efficiency is improved, but system complexity and water consumption increase
Solution Approach 1:
The water cooling system is replaced with an air-cooled heat exchanger system. This substitution eliminates the need for water circulation pumps, water storage, and drainage systems, significantly reducing mechanical complexity while maintaining effective heat rejection through convection and radiation to the surrounding air.
4Temperature
If oil circulation rate is increased to cool the compressor, then heat rejection from oil is improved, but oil separation from helium becomes more difficult
Solution Approach 1:
The cooling functions are segmented: the oil circulation system handles heat removal from the compression chamber, while a separate helium cooling system handles the cooling of compressed helium. This segmentation allows oil to be circulated at rates optimized for cooling without compromising separation, since the helium is cooled independently after separation.
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 effectively reduces the load on the adsorber, maintains lower helium temperatures, and allows for efficient heat rejection, reducing the frequency of adsorber replacement and improving compressor start-up, while offering cost savings by adjusting heat rejection based on seasonal needs.
Implementation Method 1
a first heat exchanger that cools the compressed helium
Implementation Method 2
a second heat exchanger that cools the compressed gas and oil mixture
Implementation Method 3
an expansion valve that expands the cooled helium to a lower pressure
Data Source
AI summary
This invention relates generally to oil lubricated helium compressor units for use in cryogenic refrigeration systems, operating on the Gifford McMahon (GM) cycle. The objective of this invention is to keep the oil separator and absorber, which are components in an oil lubricated, helium compressor, in an indoor air conditioned environment while rejecting at least 65% of the heat from the compressor outdoors during the summer. The balance of the heat is rejected to either the indoor air conditioned air, or cooling water. This is accomplished by circulating hot oil at high pressure to an outdoor air cooled heat exchanger and returning cooled oil to the compressor inlet, while hot high pressure helium is cooled in an air or water cooled heat exchanger in an indoor assembly that includes the compressor, an oil separator, an oil absorber, and other piping and control components. It is an option to reject the heat from the oil to the indoor space during the winter to save on the cost of heating the indoor space.