NMR Cold-Gas Supply Pre-Cooling to Cut Liquid Nitrogen Use
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Solution Overview
Problem
Current NMR LT MAS devices consume a large quantity of liquid nitrogen, leading to high operating costs and frequent handling requirements, due to inefficient use of cold gas streams and lack of practical methods to reduce nitrogen consumption.
Innovation Solution
The implementation of additional pre-cooling exchangers that utilize 'boil-off' gases and gases evacuated from the probe to pre-cool the gas streams before they enter the main exchangers, reducing the thermal load on the nitrogen refrigeration system and optimizing the use of cold gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional cooling devices with three exchangers in pressurized chambers are used, then gas cooling and rotor rotation are achieved, but liquid nitrogen consumption is high (up to 20 L/hr)
Solution Approach 1:
The patent applies pre-cooling of the gas streams before they enter the main exchangers in the pressurized chambers. This preliminary cooling action reduces the thermal load on the liquid nitrogen system, allowing the main exchangers to operate more efficiently and reducing overall liquid nitrogen consumption while maintaining the required cooling temperature for gas streams
Solution Approach 2:
The patent introduces an intermediary pre-cooling stage between the gas source and the main cooling exchangers. This intermediary system prepares the gas streams by removing excess heat before they reach the liquid nitrogen-dependent exchangers, thereby reducing the burden on the liquid nitrogen consumption without compromising the final cooling performance
2Speed
If high rotational speed of the rotor is achieved, then better NMR measurement performance is obtained, but liquid nitrogen consumption increases proportionally
Solution Approach 1:
The pre-cooling system prepares gas streams in advance before they are used for rotor rotation, reducing the thermal power that must be evacuated during high-speed operation. This allows the system to sustain higher rotation speeds without proportionally increasing liquid nitrogen consumption, as the pre-cooled gas requires less additional cooling during actual rotor operation
3Duration of action of stationary object
If frequent handling of liquid nitrogen tanks is performed, then continuous operation is maintained, but operational complexity and user burden increase
Solution Approach 1:
By implementing pre-cooling, the system extends the duration between liquid nitrogen refills, reducing the frequency of user interventions. The pre-cooled gas streams reduce the overall thermal load, allowing the liquid nitrogen to last longer before depletion, thereby maintaining continuous operation with less frequent tank handling
Solution Approach 2:
The system recovers and utilizes cold gases that would otherwise be wasted, creating a self-sustaining cooling loop. The cold gases from the NMR probe are redirected to pre-cool incoming gas streams, reducing the burden on the liquid nitrogen system and extending operational duration without requiring additional user intervention or tank handling
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 significantly reduces liquid nitrogen consumption by up to 50%, minimizing the need for frequent refills and maintaining consistent gas quality for rotor operation, while ensuring continuous operation with reduced handling of nitrogen containers.
Implementation Method 1
The implementation of additional pre-cooling exchangers that utilize 'boil-off' gases and gases evacuated from the probe to pre-cool the gas streams before they enter the main exchangers
Implementation Method 2
The total consumption of liquid nitrogen is directly proportional to the internal pressure of the chambers containing the exchangers... exploitation of gas leaks produced by 'boil-off' boiling
Implementation Method 3
gases, coming from cylinders, cans or similar tanks at ambient temperature, are cooled by passing through three exchangers (one per gas) contained in three pressurized chambers partly filled with liquid nitrogen
Implementation Method 4
The heat exchange surfaces of the chambers are sized to be able to evacuate the maximum thermal power
Data Source
AI summary
The device (1) has an insulated tank (4) containing liquid gas (5) at a boiling point and arranged exchangers (6, 6', 6'') through gas streams to be cooled with exchangers that are connected with transfer lines (7, 7', 7''). An additional exchanger (8) ensures the pre-cooling of cold gas designed to cool a sample that is supplied with gaseous vapor (5') produced by the boiling of the liquid gas. Additional exchangers (8', 8'') ensure the pre-cooling of the cold gases to ensure the lift and rotation of the samples supplied by the gases that are evacuated.