NMR MAS Rotor Temperature Control via High-Velocity Gas Nozzles
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Solution Overview
Problem
Existing NMR MAS rotor temperature control methods fail to maintain uniform temperature distribution, especially at high rotation frequencies, leading to unwanted heating and potential sample destruction due to inefficient cooling and temperature gradients.
Innovation Solution
The method involves blowing temperature control gas through nozzles with a flow rate at least half the peripheral speed of the rotor and a pressure of 0.1MPa to 0.5MPa, using nozzles with an inner diameter between 0.04mm and 0.5mm, and directing the gas flow at an angle to enhance cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotor rotates at high frequency (f ≥ 30kHz), then the NMR measurement quality improves, but the rotor wall heating due to air friction increases
Solution Approach 1:
The patent converts the harmful effect of air friction (which causes heating) into a beneficial cooling mechanism by intentionally introducing temperature control gas through nozzles. The gas flow exploits the rotor's rotation to create effective cooling, transforming the aerodynamic heating problem into a controlled thermal management solution
Solution Approach 2:
The patent employs pneumatic cooling by introducing temperature control gas through nozzles positioned around the rotor. The gas flow rate is specifically controlled to match a significant portion (at least half) of the rotor's peripheral speed, creating an effective pneumatic cooling system that removes heat generated during high-speed rotation
2Stability of the object's composition
If temperature control gas is injected at low velocity, then the rotor rotation stability improves, but the cooling efficiency decreases
Solution Approach 1:
The patent optimizes the gas flow velocity parameter by setting it to at least half of the rotor's peripheral speed. This specific parameter relationship creates an optimal balance where the gas flow is fast enough to provide effective cooling through enhanced heat transfer, yet controlled enough to maintain rotor rotation stability
3Device complexity
If conventional VT channels are used for temperature control, then the device complexity is reduced, but temperature gradients in the sample substance increase
Solution Approach 1:
The patent implements localized temperature control by positioning nozzles at specific locations around the rotor perimeter. Each nozzle targets a specific region, creating locally optimized cooling zones that collectively eliminate temperature gradients across the entire sample volume, achieving uniform temperature distribution
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 provides significantly better temperature control, reducing heating and temperature gradients, even at high rotational frequencies, by ensuring a rapid gas flow that exchanges air layers on the rotor surface, thus improving cooling efficiency.
Implementation Method 1
The MAS rotor is supported by compressed gas by means of a device for supplying gas with a bearing nozzle
Implementation Method 2
The MAS rotor is rotated by means of a pneumatic drive about the cylinder axis of the MAS rotor
Implementation Method 3
a tempering gas being injected during the NMR-MAS measurement by means of a tempering nozzle is blown onto the outer shell of the MAS rotor
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A method for operating an NMR probe head (10) with a MAS stator (11) for receiving a circular cylindrical hollow MAS rotor (13) with an outer shell with outer diameter D and a sample substance in a sample volume, wherein the MAS rotor is pressurized in a measuring position within the MAS stator by means of a gas supply device with a bearing nozzle (12') and is set into rotation about the cylinder axis of the MAS rotor with a rotation frequency f ≥ 30 kHz by means of a pneumatic drive, wherein during the NMR-MAS measurement a temperature control gas is blown onto the outer shell of the MAS rotor by means of a temperature control nozzle (12) at an angle α < 90° with respect to the longitudinal axis of the cylindrically symmetric MAS rotor, is characterized in thatthat the flow velocity of the temperature control gas blown through the temperature control nozzle onto the MAS rotor in the nozzle cross-section corresponds to at least half the circumferential speed of the outer shell of the rotating MAS rotor and at most the speed of sound in the temperature control gas. This ensures significantly better temperature control even with very fast rotating MAS rotors.