NMR Sample Tube Temperature Control With Nested Flow Channels
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Solution Overview
Problem
Conventional temperature control devices for NMR sample tubes suffer from significant axial temperature gradients, leading to unstable temperature conditions and interference in NMR measurement signals, especially when the ambient temperature differs from the sample chamber temperature.
Innovation Solution
A temperature control device with nested flow channels around the NMR sample tube, where the radially outermost flow channel has an outer compartment in thermal contact with both axial walls and an inner compartment with a capillary design, allowing for controlled fluid flow to minimize temperature gradients by adjusting flow velocities and cross-sectional areas, and potentially reversing the temperature gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct airflow temperature control is used, then the device structure is simple, but significant axial temperature gradients occur in the sample tube
Solution Approach 1:
The patent implements nested flow channels where an inner flow channel is positioned within an outer flow channel. The inner channel has a smaller cross-sectional area and is surrounded by the outer channel, creating a nested configuration. This allows two fluid streams to flow concurrently or countercurrently, enabling precise temperature control with minimized axial temperature gradients while maintaining structural efficiency.
2Temperature
If conventional countercurrent temperature control is used, then axial temperature gradients are reduced, but temperature stability is insufficient due to heat loss through the outer wall
Solution Approach 1:
The temperature control system is segmented into multiple independent flow channels (inner and outer channels), each capable of carrying temperature control fluid separately. This segmentation allows independent control of temperature profiles in different radial zones, enabling the system to compensate for heat losses through the outer wall while maintaining stable axial temperature gradients.
3Quantity of substance
If the radially outermost flow channel has large cross-sectional area, then fluid flow capacity is high, but temperature gradient control precision is reduced
Solution Approach 1:
The patent applies different cross-sectional areas to different flow channels based on their specific functions. The outer flow channel has a larger cross-sectional area optimized for high fluid flow capacity and heat exchange with the environment, while the inner flow channel has a smaller cross-sectional area optimized for precise temperature gradient control directly at the sample tube. This local optimization of geometric parameters resolves the contradiction between flow capacity and control precision.
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 design achieves minimal or zero axial temperature gradients within the sample tube, ensuring stable temperature conditions and improved NMR measurement quality by uniformly controlling the sample temperature.
Implementation Method 1
the temperature control fluid is guided through the flow channels... the radially outermost flow channel is in planar thermal contact with both axial walls
Implementation Method 2
the temperature control fluid consists of a common inflow that flows into both sections... fluid flow through the outer section is lower than through the inner section
Data Source
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AI summary
The invention relates to a system for controlling the temperature of an NMR sample tube (22) using a temperature control device (20) comprising an interior (21), which is outwardly delimited in a radial direction by a cylindrical wall (39), and multiple flow channels for a temperature control fluid, which run radially about the interior and the radially outermost flow channel (28) of which and the innermost flow channel (31) of which are outwardly delimited by a wall (29 and 30, respectively) and are connected together by a first fluid passage (34), wherein the innermost flow channel has a second fluid passage (36) to the interior, and the outermost flow channel has a fluid inlet (32), said fluid being conducted through the flow channels. The invention is characterized in that during operation, the temperature of the wall which outwardly delimits the interior in a radial direction is controlled by the fluid such that the relation abs(Tu-Tw) ≤ abs(Tu-TFD) between the absolute differential values applies for the temperature Tw of the wall and the temperature TFD of the fluid at the first fluid passage in relation to the ambient temperature Tu outside of the wall outwardly delimiting the outermost flow channel. In this manner, the axial temperature gradient in the sample tube is minimized, and the temperature stability is increased.