NMR Sample Tube Temperature Control With Nested Flow Channels
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Solution Overview
Problem
Conventional temperature control systems for NMR sample tubes suffer from significant axial temperature gradients, leading to disrupted measurement signals due to convection and inadequate temperature stability, especially when the ambient temperature differs from the sample space temperature.
Innovation Solution
A temperature control device with nested flow channels, where the radially outermost flow channel has an outer and inner compartment, with the temperature-controlling fluid flowing in the same direction, and the inner compartment receiving significantly more fluid than the outer compartment, allowing for precise control of the temperature gradient by regulating fluid flow rates and using heat-conductive materials or heating elements to maintain the cylindrical wall at a temperature close to the ambient temperature, thereby minimizing axial temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple direct fluid flow is used around the sample tube, then the device complexity is reduced, but significant axial temperature gradients occur leading to convection and disrupted measurement signals
Solution Approach 1:
The fluid flow path is segmented into multiple nested flow channels (outer flow channel, inner flow channel, and central flow channel) that are spatially separated but thermally coupled. This segmentation allows independent temperature control of different regions, enabling the outer wall temperature to be maintained close to ambient temperature while the sample space is heated or cooled, thus preventing convection and measurement disruptions
Solution Approach 2:
The patent implements a nested structure where the inner flow channel is positioned within the outer flow channel, and the central flow channel is positioned within the inner flow channel. This nested arrangement allows the temperature-controlling fluid to flow through multiple concentric channels, with the outermost channel serving to stabilize the external wall temperature while inner channels provide the primary heating or cooling effect
2Device complexity
If the temperature-controlling fluid flows through a single channel, then the device complexity is reduced, but the temperature stability of the sample tube is insufficient
Solution Approach 1:
The single fluid flow path is divided into multiple nested channels, each contributing to different aspects of temperature control. The outer channel stabilizes the external wall temperature, while inner channels provide primary thermal regulation, and the central channel offers additional stabilization. This segmented approach achieves superior temperature stability without requiring complex external control systems
Solution Approach 2:
The nested flow channel structure creates an inherent feedback mechanism where the outer flow channel compensates for temperature variations at the external wall, preventing heat loss or gain that would otherwise affect the sample temperature. This passive feedback system maintains temperature stability without requiring active sensing or control
3Temperature
If the outer wall temperature differs significantly from ambient temperature, then the sample space temperature control is improved, but heat flow across the outer wall causes axial temperature gradients
Solution Approach 1:
The patent applies different temperature conditions to different spatial locations: the outer wall is maintained at a temperature close to ambient temperature to prevent heat flow across the outer wall, while the sample space interior is allowed to have different temperature conditions for the desired heating or cooling effect. This local differentiation of temperature conditions eliminates axial temperature gradients while maintaining effective sample space temperature control
Solution Approach 2:
The temperature control function is segmented between the outer flow channel (which stabilizes the external wall temperature) and the inner/central flow channels (which control the sample space temperature). This functional segmentation allows the outer wall to act as a thermal buffer, preventing heat flow that would create axial gradients while the inner channels provide the necessary thermal treatment to the sample
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 achieves enhanced temperature stability and minimizes axial temperature gradients in the NMR sample tube, ensuring uniform temperature distribution and preventing convection, thereby improving the quality of NMR measurements.
Implementation Method 1
the temperature-controlling fluid is guided through the flow channels... around an interior delimited in a radially outward direction by a cylindrical wall, a plurality of nested flow channels for the fluid to be temperature-controlled running radially around the interior
Implementation Method 2
the cylindrical wall that delimits the interior during operation in the radially outward direction... the temperature control device minimizes heat flow between the sample space and the ambient environment
Data Source
AI summary
Temperature control system for an NMR sample tube (22) using a temperature control device (20) with an interior (21) delimiting a cylindrical wall (39) in the radially outward direction and a plurality of flow channels for temperature-controlling fluid running radially around the interior, of which the radially outermost flow channel (28) is delimited to the outside by a wall (29), and the innermost flow channel (31) by a wall (30) and connected to one another by a first fluid passage (34). The innermost flow channel has a second fluid passage (36) to the interior and the outermost flow channel has a fluid inlet (32). During operation, the wall delimiting the interior in the radially outward direction is temperature-controlled by the fluid so that: abs (TU−TW)≤abs (TU−TFD), where TW is the wall temperature, TFD is the fluid temperature at the first fluid passage and TU is the ambient temperature.