Patient heat exchange system
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Solution Overview
Problem
Current patient temperature control systems face inefficiencies in heat exchange due to the design of fluid cassettes and heat exchangers, which can lead to increased backpressure and reduced heat transfer efficiency, especially in narrow spaces between cold plates.
Innovation Solution
A heat exchange system with a refrigerant circuit and transparent cold plates that allow for a narrow cassette slot for efficient working fluid flow, featuring a serpentine passageway and a disposable cassette with a membrane assembly that minimizes impedance and promotes effective heat transfer through conduction, while enabling visualization of refrigerant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a narrow slot is used between cold plates to improve heat transfer efficiency, then heat transfer efficiency is improved, but backpressure increases
Solution Approach 1:
The serpentine passageway uses curved paths instead of straight lines to guide refrigerant flow through the cold plate. This curved configuration allows the refrigerant to follow a longer path within the same footprint, improving heat transfer efficiency while managing pressure drop through smooth transitions that reduce turbulence and energy loss.
Solution Approach 2:
The serpentine path transforms a one-dimensional straight flow into a two-dimensional winding path through the cold plate. This dimensional change allows the refrigerant to access more surface area of the cold plate for heat exchange without increasing the linear distance, thereby improving heat transfer efficiency while controlling backpressure.
2Temperature
If a serpentine passageway is used to improve heat transfer, then heat transfer efficiency is improved, but device complexity increases
Solution Approach 1:
The serpentine passageway merges multiple heat transfer zones into a single continuous flow path. Instead of using separate channels or multiple components to achieve comprehensive heat exchange, the refrigerant flows through one integrated serpentine route that covers the entire cold plate surface, simplifying the overall device structure while maintaining high heat transfer efficiency.
Solution Approach 2:
The serpentine configuration changes the flow parameters (path length, flow velocity distribution, pressure gradient) to optimize heat transfer. By carefully designing the curvature and spacing of the serpentine path, the system achieves enhanced heat exchange without requiring complex valve systems or multiple components, thus managing device complexity.
3Measurement precision
If transparent material is used for cold plates to enable viewing of refrigerant flow, then measurement capability is improved, but heat conduction capability deteriorates
Solution Approach 1:
The cold plate is designed with non-uniform material properties: the viewing section uses transparent material to allow observation of refrigerant flow, while other sections use highly conductive opaque materials to maximize heat transfer. This local differentiation of material quality allows the system to simultaneously achieve both visualization capability and optimal heat conduction where needed.
Solution Approach 2:
The cold plate is segmented into different functional zones: transparent viewing zones for monitoring refrigerant flow and opaque highly conductive zones for primary heat exchange. This segmentation allows each zone to be optimized for its specific function, with the transparent portions providing measurement capability and the opaque portions providing superior thermal performance.
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
The system enhances heat transfer efficiency by reducing backpressure and conductive path length, allowing for effective cooling and heating of patients with reduced pump work and maintaining laminar flow, thus improving temperature control in medical applications.
Implementation Method 1
a refrigerant circuit configured for circulating refrigerant between a compressor and first and second cold plates between which a working fluid cassette is disposable
Implementation Method 2
promotes effective heat transfer through conduction
Implementation Method 3
maintaining laminar flow
Implementation Method 4
at least one of the heat transfer plates is at least partially transparent to permit viewing the refrigerant as it flows in the refrigerant circuit
Data Source
Figure 1
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AI summary
A heat exchange system for exchanging heat with working fluid from an intravascular heat exchange catheter (12) or an external heat exchange pad (18) includes a working fluid that circulates between the catheter (12) or pad (18) and a fluid cassette (50), and a refrigerant system that flows against the outer sides of cold plates (30, 32) between which the cassette (50) is disposed. An outer wall (32a) of the system is transparent so that a person can view the refrigerant as it circulates, ensuring proper operation.