Patient heat exchange system with two and only two fluid loops
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Solution Overview
Problem
Current patient temperature control systems for neuro ICU patients and those suffering from neurologic maladies like stroke or cardiac arrest face inefficiencies in heat exchange due to complex fluid circuits and high backpressure, which can hinder effective cooling and increase operational costs.
Innovation Solution
A heat exchange system with a working fluid circuit and a refrigerant circuit, featuring a narrow slot between cold plates for a fluid cassette, allowing for efficient heat exchange between the working fluid and refrigerant, reducing backpressure and operational demands, and utilizing a serpentine passageway for refrigerant flow to enhance heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a complex fluid circuit is used for heat exchange, then heat transfer capability is improved, but backpressure increases and operational costs increase
Solution Approach 1:
The system divides the heat exchange function into two separate circuits: a refrigerant circuit containing the compressor and condenser, and a working fluid circuit containing the heat exchange catheter. This segmentation allows each circuit to be optimized independently, reducing backpressure in the working fluid circuit while maintaining heat transfer capability.
Solution Approach 2:
The compressor and condenser are extracted from the working fluid circuit and placed in a separate refrigerant circuit. This extraction eliminates the high backpressure components from the patient-facing circuit, reducing backpressure on patients while maintaining cooling effectiveness through the separate refrigerant loop.
2Temperature
If a narrow slot between cold plates is used, then heat exchange efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The cold plates are designed with a narrow slot (less than 0.040 inches, preferably 0.029-0.031 inches) specifically at the heat exchange interface between the refrigerant circuit and working fluid circuit. This localized precision feature maximizes thermal contact and heat transfer efficiency where needed most, while the rest of the system components can be manufactured with standard tolerances.
3Temperature
If a serpentine passageway is used for refrigerant flow, then heat transfer is enhanced, but device complexity increases
Solution Approach 1:
The refrigerant flow path in the cold plate is configured as a serpentine (sinuous) passageway rather than straight channels. This curved, winding path increases the surface area contact between refrigerant and cold plate, enhancing heat transfer efficiency. The serpentine design achieves this within a compact footprint without requiring additional external heat exchange components.
4Ease of manufacture
If a disposable cassette design is used, then operational costs are reduced, but device complexity increases
Solution Approach 1:
The fluid cassette containing the working fluid is designed as a disposable component that can be easily replaced. This eliminates the need for complex cleaning, sterilization, and maintenance systems, reducing operational costs. The cassette integrates the working fluid reservoir and flow paths in a single replaceable unit that interfaces with the reusable heat exchange system.
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 achieves efficient heat transfer with reduced backpressure and operational costs, enabling effective temperature control for patients by minimizing the conductive path length and using a low-cost, disposable cassette design that promotes laminar flow and high heat transfer rates.
Implementation Method 1
The system achieves efficient heat transfer with reduced backpressure and operational costs, enabling effective temperature control for patients by minimizing the conductive path length
Implementation Method 2
using a low-cost, disposable cassette design that promotes laminar flow and high heat transfer rates
Implementation Method 3
The refrigerant circuit includes a compressor and is the only fluid circuit in thermal contact with the working fluid circuit
Data Source
AI summary
A heat exchange system for exchanging heat with working fluid from an intravascular heat exchange catheter or an external heat exchange pad includes a working fluid that circulates between the catheter or pad and a fluid cassette, and a refrigerant system that flows against the outer sides of cold plates between which the cassette is disposed.