Conformable Evaporative Cooling Structure That Resists Vacuum Collapse
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Solution Overview
Problem
Existing evaporative structures for human body cooling, such as those using the heat pipe principle, face challenges with water as the working fluid due to its low vapor pressure requiring a substantial vacuum, which can cause the structure to collapse and limit efficient heat transfer, especially when worn under personal protective equipment (PPE) that restricts heat loss.
Innovation Solution
A generally planar, conformable evaporative structure with a flexible impermeable envelope, a layer of wick material for liquid phase evaporation, a breathable spacer fabric for vapor flow, and flexible ribs to maintain vapor pathways, along with a felted layer for enhanced heat conductivity and sweat absorption, and an integrated or separate heat sink for condensation, optionally with a pump for condensate return.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a substantial vacuum is maintained within the envelope to enable evaporation of water at body temperature, then evaporation efficiency is improved, but the woven structure collapses into its vapour flow voids preventing operation
Solution Approach 1:
The patent replaces the rigid woven structure with a flexible membrane envelope that can maintain its shape under vacuum conditions. The membrane acts as a continuous barrier that prevents collapse while allowing the heat pipe cycle to operate effectively under substantial vacuum levels.
Solution Approach 2:
The invention uses a composite structure combining the membrane envelope with internal support elements and working fluid reservoirs. This composite design provides both the vacuum seal needed for efficient evaporation and the structural integrity to prevent collapse of the internal components.
2Reliability
If water is used as the working fluid due to its high latent heat of evaporation and non-toxicity, then safety and cooling efficiency are improved, but a substantial vacuum is required which causes structural collapse
Solution Approach 1:
The flexible membrane envelope is specifically designed to maintain substantial vacuum levels without collapsing, enabling water to be used as the working fluid at body temperature. The membrane provides the necessary structural support to keep the vacuum intact while allowing efficient heat transfer and evaporation.
3Productivity
If the envelope is evacuated to enable water evaporation at body temperature, then evaporation rate is improved, but the area over which efficient heat transfer can take place is limited
Solution Approach 1:
The flexible membrane envelope can be expanded to large surface areas while maintaining vacuum integrity. This allows extensive heat transfer area to be available for efficient heat transfer from the body to the working fluid, while the membrane prevents collapse that would limit the effective area.
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 structure effectively maintains vapor flow and heat transfer while preventing collapse under vacuum, enhancing cooling efficiency and reducing heat strain for individuals wearing PPE by maximizing heat transfer and vapor flow area, thus improving thermal comfort and performance.
Implementation Method 1
a layer of flexible wick material disposed adjacent to a major face of said envelope, adapted to hold a working fluid in liquid phase for evaporation by heat conducted through said envelope
Implementation Method 2
evaporation by heat conducted through said envelope
Implementation Method 3
adapted to hold a working fluid in liquid phase for evaporation by heat conducted through said envelope
Implementation Method 4
the so-called heat pipe principle, that is to say the transfer of heat from a source to a sink by a continuous working fluid cycle which involves evaporation of the fluid at the source
Implementation Method 5
transfer of the vapour to the sink, condensation of the fluid at the sink
Implementation Method 6
the transfer of heat from a source to a sink by a continuous working fluid cycle which involves evaporation of the fluid at the source, transfer of the vapour to the sink, condensation of the fluid at the sink
Implementation Method 7
the felt layer will tend to absorb sweat from the body and provide a better heat conductive path into the structure
Data Source
AI summary
A generally planar, conformable evaporative structure, particularly for incorporation in a garment or an item of personal protective equipment as part of a system to cool the wearer's body, includes an envelope of substantially impermeable, flexible material containing: a layer of flexible wick material disposed adjacent to a major face of the envelope and adapted to hold a working fluid in liquid phase for evaporation by heat conducted through the envelope; a layer of flexible, breathable fabric in parallel with the layer of wick material; and an array of flexible ribs such as open helical coils within the layer of breathable fabric adapted to maintain pathways for the flow of working fluid in vapour phase towards a condensation zone.