Phase-Change Heat Pack With Thermal Buffer for Temperature Control
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Solution Overview
Problem
Existing nonelectric reusable heat sources lack a controlled temperature regulation system that can maintain a consistent heat output over an extended period without the need for electrical power, limiting their application in cold weather and therapeutic uses.
Innovation Solution
A heat pack system utilizing a first phase change material, such as sodium acetate trihydrate, and a thermal storage buffer like paraffin wax, activated by a stainless steel initiator to provide heat within a predetermined temperature range (36-44°C) through crystallization, allowing for controlled heat generation and storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a phase change material is used to provide heat, then the heat pack can be reused and does not require electrical power, but the temperature cannot be controlled within a specific range
Solution Approach 1:
The patent uses a eutectic salt composition with specific ratios of sodium acetate trihydrate (70-80 wt%), potassium acetate (10-20 wt%), and disodium phosphate dihydrate (5-15 wt%) to precisely control the phase change temperature within 36-44°C. This parameter optimization allows the heat pack to maintain a specific temperature range while remaining reusable and electricity-free
Solution Approach 2:
The patent employs a composite phase change material system combining multiple salts (sodium acetate trihydrate, potassium acetate, disodium phosphate dihydrate) in specific proportions. This composite approach enables precise temperature control within the 36-44°C range while maintaining the reusable, non-electric properties of phase change materials
2Duration of action of moving object
If a chemical reaction is used to generate heat, then heat can be provided for a limited period, but the heat pack becomes single-use and non-reusable
Solution Approach 1:
The patent utilizes the reversible phase transition (melting and freezing) of eutectic salt composition to provide heat. During freezing, the phase change material releases heat for an extended period, and during melting, it absorbs heat to reset. This reversible phase transition enables the heat pack to be reused multiple times while providing heat for extended durations
Solution Approach 2:
The patent pre-prepares the phase change material in a liquid state by heating it above its melting point (45-50°C) before use. This preliminary heating action ensures the material is ready to undergo controlled freezing and release heat over an extended period, while the system design maintains reusability through proper thermal management
3Power
If the phase change material crystallizes exothermically, then heat is provided at a high temperature, but the temperature exceeds the desired therapeutic range
Solution Approach 1:
The patent optimizes the eutectic composition parameters to achieve a phase change temperature within 36-44°C, which is suitable for therapeutic applications. By adjusting the ratios of sodium acetate trihydrate, potassium acetate, and disodium phosphate dihydrate, the heat output is maintained while the temperature is precisely controlled within the desired range
Solution Approach 2:
The patent uses a composite eutectic salt system where multiple components work together to control the phase change temperature. The specific combination of sodium acetate trihydrate, potassium acetate, and disodium phosphate dihydrate creates a material that releases heat at a controlled temperature within 36-44°C, matching therapeutic requirements
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 provides a nonelectric, reusable, and temperature-controlled heat source that can maintain a consistent output for an extended period, suitable for applications like infant warming and outdoor use, with adjustable temperature settings and rechargeable functionality.
Implementation Method 1
Activation of the initiator causes crystallization of the first PCM
Implementation Method 2
crystallizes exothermically when activated
Implementation Method 3
The heat provided by the first PCM melts the second PCM of the thermal storage buffer at a second temperature such that the second PCM of the thermal storage buffer absorbs part of the heat provided by first PCM
Implementation Method 4
a thermal storage buffer that is contained in the housing. The thermal storage buffer includes a second PCM
Data Source
AI summary
A heat pack includes a housing, a first phase change material (PCM) that is contained in the housing, and a thermal storage buffer that is contained in the housing. The thermal storage buffer includes a second PCM. An initiator is in operative contact with the first PCM. Activation of the initiator causes crystallization of the first PCM, and the first PCM cooperates with the thermal storage buffer to provide heat at a predetermined temperature range upon crystallization of the first PCM.