Phase-Change Vaccine Cooler for Off-Grid Cold Chain Storage
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Solution Overview
Problem
Maintaining the efficacy of vaccines in remote or rural areas where electrical power is unavailable, making it difficult to achieve and sustain a cold chain for temperature-controlled storage.
Innovation Solution
A portable device with a thermally insulated container containing phase change material and evaporative coils, powered by a battery-driven compressor, which maintains a temperature range of 2-8 °C for an extended period without constant electrical supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical power is used to maintain cold chain storage, then temperature control reliability is improved, but device portability and usability in remote areas deteriorates
Solution Approach 1:
The compressor is operated periodically to pre-cool the phase change material before the critical storage period begins. This preliminary cooling action ensures that the phase change material is ready to absorb heat and maintain temperature when electrical power becomes unavailable, resolving the contradiction between reliability and portability.
Solution Approach 2:
The invention utilizes phase change material that transitions between solid and liquid states at specific temperatures. During the phase transition, the material absorbs or releases latent heat, maintaining a stable temperature environment for vaccines without requiring continuous electrical power, thus enabling portability while maintaining reliability.
2Temperature
If compressor operation frequency is increased to maintain temperature, then temperature stability is improved, but energy consumption increases
Solution Approach 1:
The compressor operates periodically rather than continuously, cycling on and off based on temperature thresholds. This periodic operation maintains temperature stability by utilizing the thermal mass and phase change material to bridge temperature fluctuations during compressor off-periods, significantly reducing energy consumption compared to continuous operation.
Solution Approach 2:
The phase change material absorbs excess heat when temperature rises and releases heat when temperature drops, during phase transitions. This natural thermal regulation reduces the frequency and duration of compressor operation needed to maintain temperature stability, thereby reducing energy consumption.
3Duration of action of moving object
If thermal insulation is enhanced to prolong storage duration, then storage duration is improved, but device weight and size increases
Solution Approach 1:
The phase change material provides extended storage duration by absorbing and releasing latent heat during phase transitions, creating a thermal buffer that prolongs cold chain maintenance. This approach achieves extended storage duration without requiring excessive thermal insulation, thus avoiding significant increases in device weight.
Solution Approach 2:
The invention uses a composite structure combining phase change material with moderate thermal insulation layers. This composite approach optimizes the balance between storage duration and weight, as the phase change material provides active thermal management that reduces the amount of passive insulation material needed.
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 device effectively prolongs the storage of vaccines within a desired temperature range, ensuring vaccine efficacy in remote areas by minimizing heat leakage and requiring infrequent compressor operation, thus enhancing vaccine availability in areas without reliable power.
Implementation Method 1
The inner cylinder includes phase change material disposed therein
Implementation Method 2
phase change material disposed therein, and the phase change material is in thermal communication with the storage region
Implementation Method 3
The inner cylinder also includes evaporative coils disposed therein
Implementation Method 4
evaporative coils disposed therein
Implementation Method 5
The container also includes a thermally insulated outer cylinder
Data Source
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AI summary
Disclosed embodiments include portable devices for cold chain storage and methods of fabricating portable devices for cold chain storage. In an illustrative embodiment, a portable device for cold chain storage includes a container defining therein a storage region. The container includes an inner cylinder, and the storage region is defined coaxially inwardly of the inner cylinder. The inner cylinder includes phase change material disposed therein, and the phase change material is in thermal communication with the storage region. The inner cylinder also includes evaporative coils disposed therein. The evaporative coils are embedded in the phase change material. The container also includes a thermally insulated outer cylinder. An outer wall of the outer cylinder is disposed radially outwardly of an outer wall of the inner cylinder.