Passive Thermal Diode with Shape Memory Alloy Spring
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Solution Overview
Problem
Solid state thermal diodes have a low diodicity (rectification coefficient) of η˜1 or lower, making them impractical for most engineering applications, while phase change thermal diodes are limited by gravitational orientation and one-dimensional configuration.
Innovation Solution
A passive solid thermal diode is developed using a heat source, heat sink, and a thermal coupling element with a lever connected via a pivot point and a shape memory alloy spring, which displaces the thermal coupling element to control heat transfer between the heat source and sink, maximizing forward heat transfer and minimizing reverse heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid state thermal diodes are used, then the device is durable and easy to operate, but the diodicity is low (η˜1 or lower)
Solution Approach 1:
The patent employs a movable thermal coupling element that can dynamically change its position between contacting and non-contacting states with the heat source and sink. This dynamic mechanism allows the system to achieve high diodicity (η>10) while maintaining the durability and simplicity of solid-state construction, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent changes the thermal conductivity parameter by moving the thermal coupling element between two positions: when contacted, thermal conductivity is high (forward mode); when not contacted, thermal conductivity is low (reverse mode). This parameter change enables high diodicity while preserving solid-state durability and ease of operation.
2Productivity
If phase change thermal diodes are used, then heat transport rectification is effective, but the device is limited by gravitational orientation and one dimensional configuration
Solution Approach 1:
The patent replaces the phase change mechanism with a mechanical movement system consisting of a movable thermal coupling element actuated by a spring. This substitution eliminates the gravitational orientation limitation and one-dimensional configuration constraint of phase change diodes, allowing the device to achieve effective heat transport rectification while gaining adaptability to various orientations and configurations.
Solution Approach 2:
The patent transitions from the one-dimensional configuration of phase change diodes to a multi-dimensional arrangement where the movable thermal coupling element can move in multiple directions. The spring mechanism provides restorative force in different orientations, enabling the device to function effectively regardless of gravitational orientation, thus resolving the adaptability limitation.
3Ease of operation
If an electrical motor is used to control the thermal coupling element, then the movement is controlled, but electrical energy is required
Solution Approach 1:
The patent employs a spring mechanism that automatically controls the movement of the thermal coupling element without requiring external electrical energy. The spring stores and releases mechanical energy to move the coupling element between contacting and non-contacting positions, achieving controlled movement while eliminating electrical energy consumption and enhancing the passive, energy-efficient operation of the thermal diode.
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 solution achieves a high diodicity of 93.24±23.01, enabling effective thermal rectification and allowing for the development of a thermal switch with a high 'OFF' state thermal resistance to 'ON' state thermal resistance ratio of 98.73±20.48, enhancing thermal control in devices.
Implementation Method 1
at least one spring comprised of a shape memory alloy connected to the pistol assembly, wherein the at least one spring is configured to displace the pistol assembly in a first direction running along the center axis of the pistol assembly at a predetermined temperature
Implementation Method 2
In the forward mode, the thermal coupling element is in contact with the heat source and heat sink. Since metal is a good thermal conductor, a good heat transfer occurs in the forward mode.
Implementation Method 3
In the reverse mode, the thermal coupling element is moved out of the thermal contact with the heat source and heat sink. Since air is a good thermal insulator, heat transfer is effectively prevented in the reverse mode.
Data Source
AI summary
A passive thermal diode (10), comprising: a heat source (12); a heat sink (14); a thermal coupling element (16) removably coupled to the heat source (12) and the heat sink (14); a lever (18), the lever (18) connected to the thermal coupling element (16) via a pivot point (19); and at least one spring (20) connected to the lever (18), the spring (20) comprised of a shape memory alloy, wherein the lever (18) transmits a force to displace the thermal coupling element (16) when the force is produced by the spring (20) on the lever (18).