Thermal diode and thermal switch for bi-directional heat transfer in building envelopes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current thermal management systems in buildings face challenges such as high energy consumption due to heat loss and gain, limited scalability, and material compatibility issues, particularly with thermosiphons and heat pipes, which are gravity-dependent and costly to install.
Innovation Solution
The use of a dual phase change thermal diode and an active contact-based thermal switch, incorporating positive and negative temperature coefficient materials like poly (N-isopropylacrylamide) and calcium chloride hexahydrate, and a wax motor, to control heat flow directionally and efficiently by switching thermal conductivity based on temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thermosiphons and heat pipes are used for directional heat transfer, then heat loss is reduced, but the systems require vertical installation and are gravity-dependent
Solution Approach 1:
The patent replaces the gravity-dependent mechanical operation of thermosiphons and heat pipes with a magnetic field-based thermal switching system. The magnetic thermal switch uses magnetic particles suspended in a fluid that can be controlled by external magnetic fields to open or close thermal pathways, eliminating the need for gravity-driven operation while maintaining directional heat transfer capability.
Solution Approach 2:
The patent changes the operating parameter from gravity-dependent passive operation to magnetically-controlled active operation. By using magnetic fields to control the thermal conductivity of the switching medium, the system can dynamically adjust heat flow direction without relying on gravitational forces, enabling flexible installation orientations.
2Loss of energy
If thermosiphons and heat pipes are installed in existing buildings, then heat loss is reduced, but installation requires demolition of building envelope portions
Solution Approach 1:
The magnetic thermal switch system replaces the complex installation requirements of traditional heat pipes with a simpler, non-intrusive device that can be integrated into existing building envelopes without major demolition. The magnetic field-based operation eliminates the need for precise vertical alignment and structural modifications.
3Loss of energy
If contact-based thermal switches using shape memory alloys are used, then thermal rectification ratio is improved, but material cost and scalability are reduced
Solution Approach 1:
The patent uses inexpensive magnetic particles suspended in a fluid medium as the switching element, replacing expensive shape memory alloys. The magnetic particles can be readily obtained and the system can be scaled up without proportionally increasing material costs, improving both economic viability and scalability.
Solution Approach 2:
The patent changes the switching mechanism from phase-change-based (shape memory alloys) to magnetically-controlled particle suspension. This parameter change allows for lower material costs while maintaining or improving thermal rectification performance through magnetic field control.
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
These systems achieve high thermal rectification ratios, reducing energy consumption by optimizing heat transfer and allowing for efficient directional heat management in building envelopes, enhancing both heating and cooling efficiency.
Implementation Method 1
a positive temperature coefficient (PTC) switching material... when the heat source is at a first temperature the device is configured to allow heat to flow from the heat source to the heat sink
Implementation Method 2
a negative temperature coefficient (NTC) switching material... at a second temperature the device is configured to not allow heat to flow from the heat source to the heat sink
Implementation Method 3
the PTC switching material has a first transition temperature, and the NTC switching material has a second transition temperature
Implementation Method 4
a motor includes a wax, the wax is configured to melt at approximately the first temperature, and the wax is configured to expand when melted, thereby moving the piston to the second position
Data Source
AI summary
The present disclosure relates to a directional heat transfer using thermal control devices, including a dual phase change thermal diode and an active contact-based thermal switch. The thermal diode includes a positive temperature coefficient switching material and a negative temperature coefficient switching material arranged in series. The thermal switch includes two thermally conducting surfaces which may be moved to contact (i.e., having a distance between them of substantially zero) creating minimal thermal contact resistance. Both thermal control devices may be used to control heat flow into and/or out of a building.