Evaporative thermal management systems and methods
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Solution Overview
Problem
Thermal management systems face challenges in minimizing size, weight, and power while efficiently controlling substrate temperatures, particularly in applications requiring low or optimized size, weight, and power (SWaP), as they often rely on additional mass and equipment like pumps and heat exchangers.
Innovation Solution
An evaporative thermal management device with a housing that includes a working fluid and supports, which increases the surface area to volume ratio for enhanced heat transfer, using evaporation to control substrate temperature without the need for circulation equipment, and employing porous media and pressure regulation to manage the boiling point of the working fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If passive thermal management systems use additional thermal mass in the form of working fluid, then temperature control efficiency is improved, but system weight and size increase
Solution Approach 1:
The patent utilizes the phase transition (evaporation) of a working fluid to transfer heat away from the substrate. The fluid evaporates at a controlled rate, absorbing latent heat of vaporization, which provides efficient passive cooling without requiring heavy thermal mass or active circulation components.
Solution Approach 2:
The patent employs a porous medium to hold and distribute the working fluid across the substrate surface. The porous structure increases the surface area for heat transfer while maintaining a minimal amount of working fluid, thus achieving efficient cooling with reduced weight compared to traditional fluid reservoirs.
2Productivity
If active thermal management systems use pumps and heat exchangers to circulate working fluid, then heat transfer efficiency is improved, but device complexity and power consumption increase
Solution Approach 1:
The system eliminates the need for external pumps and active circulation equipment by utilizing the natural evaporation process of the working fluid. The porous medium and capillary action enable the fluid to move and distribute itself automatically, providing self-regulating passive thermal management without additional mechanical components.
Solution Approach 2:
The patent removes complex active components (pumps, motors, control systems) from the thermal management system, retaining only the essential elements (porous medium, working fluid, vent) needed for passive evaporation-based cooling, thereby significantly reducing device complexity.
3Productivity
If the surface area to volume ratio is increased for enhanced heat transfer, then cooling efficiency is improved, but system size increases
Solution Approach 1:
The porous medium provides an extremely high internal surface area within a compact volume. The working fluid distributes throughout the porous structure, creating numerous evaporation sites that enhance heat transfer efficiency without requiring a large external system volume, thus achieving high cooling efficiency in a compact form factor.
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 effectively minimizes size and weight while maintaining efficient heat transfer, allowing for temperature control of substrates with reduced power consumption and no requirement for additional equipment like pumps or heat exchangers, making it suitable for applications with stringent SWaP constraints.
Implementation Method 1
evaporation of the working fluid controls the temperature of the substrate
Implementation Method 2
evaporation of the working fluid controls the temperature of the substrate
Implementation Method 3
supports, which increases the surface area to volume ratio for enhanced heat transfer
Data Source
Figure 1
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Figure 3
AI summary
Devices and methods are provided herein useful to thermal management. In some embodiments, a thermal management device (10, 48, 66) includes a housing (14, 52, 68) with a fixed amount of working fluid (30, 78) disposed therein. The substrate (12, 70) is in thermal communication with the thermal management device (10, 48, 66) such that evaporation of the working fluid (30, 78) controls the temperature of the substrate (12, 70). Evaporated working fluid (30, 78) exits the housing (14, 52, 68) through one or more vents (28, 40, 56, 72). The housing (14, 52, 68) further includes a plurality of supports (20, 38, 74) that increase the surface area to volume ratio of the housing (14, 52, 68). The high surface area to volume ratio of the housing (14, 52, 68) increases the rate of heat transfer and also minimizes or otherwise reduces the size and weight of the thermal management device (10, 48, 66). The supports (20, 38, 74) may further serve to mechanically support the substrate (12, 70), enabling the housing (14, 52, 68) to act as a combined thermal and mechanical device.