Variable Conductance Heat Pipe for Photonic Circuit Thermal Control
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Solution Overview
Problem
Conventional heat pipes can lead to overcooling of photonic and electronic components due to fixed conductance, and active thermal management solutions increase power requirements and complexity.
Innovation Solution
A variable conductance heat pipe with a non-condensable gas is used, where the gas accumulates at the condenser end to inhibit vapor condensation, creating a temperature-dependent heat conductance that prevents overcooling and maintains the component temperature within a desired range by balancing heat transfer with heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional heat pipe with fixed conductance is used, then heat transfer efficiency is maintained, but overcooling of components occurs when heat sink temperature drops too low
Solution Approach 1:
The heat pipe conductance is made variable through the introduction of a non-condensable gas that dynamically adjusts the vapor flow resistance based on temperature conditions. At low heat sink temperatures, the gas accumulates at the condenser end, reducing conductance and preventing overcooling. At high temperatures, the gas redistributes, increasing conductance to maintain cooling efficiency.
Solution Approach 2:
The thermal conductance parameter of the heat pipe is changed from fixed to variable by controlling the distribution and pressure of the non-condensable gas. The gas pressure and distribution ratio are adjusted as control parameters to achieve the desired variable conductance characteristic that adapts to different operating conditions.
2Measurement precision
If active thermal management with thermoelectric cooler is used, then temperature control precision is improved, but power requirements and system complexity increase
Solution Approach 1:
The heat pipe system with non-condensable gas is self-regulating and requires no external control mechanisms. The gas automatically redistributes in response to temperature changes, adjusting the heat transfer conductance without requiring sensors, controllers, or additional power input, thereby achieving passive temperature control.
Solution Approach 2:
The active mechanical/electrical control system (thermoelectric cooler with sensors and power supply) is replaced by a passive thermal system utilizing the physical properties of the non-condensable gas. The gas pressure distribution and phase change mechanisms naturally provide the required temperature control without mechanical actuators or electrical control circuits.
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 variable conductance heat pipe effectively manages temperature by maintaining the component temperature within a narrower range than the heat sink, preventing overcooling while ensuring efficient cooling at varying temperatures, thus reducing power consumption and complexity.
Implementation Method 1
a heat pipe, that is, a sealed chamber filled with a working fluid that evaporates in a high-temperature region in contact with a heat source and condenses in low-temperature region in contact with a heat sink, transferring heat by a combination of convection and phase change
Implementation Method 2
a heat pipe, that is, a sealed chamber filled with a working fluid that evaporates in a high-temperature region in contact with a heat source and condenses in low-temperature region in contact with a heat sink
Implementation Method 3
transferring heat by a combination of convection and phase change
Implementation Method 4
A variable conductance heat pipe with a non-condensable gas is used, where the gas accumulates at the condenser end to inhibit vapor condensation, creating a temperature-dependent heat conductance
Implementation Method 5
transferring heat by a combination of convection and phase change, in addition to heat conduction through the pipe wall
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Photonic and electronic integrated circuits can be cooled using variable conductance heat pipes containing a non-condensable gas in addition to a phase-changing working fluid. To package the heat pipe with a subassembly including the integrated circuits in a standard housing providing a heat sink contact area, the heat pipe is oriented, in some embodiments, with its axis between evaporator and condenser ends substantially perpendicular to the direction along which the integrated circuit subassembly is separated from the heat sink contact area, and a portion of the exterior surface of the heat pipe is thermally insulated, with a suitable thermal insulation structure, from the heat sink contact area.