Microchannel Heat Pipe Layout for Higher Passive Heat Transfer
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Solution Overview
Problem
Conventional heat pipes have limitations in heat transfer rates due to the thermal resistance of thick conductive materials and fluid film resistance at the boundary layer, which restricts the efficiency of heat transfer between the heat source and sink.
Innovation Solution
The use of microchannel heat exchangers as heat absorbers and sinks in heat pipes, with channels less than 1000 microns in diameter, significantly reduces thermal and convective resistance, enabling higher heat transfer rates through enhanced conductive and convective heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional heat exchangers with thick conductive materials are used, then structural strength is improved, but thermal resistance increases and heat transfer rate decreases
Solution Approach 1:
The patent changes the geometric parameters of the heat exchanger by transitioning from conventional large-channel designs to microchannel designs with dimensions less than 1000 microns. This parameter change reduces the thermal resistance of conductive materials while maintaining structural integrity, thereby increasing the heat transfer rate without sacrificing structural strength.
Solution Approach 2:
The patent introduces a new dimensional scale by implementing microchannel geometry, effectively moving from millimeter-scale conventional channels to sub-millimeter-scale microchannels. This dimensional transition increases the surface area to volume ratio, enhancing heat transfer efficiency while using thinner conductive materials that reduce thermal resistance.
2Device complexity
If conventional heat exchangers are used, then device complexity is reduced, but heat transfer efficiency deteriorates due to fluid film resistance
Solution Approach 1:
The patent changes the flow regime parameters by reducing channel dimensions to microscale, which transforms the fluid flow characteristics and reduces fluid film resistance. This parameter change enhances convective heat transfer efficiency while maintaining a relatively simple device structure without requiring complex internal components.
3Productivity
If microchannel heat exchangers are used, then heat transfer rate is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the microchannel dimension parameters to be greater than 100 microns, establishing a feasible manufacturing window. This parameter optimization balances the need for high heat transfer rates with practical manufacturing capabilities, ensuring that channels are small enough to reduce thermal resistance but large enough to be manufactured with conventional precision techniques.
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
This configuration enhances heat transfer efficiency by maximizing heat exchange at the absorber and sink, allowing for passive operation without pumps or fans, and effectively addresses the limitations of conventional heat pipes, particularly in electronic device cooling and photovoltaic systems.
Implementation Method 1
enhanced conductive and convective heat transfer
Implementation Method 2
enhanced conductive and convective heat transfer
Implementation Method 3
the fluid to evaporate
Implementation Method 4
the evaporation and condensation of which mediates heat transfer
Implementation Method 5
where it condenses and gives up its heat
Implementation Method 6
Heat pipes are used for cooling and transferring heat away from hot objects to a physically separated cooler area or cooling device
Data Source
AI summary
A heat pipe can include a microchannel heat exchanger at the heat absorbing end and another heat exchanger which is optionally also a microchannel heat exchanger at the heat sink end, with one or more pipes flowably connecting the two ends for transporting liquid working fluid to the head absorber and vaporized working fluid to the heat sink. The heat pipes may be used to cool electronic devices with rejection of heat outside an enclosure, and optionally outside a room, containing the electronic devices. The heat pipes may be used to cool photovoltaic or solar collection devices with rejection of heat to ambient air at a distance removed from the photovoltaic devices. Heat pipe systems are disclosed wherein the working fluid is a hydrofluorocarbon or a mono-chlorinated hydrofluoroalkene having a normal boiling point in a range from 10° C. to 80° C.