Two-Phase Heat Transfer Assembly with Wettability Gradient
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Solution Overview
Problem
Conventional heat sinks are inadequate in effectively lowering the operating temperature of power electronics due to increased heat flux generated by higher power levels in newly developed electrical systems, necessitating enhanced thermal energy transfer solutions.
Innovation Solution
A two-phase heat transfer assembly featuring a cold plate with an impingement surface having a central hydrophilic region surrounded by a hydrophobic perimeter, where the wettability gradually transitions from hydrophilic to hydrophobic, and an array of spray nozzles directing coolant droplets toward the impingement surface, causing them to migrate inwardly toward the central hydrophilic region for improved heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional heat sinks are used, then the structure is simple and easy to manufacture, but the thermal energy transfer capability is insufficient to handle increased heat flux from high power electronic devices
Solution Approach 1:
The impingement surface is engineered with spatially varying wettability properties: a central hydrophilic region surrounded by a hydrophobic perimeter. This local differentiation causes coolant droplets to migrate toward the center where heat flux is maximum, enhancing thermal energy transfer at the most critical location without requiring complete system redesign
Solution Approach 2:
The wettability parameter of the impingement surface is modified through chemical treatment or surface coating to create distinct hydrophilic and hydrophobic zones. This parameter change enables passive directional control of coolant distribution, improving heat transfer efficiency without adding mechanical complexity
2Loss of energy
If spray nozzles are added to direct coolant droplets, then thermal transfer is enhanced, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The hydrophobic perimeter passively directs coolant droplets toward the central hydrophilic region without requiring active control mechanisms. The surface wettability gradient automatically guides coolant flow to match the heat flux distribution, eliminating the need for complex valve systems or active flow control
Solution Approach 2:
Mechanical flow control mechanisms are replaced with surface chemistry-based wettability gradients. The passive capillary and surface tension effects at the hydrophobic-hydrophilic interface substitute for mechanical pumping or valving systems, simplifying the overall device architecture
3Loss of energy
If coolant droplets are distributed uniformly across the surface, then the system is simple to control, but the coolant is not concentrated at the area of maximum heat flux where it is most needed
Solution Approach 1:
The impingement surface features a central hydrophilic region surrounded by a hydrophobic perimeter, creating localized wettability differences that passive direct coolant migration toward the center. This local quality variation ensures coolant concentrates at the heat flux maximum without requiring complex distribution control systems
Solution Approach 2:
The wettability gradient acts as an intermediary mechanism between the spray nozzle and the heat generating device. It passively mediates coolant distribution by guiding droplets from the periphery toward the central region through surface tension and capillary effects, eliminating the need for active 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
This configuration enhances thermal energy transfer by ensuring more coolant is present at the area of maximum heat flux, thereby improving cooling efficiency and effectively managing the increased heat generated by power electronics.
Implementation Method 1
The wettability of the impingement surface gradually progresses from hydrophilic at the central hydrophilic region to hydrophobic at the hydrophobic perimeter, and the central hydrophilic region receives a heat flux from a heat generating device coupled to the cold plate. The wettability of the impingement surface of the cold plate causes the coolant droplets to move inwardly toward the central hydrophilic region from the hydrophobic perimeter.
Implementation Method 2
The wettability profile of the impingement surface causes the coolant droplets to move inwardly toward the individual central hydrophilic regions from each hydrophobic perimeter
Implementation Method 3
Cooling fluid may be used in heat transfer devices to receive heat generated by the heat generating device by convective thermal transfer, and remove such heat from the heat generating device
Implementation Method 4
Other heat transfer devices may remove thermal energy by two-phase heat transfer, wherein coolant fluid is converted from a liquid phase to a gas phase at the location of thermal flux
Data Source
AI summary
A two-phase heat transfer assembly includes a cold plate having an impingement surface, an array of heat generating device coupled to the cold plate, and an array of spray nozzles. The impingement surface has an array of central hydrophilic regions. Each individual central hydrophilic region is surrounded by a hydrophobic perimeter. A wettability of the impingement surface gradually progresses from hydrophilic at each individual central hydrophilic region to hydrophobic at each hydrophobic perimeter. The array of heat generating devices is coupled to a heated surface of the cold plate such that the array of central hydrophilic regions is aligned with the array of heat generating devices. The array of spray nozzles is configured to direct coolant droplets toward the impingement surface. The wettability profile of the impingement surface of the cold plate causes the coolant droplets to move inwardly toward the individual central hydrophilic regions from each hydrophobic perimeter.