Liquid cooled heat exchanger
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Solution Overview
Problem
Existing liquid cooled heat exchangers face challenges with high pressure drops and fluid maldistribution due to phase changes in coolant, leading to inefficient heat transfer and temperature gradients, particularly in high-power electronics cooling applications.
Innovation Solution
A dual-chamber heat exchanger design with a first chamber for boiling and a second chamber for pre-heating subcooled fluid, utilizing capillary tubes and flow restrictors to stabilize pressure drop and promote efficient two-phase cooling, minimizing temperature gradients and ensuring consistent fluid distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a liquid cooled heat exchanger uses phase change cooling, then heat transfer efficiency is improved, but pressure drop increases and fluid maldistribution occurs
Solution Approach 1:
The heat exchanger is divided into multiple independent channels, each containing its own heat sink and flow path. This segmentation ensures uniform fluid distribution across all channels while maintaining efficient two-phase heat transfer in each individual channel, preventing the fluid maldistribution that would occur in a single large channel system
Solution Approach 2:
Each channel is equipped with localized flow distribution features including flow distributors and capillary wicking structures at the inlet regions. These local modifications ensure that cooling fluid is evenly distributed to each channel's heat sink, addressing the fluid maldistribution problem at the specific location where it occurs without affecting the overall phase change cooling efficiency
2Quantity of substance
If cooling fluid pressure is reduced to improve flow, then fluid flow rate increases, but pressure drop becomes more sensitive to vapor quality
Solution Approach 1:
Traditional mechanical flow control valves and pressure regulation systems are replaced with passive capillary wicking structures and microstructured flow channels. These structures provide flow resistance through capillary forces and viscous effects rather than mechanical components, enabling stable flow rate control that is less sensitive to vapor quality changes while maintaining adequate cooling fluid supply
Solution Approach 2:
The flow channel geometry and capillary dimensions are specifically designed to optimize the balance between flow rate and pressure drop sensitivity. By adjusting parameters such as channel diameter, length, and capillary pore size, the system achieves stable operation across varying vapor qualities without requiring active pressure regulation
3Productivity
If heat sink fins are enclosed in a sealed cavity, then heat transfer to circulating fluid is improved, but manufacturing complexity increases
Solution Approach 1:
The heat sink fins are permanently bonded to the base plate, forming an integrated heat transfer assembly. This merging of components eliminates the need for separate assembly steps for attaching fins to the base, reducing manufacturing complexity while maintaining the sealed cavity design that enables efficient heat transfer to the circulating cooling fluid
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 design achieves stable pressure drop and uniform fluid distribution across multiple heat exchangers, maintaining consistent cooling performance despite varying power demands and phase changes, enhancing heat transfer efficiency and reducing temperature variations.
Implementation Method 1
the working fluid can be boiled by heat received from the first heat sink in the first heat exchange chamber
Implementation Method 2
where the cooling fluid can be at least partially vaporized
Implementation Method 3
the second heat exchange chamber can be thermally coupled to the first heat exchange chamber to receive heat from the first heat exchange chamber and transfer the heat to the liquid working fluid in the second heat exchange chamber
Implementation Method 4
Cooling fluid can be provided to the second heat sink via a capillary tube, which can function to suitably reduce a pressure of the cooling liquid, provide an appropriate flow rate of cooling fluid to the system
Data Source
AI summary
A liquid cooled heat exchanger includes first and second heat exchange chambers that are in thermal communication. The first heat exchange chamber is downstream of the second heat exchanges chamber and receives heat from a heat generating device, such as an electronic circuit. Heat in the first heat exchange chamber can be transferred to the second heat exchange chamber to increase the temperature of a subcooled liquid working fluid in the second heat exchange chamber. This can render a pressure drop across the heat exchanger that is relatively insensitive to a fraction of liquid that is vaporized in the first heat exchange chamber.