Subsea Two-Phase Cooling System Pressure Equalization
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Solution Overview
Problem
Current subsea cooling systems for power electronics face challenges in reducing the size and cost of thick-walled heat exchangers and maintaining efficient cooling while withstanding deep-sea pressures, with single-component fluids lacking suitable critical pressures and boiling temperatures for effective two-phase cooling.
Innovation Solution
A two-phase cooling system with a closed loop comprising an evaporator, condenser, and conduit, using a mixture of cooling fluid components that provide a thermodynamic two-phase state at deep-sea pressures, and a pressure compensating vessel with a valve to adapt pressure and prevent overpressure, along with a mechanically flexible enclosure to transmit ambient pressure, allowing for efficient and robust cooling without thick walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard electric/electronic components are used in atmospheric pressure enclosures, then component availability is improved, but wall thickness must be increased to withstand pressure difference
Solution Approach 1:
The invention changes the pressure parameter inside the enclosure from atmospheric pressure to hydrostatic pressure matching the surrounding seawater. This parameter change eliminates the pressure differential across the walls, allowing the use of thin-walled enclosures while still protecting standard atmospheric-pressure-rated electronic components through pressure equalization rather than pressure resistance.
Solution Approach 2:
The invention introduces a pressure equalization system that acts as an intermediary between the external hydrostatic pressure and the internal atmospheric pressure environment. By using a flexible diaphragm or bellows mechanism coupled with a compensating fluid or spring system, the invention mediates the pressure difference, allowing thin walls to suffice while maintaining component safety.
2Strength
If thick walls are used to withstand pressure difference, then structural strength is improved, but heat transfer efficiency deteriorates
Solution Approach 1:
The invention changes the internal pressure parameter to match external hydrostatic pressure, eliminating the need for thick pressure-resistant walls. This parameter change directly resolves the heat transfer problem by allowing thin-walled enclosures that conduct heat efficiently while still providing adequate mechanical strength through pressure equalization rather than pressure resistance.
3Device complexity
If single-component cooling fluids are used, then system simplicity is improved, but cooling effectiveness deteriorates due to lack of suitable critical pressures and boiling temperatures
Solution Approach 1:
The invention uses composite cooling fluids consisting of multiple components (e.g., refrigerant mixtures like R-125/R-134a or R-32/R-125) rather than single-component fluids. These composite fluids are specifically selected to have critical pressures and boiling temperatures suitable for deep-sea operating conditions, enabling effective two-phase cooling cycles at high ambient pressures where single-component fluids fail to provide adequate thermal performance.
Solution Approach 2:
The invention changes the thermodynamic parameters of the cooling fluid by using multi-component mixtures with tailored phase change characteristics. The composite fluids are engineered to maintain appropriate boiling points and critical pressures at deep-sea ambient conditions, fundamentally changing the thermal properties to match the high-pressure environment and enable reliable two-phase cooling.
4Length of stationary object
If equipment is pressurized to hydrostatic pressure level, then wall thickness can be reduced, but components with gas inclusions implode
Solution Approach 1:
The invention changes the internal pressure parameter from atmospheric to hydrostatic pressure, but implements this change gradually and controllably. By using pressure equalization mechanisms with flexible diaphragms and compensating systems, the invention allows components to adapt to pressure changes slowly, preventing implosion of components with gas inclusions while still enabling thin-walled construction.
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
Enables robust, efficient, and cost-effective subsea cooling by maintaining a vapour-liquid equilibrium at deep-sea pressures, reducing the need for thick walls and ensuring continuous pressure adaptation, thus enhancing thermal performance and reducing equipment failure risks.
Implementation Method 1
a two-phase cooling system arranged to cool an electronic or electric device
Implementation Method 2
maintaining a vapour-liquid equilibrium at deep-sea pressures
Implementation Method 3
The evaporator is arranged to be in thermal connection with the electric or electronic device
Implementation Method 4
The condenser is arranged to be in thermal connection with an exterior of the enclosure
Implementation Method 5
The condenser is arranged to be in thermal connection with an exterior of the enclosure
Implementation Method 6
which enclosure has a portion that is mechanically flexible such that an ambient subsea pressure can be transmitted to the inside of the enclosure
Implementation Method 7
wherein the subsea unit comprises a liquid for counteracting deformation of the enclosure when subject to an ambient subsea pressure higher than a pressure that the enclosure can withstand
Data Source
Figure 1a~1b
Figure 2a~2b
AI summary
The present disclosure relates to a subsea unit (1-A) arranged to house an electric or electronic device (11). The subsea unit (1-A) comprises a two-phase cooling system (2) arranged to cool the electric or electronic device (11), which two-phase cooling system (2) has an evaporator (4), a condenser (5), and a conduit (3) which together with the evaporator (4) and condenser (5) forms a closed loop for circulating a cooling fluid, wherein the evaporator (4) is arranged to be in thermal connection with the electric or electronic device (11), and wherein the subsea unit (1-A) has an enclosure (1-1) arranged to enclose the two-phase cooling system (2), which enclosure (1-1) has a portion that is mechanically flexible such that an ambient subsea pressure can be transmitted to the inside of the enclosure, and wherein the subsea unit (1-A) comprises a liquid (L) for counteracting deformation of the enclosure when subject to an ambient subsea pressure higher than a pressure that the enclosure can withstand. A subsea power system is also presented herein.