Passive Internal Return Loop for Two-Phase Fluid Cooling

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Solution Overview

Problem

Existing two-phase cooling systems are inefficient due to the need for active coolant return, which requires energy input and can lead to increased heat generation, making it challenging to maintain optimal thermal environments in data centers with high-performance servers.

Innovation Solution

The implementation of a passive internal return loop that separates coolant in vapor and liquid states within a circulation cycle, allowing the liquid coolant to passively return to the supply line via gravity, thereby reducing energy consumption and improving cooling efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If active coolant return is used in two-phase cooling systems, then coolant circulation is achieved, but energy input increases and cooling efficiency decreases

Engineering Contradiction:

Improveenergy input for coolant circulationVSAvoidcooling efficiency

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The system uses the buoyancy force generated by the two-phase fluid itself to drive the return of liquid coolant to the supply manifold, eliminating the need for external pumps or active energy input. The vapor rises naturally to the condenser and the condensed liquid returns via gravity and pressure differential, creating a self-sustaining circulation loop

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces the mechanical pump system with a passive thermodynamic system that uses phase change, buoyancy, and pressure differentials to drive coolant circulation. This substitution eliminates mechanical energy input while maintaining effective coolant flow through the server racks

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If coolant is not separated by phase state, then circulation is simplified, but energy consumption increases due to active return requirements

Engineering Contradiction:

Improvecirculation system complexityVSAvoidenergy consumption for coolant return

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The system separates the coolant circulation into distinct phases: vapor上升 to the condenser, liquid return to the supply manifold, and distribution back to servers. This segmentation allows each phase to be handled by appropriate passive mechanisms (buoyancy for vapor, gravity/pressure for liquid), reducing overall energy consumption

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a separator as an intermediary component that divides the two-phase fluid into vapor and liquid portions. This intermediary enables the system to exploit the different physical properties of each phase (buoyancy of vapor, density of liquid) to achieve passive circulation without requiring active energy input

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If passive return loop is implemented, then energy consumption is reduced, but system complexity increases due to phase separation requirements

Engineering Contradiction:

Improveenergy consumption for coolant circulationVSAvoidsystem complexity for phase separation

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The system is designed with the supply manifold positioned at a higher elevation than the servers, creating a gravitational potential difference that drives liquid coolant return. This equipotentiality principle allows the liquid to flow back passively without requiring additional energy input, offsetting the added complexity of phase separation

Inventive Principle:

Principle #12Equipotentiality

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 solution enhances cooling efficiency by minimizing energy input required for coolant circulation, improving coolant management, and accommodating varying heat production discrepancies across server racks, thus maintaining optimal thermal conditions in data centers.

Implementation Method 1

the coolant operates to remove heat from the one or more electronic devices by transforming into a two-phase fluid comprising a liquid portion and a non-liquid portion

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 2

a separator disposed on an end of the one or more exit manifolds to receive the two-phase fluid therefrom. The separator separates the coolant in the vapor state from the coolant in the liquid state

Methodology Applied

Scientific EffectPhase separation: Phase Change

Implementation Method 3

a pump-free conduit connecting the separator and the supply manifold for transferring, using gravity, the liquid portion of the two-phase fluid back to the supply manifold

Methodology Applied

Scientific EffectGravity: Gravitation

Data Source

PatentUS12219741B2Server rack using a passive internal return loop for two-phase fluid cooling

Publication Date: 2025.02.04 BAIDU USA LLC

AI summary

The present disclosure provides apparatus, systems, methods, and techniques for cooling using a passive internal return loop with two-phase fluids. The cooling techniques may be applied to an advanced server rack having high power density servers. The server rack may be either packaged with one or more cooling modules or employ a fully sealed immersion configuration. For example, coolant in the vapor state may be separated from coolant in the liquid state in the two-phase coolant, and the coolant in the liquid state may be recirculated to cool the server (or other sub cooling systems) by gravity (i.e., pump-free).