Pulsating Heat Pipe Tube Diameter for Vertical Startup Stability

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Solution Overview

Problem

Pulsating heat pipes are limited by the maximum hydraulic diameter, preventing them from functioning when the tube diameter exceeds this limit, which restricts their development and heat transfer performance.

Innovation Solution

A method for designing the startup critical tube diameter of pulsating heat pipes in a vertical state is developed by establishing mass models before and after heat addition, considering the physical properties, temperatures, and filling ratio to determine the optimal diameter for enhanced heat transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the tube diameter of pulsating heat pipe is increased beyond maximum hydraulic diameter, then heat transfer performance and application scope are improved, but the pulsating heat pipe cannot function properly

Engineering Contradiction:

Improveheat transfer performanceVSAvoidfunctional reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the design parameter from maximum hydraulic diameter to startup critical tube diameter, which is a larger diameter value. This parameter change allows the pulsating heat pipe to maintain functional reliability (vapor plug formation) while achieving improved heat transfer performance through larger tube diameter operation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs preliminary analysis of mass conservation before and after heat addition to establish the startup critical tube diameter design method. This preliminary theoretical work enables the pulsating heat pipe to be designed with larger diameters while ensuring proper functioning from the outset.

Inventive Principle:

Principle #10Preliminary action

2Stability of the object's composition

If the tube diameter is limited by maximum hydraulic diameter, then liquid slug can be suspended in vapor plug, but the development towards large pipe diameter is restricted

Engineering Contradiction:

Improveliquid slug suspension stabilityVSAvoidpipe diameter range

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent transitions from the maximum hydraulic diameter parameter to the startup critical tube diameter parameter, which permits a broader pipe diameter range. This parameter substitution maintains liquid slug suspension stability through proper vapor plug formation while enabling adaptation to various larger diameter applications.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extends the design criterion from a diameter-limiting constraint to a startup critical diameter based on mass conservation principles. This dimensional shift in design approach allows the system to operate in a broader diameter dimension while maintaining compositional stability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 approach allows pulsating heat pipes to operate effectively with larger diameters, improving heat transfer performance and expanding their application scope, especially in high heat flux density conditions, while reducing costs by using cheaper working media and thicker pipe diameters.

Implementation Method 1

the phase change heat transfer of the working fluid

Methodology Applied

Scientific EffectPhase change heat transfer: Phase Change

Implementation Method 2

the working fluid absorbs heat at the heat-absorbing end to generate bubbles at an evaporation temperature lower than the temperature at normal pressure

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

rapidly expands and boosts pressure

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 4

the oscillation of the working fluid of the pulsating heat pipe in the evaporation section and the condensation section can cause forced convection in the pipe

Methodology Applied

Scientific EffectForced convection: Forced Convection

Implementation Method 5

filled with working fluid under vacuum to form vapor-liquid interval state under the action of surface tension and flow resistance

Methodology Applied

Scientific EffectSurface tension: Surface Tension

Data Source

PatentUS11460253B2Method for designing startup critical tube diameter of pulsating heat pipe in vertical state

Publication Date: 2022.10.04 DALIAN MARITIME UNIVERSITY

AI summary

A method for designing startup critical tube diameter of pulsating heat pipe in vertical state, including the following steps: step 1. establishing a first model of working medium mass in pulsating heat pipe; step 2. establishing a second model of working medium mass in pulsating heat pipe, the second model including the vapor working medium mass model and the liquid working medium mass model in the pulsating heat pipe; step 3. according to the law of conservation of mass, combining the first model and the second model, and determining the volume percentage of the liquid working medium in the total length of the pulsating heat pipe under the condition of heat addition; step 4. determining the startup critical tube diameter of the pulsating heat pipe according to the volume percentage of the liquid working medium in the total length of the pulsating heat pipe under the condition of heat addition obtained in step 3, the physical properties of the working medium in the pulsating heat pipe, the temperatures at the heat-absorbing end and heat-releasing end, the heating power, and the filling factor.