Pool Boiling Heat Exchanger Tubes with Controlled Microcavities
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Solution Overview
Problem
Existing pool boiling systems in refrigeration and air-conditioning applications are inefficient and lack the ability to effectively utilize low global warming potential refrigerants, leading to suboptimal heat transfer performance and energy consumption.
Innovation Solution
A pool boiling system utilizing a heat exchanger tube with a microstructured surface featuring controlled size cavities, promoting efficient pool boiling through enhanced boiling heat transfer coefficients (HTC) using common and next-generation low-GWP refrigerants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional smooth surfaces are used in pool boiling systems, then the system structure is simple and easy to manufacture, but the heat transfer coefficient is low and energy efficiency is poor
Solution Approach 1:
The patent applies porous materials by creating a microstructured surface with controlled pore sizes (5-50 micrometers) on the heat exchanger tube. This porous structure increases the surface area and provides nucleation sites for bubble formation, significantly enhancing the boiling heat transfer coefficient by up to 250% compared to smooth surfaces, thereby improving energy efficiency without requiring complex external components
Solution Approach 2:
The patent changes the surface parameter from smooth to microstructured by controlling pore size, porosity, and surface roughness. These parameter changes optimize the boiling heat transfer process by facilitating bubble nucleation and growth, allowing the system to achieve higher heat transfer coefficients with low-GWP refrigerants while maintaining manufacturing feasibility through established surface treatment techniques
2Reliability
If microstructured surfaces with small cavities are used, then boiling heat transfer coefficient is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes porous materials with controlled pore diameters in the range of 5-50 micrometers, which can be manufactured using established techniques such as anodizing, etching, or sintering. These porous structures provide sufficient nucleation sites for effective boiling heat transfer while remaining within achievable manufacturing tolerances for industrial production
Solution Approach 2:
The patent may employ composite material approaches by combining base metal materials with porous surface coatings or treatments. This allows the bulk material to maintain structural integrity while the surface layer provides the optimized microstructure for heat transfer, separating the structural requirements from the heat transfer requirements and reducing manufacturing precision challenges
3Object-affected harmful factors
If low-GWP refrigerants are used, then environmental impact is reduced, but heat transfer performance may be suboptimal
Solution Approach 1:
The patent optimizes surface parameters including pore size (5-50 μm), porosity (10-50%), and surface roughness specifically tailored for low-GWP refrigerants. These parameter adjustments compensate for the different thermophysical properties of low-GWP refrigerants, enabling them to achieve heat transfer coefficients comparable to or exceeding those of traditional refrigerants
Solution Approach 2:
The porous microstructured surface enhances heat transfer performance with low-GWP refrigerants by providing numerous nucleation sites that facilitate bubble formation and improve liquid-vapor interface area. This porous structure compensates for the potentially lower heat transfer coefficients of low-GWP refrigerants, maintaining system reliability while reducing environmental impact
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 system achieves boiling heat transfer coefficients of at least 8 kW/m²K, with enhancements up to 250% for certain refrigerants, improving energy efficiency and reducing environmental impact.
Implementation Method 1
Pool boiling is a primary heat transfer mode widely used in flooded evaporators in water or air-cooled chillers
Implementation Method 2
heat can be absorbed by the pool boiling process from the chips, thereby efficiently cooling the component and taking advantage of the high latent heat
Implementation Method 3
the microstructured surface may promote highly efficient pool boiling... with a boiling heat transfer coefficient (ho) of at least about 8 kW/m2K
Implementation Method 4
heat can be absorbed by the pool boiling process from the chips, thereby efficiently cooling the component and taking advantage of the high latent heat
Data Source
AI summary
A system for transferring heat via pool boiling comprises a pool containing a liquid refrigerant and a component which is partially or fully submerged in the pool. The component has a microstructured surface including cavities having a linear size of at least 5 μm, and the microstructured surface is in contact with the liquid refrigerant. The system exhibits a pool boiling heat transfer coefficient (HTC) of at least 8 kW/m2K for a heat flux in a range from 15-85 kW/m2. In some examples, a refrigerant boiling HTC enhancement ratio of up to 2.5 or higher may be achieved using the component with the microstructured surface, in comparison with a plain (unetched) component.