Microtube Heat Exchanger Header With Porous Capillary Wicking
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Solution Overview
Problem
Traditional microtube heat exchangers face inefficiencies due to poor refrigerant distribution, leading to phase separation and reduced heat exchange efficiency, especially in systems with thousands of microtubes, as refrigerant vapor hinders liquid entry and causes uneven distribution.
Innovation Solution
Incorporating a porous insert with capillary force to distribute refrigerant uniformly across microtubes, utilizing capillary action to pull liquid refrigerant into the microtubes, thereby maintaining a mixture phase and minimizing phase change within the header.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional refrigerant distribution technology is used, then the system structure is simple, but the refrigerant distribution is uneven causing phase separation and reduced heat exchange efficiency
Solution Approach 1:
The patent applies porous materials (porous metal inserts or porous coatings on microtube surfaces) to the heat exchanger header to enable capillary wicking of refrigerant. The porous structure creates capillary forces that actively distribute two-phase refrigerant uniformly across all microtube inlets, preventing vapor-liquid separation and ensuring all channels receive adequate liquid refrigerant for efficient heat exchange.
Solution Approach 2:
The patent introduces a porous insert or porous coating as an intermediary element between the refrigerant flow and microtube inlets. This intermediary structure mediates the distribution process by using capillary action to actively transport and evenly distribute the refrigerant mixture, transforming passive gravitational flow into active capillary-driven distribution without requiring complex mechanical mixing devices.
2Productivity
If mixing devices or orifices are used to combine vapor and liquid, then refrigerant distribution improves, but the device complexity and weight increase
Solution Approach 1:
The patent enables the refrigerant distribution system to be self-service by utilizing the inherent capillary properties of porous materials. The porous structure automatically generates the force needed for distribution through capillary action, eliminating the need for external mixing devices, pumps, or complex mechanical components. The system uses the refrigerant's own properties and the porous material's capillary forces to achieve uniform distribution.
Solution Approach 2:
The patent replaces mechanical mixing devices and orifices with a passive porous structure that uses capillary forces instead of mechanical means. This substitution eliminates complex mechanical components while achieving superior refrigerant distribution through the physical phenomenon of capillary wicking in porous materials.
3Productivity
If open header configuration is used, then manufacturing is simple, but vapor expansion and separation are exacerbated reducing efficiency
Solution Approach 1:
The patent modifies the open header configuration by incorporating porous materials (inserts or surface coatings) that maintain the simplicity of the open structure while adding capillary wicking functionality. The porous structure prevents vapor expansion and separation by actively wicking liquid refrigerant across all microtube inlets, combining structural simplicity with enhanced distribution capability.
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
Enhances heat exchanger efficiency by ensuring even distribution of refrigerant, reducing phase separation, and eliminating the need for mixing devices, while maintaining weight and pressure drop minimal.
Implementation Method 1
a wicking insert disposed at a tube stack opening of inlet housing adjacent to and covering the refrigerant fluid inlet end of the tube stack assembly, where the wicking insert comprises a metal material and has a porous structure configured to provide a capillary force within the porous structure
Data Source
AI summary
A heat exchanger including a tube stack having a plurality of microtubes configured to transfer heat from a refrigerant to an external fluid. The heat exchanger includes an inlet housing disposed adjacent to a fluid-inlet side of the tube stack. The inlet housing includes a reservoir where refrigerant is stored and where, due to gravity, liquid of the refrigerant pools in a bottom of the reservoir. The heat exchanger includes a wicking insert disposed at a tube stack opening of inlet housing adjacent to and covering the fluid-inlet side of the tube stack. The wicking insert has a porous structure configured to provide a capillary force within the porous structure, and is disposed within the pooled liquid to draw the liquid from the bottom of the reservoir through the porous structure of the wicking insert by the capillary force.