Multi-Zone Tube Circuiting for Plate-Fin Heat Exchangers
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Solution Overview
Problem
Existing plate-fin continuous tube heat exchangers are limited to single-zone circuiting, leading to unbalanced superheat conditions and thermal inefficiencies due to non-uniform airflow distribution and refrigerant leakage at joints, which restricts heat transfer efficiency.
Innovation Solution
A multi-zone circuiting design for continuous tube heat exchangers that allows refrigerant circuits to span across multiple airflow zones, utilizing nested tube arrangements and crossover bend portions to balance superheat levels and enhance heat transfer, while minimizing refrigerant leaks through continuous tube construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-zone circuiting is used in plate-fin continuous tube heat exchangers, then the structure is simple and manufacturing is easier, but unbalanced superheat conditions and thermal inefficiencies occur due to non-uniform airflow distribution
Solution Approach 1:
The heat exchanger is divided into multiple airflow zones (first airflow zone, second airflow zone, etc.) with each zone having dedicated tube circuits. This segmentation allows independent optimization of refrigerant flow in each zone to match the non-uniform airflow distribution, balancing superheat levels across all zones and improving thermal efficiency without excessive complexity
Solution Approach 2:
Different tube circuits are designed with different configurations (e.g., number of passes, tube arrangements) tailored to specific airflow zones. For example, zones with higher airflow rates can have circuits optimized for those conditions, allowing local adaptation to airflow variations and preventing unbalanced superheat conditions that would occur with uniform single-zone circuiting
2Ease of manufacture
If brazed joints are used in hairpin and return bend copper tubes, then tube circuits can be formed, but refrigerant leakage occurs and manufacturing time and effort increase
Solution Approach 1:
The patent employs continuous tubes that extend through multiple passes and zones without interruption, eliminating the need for brazed joints at bend locations. The continuous tube design maintains uninterrupted refrigerant flow and eliminates leakage points, while still forming complex multi-zone circuit patterns through careful routing and nesting of continuous tubes
Solution Approach 2:
Multiple continuous tube circuits are nested within each other to form compact multi-zone circuit configurations. The tubes are arranged in nested patterns that allow them to pass through the same fin sections at different positions, creating complex circuit paths without requiring joints or connections, thus maintaining reliability while achieving desired circuit complexity
3Shape
If circuits are exposed to non-uniform airflow rates, then geometric constraints are satisfied, but superheat levels vary dramatically resulting in unbalanced superheat conditions
Solution Approach 1:
The heat exchanger is divided into multiple airflow zones with dedicated tube circuits for each zone. This segmentation allows the superheat control to be localized to each zone, with circuits in high airflow zones and low airflow zones independently optimized to achieve balanced superheat levels across all zones despite the non-uniform overall airflow distribution
Solution Approach 2:
The patent varies circuit parameters (number of passes, tube arrangement, circuit length) across different airflow zones to compensate for airflow rate variations. By changing these parameters locally in each zone, the heat transfer characteristics are adjusted to balance superheat levels despite exposure to different airflow rates, converting the geometric constraint into a controllable parameter for superheat management
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 multi-zone circuiting design balances superheat levels, maximizes heat transfer efficiency, and reduces refrigerant leakage, improving thermal performance and manufacturing efficiency by allowing airflow to evenly distribute across the heat exchanger width.
Implementation Method 1
a first tube of continuous construction is coupled to the inlet port and to the outlet port and forms a first refrigerant circuit spanning three or more passes from the first end to the second end. The first refrigerant circuit passes between at least two zones of the plurality of zones.
Data Source
AI summary
A multi-zone heat exchanger has a first end and a second end and a width divided into a plurality of parallel airflow zones. Each zone defines an airflow section of the heat exchanger that receives a portion of the airflow through the heat exchanger. A first tube of continuous construction is coupled to an inlet port and to an outlet port and forms a first refrigerant circuit spanning three or more passes from the first end to the second end. The first refrigerant circuit passes between at least two zones of the plurality of zones. A second tube of continuous construction is coupled to the inlet port and to the outlet port and forms a second refrigerant circuit spanning three or more passes from the first end to the second end. The second refrigerant circuit passes between the at least two zones of the plurality of zones.