Heat exchanger for heat pump applications
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Solution Overview
Problem
Microchannel heat exchangers are sensitive to refrigerant charge imbalances, leading to performance degradation and nuisance shutdowns due to their smaller internal volume, and their refrigerant charge reduction potential is limited, especially when operating as a condenser.
Innovation Solution
A heat exchanger design featuring a flow restricting device with a longitudinally elongated distributor and a dividing plate, which includes angled openings to distribute refrigerant fluid oppositely to air flow and is integrated into a multi-pass configuration with headers that can be bent into desired shapes, optimizing refrigerant distribution and reducing pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If microchannel heat exchangers are used to reduce refrigerant charge, then refrigerant charge is reduced, but the system becomes more sensitive to charge imbalances causing performance degradation and shutdowns
Solution Approach 1:
The distributor creates local variations in flow characteristics by having openings at different angles (60-120 degrees) and positions relative to the heat exchange tubes. This local differentiation in flow distribution compensates for the overall reduced refrigerant charge, ensuring each section receives appropriate refrigerant flow to maintain system reliability.
Solution Approach 2:
The distributor modifies flow parameters by creating pressure drops through its angular openings and positioning them offset from the heat exchange tubes. This changes the refrigerant flow distribution pattern, allowing the system to operate reliably with reduced total refrigerant charge by optimizing local flow conditions.
2Manufacturing precision
If flow restricting devices are added to improve refrigerant distribution, then refrigerant distribution is enhanced, but device complexity increases
Solution Approach 1:
The distributor is segmented into multiple openings arranged at different angles (60-120 degrees) and positions along its length. This segmentation allows independent control of refrigerant flow to different sections, improving distribution uniformity while keeping each individual opening simple in structure.
Solution Approach 2:
The distributor serves multiple functions simultaneously: it restricts flow to create pressure drops, distributes refrigerant to multiple heat exchange tubes, and its angular openings create both flow restriction and directional control. This multi-functionality reduces the need for separate components, managing device complexity.
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 design enhances refrigerant distribution within the heat exchanger, improves system performance, and reduces manufacturing costs by maximizing the refrigerant charge efficiency and minimizing pressure drops, thus addressing the sensitivity to charge imbalances and enhancing operational reliability.
Implementation Method 1
the inlet having a generally angular contour that creates a pressure drop in the heat exchange fluid as it passes through the inlet
Implementation Method 2
a plurality of openings in the distributor arranged at an angle to each of the plurality of heat exchange tubes such that one or more of the openings does not directly face a corresponding tube
Implementation Method 3
a plurality of heat exchange tubes extending in a spaced parallel relationship between and fluidly connecting the first header and the second header
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A heat exchanger includes a first header and a second header. The second header has at least a first volume and a second volume. The second header additionally includes a bend region such that the second header has a non-linear configuration. A flow restricting element is arranged within the second header within the bend region. A plurality of heat exchange tubes is arranged in spaced parallel relationship and fluidly coupling the first header and second header.