Sub-freezing Heat Exchanger Bypass Valve Segmentation
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Solution Overview
Problem
Existing aircraft environmental control systems (ECS) face issues with air-liquid heat exchanger freezing and inadequate operating conditions due to bypass valve placement, leading to inefficient heat transfer and potential freezing of components.
Innovation Solution
An air-liquid heat exchanger assembly with a rotatable bypass valve positioned between two chambers, allowing all available liquid to flow through the first chamber and optionally bypassing the second chamber, ensuring efficient heat transfer and maintaining a melt margin by preventing the coldest air stream from interacting with the warmest liquid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a bypass valve is positioned upstream of the entire air-liquid heat exchanger to allow liquid to bypass the heat exchanger assembly, then the downstream mix temperature can be attained, but portions of the heat exchanger cold air circuit may freeze or deviate from adequate operating conditions
Solution Approach 1:
The heat exchanger is divided into two separate chambers (first chamber and second chamber) with the bypass valve positioned between them. This segmentation allows the bypass valve to control liquid flow to the second chamber independently, ensuring that the first chamber always receives full liquid flow to prevent freezing, while the second chamber can be bypassed to adjust downstream mix temperature.
Solution Approach 2:
The bypass valve acts as an intermediary element positioned between the two chambers, controlling the distribution of liquid flow. By positioning the valve between chambers rather than upstream of the entire assembly, it mediates the flow distribution to ensure the first chamber receives adequate liquid flow while allowing optional bypassing of the second chamber for temperature control.
2Temperature
If the bypass valve is positioned upstream of the entire heat exchanger, then temperature control is achieved, but heat transfer efficiency decreases due to potential freezing
Solution Approach 1:
Dividing the heat exchanger into two chambers with the bypass valve positioned between them ensures that the first chamber always operates with full liquid flow, maintaining optimal heat transfer efficiency and preventing freezing, while the second chamber can be bypassed for temperature adjustment without compromising overall heat transfer performance.
3Productivity
If the heat exchanger is designed to meet performance requirements, then heat transfer efficiency is maintained, but the risk of freezing increases with upstream bypass valve placement
Solution Approach 1:
The heat exchanger is segmented into two chambers with the bypass valve positioned between them, ensuring that the first chamber always receives full liquid flow to prevent freezing while maintaining heat transfer performance. The second chamber can be bypassed when needed without affecting the protective flow through the first chamber.
Solution Approach 2:
The design proactively prevents freezing by ensuring the first chamber always receives full liquid flow through the bypass valve positioning, countering the potential harmful effect of freezing before it can occur. This preliminary protective action maintains heat transfer performance while eliminating freezing risk.
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 design prevents freezing, enhances heat transfer efficiency, and allows for a compact, efficient heat exchanger that meets performance and pressure drop requirements across all operating conditions.
Implementation Method 1
an air-liquid heat exchanger assembly for an environmental control system of an aircraft includes a first chamber and an adjacent second chamber. A surface of the first chamber is slightly separated from an opposite surface of the second chamber by a separator, such as by an insulation gap or double closure bars for example.
Data Source
AI summary
An air-liquid heat exchanger assembly (100) for an environmental control system (10) of an aircraft is provided including a heat exchanger configured to transfer heat between air (B) and a liquid (L). The heat exchanger includes a first chamber (110) and a second chamber (120) arranged generally in series relative to a flow of the liquid (L). A movable bypass valve (130) is operably coupled to a controller (140). The bypass valve (130) is positioned between and coupled to the first chamber (110) and the second chamber (120). The bypass valve (130) is configured to control the flow of the liquid (L) through the second chamber (120) and a bypass conduit (146) in response to measured operating conditions of the assembly.