Vehicle Heat Exchanger Airflow Layout for Faster Defrost Drainage
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Solution Overview
Problem
Vehicle air conditioners with heat pump devices face inefficiencies in defrosting, as stopping the exterior fan during defrosting mode allows water to remain on the heat exchanger, increasing the time required to remove heat and affecting occupant comfort, especially at low temperatures, due to uneven frosting and heat exchange issues.
Innovation Solution
The air conditioner adjusts airflow rates through the exterior heat exchanger, with higher flow rates near the refrigerant outlet during defrosting to efficiently drain water and reduce heat removal from the refrigerant, using multiple fans or a single fan offset towards the outlet to enhance airflow distribution and defrosting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exterior fan is stopped during defrosting mode to prevent water from being blown onto the heat exchanger, then water drainage is improved, but the defrosting time increases significantly because water remains on the heat exchanger and absorbs heat from the refrigerant
Solution Approach 1:
The patent applies dynamics by making the exterior fan's operating state variable rather than fixed. The fan operates at different speeds or states depending on the defrosting phase: stopped or low-speed during initial defrosting to prevent water dispersal, then activated at higher speed after water drainage is complete to accelerate water removal from the heat exchanger surface, thus resolving the contradiction between preventing water dispersal and accelerating water removal
Solution Approach 2:
The patent applies preliminary action by implementing a pre-defined multi-stage control sequence. Before the main water removal phase, the system first allows water to drain naturally by stopping or reducing fan operation, then activates the fan at optimized speeds in subsequent stages. This preliminary staged approach ensures water is properly drained before aggressive water removal begins, shortening overall defrosting time while preventing premature water dispersal
2Productivity
If the exterior fan runs at maximum speed during defrosting to quickly remove water, then water drainage is improved, but the heat exchange efficiency decreases because water on the heat exchanger absorbs heat from the refrigerant
Solution Approach 1:
The patent applies periodic action by dividing the defrosting process into distinct time stages with different fan operating modes. In the first period, the fan is stopped or runs at low speed to allow water drainage without aggressive air flow. In subsequent periods, the fan operates at progressively higher speeds to remove water efficiently. This periodic staged approach prevents water from absorbing excessive heat during the critical initial defrosting phase while still achieving rapid water removal later, thus resolving the contradiction between water removal rate and refrigerant heat loss
3Reliability
If the exterior fan is stopped during defrosting to allow water to drain, then water drainage is improved, but occupant comfort deteriorates due to extended defrosting time affecting heating performance
Solution Approach 1:
The patent applies dynamics by implementing variable fan speed control that adapts to different defrosting phases. Rather than simply stopping the fan throughout defrosting (which extends defrosting time and reduces occupant comfort), the system uses low speed initially to allow drainage, then transitions to higher speeds to quickly remove water and complete defrosting. This dynamic adjustment minimizes defrosting duration while maintaining effective water drainage, thereby preserving heating performance and occupant comfort
Solution Approach 2:
The patent applies preliminary action by implementing a pre-planned multi-stage fan control sequence during defrosting. The first stage allows water drainage with minimal fan operation, and subsequent stages progressively increase fan speed to rapidly remove water and complete defrosting. This preliminary staged approach ensures that while water drainage is effective, the overall defrosting time is minimized, thus maintaining heating performance and occupant comfort
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 configuration shortens the defrosting time, improves occupant comfort, and reduces the heat load on the refrigerant, ensuring efficient heating and defrosting performance even at low temperatures by effectively managing airflow and water drainage.
Implementation Method 1
an exterior blower which blows air toward the exterior heat exchanger
Implementation Method 2
the exterior heat exchanger functions as a heat absorber
Implementation Method 3
the frost formed on the exterior heat exchanger melts and turns into water
Data Source
AI summary
An exterior heat exchanger is provided with paths P1-P4. The flow rate of the air being blown by an exterior blower to pass through the path P4 closer to a refrigerant outlet of the exterior heat exchanger is set to be higher than that of the air being blown by the exterior blower to pass through the path P1 closer to a refrigerant inlet of the exterior heat exchanger. An air-conditioning controller activates cooling fans during a defrosting mode of operation.