Reversible Heat Exchanger Airflow for EV Heat Pump Deicing
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Solution Overview
Problem
Heat pump systems in electric vehicles face evaporator icing due to frost accumulation, leading to reduced heat transfer and airflow, and the need for battery heating consumes electrical power, which is not supplemented by waste heat generation.
Innovation Solution
A thermal management system with reversible air-side heat exchangers and a reversible impeller that can operate in forward and reverse airflow directions, using a selectable heat source to deice and recover heat, and an HVAC system to manage cabin heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the external heat exchanger operates in cold ambient temperatures below freezing, then heat can be drawn from ambient air, but frost accumulates on the evaporator surface leading to reduced heat transfer and airflow
Solution Approach 1:
The patent reverses the airflow direction through the heat exchangers during deicing mode. By switching the impeller rotation direction, ambient air flows through the previously downstream heat exchanger first, allowing it to serve as the deicing heat exchanger while the previously upstream heat exchanger becomes the cooling heat exchanger. This inversion enables effective deicing without compromising the cooling function.
Solution Approach 2:
The system uses itself to deice by switching between two heat exchangers. One heat exchanger performs cooling while the other performs deicing, and they periodically swap roles. This self-service approach eliminates the need for external deicing systems while maintaining continuous cooling capability.
2Temperature
If electric heating is used to heat the battery to threshold temperatures, then the battery can operate at optimal performance, but electrical power consumed from the battery increases
Solution Approach 1:
The patent converts the cold ambient air, which previously caused icing problems, into a useful resource for battery heating. By operating one heat exchanger in deicing mode with heated thermal fluid, the system recovers heat that would otherwise be wasted and uses it to warm the battery, eliminating the need for electric heating while maintaining battery performance.
Solution Approach 2:
The thermal management system performs multiple functions simultaneously: cooling the vehicle through one heat exchanger while heating the battery through the other heat exchanger using the same ambient air source. This multi-functionality eliminates the need for separate heating systems and reduces overall energy consumption.
3Use of energy by moving object
If ambient air is used as the heat source for cooling, then the system operates efficiently, but when the heat exchanger is below the dew point, moisture condenses and freezes on the heat exchanger
Solution Approach 1:
The system periodically switches between cooling and deicing modes for each heat exchanger. During normal operation, one heat exchanger cools while the other deices; after a set period, they swap roles. This periodic action prevents excessive frost accumulation on either heat exchanger while maintaining continuous cooling efficiency.
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
Effectively prevents frost formation on heat exchangers and recovers waste heat, reducing electrical power consumption for heating and improving system efficiency.
Implementation Method 1
supply heat to elevate a temperature of a first thermal fluid to supply a heated first thermal fluid to the air-side heat exchanger
Implementation Method 2
by operation of a reversible impeller, the airflow can be directed in a reverse direction as the air-side heat exchanger is operated as the heat rejecting heat exchanger
Implementation Method 3
operate, as the air-side heat exchanger is operated as the heat rejecting heat exchanger, the other air-side heat exchanger as a heat absorbing heat exchanger to recover at least a portion of a heat rejected
Data Source
AI summary
A thermal management system configured to selectively control a flow direction of ambient air across a stack of air-side heat exchangers. During a first mode of operation, an impeller can facilitate ambient air flowing over a second air-side heat exchanger, through which a refrigerant may flow, before the ambient air flows over a first air-side heat exchanger, thereby exposing the second air-side heat exchanger, which can be operating as a condenser, to potentially colder ambient air. In a second mode of operation, the impeller can facilitate an airflow over the first-air side heat exchanger before flowing over the second air-side heat exchanger. As the second air-side heat exchanger can operate as an evaporator during the second mode, the second air-side heat exchanger can recapture from the ambient air at least a portion of heat transferred from the first air-side heat exchanger, and transfer the recaptured heat to the refrigerant.