Heat Pump Defrost Initiation Using Coolant Temperature Feedback
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Solution Overview
Problem
Existing methods for initiating defrosting processes in heat exchangers of motor vehicle heat pumps are prone to unnecessary activations due to temporary suction pressure drops and external influences, leading to incorrect detection of icing conditions.
Innovation Solution
A method that determines the icing state of the heat exchanger using the coolant outlet temperature from the coolant heat exchanger, initiating defrosting when icing is detected, and can be combined with other methods to reduce sensitivity to external factors, involving parameters like coolant temperature difference, coolant volume flow, and ambient air speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If suction pressure monitoring is used to detect icing conditions, then defrosting can be initiated when ice forms on the heat exchanger, but unnecessary defrosting may occur due to temporary suction pressure drops during motor vehicle start-up
Solution Approach 1:
The patent introduces an intermediary parameter (coolant outlet temperature or coolant temperature difference) to detect icing conditions indirectly. Instead of directly monitoring suction pressure which is affected by multiple factors including start-up transients, the system uses the coolant temperature at the outlet of the coolant heat exchanger as a mediator that reflects the air mass flow conditions through the heat exchanger. This intermediary measurement is less sensitive to temporary pressure drops and provides a more reliable indication of actual icing conditions.
Solution Approach 2:
The system implements feedback by continuously monitoring the coolant outlet temperature and comparing it against reference values or thresholds. When the temperature deviates from the expected range (indicating reduced air flow due to icing), the system triggers a defrosting process. This closed-loop feedback mechanism allows the system to adapt to changing operating conditions and distinguish between temporary disturbances and actual icing events.
2Measurement precision
If additional sensors are used to measure ice layer thickness on the heat exchanger, then detection precision can be improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing coolant heat exchanger serve a dual function: its primary function remains cooling the motor vehicle components, and its secondary function becomes the detection of icing conditions on the heat exchanger. By measuring the coolant outlet temperature from this existing component, the system achieves ice detection without adding dedicated sensors to the heat exchanger itself, thus maintaining measurement precision while avoiding increased device complexity.
Solution Approach 2:
The system uses the coolant flow through the heat exchanger as a self-diagnostic tool. The coolant acts as a probe that automatically provides information about the heat exchanger's performance by changing its outlet temperature when air flow is restricted by ice. This self-service approach eliminates the need for separate detection sensors, as the coolant itself reveals the icing condition through its temperature characteristics.
3Speed
If suction pressure monitoring is used, then the system can respond quickly to icing conditions, but external influences cause false detection of icing states
Solution Approach 1:
The patent changes the detection parameter from suction pressure to coolant outlet temperature. This parameter change makes the detection system more reliable because the coolant temperature is less susceptible to external influences such as temporary pressure drops, ambient temperature fluctuations, and vehicle dynamics. The coolant temperature provides a more stable and accurate indicator of the actual thermal conditions at the heat exchanger, reducing false detections while maintaining responsive defrosting initiation.
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 approach ensures accurate detection of icing conditions, reducing unnecessary defrosting and allowing for combination with existing methods, thereby enhancing the reliability and efficiency of heat pump operation by using coolant outlet temperature and other parameters to determine the icing state.
Implementation Method 1
a coolant outlet temperature of a coolant from the coolant heat exchanger is determined
Implementation Method 2
The heat required for heating is taken from the outside air. To do this, a heat exchanger of the heat pump, also called an ambient heat exchanger, must be cooled below the ambient temperature.
Implementation Method 3
If the outside air falls below its dew point, frost forms on the surface of the heat exchanger, which prevents the air from flowing through the heat exchanger.
Implementation Method 4
During the defrost cycle, the ice melts and outside air can flow through the heat exchanger again.
Data Source
Figure 1
AI summary
To provide a method for initiating a defrosting process of a heat exchanger of a heat pump of a motor vehicle that is insensitive to external influences and can also be used in combination with other methods, a method (100) for initiating a defrosting process of a heat exchanger (10) of a heat pump (11) of a motor vehicle (200), in particular an electric vehicle or a battery electric vehicle (12) or a hybrid electric vehicle, is proposed, wherein the heat exchanger (10) and a coolant heat exchanger (13) of a cooling circuit (14) of the motor vehicle (200) are arranged in a common air path (15), wherein a coolant outlet temperature of a coolant from the coolant heat exchanger (13) is determined, wherein an icing state of the heat exchanger (10) is determined using the coolant outlet temperature.wherein a defrosting process of the heat exchanger (10) is initiated when icing of the heat exchanger (10) is detected.