Determining a defrosting time of an evaporator of a domestic refrigeration appliance
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Solution Overview
Problem
Existing methods for determining the defrosting time of evaporators in household refrigerators are not precise and can lead to unnecessary energy consumption and equipment failures due to indirect measurements, such as door openings, which do not account for actual moisture introduction or frost accumulation.
Innovation Solution
A method using a physical model to calculate an initial evaporator temperature assuming no frost, combined with real-time measured temperatures to calculate a deviation measure, triggering defrosting when this deviation exceeds a specified limit, ensuring precise and necessary defrosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect measurement methods (door openings) are used to determine defrosting time, then the control system is simple to implement, but the measurement precision is poor and does not reflect actual frost accumulation
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the evaporator temperature and comparing it with the setpoint temperature. The temperature deviation serves as feedback information that directly reflects the actual frost accumulation state, enabling precise defrosting control based on real thermal conditions rather than indirect proxies.
Solution Approach 2:
The patent replaces indirect mechanical/sensor-based frost detection methods with a thermal model-based approach. By using the temperature deviation from the evaporator surface, the system substitutes direct frost measurement with a thermal field-based inference that more accurately represents the actual frost condition.
2Reliability
If defrosting is triggered frequently to ensure reliable operation, then the reliability is improved, but the energy consumption increases due to unnecessary defrosting cycles
Solution Approach 1:
The patent implements dynamic defrosting control by continuously adjusting the defrosting decision based on real-time temperature deviation. Instead of fixed-time or fixed-cycle defrosting, the system dynamically responds to actual thermal conditions, triggering defrosting only when the temperature deviation indicates significant frost accumulation, thereby optimizing the balance between reliability and energy consumption.
Solution Approach 2:
The patent changes the control parameter from fixed time-based or door-opening-based triggers to temperature deviation-based triggers. By monitoring the evaporator temperature deviation from the setpoint, the system adapts the defrosting timing to actual operational conditions, reducing unnecessary defrosting cycles while maintaining reliable evaporator performance.
3Measurement precision
If direct temperature measurement on the evaporator is used, then the measurement precision is improved, but the device complexity increases due to additional sensors and measurement points
Solution Approach 1:
The patent makes the evaporator temperature sensor serve multiple functions: it simultaneously monitors the evaporator thermal state for control purposes and provides data for frost detection through temperature deviation analysis. This multi-functional use of a single sensor reduces the need for additional dedicated frost sensors while maintaining high measurement precision.
Solution Approach 2:
The patent merges the frost detection function with the existing evaporator temperature measurement system. By analyzing the temperature deviation of the evaporator surface from the setpoint, the system combines thermal monitoring and frost detection into a single integrated approach, eliminating the need for separate direct frost sensors and reducing overall system 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
This approach ensures reliable and precise defrosting only when necessary, saving energy and preventing unforeseen equipment failures by continuously monitoring and comparing model calculations with measured values.
Implementation Method 1
a first evaporator temperature is calculated by means of a physical model which has been set up without taking into account a layer of frost on the evaporator
Implementation Method 2
a second evaporator temperature is measured at the same time
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method (S1-S6) for determining the defrosting time of an evaporator (5) of a household refrigeration appliance (1), in which a first evaporator temperature (Tv_calc) is calculated using a physical model that has been established without considering a frost layer on the evaporator (5) (S1), a second evaporator temperature (Tv_mess) is measured simultaneously (S2), a deviation measure (Δ) between the first evaporator temperature (Tv_calc) and the second evaporator temperature (Tv_mess) is calculated (S3), and then, when the deviation measure (Δ) reaches or exceeds a predetermined limit value (S4), at least one defrosting operation is triggered by the household refrigeration appliance (1) (S5). The invention also relates to a household refrigeration appliance (1) configured to carry out the method (S1-S6). The invention is particularly advantageously applicable to refrigerators and freezers with finned evaporators.