Refrigerator Defrost Control Using Temperature Stable State Duration
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Solution Overview
Problem
In refrigerating apparatuses, the defrosting mode duration is often longer than necessary due to fixed factory-set conditions, which are not easily adjusted for varying temperature and humidity conditions, leading to increased internal temperatures.
Innovation Solution
The controller dynamically adjusts the defrosting termination conditions and capabilities based on the duration of the temperature stable state of the internal heat exchanger, allowing for earlier termination or enhanced defrosting capabilities by modifying target temperatures or compressor and fan operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the defrosting mode uses a fixed factory-set termination temperature, then the control logic is simple, but the defrosting time becomes longer than necessary when frost amount is small, resulting in increased internal temperature and energy waste
Solution Approach 1:
The patent applies dynamics by making the defrosting termination temperature dynamic rather than fixed. The controller adjusts the termination temperature based on the detected frost amount, allowing the system to adapt its operation parameters in real-time. When frost amount is small, the termination temperature is set lower to enable earlier termination; when frost amount is large, the termination temperature is set higher to ensure complete defrosting.
Solution Approach 2:
The patent changes the parameter of defrosting termination temperature based on the detected frost amount. By measuring the electrical resistance of the heat exchanger (which correlates with frost thickness) and adjusting the termination temperature accordingly, the system optimizes defrosting time while ensuring complete frost removal when necessary.
2Productivity
If the set condition for defrosting termination is changed manually, then the defrosting operation can be optimized for current conditions, but frequent manual adjustments are required due to seasonal temperature and humidity variations
Solution Approach 1:
The patent implements self-service by enabling the system to automatically detect frost amount and adjust the defrosting termination condition without manual intervention. The controller continuously monitors the heat exchanger's electrical resistance to determine frost thickness and autonomously sets the appropriate termination temperature, allowing the system to adapt to varying environmental conditions independently.
Solution Approach 2:
The patent uses feedback by continuously monitoring the electrical resistance of the heat exchanger during defrosting operation. This resistance measurement provides real-time information about the remaining frost amount, enabling the controller to adjust the termination condition dynamically and optimize defrosting efficiency based on actual system state.
3Reliability
If the defrosting mode terminates at a higher temperature to ensure complete frost removal, then frost removal is more reliable, but the defrosting mode takes longer to complete when only a small amount of frost is present
Solution Approach 1:
The patent applies local quality by setting different termination temperatures for different frost amount conditions. Instead of using a single high termination temperature for all cases, the system detects the local frost condition through electrical resistance measurement and applies the appropriate termination temperature - a lower temperature for small frost amounts and a higher temperature for large frost amounts.
Solution Approach 2:
The patent uses partial action by adjusting the defrosting termination condition to match the actual frost amount. When frost amount is small, the system uses a lower termination temperature (partial defrosting) rather than the full high temperature setting, thereby reducing defrosting time while still achieving complete frost removal for the actual frost present.
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 reduces unnecessary defrosting time and prevents prolonged defrosting operations without manual intervention, optimizing energy use and performance across varying conditions.
Implementation Method 1
during the defrosting mode, frost (ice) forming on the internal heat exchanger (71) is deprived of its latent heat and turns into water when removed by melting
Implementation Method 2
a heat exchanger is generally provided with a thermistor that senses the temperature of the heat exchanger
Data Source
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AI summary
A refrigerating apparatus (10) includes a controller (120). The controller (120) performs control to change conditions on which defrosting terminates or defrosting capability in accordance with a period of time during which a temperature stable state (i.e., a state where a temperature of an internal heat exchanger (71) is stable within a predetermined temperature range including 0°C) continues, during a defrosting mode in which frost on the internal heat exchanger (71) is removed. This prevents the period of time during which the defrosting is performed from being longer than required, without manually setting the conditions on which the defrosting mode terminates.