Evaporator Defrost Control Using Variable Compressor Cooling Capacity
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Solution Overview
Problem
Current adaptive defrost algorithms for refrigerators with variable cooling capacity compressors overestimate frost buildup, leading to frequent defrost procedures and reduced performance, as they fail to account for the variable cooling capacity's impact on frost creation, resulting in higher energy consumption and lower efficiency.
Innovation Solution
A control algorithm that estimates cooling capacity using only the frequency of the inverter driving the compressor, allowing for improved defrost timing and reducing the need for additional sensors, by translating existing adaptive defrost algorithms to accommodate variable cooling capacity compressors through the relationship ice ∝ CC ∼ A0 + A1 ⋅ freq, where CC is the cooling capacity and freq is the compressor frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current adaptive defrost algorithms are used without considering variable cooling capacity, then the control system is simple, but frost buildup is overestimated leading to frequent unnecessary defrost procedures
Solution Approach 1:
The patent changes the parameter used for defrost estimation from constant assumptions to variable parameters that reflect actual compressor operation. By using compressor run time percentage and cooling capacity data, the system dynamically adjusts frost buildup estimation to match actual operating conditions, preventing overestimation and unnecessary defrost cycles.
Solution Approach 2:
The system implements feedback by continuously monitoring actual compressor performance data and using it to refine defrost timing decisions. The control algorithm compares estimated frost buildup with actual operating conditions and adjusts defrost scheduling accordingly, creating a closed-loop system that improves accuracy over time.
2Loss of energy
If variable cooling capacity is used to reduce frost creation, then energy efficiency improves, but existing defrost algorithms overestimate frost buildup
Solution Approach 1:
The patent transforms the estimation approach by changing from fixed parameter assumptions to variable parameters that track actual compressor performance. The system uses real-time data on compressor run time and cooling capacity to dynamically calculate frost buildup, ensuring accurate estimation even when operating at reduced cooling capacities for energy efficiency.
3Loss of energy
If compressor run time is reduced to lower cooling capacity and frost creation, then energy efficiency improves, but defrost algorithms cannot accurately estimate frost without additional sensors
Solution Approach 1:
The system uses self-service by leveraging data already collected from existing sensors for other control functions. Instead of adding dedicated sensors for frost estimation, the algorithm repurposes existing compressor performance data (run time, cooling capacity) to accurately estimate frost buildup, making the system self-sufficient with available information.
Solution Approach 2:
The patent applies multi-functionality by using existing sensor data for multiple purposes. The same sensors that monitor compressor operation for cooling control are also used to estimate frost buildup for defrost control, eliminating the need for separate measurement systems and reducing overall device complexity.
Data Source
Figure 1~3
AI summary
A method for controlling the defrost of an evaporator in a refrigeration appliance having a cooling circuit with a variable cooling capacity compressor comprises the steps of assessing the cooling capacity of the cooling circuit and calculating the defrost time on the basis of such cooling capacity which is preferably assessed on the basis of the inverter frequency driving the compressor and/or the percentage of insertion of the compressor.