Adaptive control method for refrigeration systems
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Solution Overview
Problem
Refrigeration systems face inefficiencies due to frost buildup in evaporators, leading to unnecessary defrosting and excessive power consumption, as current methods lack adaptive control mechanisms to manage frost levels effectively across various system types.
Innovation Solution
An adaptive control method that detects frost levels using a new FVT indicator and NTU rate calculation, allowing for intelligent management of evaporator fans and defrosting processes, enabling operation in different modes and optimizing defrosting times based on real-time frost conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If defrosting processes are programmed at fixed intervals (every 6 or 8 hours), then the evaporator is regularly maintained, but unnecessary defrosting occurs and power consumption increases
Solution Approach 1:
The patent implements dynamic defrosting control by continuously monitoring the NTU parameter and adjusting defrosting timing based on actual frost accumulation levels. The system transitions from static fixed-interval defrosting to dynamic condition-based defrosting, where defrosting operations are triggered only when the NTU parameter indicates sufficient frost accumulation, thereby eliminating unnecessary defrosting cycles and reducing power consumption.
Solution Approach 2:
The patent employs feedback control mechanisms by measuring the NTU parameter (Number of Transfer Units) which reflects the actual heat transfer performance and frost level in the evaporator. This measured feedback is used to adjust defrosting timing decisions, creating a closed-loop control system that adapts to real-time evaporator conditions rather than following predetermined schedules.
2Use of energy by moving object
If defrosting frequency is reduced to save energy, then power consumption decreases, but excessive frost may accumulate and halt the evaporator
Solution Approach 1:
The system continuously monitors the NTU parameter as feedback on evaporator frost conditions. When NTU exceeds a predetermined threshold indicating excessive frost accumulation, the control system automatically triggers defrosting operations, ensuring reliable evaporator operation while minimizing unnecessary defrosting cycles for energy savings.
Solution Approach 2:
The evaporator effectively monitors its own condition through NTU parameter measurement and autonomously determines when defrosting is needed. The system uses the evaporator's own performance characteristics (heat transfer efficiency reflected in NTU) to trigger defrosting, eliminating the need for external scheduling or estimation-based control.
3Measurement precision
If a new FVT indicator and NTU rate calculation method is implemented to detect frost levels, then accurate real-time frost detection is achieved, but system complexity increases
Solution Approach 1:
The patent replaces complex physical frost measurement systems with a calculated parameter approach. Instead of using sensors to directly measure frost thickness or mass, the system calculates the NTU parameter based on readily available operational data (temperatures, heat transfer coefficients), substituting direct mechanical measurement with a computational model that achieves equivalent information using existing system parameters.
Solution Approach 2:
The NTU parameter serves multiple functions simultaneously: it characterizes heat exchanger performance, indicates frost accumulation levels, and triggers defrosting decisions. This multi-functional parameter reduces the need for separate measurement systems for each function, simplifying the overall control architecture while maintaining high measurement precision for frost detection.
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 significantly reduces energy consumption by minimizing unnecessary defrosting, optimizing fan operation, and ensuring efficient frost management across self-contained and centralized refrigeration systems, thereby enhancing overall system performance.
Implementation Method 1
The evaporator fan may be managed in different ways, depending on the level of frost in the evaporator
Implementation Method 2
defrosting processes should be maintained at a minimum
Data Source
Figure 1
AI summary
which comprises the detection of the frost level in the evaporator by means of a calculation method of NTU rate, allowing to define: the most suitable defrosting time, the energization of the drainage resistors and the adaptive management of the evaporator fan combining different operating modes. An ice-free mode which uses only the cooling capacity of the refrigerant, and different modes with ice which benefits from the latent heat stored in the ice to produce energy savings, depending on the level of frost in the evaporator. For calculating the NTU rate, it uses the evaporator as a reference when it is dry at the beginning, and when the cooling system is in operation, it calculates the NTU rate with a variable frequency operating mode depending on the evaporator performance or level of ice and its comparison with the cited reference.