Method and associated computer readable medium for controlling the defrost cycle of a vapor compression system
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Solution Overview
Problem
Vapor compression systems face inefficiencies due to ice buildup on the evaporator, leading to wasteful defrost cycles that consume significant energy and disrupt the intended heating or cooling process, as current methods rely on fixed time intervals rather than real-time operating conditions.
Innovation Solution
A controller system that calculates a cumulative coefficient of performance (CCOP) based on total heat delivered, total electrical energy consumed for heating, and defrosting energy, determining the optimal time for defrost cycles by analyzing the derivative of CCOP to initiate defrosting when efficiency is maximized, thereby reducing energy waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If defrost cycles are controlled to occur at regular fixed time intervals, then the evaporator is periodically cleared of ice buildup, but significant electrical energy is consumed and the intended heating or cooling is disrupted
Solution Approach 1:
The patent transitions from fixed-time defrost cycles to a dynamic control system that monitors real-time evaporator performance metrics (temperature, pressure, power consumption) and adjusts defrost timing based on actual ice buildup conditions. The controller dynamically determines when defrosting is necessary by evaluating system efficiency parameters, ensuring defrost cycles occur only when performance degradation reaches a threshold, thereby minimizing unnecessary energy consumption while maintaining reliable evaporator function.
Solution Approach 2:
The system implements feedback control by continuously monitoring evaporator temperature, refrigerant pressure, and power consumption during operation. These measurements are fed back to the controller, which compares actual performance against expected performance to detect ice buildup. When performance degradation indicates significant icing, the controller triggers a defrost cycle. This feedback mechanism ensures defrosting occurs based on actual conditions rather than predetermined schedules, optimizing energy usage.
2Reliability
If defrosting occurs too early, then the evaporator is cleared of ice, but energy is wasted by unnecessarily heating an evaporator that is still operating relatively efficiently
Solution Approach 1:
The patent replaces the mechanical/timed defrost trigger with an intelligent control system that uses sensors and algorithms to detect ice buildup. Instead of relying on fixed time intervals or simple temperature thresholds, the system substitutes a sophisticated evaluation process that monitors multiple parameters (temperature differential, pressure drop, power consumption rate) and calculates when ice buildup actually impacts performance. This substitution enables precise timing of defrost cycles, triggering them only when necessary and avoiding premature defrosting that would waste energy.
3Use of energy by moving object
If defrosting occurs too late, then energy consumption is reduced during operation, but the vapor compression system operates with a heavily iced up evaporator reducing efficiency
Solution Approach 1:
The system continuously monitors evaporator performance parameters including temperature, pressure, and power consumption, comparing actual values against expected values for optimal operation. When deviations indicate ice buildup is reducing efficiency, the feedback loop triggers a defrost cycle before severe icing occurs. This real-time feedback ensures the system maintains high productivity by preventing excessive ice accumulation while avoiding unnecessary defrost cycles.
Solution Approach 2:
The patent implements preliminary detection of ice buildup conditions by monitoring trends in performance parameters before they reach critical levels. The controller detects early signs of icing through subtle changes in temperature differential, pressure drop, or power consumption patterns and proactively schedules defrosting before the evaporator becomes heavily iced. This preliminary action maintains system efficiency by addressing ice buildup at the optimal moment, preventing the efficiency losses associated with heavy icing.
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 optimizes defrost cycle timing to enhance energy efficiency by aligning defrosting with peak system performance, minimizing energy consumption and maintaining efficient operation of vapor compression systems.
Implementation Method 1
determining a cumulative coefficient of performance (CCOP) of the vapor compression system based on the total heat delivered, the total electrical energy consumed, and the total defrosting energy
Implementation Method 2
determining the optimal time for defrost cycles by analyzing the derivative of CCOP to initiate defrosting when efficiency is maximized
Implementation Method 3
a refrigerant pressurized by the compressor is cooled by a reduction in pressure through the expansion valve. The cooled refrigerant extracts heat via the evaporator at a cold region. The heated refrigerant is re-pressurized by the compressor and delivered to the condenser. The condenser releases the heat to a hot region.
Implementation Method 4
The cooled refrigerant extracts heat via the evaporator at a cold region. The condenser releases the heat to a hot region.
Implementation Method 5
a refrigerant pressurized by the compressor is cooled by a reduction in pressure through the expansion valve. The cooled refrigerant extracts heat via the evaporator
Implementation Method 6
the surface temperature of the evaporator can fall below the dew point of air and below the freezing point of water, which can result in water vapor in the air condensing on the outside of the evaporator and form a layer of ice
Implementation Method 7
the surface temperature of the evaporator can fall below the dew point of air and below the freezing point of water, which can result in water vapor in the air condensing on the outside of the evaporator and form a layer of ice
Implementation Method 8
the ice is typically periodically eliminated by reversing the vapor compression system for a short time, during what is referred to as a defrost cycle, which heats the evaporator and melts the ice
Implementation Method 9
during what is referred to as a defrost cycle, which heats the evaporator and melts the ice
Data Source
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Figure 3A
AI summary
Operating a vapor compression system including determining a total heat delivered by the vapor compression system, determining a total electrical energy consumed by the vapor compression system while delivering heat, maintaining a total electrical energy consumed by the vapor compression system during a defrosting cycle, determining a cumulative coefficient of performance of the vapor compression system based on the total heat delivered, the total electrical energy consumed by the vapor compression system while delivering heat, and the total electrical energy consumed by the vapor compression system during the defrosting cycle, and initiating a defrosting cycle based the cumulative coefficient of performance.