Heat Pump Frost Detection Using Temperature-Frequency Normalization
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Solution Overview
Problem
Existing heat pumps struggle to accurately detect frost formation on evaporators due to changes in indoor environments and compressor frequencies, leading to erroneous decisions about frost formation.
Innovation Solution
A heat pump system that includes evaporator refrigerant saturation temperature detecting means, evaporator sucked air temperature detecting means, and compressor frequency detecting means, which calculate a characteristic value by dividing the difference between evaporator sucked air and evaporator temperatures by compressor frequency to accurately detect frost formation without being affected by indoor changes or compressor frequency variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If evaporation temperature is used to detect frost formation, then detection simplicity is maintained, but detection accuracy deteriorates due to changes in indoor environment and compressor frequency
Solution Approach 1:
The patent changes the detection parameter from simple evaporation temperature to a composite parameter that includes evaporator sucked air temperature, evaporation temperature, and compressor frequency. This composite parameter approach maintains detection simplicity while improving accuracy by accounting for factors that affect evaporation temperature independently of frost formation.
Solution Approach 2:
The patent introduces compressor frequency as an intermediary factor in the detection process. By incorporating compressor frequency into the detection calculation, the system can distinguish between temperature changes caused by compressor operation and those caused by frost formation, thereby improving detection accuracy without significantly increasing system complexity.
2Device complexity
If evaporation temperature alone is monitored, then detection system complexity is reduced, but false detection of frost formation increases due to indoor environment changes
Solution Approach 1:
The patent changes from monitoring a single parameter (evaporation temperature) to monitoring multiple parameters (evaporator sucked air temperature, evaporation temperature, and compressor frequency). This multi-parameter approach reduces false detections by providing a more comprehensive view of system conditions, while the integrated calculation method keeps the overall system complexity manageable.
Solution Approach 2:
The patent implements a feedback mechanism where compressor frequency information is fed back into the frost formation detection calculation. This feedback allows the system to adjust its interpretation of temperature changes based on actual compressor operation, thereby reducing false positives while maintaining a relatively simple detection architecture.
3Device complexity
If compressor frequency variations are not considered, then detection calculation is simplified, but detection accuracy deteriorates during variable speed operation
Solution Approach 1:
The patent explicitly adds compressor frequency as a third parameter to the detection calculation, changing it from a two-parameter system (temperatures only) to a three-parameter system. This allows the detection calculation to account for variable speed operation effects, improving accuracy during dynamic compressor operation while maintaining reasonable calculation simplicity through the use of a standardized formula.
Data Source
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AI summary
A heat pump that can accurately detect a frost formation state on an evaporator without being affected by changes in an indoor environment and changes in a compressor frequency, and an air conditioner or water heater on which the heat pump is mounted are provided. In the heat pump having a refrigerant circuit in which a compressor 3, an indoor heat exchanger 8 (condenser), an expansion valve 5, and an outdoor heat exchanger 6 (evaporator) are sequentially connected, evaporator refrigerant saturation temperature detecting means 10 for detecting an evaporation temperature Te of the outdoor heat exchanger 6, evaporator sucked air temperature detecting means 11 for detecting an evaporator sucked air temperature Ta of the outdoor heat exchanger 6, compressor frequency detecting means 12 for detecting a compressor frequency f of the compressor 3, and frost formation state detecting means 103 for detecting a frost formation state on the outdoor heat exchanger 6 are provided, and the frost formation state detecting means 103 detects a drop in heat exchange performance caused by a frost formation on the outdoor heat exchanger 6 on the basis of a characteristic amount T1, which is a calculation value obtained by dividing a difference between the evaporator sucked air temperature Ta and the evaporation temperature Te by a compressor frequency f.