Method and system for preventing freezing when four-way valve in heat pump water heater is failed, and heat pump water heater
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Solution Overview
Problem
Existing heat pump water heater systems lack an effective method to determine if a four-way valve is failed, leading to potential freezing of low-temperature water and subsequent ice blockages, which can misjudge the valve's failure and affect user usage.
Innovation Solution
A method and system that detect the current water temperature in the tank, assess its cooling rate, and determine if it satisfies specific temperature and time conditions to decide whether to stop the heat pump system and start an electric auxiliary heating system, thereby preventing freezing and accurately judging the valve's failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the heat pump system continues to operate without accurate four-way valve failure detection, then energy consumption is reduced, but water freezing occurs and water inlet may be blocked due to ice blockage
Solution Approach 1:
The system performs preliminary detection of four-way valve failure by monitoring temperature differences between the heat exchanger and environment before freezing occurs. When the temperature difference exceeds a threshold, the system proactively switches to electric auxiliary heating mode, preventing ice blockage before it happens and ensuring continuous water supply reliability.
Solution Approach 2:
The patent introduces an intermediary detection mechanism (temperature difference monitoring) between the four-way valve failure and the actual freezing damage. This intermediary system detects early signs of valve failure through temperature anomalies and triggers a mode switch, acting as a mediator that prevents the harmful effect of freezing while maintaining energy efficiency.
2Device complexity
If the existing temperature difference method is used to judge four-way valve failure, then the judgment process is simple, but misjudgment occurs in low temperature conditions and low-temperature water scenarios
Solution Approach 1:
The patent changes the detection parameter from simple temperature difference to a multi-parameter evaluation system that includes temperature difference, cooling rate, and time duration. By introducing cooling rate (dT/dt) as an additional parameter, the system can distinguish between normal low-temperature operation and actual four-way valve failure, eliminating misjudgments in cold environments while maintaining reasonable system complexity.
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring temperature changes and comparing them against threshold values. When the cooling rate exceeds a predetermined threshold for a sustained period, the system confirms four-way valve failure and switches modes. This feedback loop ensures accurate judgment by verifying abnormal conditions persist beyond transient fluctuations.
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 effectively prevents freezing by accurately determining the four-way valve's failure, avoiding misjudgments and ensuring continuous hot water supply by controlling the heat pump and auxiliary heating systems appropriately.
Implementation Method 1
a heat exchanger and environment temperature
Implementation Method 2
a heat pump system is controlled to stop
Implementation Method 3
an electric auxiliary heating system is started
Data Source
AI summary
The present disclosure relates to a method for preventing freezing when a four-way valve in a heat pump water heater is failed, including following acts: S1, it is judged that whether current water temperature T is lower than a preset minimum temperature Tmin for the water tank, if yes, perform act S2; if no, perform act S1 again; S2, it is judged that whether a cooling rate Td of the current water temperature T is greater than or equal to a preset rate ΔT; or, it is judged that whether the current water temperature T satisfies T<Tmin−a and whether T<Tmin−a stands for a first time period t1, in which a is a limit value of a temperature difference; if at least one yes, perform act S3, otherwise, return to act S1; S3, a heat pump system is controlled to stop and an electric auxiliary heating system is started.