A method for generating early temperature warning in a vapour compression system
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Solution Overview
Problem
Vapour compression systems often fail to maintain refrigerated volumes at optimal temperatures, leading to potential bacterial growth and faster degradation of stored goods due to inadequate temperature control, with existing alarm systems generating alerts too late or not at all when temperatures rise above acceptable limits.
Innovation Solution
A method for operating vapour compression systems that sets control parameters including a cut-in temperature, high temperature alarm limit, and alarm delay time, continuously monitors the weighted mean temperature within a moving time window, and generates a warning when a derived delay time is reached, allowing early detection of potential faults and non-optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high temperature alarm is generated only when temperature reaches a specified elevated level (e.g., 8°C), then false alarms are reduced, but early detection of temperature issues is delayed
Solution Approach 1:
The system performs preliminary action by calculating a dynamic delay time based on the current temperature and the maximum acceptable relative decay value before generating an alarm. This allows the system to detect temperature issues earlier by providing advance warning before the temperature reaches critical levels, while still accounting for acceptable temperature variations and avoiding false alarms.
Solution Approach 2:
The alarm delay time is made dynamic rather than fixed. The control unit continuously calculates the delay time based on the current temperature reading and the maximum acceptable relative decay value. This dynamic adjustment allows the system to adapt to changing temperature conditions, providing shorter delays when temperatures are rising quickly and longer delays when temperatures are stable, thereby optimizing both early detection and false alarm prevention.
2Temperature
If the expansion valve is kept fully open to drive temperature down below cut-in temperature, then cooling capacity is maximized, but energy consumption increases and system wear accelerates
Solution Approach 1:
The system uses feedback by continuously monitoring the temperature inside the refrigerated volume and using this information to control the expansion valve. The control unit adjusts the valve opening based on the actual temperature readings, ensuring that the temperature is maintained within the desired range without excessive cooling. This feedback mechanism prevents energy waste by avoiding unnecessary full-opening of the expansion valve when the temperature is already adequate.
Solution Approach 2:
The system changes the operating parameters dynamically by adjusting the expansion valve opening degree based on temperature conditions. Instead of keeping the valve fully open, the control unit modulates the valve opening to match the actual cooling demand, thereby reducing energy consumption and system wear while maintaining effective temperature control.
3Loss of time
If temperature monitoring is continuous to enable early detection, then response time is improved, but system complexity and processing load increase
Solution Approach 1:
The system applies partial action by calculating the alarm delay time based on the maximum acceptable relative decay value rather than continuously monitoring and reacting to every temperature change. This approach provides early detection by calculating a predicted alarm time based on current temperature trends, reducing the processing load while maintaining effective monitoring and response capabilities.
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 method enables early detection of temperature-related issues, allowing for timely maintenance and preventing goods degradation by generating warnings before temperatures reach critical levels, thus reducing the risk of spoilage and extending the shelf-life of stored goods.
Implementation Method 1
each evaporator being arranged in thermal contact with a refrigerated volume for storing goods
Data Source
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AI summary
A method for operating a vapour compression system (1) is disclosed. A cut-in temperature, a high temperature alarm limit and a high temperature alarm delay time are set. A maximum acceptable relative decay value is derived, based on the high temperature alarm limit and the high temperature alarm delay time. The vapour compression system (1) is operated while monitoring a temperature inside a refrigerated volume and continuously deriving a weighted mean temperature prevailing inside the refrigerated volume, during a moving time window of a predefined length. In the case that the weighted mean temperature inside the refrigerated volume exceeds the cut-in temperature, a timer is started, and a delay time is derived, based on the weighted mean temperature and the maximum acceptable relative decay value. A warning is generated when the timer reaches the derived delay time.