Method for operating a refrigeration system
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Solution Overview
Problem
Refrigeration systems face challenges in maintaining minimal fluctuations in state variables and optimizing overall compressor output to adapt to changing conditions, leading to inefficient operation and increased control bandwidth.
Innovation Solution
The method involves transitioning between two operating states based on measured state variables, with transitions occurring when these variables reach specific threshold values, ensuring that each state is maintained for a minimum period to minimize state variable differences and optimize compressor output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the compressor output is continuously adjusted to maintain state variable at setpoint, then the state variable fluctuations are minimized, but the control bandwidth increases and system stability deteriorates
Solution Approach 1:
The patent applies periodic action by alternating between two operating states (first and second states) with different compressor outputs. Instead of continuous adjustment, the system periodically switches between these two states, each maintained for a minimum period of time. This periodic switching reduces control bandwidth requirements and improves system stability while still achieving acceptable state variable control through the alternating compression and decompression cycles of the state variable.
2Adaptability or versatility
If the compressor output is frequently switched to adapt to changing conditions, then the adaptability improves, but the control complexity and switching frequency increase
Solution Approach 1:
The patent applies dynamics by making the compressor output adjustable between two distinct operating states rather than fixed. The system dynamically adapts to changing conditions by switching between the first operating state (with first compressor output) and the second operating state (with second compressor output), where the compressor output can be varied depending on the measured state variable and current system conditions, thereby achieving adaptability without excessive control complexity.
3Measurement precision
If the difference between threshold values is reduced, then the state variable control precision improves, but the switching frequency increases and minimum period requirements cannot be met
Solution Approach 1:
The patent applies partial or excessive action by intentionally setting a larger difference between the first and second threshold values than would be ideal for precision control. This excessive threshold difference ensures that each operating state can be maintained for the required minimum period of time, preventing excessive switching frequency. The system accepts slightly reduced control precision in exchange for meeting the minimum operating period requirements and avoiding excessive switching.
4Productivity
If the compressor output is optimized for immediate conditions, then the instantaneous efficiency improves, but the fluctuations in state variable increase
Solution Approach 1:
The patent applies periodic action by alternating between two operating states with different compressor outputs. The system switches between the first operating state (optimized for one condition) and the second operating state (optimized for another condition), thereby achieving a balance between instantaneous efficiency and state variable stability. The periodic switching ensures that neither extreme is maintained continuously, reducing fluctuations while still adapting to changing conditions over time.
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 allows for optimal operation of the refrigeration system by maintaining state variables within a controlled bandwidth, reducing fluctuations and adapting compressor output to system conditions, thereby improving efficiency and stability.
Implementation Method 1
in a downstream heat exchanger absorbs heat
Implementation Method 2
the compressed refrigerant is cooled by a heat exchanger on the high-pressure side
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In order, in the context of a method for operating a refrigeration system comprising a circuit carrying a cold-transfer medium, in which for controlling a total compressor power of the refrigeration system at least one state variable in a system is measured, to operate the refrigeration system with the smallest possible variations in the state variable, it is proposed that, corresponding to this at least one state variable, the compressor unit is operated either in a first operating state at a first total compressor power at which the state variable decreases, or in a second operating state at a second total compressor power at which the state variable increases, wherein the first and second operating states directly follow one another in alternation, that a transition from the second operating state to the first operating state then takes place when the measured state variable reaches or exceeds a first threshold value, that a transition from the first operating state to the second operating state then takes place when the measured state variable reaches or drops below a second threshold value, and that a difference between the first value and the second value corresponds to the largest of the state variable differences which result during the respective minimum duration in the first operating state or in the second operating state.