Method and correspondingly designed device for regulating a refrigeration circuit and compression refrigeration system
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Solution Overview
Problem
Existing refrigeration systems face challenges in precisely controlling the degree of opening of the throttle element, leading to inefficiencies and potential compressor damage due to improper refrigerant superheat management, especially in systems with internal heat exchangers or refrigerants with temperature glide.
Innovation Solution
A method involving a model-based approach to determine control values for the throttle element using direct measured variables and adaptive coefficients, incorporating compressor speed and refrigerant properties to optimize superheat control, including filtering and delay mechanisms to account for dynamic system changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional controller with preset parameters is used, then the device complexity is low, but the manufacturing precision of superheat control deteriorates under varying operating conditions
Solution Approach 1:
The controller dynamically adapts its parameters based on the current operating point of the refrigeration circuit. The controller receives actual operating parameters (evaporator temperature, condenser temperature, compressor speed) and adjusts the superheat setpoint and control parameters in real-time according to the characteristic curve map, rather than using fixed preset parameters. This dynamic adaptation resolves the contradiction by maintaining high control precision across varying operating conditions without requiring an overly complex fixed-structure controller.
Solution Approach 2:
The invention changes the control parameters of the controller based on the operating point. The superheat setpoint is adjusted according to the characteristic curve map that correlates with operating conditions (evaporator temperature, condenser temperature, compressor speed). Additionally, the controller parameters (proportional band, integration time) are adapted based on the current operating point, allowing the system to maintain optimal control precision across different operating conditions without increasing fundamental device complexity.
2Manufacturing precision
If the superheat setpoint is adapted to operating point, then the manufacturing precision of superheat control is improved, but the device complexity increases due to characteristic curve map and adaptive mechanisms
Solution Approach 1:
The controller performs self-adaptation by automatically determining the current operating point from measured parameters (evaporator temperature, condenser temperature, compressor speed) and autonomously adjusting the superheat setpoint and control parameters according to the characteristic curve map. The system serves itself by eliminating the need for external manual calibration or complex additional hardware, resolving the contradiction by achieving high precision through software-based adaptive logic rather than hardware complexity.
Solution Approach 2:
The characteristic curve map serves multiple functions: it provides the superheat setpoint adaptation, guides the adjustment of controller parameters (proportional band, integration time), and enables the controller to adapt to different operating conditions. This multi-functionality resolves the contradiction by consolidating multiple control functions into a single adaptive mechanism, achieving high precision control without proportionally increasing device complexity.
3Productivity
If pilot control of throttle element is implemented, then the productivity of refrigeration control is improved, but the reliability deteriorates due to potential inaccuracy in sensitive circuits
Solution Approach 1:
The controller performs preliminary action by calculating the required throttle element opening in advance based on the current operating point and superheat requirements. The controller determines the target superheat from the characteristic curve map and pre-calculates the appropriate throttle opening position before actual superheat deviation occurs, enabling proactive control adjustment. This resolves the contradiction by improving response speed through advance calculation while maintaining reliability through model-based accurate prediction suitable for sensitive circuits.
Solution Approach 2:
The system implements feedback by continuously monitoring the actual superheat (calculated from evaporator outlet temperature and evaporator pressure) and comparing it with the target superheat from the characteristic curve map. The controller adjusts the throttle element opening based on the superheat deviation feedback, ensuring accurate control in sensitive circuits. This feedback mechanism resolves the contradiction by maintaining both fast response (through continuous monitoring) and high reliability (through accurate deviation-based adjustment).
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 precise pre-control of the throttle element, enhancing system efficiency and stability, particularly in sensitive refrigeration circuits, by quickly adapting to varying operating conditions and detecting refrigerant deficiencies.
Implementation Method 1
the refrigerant in the refrigeration circuit is essentially evaporated in the evaporator by removing heat from the medium to be cooled
Implementation Method 2
The compressor increases the pressure and thus the temperature
Implementation Method 3
The refrigerant is then liquefied again in the condenser, releasing heat
Implementation Method 4
The throttle valve expands the refrigerant to the evaporation pressure
Data Source
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AI summary
The present invention relates to a method for operating a compression refrigeration machine (200) and a corresponding compression refrigeration machine (200), comprising a refrigerant, an evaporator (11, 240), a pressure boosting unit (12, 210), a condenser (13, 220), and a throttle element (15, 230). The method comprises calculating a control value for the throttle element (15, 230) as a function of process variables of the compression refrigeration machine (200) using a physical model containing coefficients, wherein the coefficients have at least one coefficient describing a universal physical dependency and one coefficient describing a tolerance-related dependency. The method further comprises the steps: a) adaptively correcting the coefficients describing tolerance-related dependencies, and b) adjusting the throttle element (15, 230) to the control value.