Compression cooling system and method for operating the same
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Solution Overview
Problem
The control of compressor inlet superheat in compression refrigeration systems is challenging due to tolerances in wet steam characteristics, leading to difficulties in maintaining optimal operating conditions and efficiency, especially with refrigerants like R454C that have temperature glide, which affects the coefficient of performance and component longevity.
Innovation Solution
A method is introduced to calculate a correction value for the evaporator outlet superheat setpoint based on the compressor inlet superheat control deviation, allowing for adaptive compensation of systematic tolerances and precise regulation of the expansion valve, ensuring both compressor inlet and evaporator outlet superheat control deviations are zero in steady state, thereby improving control reaction speed and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional superheat control methods are used, then the control system is simple, but the control precision of compressor inlet superheat is insufficient due to wet steam characteristic tolerances
Solution Approach 1:
The patent implements feedback control by continuously measuring the actual compressor inlet superheat and comparing it with the target value, then adjusting the expansion valve opening based on the control deviation. This closed-loop feedback mechanism compensates for wet steam characteristic tolerances and maintains precise superheat control despite system variations.
Solution Approach 2:
The patent calculates a predetermined correction value based on the control deviation before making adjustments to the expansion valve. This preliminary calculation allows the system to proactively compensate for deviations rather than reactively adjusting, improving control precision while maintaining systematic operation.
2Measurement precision
If the expansion valve opening is adjusted frequently to maintain superheat, then the superheat control is precise, but the control reaction time is slow
Solution Approach 1:
The patent calculates a predetermined correction value based on the control deviation and applies it to adjust the expansion valve opening. This preliminary calculation approach allows the system to prepare the correction before execution, reducing the overall reaction time while maintaining control precision.
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with electronic calculation and control of the expansion valve opening. By using electronic computation to determine the predetermined correction value, the system achieves faster response times compared to traditional mechanical adjustment methods.
3Measurement precision
If additional components are added to improve superheat control, then the control precision improves, but the device complexity increases
Solution Approach 1:
The patent makes the control unit perform multiple functions: it calculates the evaporator outlet superheat, determines the compressor inlet superheat target value, calculates control deviations, computes predetermined correction values, and controls the expansion valve. This multi-functionality eliminates the need for separate dedicated components for each control function, maintaining precision while avoiding increased complexity.
Solution Approach 2:
The patent combines the superheat control functions with the existing control unit that already manages the refrigeration system. By merging the superheat control logic into the centralized control unit, the system achieves precise control without adding separate standalone components, thus avoiding increased device complexity.
4Reliability
If the system adapts to individual component tolerances, then the reliability improves, but the control algorithm complexity increases
Solution Approach 1:
The patent uses feedback control to continuously monitor the actual compressor inlet superheat and adjust the expansion valve opening based on the control deviation. This feedback mechanism automatically adapts to individual component tolerances and system variations, improving reliability through systematic adjustment rather than complex algorithmic predictions.
Solution Approach 2:
The patent dynamically adjusts the expansion valve opening parameter based on the calculated control deviation and predetermined correction value. By changing this key parameter in response to measured conditions, the system adapts to component tolerances and maintains reliable operation without requiring complex algorithms to predict or compensate for variations.
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 enhances the control reaction speed to operating point changes by up to 10 times, optimizing overall response time and refrigeration circuit efficiency, while adapting to individual component tolerances and refrigerant composition deviations, ensuring reliable operation and extended component lifespan.
Implementation Method 1
Internal heat is transferred in an internal heat exchanger, for example, in the form of a recuperator, between the refrigerant flowing at high pressure from the condenser to the expansion valve and the refrigerant flowing at low pressure from the evaporator to the compressor
Implementation Method 2
The low-pressure refrigerant evaporates in the evaporator by absorbing source heat
Implementation Method 3
The low-pressure refrigerant evaporates in the evaporator by absorbing source heat
Implementation Method 4
a gaseous refrigerant is compressed from a low pressure to a high pressure by a compressor
Implementation Method 5
The refrigerant is forced through the condenser, where it transfers heat to a heating medium located in a heat sink system
Implementation Method 6
The refrigerant is forced through the condenser, where it transfers heat to a heating medium located in a heat sink system
Data Source
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AI summary
The present invention relates to a method for controlling a compression refrigeration system (200), in particular a heat pump (100), and an associated compression refrigeration system, comprising the following method steps: determining a target value (ZÜA) for the evaporator outlet superheat (TÜA) and a target value (ZÜE) for the compressor inlet superheat (TÜE), calculating a correction value based on a control deviation of the compressor inlet superheat (TÜE) from the target value (ZÜE) of the compressor inlet superheat (TÜE), correcting the target value (ZÜA) of the evaporator outlet superheat (TÜA) with the calculated correction value, and calculating a control value (R) after a commissioning phase of the compression refrigeration system (200) depending on the target value (ZÜA) of the evaporator outlet superheat (TÜA) and the target value (ZÜE) of the compressor inlet superheat. (TÜE), and control of the expansion valve (230) based on the control value (R).