Variable-Speed Centrifugal Chiller COP Evaluation Under Real-Time Load
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Solution Overview
Problem
Existing performance evaluation methods for variable-speed centrifugal chillers are unable to accurately calculate planned COP (coefficient of performance) in real-time due to complex calculations and high data requirements, making it difficult to compare actual operating conditions with rated specifications, thus hindering efficient energy management.
Innovation Solution
A performance evaluation device that includes a data acquisition unit, storage unit, and arithmetic unit to sequentially calculate planned COP using simplified arithmetic equations based on mechanical characteristics, relative load factors, and correction coefficients, allowing for accurate expression of COP characteristics and elimination of complex data processing needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex convergent calculations are performed to calculate planned COP using heat exchanger performance, compressor performance, and refrigerant thermal properties, then calculation accuracy is improved, but calculation time and computational complexity increase significantly
Solution Approach 1:
The patent transforms the complex multi-parameter convergent calculation into a simplified calculation using pre-stored arithmetic equations with key parameters (coolant inlet temperature, load factor, and correction coefficient). This parameter substitution approach maintains sufficient accuracy while dramatically reducing computational time and complexity.
Solution Approach 2:
The patent performs preliminary work by storing arithmetic equations and correction coefficients in advance based on chiller mechanical characteristics. This pre-processing allows the actual planned COP calculation to use simple equation substitution rather than complex real-time convergent calculations, resolving the time-accuracy contradiction.
2Measurement precision
If sequential planned COP calculation is performed for each operating condition, then performance evaluation accuracy is improved, but computational load exceeds control board capabilities
Solution Approach 1:
The patent simplifies the computational model by changing from complex multi-variable convergent calculations to simple arithmetic equations with three key parameters. This parameter reduction makes sequential calculation feasible within control board capabilities while maintaining evaluation accuracy.
Solution Approach 2:
The patent creates simplified arithmetic equations that copy the essential relationships from complex thermodynamic models. These equations replicate the behavior of detailed simulations without requiring the full computational complexity, enabling real-time sequential calculations.
3Measurement precision
If enormous amounts of operating data are collected and processed to determine heat exchanger and compressor performance, then calculation accuracy is improved, but data processing complexity and time requirements increase
Solution Approach 1:
The patent extracts only the essential parameters (coolant inlet temperature, load factor, and correction coefficient) needed for planned COP calculation, discarding the need to process enormous amounts of detailed operating data. This extraction approach maintains accuracy while dramatically simplifying data requirements.
Solution Approach 2:
The patent performs preliminary analysis to determine the minimal set of parameters required for accurate planned COP calculation. By identifying these key parameters in advance, the system avoids the need to collect and process extensive operating data during actual operation.
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
Enables real-time, accurate calculation of planned COP at each operating point, enhancing energy management by simplifying the calculation process and reducing the need for extensive data processing, while being versatile enough to apply to various types of variable-speed centrifugal chillers.
Implementation Method 1
a third arithmetic equation used for calculating a planned COP by using the correction coefficient to correct a COP calculation equation derived from a reverse Carnot cycle
Data Source
AI summary
An object is to sequentially calculate planned COPs. Provided is a performance evaluation device for a variable-speed centrifugal chiller that includes a data acquisition unit that acquires operating data of the variable-speed centrifugal chiller as input data; a storage unit that stores a first arithmetic equation derived on the basis of mechanical characteristics of the chiller and used for calculating a relative load factor that relatively expresses a relationship between a current load factor at a current coolant inlet temperature and a predetermined load factor at a predetermined coolant inlet temperature set as a reference operating point, a second arithmetic equation that expresses a relationship between the relative load factor and a correction coefficient, and a third arithmetic equation used for calculating a planned COP by using the correction coefficient to correct a COP calculation equation derived from a reverse Carnot cycle; and an arithmetic unit that calculates the planned COP under current operating conditions by using the operating data acquired by the data acquisition unit in the first, second, and third arithmetic equations stored in the storage unit.