Variable-Speed Centrifugal Chiller COP Calculation Under Changing Load
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Solution Overview
Problem
Current methods for evaluating the performance of variable-speed centrifugal chillers are hindered by the complexity and time-consuming nature of calculating planned COP (coefficient of performance) values, which are essential for determining energy efficiency, as they require extensive data processing and are difficult to implement in control boards due to their computational intensity.
Innovation Solution
A performance evaluation device that includes a data acquisition unit, storage unit, and arithmetic unit, utilizing simplified arithmetic equations to calculate planned COP by expressing relationships between load factors, correction coefficients, and COP characteristics based on reverse Carnot cycle principles, allowing for accurate and efficient sequential calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to calculate planned COP values, then measurement precision is improved, but device complexity increases and productivity decreases
Solution Approach 1:
The patent transforms the complex multi-parameter convergent calculation into a simplified calculation based on key operating parameters (chilled liquid temperature, coolant temperature, load factor). By changing the calculation parameters from comprehensive system performance data to essential operating conditions, the patent achieves both accuracy and simplicity.
Solution Approach 2:
The patent extracts only the essential parameters needed for COP calculation (chilled liquid temperature, coolant temperature, load factor) from the complete system data set. This extraction eliminates unnecessary data processing steps while retaining the core information required for accurate planned COP determination.
2Measurement precision
If conventional methods are used to calculate planned COP values, then measurement precision is improved, but loss of time increases
Solution Approach 1:
By changing from comprehensive system performance parameters to essential operating parameters, the calculation time is dramatically reduced. The simplified parameter set enables real-time or near-real-time COP calculation without sacrificing measurement precision.
Solution Approach 2:
The patent skips the time-consuming convergent calculation process by directly computing COP from measured operating parameters using established thermodynamic relationships. This allows rapid succession of COP calculations for sequential operating points.
3Measurement precision
If comprehensive data processing is performed for planned COP calculation, then measurement precision is improved, but ease of operation worsens
Solution Approach 1:
The patent extracts and displays only the essential operating parameters (chilled liquid temperature, coolant temperature, load factor) and calculated COP values to the user. This extraction of relevant information from comprehensive data processing enables easy user comparison while maintaining calculation accuracy.
Solution Approach 2:
The patent creates a simplified representation of the chiller performance by copying only the essential operating parameters and COP values for display. This copied information provides users with actionable data for comparison without requiring them to process comprehensive system data.
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, reducing the need for extensive data processing and enabling user-friendly comparison with actual COP values, thus enhancing operational efficiency and versatility across various chiller models.
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
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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, aid 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.