Centrifugal Chiller COP Evaluation With Simplified Loss Correction
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Solution Overview
Problem
The existing methods for calculating the design COP of centrifugal chillers are impractical due to the need for iterative calculations involving extensive data and complex computations, making it difficult to handle in devices with limited throughput, such as control panels.
Innovation Solution
A performance evaluation system that uses a data acquisition section, storage section, and computing section to estimate design COP using a simplified formula incorporating correction values for losses, expressed as a reverse Carnot cycle COP, allowing iterative computation even in devices with limited capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative calculation of design COP is performed using conventional methods, then measurement precision is improved, but device complexity increases and productivity decreases
Solution Approach 1:
The patent transforms the complex iterative calculation problem into a simple direct calculation by changing the mathematical parameters from multiple variables requiring iteration to a single-variable linear equation. The design COP is calculated using only the load factor K as variable, with all other parameters (a1, a2, a3, a4) being constants determined from manufacturer data, eliminating the need for iterative convergence calculations.
Solution Approach 2:
The patent extracts the essential relationship between design COP and load factor from the complex iterative calculation system. By identifying that design COP varies linearly with load factor K, the invention extracts this core relationship and formulates it as a standalone linear equation, separating it from the need to simultaneously solve multiple heat exchanger and compressor performance equations.
2Measurement precision
If iterative calculation of design COP is performed using conventional methods, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent changes the calculation from an iterative multi-step process to a single-step direct calculation. The design COP is computed immediately from the load factor using a linear equation, eliminating time-consuming iterative loops and enabling real-time calculation on resource-constrained devices like control panels.
Solution Approach 2:
The patent segments the design COP calculation into two parts: (1) manufacturer determines the linear equation parameters (a1, a2, a3, a4) offline using detailed iterative calculations, and (2) end users apply the pre-determined linear equation for rapid real-time calculations. This segmentation transfers computational burden from the user device to the manufacturer setup phase.
3Measurement precision
If conventional design COP calculation methods are used, then measurement precision is improved, but ease of operation worsens
Solution Approach 1:
The patent simplifies the operational parameters from multiple measured variables requiring complex coordinate transformations to a single load factor parameter. The load factor K can be directly obtained from standard chiller operation data, making the calculation straightforward and easy to implement without requiring specialized thermodynamic property databases or complex iterative solvers.
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 precise and efficient iterative calculation of design COP, reducing computational complexity and enabling real-time calculation on devices like control panels, while providing accurate performance evaluation.
Implementation Method 1
a computational formula for ideal actual-machine COP expressed using COP characteristics of a reverse Carnot cycle
Data Source
AI summary
Design COP is iteratively computed. Provided is a centrifugal chiller performance evaluation system including a data acquisition section for acquiring operating data from a centrifugal chiller as input data; a storage section storing a design COP estimation formula obtained by adding correction values corresponding to losses occurring in an actual environment to a computational formula for ideal actual-machine COP expressed using COP characteristics of a reverse Carnot cycle; and a computing section for estimating a design COP at a current operating point using the operating data acquired by the data acquisition section and the design COP estimation formula stored in the storage section. The correction values include a first correction value calculated from a first computational formula including the load factor of the centrifugal chiller as a variable and a second correction value calculated from a second computational formula including a difference between cooling water outlet temperature and chilled water outlet temperature as a variable. The second correction value contains an offset from the first correction value depending on cooling water inlet temperature.