Control device, heat source system, method for calculating lower limit of cooling water inlet temperature, control method, and program
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Solution Overview
Problem
Current methods for controlling cooling water inlet temperature in chillers do not efficiently adjust based on the operating status of the chiller, leading to suboptimal coefficient of performance (COP).
Innovation Solution
A control device calculates a lower limit for the cooling water inlet temperature by determining the inlet/outlet required temperature difference based on the chiller's load factor and exhaust heat, then adjusts the cooling water outlet temperature to improve COP, ensuring the cooling water inlet temperature is set within a calculated lower limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a predetermined lower limit of cooling water inlet temperature is set for each chiller, then the cooling water outlet temperature can be ensured at a defined value or more, but the COP of the chiller cannot be improved beyond the predetermined limit
Solution Approach 1:
The patent applies dynamics by transitioning from a static predetermined lower limit to a dynamic calculated lower limit that adapts to real-time operating conditions. The control device continuously calculates the lower limit based on current cooling water outlet temperature, flow rate, and chiller load, allowing the system to optimize COP while ensuring outlet temperature requirements are met under varying operating conditions
Solution Approach 2:
The patent implements parameter changes by modifying the lower limit temperature parameter from a fixed predetermined value to a dynamically calculated value. The calculation incorporates multiple parameters including cooling water outlet temperature, flow rate, and chiller load factor, enabling the system to adjust the lower limit parameter to optimize energy efficiency while maintaining reliability
2Use of energy by moving object
If the cooling water inlet temperature is lowered to improve COP, then energy efficiency improves, but the cooling water outlet temperature may fall below the required defined value
Solution Approach 1:
The patent applies feedback by continuously monitoring actual cooling water outlet temperature and using this information to adjust the calculated lower limit. The control device incorporates feedback loops that measure outlet temperature, compare it with target values, and dynamically adjust the lower limit calculation to ensure outlet temperature requirements are met while optimizing COP
Solution Approach 2:
The patent implements preliminary action by calculating the lower limit before cooling water is supplied to the chiller. The control device performs preliminary calculations based on predicted operating conditions and sets the lower limit in advance, preventing outlet temperature from falling below required values while allowing maximum COP optimization
3Device complexity
If a fixed predetermined lower limit is used for all operating conditions, then the control system is simple, but the system cannot adapt to varying chiller operating statuses
Solution Approach 1:
The patent implements parameter changes by transforming the fixed lower limit parameter into a dynamic parameter that changes with operating conditions. The control device calculates the lower limit using variable parameters such as cooling water outlet temperature, flow rate, and chiller load factor, enabling the system to adapt to different operating statuses while maintaining reasonable control complexity through systematic calculation methods
Data Source
AI summary
The purpose of the invention is to provide a control device that can calculate the lower limit of cooling water inlet temperature according to the operation status of a chiller. A control device comprises: a lower limit calculation unit that calculates the lower limit of cooling water outlet temperature, where a prescribed required temperature difference is added to the cooling water outlet temperature of a chiller, and an inlet-outlet required temperature difference, which is the difference between the cooling water outlet temperature and the cooling water inlet temperature in the chiller and which is generated according to the operation status of the chiller, and that calculates a cooling water inlet temperature lower limit calculated value for the chiller by subtracting the inlet-outlet required temperature difference from the cooling water outlet temperature lower limit value; and a lower limit value determination unit that fixes the cooling water inlet temperature lower limit calculated value as the cooling water inlet temperature lower limit value.