Heat source device and method for controlling same
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Solution Overview
Problem
Centrifugal chillers face issues with temperature overshoot in chilled water output, leading to potential freezing and reduced heat exchange efficiency, especially when the set outlet temperature is around 0°C, and high heat source machine load conditions can result in inefficient operation and forced stops due to increased refrigerant condensation pressure.
Innovation Solution
A heat source machine with a computing unit that calculates an evaluation value based on inlet temperature, flow rate, and load rate, using an arithmetic expression to adjust the set outlet temperature and prevent overshoot through a set temperature changing unit, employing a heat pump cycle with two heat exchangers to maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the set outlet temperature of chilled water is set to around 0°C to improve cooling efficiency, then heat exchange efficiency is improved, but the chilled water may freeze due to temperature overshoot
Solution Approach 1:
The control device performs preliminary action by predicting future temperature trends based on current system state and adjusting the set temperature in advance. When the outlet temperature approaches the target value or when conditions suggest impending overshoot, the controller proactively modifies the set temperature to prevent freezing before it occurs.
Solution Approach 2:
The control device implements feedback control by continuously monitoring the outlet temperature and adjusting the set temperature based on the difference between actual and target values. The controller increases or decreases the set temperature according to whether the outlet temperature is below or above the target, preventing overshoot and freezing.
2Ease of operation
If conventional control is used to maintain set temperature, then temperature control is simple, but temperature overshoot occurs when inlet temperature or flow rate fluctuates significantly
Solution Approach 1:
The control device uses feedback control to continuously monitor outlet temperature and adjust the set temperature based on the difference between actual and target values. This feedback mechanism automatically compensates for disturbances in inlet temperature or flow rate, maintaining stable outlet temperature without complex manual intervention.
Solution Approach 2:
The control device performs self-service by automatically adjusting the set temperature based on real-time monitoring of system parameters. The controller independently determines when and how much to adjust the set temperature without external intervention, maintaining temperature stability while keeping the system easy to operate.
3Power
If the heat source machine operates under high load and high outside temperature conditions, then cooling capacity is increased, but refrigerant condensation pressure increases causing forced stop
Solution Approach 1:
The control device performs preliminary action by monitoring system parameters and predicting when condensation pressure may exceed safe limits. Before the pressure reaches critical levels, the controller proactively adjusts the set temperature to reduce cooling capacity and prevent forced stop, ensuring continuous operation.
Solution Approach 2:
The control device implements feedback control by continuously monitoring system state and adjusting the set temperature based on predicted condensation pressure trends. When conditions indicate rising pressure, the controller increases the set temperature to reduce the pressure, preventing forced stop while maintaining high cooling capacity when safe.
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 solution effectively suppresses temperature overshoot, allowing chilled water to be used as a heat medium without freezing, enhancing heat exchange efficiency and preventing forced stops, even under high load and high outside temperature conditions.
Implementation Method 1
performing, in the second heat exchanger, heat exchange between a heat medium supplied from an external load and a refrigerant to thereby cool or heat the heat medium
Implementation Method 2
performing, in the first heat exchanger, heat exchange between a heat source and a refrigerant
Data Source
Figure 1
Figure 2
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AI summary
The objective of the present invention is to suppress over-shooting of the exit temperature of a heat transfer medium. A device for controlling a heat source device (10a) is provided with a computation unit (22) and a set temperature alteration unit (23). The computation unit (22) calculates a load change rate using a predetermined computation formula. The set temperature alteration unit (23) determines whether or not the load change rate calculated by a unit for calculating the amount of fluctuation (22) exceeds a predetermined threshold, and when same is exceeded, alters the set temperature for cold water exit in the direction of suppressing changes in the cold water exit temperature. For example, when the cold water exit temperature is decreasing, by setting the set temperature for cold water exit to a higher value, the load of the heat source device decreases and the cold water exit temperature is controlled in a manner so as to match the post-alteration set temperature for cold water exit. As a result, it is possible to suppress overshooting.