Hot-Water Heat Exchanger Control for Stable Setpoint Reach
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Solution Overview
Problem
Conventional hot-water supply devices experience instability in hot water supply temperature and delayed temperature reach due to neglecting the residual heat amount in the heat exchanger, leading to overshooting or undershooting issues when starting a hot water supply operation.
Innovation Solution
A hot-water supply device that includes a first flowing path for a heat medium, a second flowing path to a terminal, a heat exchanger for heat exchange, flow rate detecting means, and control means to adjust the transfer flow rate based on estimated residual heat amount, using a timer to determine the held heat amount and adjust the pump's rotation accordingly to stabilize the temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of rotations of the circulation pump is determined based on the required heat amount when the hot water supply operation is started, then the hot water supply temperature can be controlled to reach the setting temperature, but the hot water supply temperature becomes unstable or takes time to reach the setting temperature due to neglecting the residual heat amount in the heat exchanger
Solution Approach 1:
The control device performs preliminary estimation of the residual heat amount in the heat exchanger before starting the hot water supply operation. Based on this preliminary knowledge, the device determines an appropriate initial number of rotations for the circulation pump, preventing temperature instability and overshooting from the outset.
Solution Approach 2:
The control device continuously monitors the hot water supply temperature and adjusts the circulation pump rotations dynamically. The control algorithm incorporates feedback from temperature sensors to modify pump speed in real-time, ensuring stable temperature control while accounting for residual heat in the heat exchanger.
2Speed
If the circulation pump operates at high speed to quickly heat the secondary fluid, then the hot water supply temperature reaches the setting temperature faster, but the temperature overshoots the setting temperature due to excessive residual heat in the heat exchanger
Solution Approach 1:
Before initiating the hot water supply operation, the control device estimates the residual heat amount in the heat exchanger and uses this information to determine the optimal initial pump speed. This preliminary assessment prevents temperature overshooting by avoiding excessively high initial pump rotations.
Solution Approach 2:
The circulation pump operates with dynamically adjusted speed rather than a fixed high speed. The control device modulates the pump rotations based on real-time temperature feedback and the estimated residual heat, allowing the system to reach the target temperature quickly while maintaining accuracy.
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
The device achieves rapid and stable hot water supply temperature reach by adjusting the transfer flow rate according to the estimated residual heat amount, preventing overshooting and undershooting, thus enhancing responsiveness.
Implementation Method 1
a heat exchanger in which heat of the first heat medium flowing through the first flowing path and heat of the second heat medium flowing through the second flowing path are exchanged heat from each other
Data Source
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AI summary
A hot-water supply device includes: a first flowing path 1 through which first heat medium flows; a pump 4 for transferring first heat medium; a hot water supply flowing path 2 through which hot water flows; a heat exchanger 3 in which heat of the first heat medium and heat of hot water are exchanged with each other; flow rate detecting means 5 provided in the hot water supply flowing path 2; and control means 9, wherein the control means 9 estimates a held heat amount of the heat exchanger 3 when the flow rate detecting means 5 detects a predetermined flow rate or more, and the control means 9 controls fluid transfer means 4 such that the relatively larger the held heat amount is, the smaller a transfer flow rate of the first heat medium when the hot water supply temperature is brought close to set temperature becomes.