Storage Water Heater Pump Control for Stable Outlet Temperature
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Solution Overview
Problem
Conventional water heaters experience instability in hot water supply temperature due to fluctuations in flow rate, leading to user discomfort and unnecessary temperature fluctuations.
Innovation Solution
A storage water heater with a pump control system that adjusts the control interval based on the absolute change in flow rate, using PID control to maintain target flow rates and prevent hunting, thereby stabilizing the hot water supply temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the control interval is long, then the device complexity is reduced, but the hot water supply temperature stability deteriorates when flow rate rapidly fluctuates
Solution Approach 1:
The control interval is made dynamic rather than fixed. The control interval determination unit adjusts the control interval based on the detected hot water supply-side flow rate and its temporal changes. When flow rate changes rapidly, the control interval is shortened to maintain temperature stability. When flow rate is stable, the control interval is extended to reduce control operations. This dynamic adjustment resolves the contradiction between control frequency and temperature stability.
2Stability of the object's composition
If the control interval is short, then the hot water supply temperature stability is improved, but unnecessary fluctuation in hot water supply temperature occurs when flow rate is stable
Solution Approach 1:
The control interval is dynamically adjusted based on flow rate conditions. When the flow rate is stable, the control interval is extended, reducing the frequency of control operations and preventing unnecessary temperature fluctuations (hunting). When flow rate changes rapidly, the control interval is shortened to maintain temperature stability. This adaptive approach eliminates harmful temperature fluctuations while maintaining stability when needed.
Solution Approach 2:
The system uses feedback from the flow rate detection to adjust control parameters. The control interval determination unit continuously monitors the hot water supply-side flow rate and its temporal changes, then adjusts the control interval accordingly. This feedback mechanism prevents unnecessary control actions when flow rate is stable, avoiding hunting phenomena, while ensuring rapid response when flow rate changes.
3Device complexity
If the pump output is not adjusted according to flow rate changes, then the device complexity is reduced, but the hot water supply temperature deviates from target temperature
Solution Approach 1:
The pump control mechanism uses feedback from flow rate detection to adjust pump output. The control unit calculates the required pump output based on the detected hot water supply-side flow rate and temporal changes, then adjusts the pump to maintain the heat source-side flow rate at the target value. This feedback control ensures temperature accuracy without requiring overly complex control mechanisms.
Solution Approach 2:
The system changes the pump output parameter dynamically based on flow rate conditions. Rather than using a fixed pump output, the control unit adjusts the pump output parameter according to the detected flow rate and its temporal changes. This parameter adjustment maintains temperature accuracy while keeping the control mechanism relatively simple.
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 system ensures stable hot water supply temperature by dynamically adjusting the control interval and gain settings in response to flow rate fluctuations, reducing user discomfort and maintaining temperature stability.
Implementation Method 1
a hot water supply heat exchanger for performing heat exchange between hot water supplied from an upper portion of the hot water storage tank and supply water
Implementation Method 2
a hot water supply heat source pump that circulates water in the hot water supply heat source conduit
Data Source
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AI summary
A storage water heater capable of ensuring hot water supply temperature stability even if there is fluctuation in hot water supply-side flow rate is provided. The storage water heater includes: a hot water supply heat exchanger 52 for performing heat exchange between hot water in the hot water storage tank 8 and supply water; a hot water supply heat source conduit 46 that guides water from an upper portion of the hot water storage tank 8 to a lower portion of the hot water storage tank 8 via the hot water supply heat exchanger 52; a hot water supply heat source pump 48 that circulates water in the hot water supply heat source conduit 46, and a control section 36. In a hot water supply operation of heating supply water using a heat source that is the hot water in the hot water storage tank 8, the control section 36 performs PID control to calculate an output of a hot water supply heat source pump 48, the output bringing a heat source-side flow rate Fl, which is a flow rate of hot water flowing in the hot water supply heat source conduit 46, to a target flow rate Ftgt, for each control interval ΔTc. Here, the control section 36 sets the control interval ΔTc to be equal to the monitoring interval ΔTf when a hot water supply-side flow rate Fk is stable, and sets the control interval ΔTc to a control interval ΔTcmin, which is shorter than the monitoring interval ΔTf, when the hot water supply-side flow rate Fk rapidly fluctuates.