Hot-Water Tank Sensor Control for Temperature Stratification
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Solution Overview
Problem
In hot-water supply systems with temperature stratification, maintaining high-temperature water after 100% storage completion is challenging due to natural heat dissipation and heat transfer, leading to reduced stored heat and conflicting relationships with heating unit efficiency and COP (coefficient of performance).
Innovation Solution
A control method that adjusts the set temperature of the first temperature sensor based on the temperature difference between sensors during heating-up and additional heating operations, using a corrected value calculated as 'set temperature + (ΔT-ΔT')/α, where α is an arbitrary coefficient, to maintain hot water temperature and balance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If additional heating operation is performed to maintain high-temperature water after 100% storage completion, then the hot water temperature is maintained, but the COP of the heating unit drops and energy efficiency decreases
Solution Approach 1:
The patent applies partial action by performing additional heating operation only for a limited duration or to a limited extent after 100% storage completion, rather than continuous heating. The control unit monitors temperature sensors and terminates additional heating when the temperature difference between sensors falls below a predetermined threshold, thus maintaining hot water temperature while avoiding excessive energy consumption and COP degradation.
2Use of energy by moving object
If additional heating operation is not performed after 100% storage completion, then the COP of the heating unit is maintained, but the hot water temperature drops due to natural heat dissipation and heat transfer
Solution Approach 1:
The patent implements feedback control by continuously monitoring temperatures at multiple heights in the storage tank using temperature sensors. The control unit compares the temperature difference between sensors and automatically activates or terminates the additional heating operation based on whether this difference exceeds a predetermined threshold, thus maintaining temperature while optimizing energy efficiency.
3Device complexity
If temperature sensor at lowest position is used to determine additional heating completion, then the control is simple, but the hot water temperature at top of tank is lower than initial set temperature
Solution Approach 1:
The patent transitions from single-point temperature measurement (lowest position only) to multi-dimensional temperature monitoring by placing temperature sensors at multiple heights in the storage tank. This dimensional expansion allows the system to detect temperature stratification and determine additional heating completion based on temperature differences between heights, ensuring the top water temperature meets the initial set temperature while maintaining simple control logic.
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 approach reduces the drop in hot water temperature during non-operating periods, allowing for the supply of hot water at a higher temperature close to the initial set temperature while minimizing COP drops, thus balancing temperature maintenance and efficiency.
Implementation Method 1
a heating unit that produces high-temperature water by heating low-temperature water
Implementation Method 2
sequentially store high-temperature water produced by the heating unit, forming temperature stratification from the top side thereof
Implementation Method 3
a plurality of temperature sensors are provided to be arranged in the vertical direction in the hot-water storage tank
Implementation Method 4
the control unit corrects the set temperature of the first temperature sensor based on a temperature difference (ΔT-ΔT') between a detected value (ΔT') from a second temperature sensor provided above the first temperature sensor and a detected value (ΔT) that the second temperature sensor detects during the heating-up operation
Data Source
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Figure 2
AI summary
In a hot-water supply system (1) that stores hot water at a set temperature inside a tank (11) and that can maintain the temperature thereof, temperature sensors (21A, 21B, 21N) are provided in the tank, wherein the sensor at the lowest position serves as a first sensor that detects 100% hot-water storage, and the hot-water supply system includes a control unit (22) that controls of the heating unit (2) during a heating-up operation and an additional heating operation on the basis of this detected value, wherein, during the additional heating operation, the control unit corrects the set temperature of the first sensor based on a temperature difference between a detected value (ΔT') from a second sensor provided thereabove and a detected value (ΔT) the second sensor detected during the heating-up operation and controls the heating unit with that corrected value serving as a target temperature.