Flat Water Heater Temperature Staging to Reduce Mixing Loss
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Solution Overview
Problem
Flat storage water heaters have a reduced useful water volume due to the mixing phenomenon, which is more pronounced in standard water heaters, leading to a larger volume requirement for the same thermal energy storage, and existing solutions to mitigate this require additional heat exchangers, increasing costs.
Innovation Solution
A flat water heater design with two cylindrical tanks connected in series, where the upstream tank is maintained at a higher temperature (Tacc + ΔTacc) than the downstream tank, reducing the mixing effect and minimizing the volume of water cooled below usage temperature when cold water enters, thereby reducing the overall tank volume without significant thermal dispersion increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single large cylindrical tank is used in a standard water heater, then the useful water volume is maximized, but the thickness and occupied space are large
Solution Approach 1:
The single large tank is divided into multiple smaller tanks (typically three cylindrical tanks arranged vertically). This segmentation allows the water heater to achieve the same useful water volume while reducing the overall thickness and occupied space, as the smaller tanks can be arranged more compactly than a single large tank
2Length of stationary object
If multiple tanks with reduced thickness are used in a flat water heater, then the thickness is reduced, but the useful water volume decreases due to the mixing phenomenon
Solution Approach 1:
The system pre-heats incoming cold water using heat exchangers that transfer thermal energy from the outgoing hot water before the cold water enters the storage tanks. This preliminary heating action reduces the temperature difference between incoming and stored water, thereby minimizing the mixing phenomenon and preserving useful water volume
Solution Approach 2:
Heat exchangers are introduced as intermediary devices between the incoming cold water and the stored hot water. These heat exchangers facilitate thermal energy transfer without direct mixing of the water masses, allowing the system to maintain higher useful water volume while using multiple thin tanks
3Quantity of substance
If the storage temperature Tacc is increased to compensate for mixing losses, then the useful water volume is improved, but the thermal dispersion and energy consumption increase
Solution Approach 1:
By pre-heating incoming water before it enters the storage tanks, the system reduces the temperature differential that drives thermal dispersion. This preliminary action allows the storage temperature to be maintained at optimal levels without excessive energy loss
Solution Approach 2:
The system uses thermostatic control with sensors that monitor water temperature and provide feedback to the heating elements and heat exchangers. This feedback mechanism optimizes energy usage by heating water only when and where needed, reducing thermal dispersion losses while maintaining adequate useful water volume
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 allows for a 13% reduction in tank volume and 6% reduction in outer shell surface area, maintaining performance and energy consumption while lowering production costs and overall dimensions, with minimal increase in thermal dispersions that can be further mitigated with additional insulation.
Implementation Method 1
an upstream storage tank (2.M) for pre-heating, to the expense of the thermal energy already stored in the water heater, the cold water coming from the waterworks
Implementation Method 2
said storage tanks (2.M and 2.V) being characterised in that the thermo-regulators (TR.M and TR.V) are calibrated so as to maintain the water in the upstream tank (2.M) at a storage temperature (TM) equal to the storage temperature (Tacc) of the downstream tank (2.V) increased by an overtemperature (ΔTacc)
Data Source
Figure 1
AI summary
The object of the present invention is a method for managing the heating temperature of a flat water heater (1) consisting of at least two storage tanks (2.M, 2.V) connected in series with one another. Said method provides for the water in the upstream tank (2.M) to be maintained at a storage temperature (TM) higher than a predetermined over-temperature (ATacc) relative to the storage temperature (Tacc) of the water contained in the downstream tank (2.V).