Tankless Water Heater Bypass Control for Stable Outlet Temperature
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Solution Overview
Problem
Conventional tankless water heaters face challenges in maintaining consistent water temperature at varying flow rates and suffer from corrosion and efficiency reduction over time due to thermal cycling of heat exchanger components.
Innovation Solution
A water heating system with a burner assembly, heat exchanger, and a bypass conduit that circulates heated water back into the inlet, using a feed-forward sensor and processor to control the burner operation, maintaining a constant set point temperature and reducing thermal cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional tankless water heaters operate without internal water retention, then energy efficiency is improved by avoiding standby heating, but water temperature consistency deteriorates at varying flow rates
Solution Approach 1:
The system continuously circulates water through the heat exchanger via the bypass conduit and pump, maintaining continuous thermal action rather than intermittent heating. This ensures consistent water temperature at the outlet regardless of flow rate variations, while the continuous circulation prevents standby energy losses by keeping water in constant motion through the heating element.
Solution Approach 2:
The feed-forward sensor monitors water temperature upstream of the heat exchanger and provides real-time data to the processor, which adjusts the burner assembly operation accordingly. This feedback mechanism enables precise temperature control at varying flow rates, maintaining consistency without requiring high standby energy input.
2Productivity
If heat exchanger components undergo thermal cycling to heat water, then water heating function is achieved, but component life deteriorates due to corrosion and thermal stress
Solution Approach 1:
The continuous circulation of water through the heat exchanger via the bypass conduit eliminates thermal cycling by maintaining constant thermal conditions. The pump keeps water flowing continuously through the heat exchanger, preventing the repeated heating and cooling cycles that cause thermal stress and corrosion, thereby extending component life while maintaining heating capability.
Solution Approach 2:
The system pre-heats water through continuous circulation before it is actually needed at the point of use. The bypass conduit allows water to be gradually heated in advance, reducing the thermal shock and rapid temperature changes that contribute to heat exchanger degradation, while still meeting heating demands when required.
3Ease of operation
If tank-type water heaters continuously heat water in the tank, then hot water availability is improved, but energy consumption increases due to maintaining heated water in standby
Solution Approach 1:
The system provides continuous hot water availability through constant circulation through the heat exchanger, eliminating the need for a storage tank. The bypass conduit and pump create a continuous flow system that heats water on-demand as it circulates, ensuring hot water is always available without the energy waste of maintaining a large volume of heated water in standby.
Solution Approach 2:
The invention extracts the water storage function by eliminating the traditional hot water tank entirely. Instead of heating and storing large volumes of water, the system heats water continuously as it flows through the heat exchanger, providing hot water availability without the energy consumption associated with tank-type standby heating.
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 maintains consistent water temperature without stagnation, reduces thermal cycling, and extends the life of heat exchanger components by continuously circulating heated water, thus minimizing the need for high heat input and reducing stress on the heat exchanger.
Implementation Method 1
A heat exchanger assembly is operatively coupled to the burner assembly, and includes a first fluid conduit in heat exchange relationship with a second fluid conduit
Implementation Method 2
a pump disposed in the bypass conduit circulates at least a portion of the heated water from the water exit conduit to the water inlet conduit
Implementation Method 3
A feed-forward sensor positioned in the water inlet conduit between the heat exchanger assembly and the bypass conduit monitors a parameter of the mixed water entering the heat exchanger assembly
Implementation Method 4
a burner assembly for providing a source of thermal energy. The burner assembly includes a combustion chamber, an air intake to supply an air stream to the combustion chamber, and a fuel inlet to supply fuel to the combustion chamber
Data Source
AI summary
A water heating system includes a burner assembly for providing a source of thermal energy to a heat exchanger. A water inlet conduit is coupled to the heat exchanger assembly for supplying fresh water to be heated, and a water exit conduit is coupled to the heat exchanger assembly for delivering the heated water to a point of use. A bypass conduit connects the water exit conduit to the water inlet conduit, and a pump disposed in the bypass conduit circulates at least a portion of the heated water from the water exit conduit to the water inlet conduit. A feed-forward sensor positioned in the water inlet conduit between the heat exchanger assembly and the bypass conduit monitors a parameter of the water entering the heat exchanger assembly, and a processor controls the operation of the of the burner assembly in response to the feed-forward sensor.