Water heating apparatus
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Solution Overview
Problem
Latent heat-recovery type water heating apparatuses face issues with freezing in cold conditions due to water remaining in the second heat exchanger, leading to inefficiencies and increased costs from requiring additional heating elements.
Innovation Solution
A bypass pipe is connected between the water supply pipe and the drain pipe at an intermediate position between the first and second heat exchangers, allowing the burner to heat the second heat exchanger directly, preventing freezing and maintaining system usability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heater and heat conduction member are added to prevent freezing in the second heat exchanger, then the antifreeze effect is improved, but the device complexity and cost increase
Solution Approach 1:
The system uses its own exhaust gas to defrost the second heat exchanger automatically when freezing is detected, eliminating the need for external heaters or heat conduction members. The exhaust gas flows through the second heat exchanger to melt frozen water, and the system self-regulates by controlling the exhaust gas flow based on temperature sensors.
Solution Approach 2:
The invention recovers waste heat from exhaust gas that would otherwise be discarded. During normal operation, exhaust gas is discharged after heat exchange. During freezing conditions, this same exhaust gas is redirected to defrost the second heat exchanger, converting a waste resource into a useful heating source for antifreeze protection.
2Productivity
If the second heat exchanger uses a smaller diameter tube to recover latent heat, then the heat exchange efficiency is improved, but water remains in the tube and freezing risk increases
Solution Approach 1:
The system dynamically adjusts the diameter of the second heat exchanger tube based on operating conditions. During normal operation, a smaller diameter is used for efficient latent heat recovery. When freezing risk is detected, the system switches to a larger diameter configuration that allows better water drainage and reduces freezing risk, thus adapting the geometry to operational requirements.
3Reliability
If additional heating elements are installed to prevent freezing, then the antifreeze capability is improved, but the energy consumption and cost increase
Solution Approach 1:
The system uses its own exhaust gas to defrost the second heat exchanger automatically when freezing is detected, eliminating the need for external heaters or heat conduction members. The exhaust gas flows through the second heat exchanger to melt frozen water, and the system self-regulates by controlling the exhaust gas flow based on temperature sensors.
Solution Approach 2:
The invention recovers waste heat from exhaust gas that would otherwise be discarded. During normal operation, exhaust gas is discharged after heat exchange. During freezing conditions, this same exhaust gas is redirected to defrost the second heat exchanger, converting a waste resource into a useful heating source for antifreeze protection.
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
Enables quick defrosting of the second heat exchanger using combustion heat, ensuring continuous operation without additional heating elements and minimizing water retention in the bypass pipe.
Implementation Method 1
a first heat exchanger for exchanging heat between sensible heat contained in an exhaust gas and water flowing through a heat exchanger tube
Implementation Method 2
a second heat exchanger for exchanging heat between latent heat contained in the exhaust gas and water flowing through the heat exchanger tube
Implementation Method 3
the burner to heat the second heat exchanger directly, preventing freezing and maintaining system usability
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A water heating apparatus 2 includes: an exhaust gas passage through which an exhaust gas from a burner 5 flows; a water flow passage through which water flows; a first heat exchanger 6 configured to exchange heat between sensible heat contained in the exhaust gas and water flowing through a heat exchanger tube, and arranged upstream of the exhaust gas passage and downstream of the water flow passage; a second heat exchanger 7 configured to exchange heat between latent heat contained in the exhaust gas and water flowing through a heat exchanger tube, and arranged downstream of the exhaust gas passage and upstream of the water flow passage; and a bypass pipe 35 arranged in the water flow passage in such a position as to bypass the second heat exchanger 7 and designed to allow a minimum amount of water required for a burner 5 combustion operation to flow therethrough into the first heat exchanger 6.