Meandering Heat Block Outlet Geometry to Prevent Air Bubble Trapping
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Solution Overview
Problem
Heating blocks for instantaneous water heaters with bare wire systems face issues with air bubbles getting trapped downstream of upper deflection areas, leading to overheating and potential burn-through, especially at low flow rates due to buoyancy and poor flow dynamics.
Innovation Solution
A heating block design with a meandering heating path featuring U-shaped deflection areas and a stepped outlet section that abruptly widens the flow cross-section, creating targeted turbulence to entrain air bubbles and prevent their settlement, while maintaining uniform flow and equalized pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gradual widening of flow cross-section is used downstream of upper deflection areas, then flow attachment of air bubbles to inner walls is promoted, but air bubbles are trapped and heating coils overheat
Solution Approach 1:
Instead of gradually widening the flow cross-section as in conventional designs, the patent inverts the approach by using a stepped outlet section that abruptly widens the flow area. This reversal prevents air bubbles from adhering to channel walls by creating immediate flow separation and turbulence, thereby eliminating overheating risks while maintaining manufacturing simplicity
Solution Approach 2:
The patent changes the geometric parameter of the flow cross-section transition from gradual to abrupt by introducing a stepped outlet section. This parameter change fundamentally alters the flow behavior, creating turbulence that prevents air bubble attachment to heating coils and resolves the overheating issue
2Ease of operation
If conically tapered inlet section and conically widened outlet section are used in upper deflection areas, then flow cross-section is adjusted, but recirculation zones form where air bubbles settle
Solution Approach 1:
The patent extracts the problematic conical transition sections from the upper deflection areas and replaces them with a stepped outlet section design. This removal eliminates the recirculation zones that cause air bubble settlement, while the stepped section maintains adequate flow rate control without creating harmful flow patterns
Solution Approach 2:
The patent converts the potential harm of abrupt flow expansion into a benefit by deliberately designing the stepped outlet section to create turbulence. This turbulence, which might seem disruptive, actually prevents air bubble accumulation by keeping bubbles suspended in the flow rather than allowing them to settle on heating coils
3Speed
If bare wire heating coils are used directly in water flow, then control dynamics are improved, but air bubbles cause incomplete water flow around coils leading to burn-through
Solution Approach 1:
The patent introduces an intermediary structure - the stepped outlet section with abrupt flow expansion - between the water supply and the heating coils. This intermediary creates turbulence that acts as a mediator to prevent air bubbles from reaching and accumulating on the heating coils, thereby protecting coil durability while maintaining the direct contact benefits for response time
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 design effectively prevents air bubbles from being trapped downstream of the upper deflection areas, even at low flow rates, ensuring robust and low-maintenance operation by enhancing flow behavior and turbulence, thus preventing overheating.
Implementation Method 1
The abrupt widening tries to create targeted turbulences, which lead to the liquid flow covering the entire cross-section of the heating channel and entraining gas bubbles such as air bubbles adhering to the inner wall of the channel
Implementation Method 2
entraining gas bubbles such as air bubbles adhering to the inner wall of the channel
Implementation Method 3
The inlet sections have a conically tapered inlet cross section, viewed in the direction of flow. By reducing the flow cross section in the area of the respective inlet section, the flow in the deflection area is made more uniform
Implementation Method 4
The buoyant force of the air bubbles counteracts the flow and the air bubbles are only entrained by the flow when the flow rate is sufficiently large
Data Source
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AI summary
Disclosed is a heating block for an electric instantaneous water heater, in particular for providing heating water, with a housing in which a meandering heating path for heating a liquid is formed, which has a large number of heating channels for accommodating heating coils and a large number of U-shaped deflection areas for deflection of the liquid between the respective adjacent heating channels, wherein in the installed position the upper deflection areas have an inlet section for reducing a flow cross section of the heating channels to a deflection cross section and an outlet section that opens out into the respective heating channel in a stepped manner, and a flow heater. The invention is particularly suitable for providing a heating block for an electrically heated instantaneous water heater in the field of domestic appliance technology, which is insensitive to changing flow rates and is therefore robust and low-maintenance.