Heating assembly and liquid heater
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Solution Overview
Problem
Positive Temperature Coefficient (PTC) liquid heaters experience electrical leakage or failure due to unpredictable movement of the PTC heat-generating unit within the metal shell during multiple heating-cooling cycles, caused by thermal expansion and contraction.
Innovation Solution
A heating assembly with a heat-conducting shell and restraining elements at both ends to prevent the PTC heat-generating unit from moving out, featuring a first restraining element with an opening smaller than the unit's outer dimension and a grounding post for electrical conductivity, ensuring the unit remains within the shell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PTC heat-generating unit is tightly pressed against the metal shell to aid heat conduction, then heat transfer efficiency is improved, but the PTC unit may move unpredictably during thermal expansion and contraction cycles, leading to electrical leakage or failure
Solution Approach 1:
The shell is divided into a first shell portion and a second shell portion that are relatively movable with respect to each other. This segmentation allows the shell to adapt to thermal expansion and contraction of the PTC unit while maintaining containment, thus preventing electrical leakage without requiring complex restraint mechanisms.
Solution Approach 2:
The shell portions are designed to be relatively movable rather than fixed, allowing dynamic adjustment during heating and cooling cycles. This dynamic structure accommodates thermal expansion and contraction while maintaining reliable electrical containment and heat transfer contact.
2Temperature
If the PTC heat-generating unit is tightly pressed against the metal shell, then heat conduction is improved, but the unit may extend outside the shell during thermal expansion, causing electrical leakage
Solution Approach 1:
The shell is segmented into movable portions that can adjust their relative positions to accommodate PTC unit expansion while maintaining containment. This ensures continuous thermal contact for efficient heat transfer while preventing electrical leakage during expansion cycles.
Solution Approach 2:
The shell structure allows for changes in the relative position parameters of the first and second shell portions during thermal cycles. This parameter adjustment enables the shell to maintain both thermal contact and electrical containment throughout the heating and cooling process.
3Reliability
If restraining elements with openings smaller than the PTC unit are added to prevent movement, then electrical safety is improved, but the device structure becomes more complex
Solution Approach 1:
The movable shell portions serve multiple functions: they provide electrical containment through their configuration, enable heat transfer through thermal contact with the PTC unit, and accommodate thermal expansion through their relative movement capability. This multi-functionality eliminates the need for separate restraining elements.
Solution Approach 2:
The containment function traditionally requiring separate restraining elements is merged into the shell structure itself. The first and second shell portions work together as an integrated containment system that also provides thermal contact and accommodates expansion, reducing overall component count.
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
Prevents electrical leakage and failure by securely containing the PTC heat-generating unit, maintaining efficient heat transfer and grounding, thus enhancing the reliability and longevity of the heating assembly.
Implementation Method 1
The heat generated by the electrified PTC heat-generating unit is transferred to the metal shell
Implementation Method 2
The heat generated by the electrified PTC heat-generating unit is transferred to the metal shell, and then the metal shell heats the liquid flowing over its surface
Implementation Method 3
The PTC heat-generating unit 11 extends within the length of the metal shell 10 when heated, and retracts when cooled
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A liquid heater is provided including a heating assembly including: a heat-conducting shell defining therein a receiving cavity extending in a length direction of the heat-conducting shell and including a first opening at a first end of the receiving cavity and a second opening at a second end of the receiving cavity; a first restraining element disposed at the first opening; a second restraining element disposed at the second opening; and a Positive Temperature Coefficient (PTC) heat-generating unit entirely disposed within the receiving cavity between the first restraining element and the second restraining element. The first restraining element prevents the PTC heat-generating unit from passing through the first end of the cavity, and the second restraining element prevents the PTC heat-generating unit from passing through the second end of the cavity.