PTC Heating Device for Rapid Urea Solution Thawing
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Solution Overview
Problem
Existing heating devices for thawing frozen aqueous urea solution in vehicles face challenges in providing sufficient heating power efficiently, particularly under varying electrical supply voltages, and require costly machining or special materials to achieve optimal performance.
Innovation Solution
The heating device employs positive temperature coefficient (PTC) thermistors with reduced minimum resistance and a dual heating element configuration to regulate heating power, ensuring efficient thawing times and protection from excessive temperatures, independent of voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the surface of the metallic heat distribution body is adapted to the geometry of the PTC element by machining or polishing, then the heat transfer to the heat distribution body is improved, but additional processing steps are required which increase production costs
Solution Approach 1:
The patent changes the material parameter of the heat distribution body from metallic to plastic, eliminating the need for machining or polishing operations. This material substitution achieves sufficient heat transfer performance without requiring additional processing steps, thereby reducing production costs while maintaining heating power.
Solution Approach 2:
The patent employs a plastic heat distribution body that can be manufactured cost-effectively without complex processing. The plastic material, while less durable than metal, provides adequate performance for the application and eliminates expensive machining operations, aligning with the principle of using cost-effective materials that suffice for the intended function.
2Loss of time
If the minimum resistance of the PTC element is reduced to increase heating power, then thawing time is reduced, but the heating device may be exposed to excessively high temperatures at higher voltages
Solution Approach 1:
The patent incorporates a feedback mechanism where the PTC element's resistance automatically increases with temperature. This intrinsic feedback property allows the system to self-regulate: at lower temperatures, the element has lower resistance and provides high heating power for rapid thawing; as temperature rises, resistance increases to prevent excessive temperature growth, protecting the system without requiring external control.
Solution Approach 2:
The patent utilizes the temperature-dependent resistance parameter of the PTC element to dynamically adapt the heating characteristic. By selecting an appropriate minimum resistance value and leveraging the material's inherent property that resistance changes with temperature, the system achieves both rapid thawing capability and temperature protection without additional control mechanisms.
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 solution provides enhanced heating power, reduces thawing times, and avoids costly production steps while maintaining consistent performance across varying voltages, meeting legal requirements for exhaust gas treatment systems.
Implementation Method 1
a heating device (3) for heating a reducing agent storage container (1), in particular for thawing a frozen aqueous urea solution
Implementation Method 2
comprising at least one positive temperature coefficient thermistor (5)
Implementation Method 3
The thus increased, or high, heating power results in shorter thawing times
Data Source
AI summary
The invention relates to a heating device (3) for a storage container with a urea reducing agent, comprising at least one electrically operatable heating element (6) and a heat distribution element (7) which is thermally coupled to the heating element (6), wherein the heating element (6) has a first heating sub-element (40) which has at least one positive temperature coefficient thermistor (5), and the first heating sub-element (40) is connected to a second heating sub-element (42, 52, 62) which is designed to reduce the dependence of the heat output of the heating device (3) on an electric voltage applied to the heating element (6) in the event of an electric voltage with large values, in particular above 13 volt, so that the heat output dispensed to the thermal conducting element and the surrounding components with plastic encapsulation is not too high.