Heating unit for heating liquids in a motor vehicle
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Solution Overview
Problem
Existing heating units for liquids in motor vehicles, particularly those with plastic housings, face challenges in achieving a large heat exchange surface area while minimizing volume, especially when used with corrosive liquids like those in SCR systems, as they often have limited heat transfer due to the shape and material properties of the housing.
Innovation Solution
A heating unit with a multi-part plastic housing featuring two heat-conducting plates and a PTC-heating element, where the plates are arranged in a heating chamber and pockets within the housing, allowing for elastic preload against the pocket sidewalls to increase contact pressure and heat transfer, and optionally using ceramic PTC-heating elements for high heat output and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a cylindrical metal housing is used, then heat transfer is efficient, but the surface area is limited and the housing cannot be flexibly configured
Solution Approach 1:
The heating unit is divided into modular components: a plastic housing, heat-conducting plates with arms, and PTC heating elements. This segmentation allows the heating unit to be configured in different shapes and sizes to match various tank geometries, increasing adaptability while maintaining effective heat transfer surfaces through the distributed plate structure.
Solution Approach 2:
The heat-conducting plates extend with arms into the liquid volume, transitioning from a surface-bound heating approach to a three-dimensional heat distribution system. This dimensional expansion increases the effective heat exchange surface area without proportionally increasing the housing volume.
2Reliability
If a plastic housing is used, then the housing is flexible and resistant to corrosive liquids, but heat transfer efficiency is reduced
Solution Approach 1:
Heat-conducting plates serve as intermediary elements between the PTC heating elements and the liquid. These plates efficiently conduct heat from the heating elements to the liquid, compensating for the poor thermal conductivity of the plastic housing and ensuring effective heat transfer while maintaining corrosion resistance.
3Loss of energy
If the heat-conducting plates are pressed against the pocket sidewalls, then contact pressure and heat transfer are increased, but the device complexity increases
Solution Approach 1:
The mechanical properties of the heat-conducting plates are changed by selecting materials with appropriate elastic characteristics. This allows the plates to automatically generate and maintain optimal contact pressure against the pocket sidewalls through elastic deformation, eliminating the need for complex adjustment mechanisms while ensuring efficient heat transfer.
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 a larger heat exchange surface area with efficient heat transfer, effectively thawing frozen reducing agents across a larger region, including the suction opening, while maintaining a compact design and protecting against corrosive liquids.
Implementation Method 1
at least one PTC-heating element located between them
Implementation Method 2
two heat-conducting plates, between which the PTC-heating element is arranged
Data Source
AI summary
A heating unit for the heating of liquids in a motor vehicle has one or more PTC-heating elements between two heat-conducting plates then between a multi-part plastic housing. The two heat-conducting plates each have a base section against the one or more PTC-heating elements and each have an arm adjacent to the base section. An insulating element is arranged between the arms of the two heat-conducting plates, where the plastic housing has a first housing part and a second housing part. The first housing part has at least one pocket into which an arm of the heat-conducting plates and interposed insulating element is inserted. The first housing part and the second housing part together form a heating chamber adjacent to the at least one pocket, in which are arranged the base sections of the heat-conducting plates and the at least one PTC-heating element which is interposed between them.