PTC Heat Exchanger With Force-Fit Insulation for Shock Safety
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Solution Overview
Problem
Motor vehicle air-conditioning systems with exclusively electrical or hybrid drives require high-voltage PTC elements for heating, posing a safety risk due to the potential for electrical shock when operating high-voltage components.
Innovation Solution
A heat exchanger design featuring a PTC element, conductor plates, and an insulation element, where the tube's varying thickness and curvature create a bending moment to secure the heating assembly within a force fit, eliminating the need for external clamping and reducing the risk of electrical shock by ensuring the insulation element is only pressed against at specific contact surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-voltage PTC elements are used for heating in motor vehicle air-conditioning systems, then heating power is improved, but safety risk increases due to potential electrical shock
Solution Approach 1:
An electrical insulation element is introduced as an intermediary between the high-voltage conductors and the heat-conducting elements/tube. This insulation element prevents direct contact and electrical shock while still allowing thermal energy to be transferred from the PTC element through the conductors to the heat-conducting elements, thus resolving the contradiction between maintaining high heating power and ensuring safety.
2Reliability
If the tube is pressed against the insulation element to secure the heating assembly, then reliability is improved, but the insulation element may be damaged by excessive pressure
Solution Approach 1:
The tube is designed with varying wall thickness, being thicker at the contact surfaces where pressure is applied to the insulation element and thinner in other regions. This local variation in thickness allows the tube to concentrate the pressing force at specific locations to securely hold the heating assembly, while the overall design prevents excessive pressure that could damage the insulation element, thus resolving the contradiction between reliability and strength.
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 allows for safe operation of high-voltage electrical heating systems in motor vehicle air-conditioning systems by preventing electrical shock and ensuring reliable, efficient heating without the need for external clamping frames, thus enhancing safety and production efficiency.
Implementation Method 1
PTC (Positive Temperature Coefficient) elements are current-conducting materials which exhibit an electrical resistance and which can conduct the current better at relatively low temperatures than at relatively high temperatures. The electrical resistance of said PTC elements thus increases with rising temperature.
Implementation Method 2
heat-conducting elements, in particular lamellae or corrugated fins, by means of which the surface area for heating the air is enlarged
Data Source
AI summary
Disclosed herein is a heat exchanger, comprising at least one electric resistance heating element, at least two conductors which are connected to the at least one electric resistance heating element in an electrically conductive manner in order to conduct electric current through the at least one electric resistance heating element and thereby heat the electric resistance heating element, at least one thermally conductive element for transferring heat from the at least one electric resistance heating element to a fluid to be heated, at least one electrically insulating element, which electrically insulates the at least two conductors, and at least one pipe, wherein the at least two conductors and the at least one electric resistance heating element are arranged within a cavity bounded by the pipe and the pipe lies on the at least one electrically insulating element under a compressive force at at least one contact surface.