Flow Heater with Calorimetric Flow Sensor to Prevent Overheating
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Solution Overview
Problem
Flow heaters in vehicles face overheating issues due to rapid changes in liquid flow rate, which can lead to damage or fire, and existing solutions like temperature and mechanical flow sensors have limitations in cost, susceptibility to damage, and differential pressure increase.
Innovation Solution
A calorimetric flow sensor is integrated into the flow heater, using a sensor resistor with a distinct temperature dependence to determine fluid flow rate, allowing for reduced heating power and quick response to alterations, implemented at lower costs with a design that includes metal or ceramic particles and conductive tracks, and positioned closer to the fluid inlet for enhanced sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical flow sensor (flap) is used to detect flow rate changes, then flow rate detection is achieved, but the device complexity increases and susceptibility to damage increases
Solution Approach 1:
The patent replaces the mechanical flap-based flow sensor with a calorimetric flow sensor that uses electrical resistance measurements. The sensor resistor's temperature-dependent resistance provides flow rate information without moving parts, eliminating mechanical complexity and damage susceptibility while maintaining measurement capability.
Solution Approach 2:
The patent introduces a sensor resistor as an intermediary element that indirectly measures flow rate through temperature changes. Instead of directly measuring flow with a mechanical flap, the sensor resistor's temperature (via resistance) serves as a mediator that reflects flow conditions, simplifying the overall system.
2Measurement precision
If a mechanical flow sensor is used to detect flow rate changes, then flow rate detection is achieved, but the cost increases
Solution Approach 1:
The patent replaces expensive mechanical flow sensors with a calorimetric sensing approach using electrical resistance measurements. This substitution significantly reduces manufacturing costs while maintaining the ability to detect flow rate changes through the sensor resistor's temperature-dependent resistance.
Solution Approach 2:
The sensor resistor can be implemented as a simple, low-cost metallic trace or thin-film element that is inexpensive to manufacture. Unlike precision mechanical components, the electrical resistance sensor can be produced cheaply through standard PCB trace fabrication or thin-film deposition techniques.
3Reliability
If a temperature sensor is used to detect overheating, then overheating detection is achieved, but the response time to rapid flow rate changes is delayed
Solution Approach 1:
The sensor resistor continuously monitors flow conditions before overheating occurs by measuring its own temperature. This preliminary detection of flow rate changes allows the control system to adjust heating power proactively, preventing overheating rather than reacting to it after temperature sensors detect the problem.
Solution Approach 2:
The sensor resistor provides continuous feedback on flow rate conditions through its temperature-dependent resistance. This feedback loop enables real-time adjustment of heating power in response to flow changes, improving response time compared to temperature sensors that only detect overheating after it has occurred.
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 calorimetric flow sensor effectively prevents overheating by accurately measuring fluid flow rate, reducing costs and susceptibility to damage, while maintaining low differential pressure and enabling diagnostic capabilities, ensuring safer operation of flow heaters.
Implementation Method 1
a sensor resistor, which in operation is heated with a predetermined electrical power
Implementation Method 2
cooled by the liquid that flows through the flow heater
Implementation Method 3
From the value of the electrical resistance of the sensor resistor, the temperature of the sensor resistor, and from this the fluid flow rate, can be determined
Implementation Method 4
an electrical heating resistor, with which a liquid can rapidly be heated
Data Source
AI summary
A flow heater for vehicles is described. The flow heater has a housing, which has an inlet and an outlet. A flow channel for fluid to be heated is disposed in the housing and leads from the fluid inlet to the fluid outlet. A heating plate forms a wall of a heated section of the flow channel and carries an electric heating resistor. A calorimetric flow sensor is provided for measuring a fluid flow in the flow channel.