Monolithic Resistive Heater Design for High-Temperature Fluid Heating
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Solution Overview
Problem
Existing resistojet designs suffer from premature failure due to thermal expansion and manufacturing defects, limiting their reliability and efficiency, especially at high temperatures, and require complex assembly processes.
Innovation Solution
An electric heating system with a monolithic resistive heater designed for high-temperature operation, manufactured via additive manufacturing, featuring a serpentine flow path and annular walls to manage thermal expansion, and electrical terminals positioned externally to reduce heat loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If concentric tubular heater structure is used with CVD and EB welding, then high temperature operation is achieved, but manufacturing complexity and assembly time increase
Solution Approach 1:
The patent merges multiple manufacturing techniques (CVD, EB welding, and additive manufacturing) into a unified process where the heater structure is additively manufactured as a single component, eliminating the need for separate assembly steps and reducing manufacturing complexity while maintaining high temperature capability
Solution Approach 2:
The heater structure is segmented into multiple flow channels with serpentine paths, allowing the fluid to traverse through different sections of the heater, maximizing heat transfer efficiency while maintaining a monolithic structure that simplifies manufacturing
2Temperature
If concentric tubular heater with multiple welding joints is used, then high temperature operation is achieved, but reliability decreases due to manufacturing defects
Solution Approach 1:
The patent combines multiple functions (heating, fluid distribution, structural support) into a single additively manufactured component, eliminating welding joints and associated manufacturing defects, thereby improving reliability while maintaining high temperature operation
Solution Approach 2:
The patent changes the manufacturing parameters from traditional subtractive or assembly-based methods to additive manufacturing, which allows for controlled material deposition and creates a monolithic structure without welding joints, improving reliability
3Reliability
If thermal expansion is managed in monolithic heater, then reliability improves, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates thermal expansion management directly into the additive manufacturing process by designing the geometry to accommodate expansion, using the manufacturing process itself to create built-in compensation features rather than adding separate mechanical components
Solution Approach 2:
The patent merges thermal management functionality into the base heater structure, where the same additively manufactured component that provides heating also manages thermal expansion, eliminating the need for separate expansion compensation 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 system achieves high thermal efficiency and reliability, allowing operation at temperatures up to 3,500 K with a lifetime exceeding 6,000 cycles, suitable for space missions, and can be produced at low cost using Selective Laser Melting.
Implementation Method 1
The resistojet is a technology within the electrothermal thruster class that heats the gas by Joule (or resistive) heating of a solid heating element
Implementation Method 2
a concentric tubular heater was manufactured as a single monolithic component using metal additive manufacturing
Data Source
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AI summary
An electric heating system for heating a fluid flow, the system comprising: a housing having an inlet for a fluid flow to be heated by the electric heating system and an outlet for the fluid flow which has been heated by the electric heating system; and a resistive heater mounted within the housing. The resistive heater comprises a fluid input and a fluid output which are fluidically coupled, respectively, to the inlet and the outlet, a plurality of annular walls composed of an electrically conductive material, the walls being nested to define a plurality of annular flow channels which are serially arranged concentrically about a longitudinal axis, wherein the walls extend between opposite first and second ends of the resistive heater which are mutually separated along the longitudinal axis, and first and second electrical terminals for connection to a source of electrical energy to heat the walls of the resistive heater, the first and second electrical terminals being electrically connected to respective first and second walls which are mutually adjacent and comprise an outer pair of the walls which are located at a radially outer side of the resistive heater. The plurality of annular walls are mechanically connected together whereby adjacent flow channels have opposite fluid flow directions and are connected at adjacent ends of the respective channels to define an alternating serpentine flow path which has an input end at the fluid input and an output end at the fluid output, wherein the input and output ends are respectively located at radially outer and radially inner positions relative to the longitudinal axis. The plurality of annular walls are electrically connected together to define a continuous electrically conductive path extending between the first and second electrical terminals, the conductive path having a first part which extends from the first wall to a centre of the resistive heater and a second part which extends from the centre of the resistive heater to the second wall. Also disclosed is a method of producing a high-temperature fluid flow using the electric heating system.