Heat exchanger for a mobile solid-fuel firing system
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Solution Overview
Problem
Mobile solid fuel combustion systems face challenges with weight due to the need for heat transfer mediums like water, and existing heat exchangers are either too heavy or lack mechanical stability under thermal and mechanical stresses.
Innovation Solution
A corrugated sheet metal heat exchanger design that transfers heat directly from hot flue gas to cooling gas, using thin, lightweight noble steel sheets for efficient heat transfer and mechanical stability, with a design that includes paired corrugated sheets forming tubes for internal gas ducts and an S-shaped external gas duct for effective flow guidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If water is used as a heat transfer medium in the furnace, then heat transfer efficiency is improved, but the weight of the system increases significantly
Solution Approach 1:
The patent extracts and eliminates the water heat transfer medium from the furnace system. Instead of using water to absorb and transport heat, the invention allows hot flue gas to flow directly through the furnace and heat exchanger, transferring heat directly to the surrounding environment or process without requiring a liquid heat carrier. This extraction of the water medium directly resolves the weight problem while maintaining heat transfer functionality through direct gas-to-surface convection.
2Reliability
If expensive heat-resistant steel is used for the heat exchanger wall, then resistance to thermal and chemical loads is improved, but the cost increases significantly
Solution Approach 1:
The patent changes the operating parameters of the heat exchanger by redirecting hot flue gas to flow externally along the heat exchanger walls rather than through internal channels. This parameter change reduces the thermal load on the wall material, allowing the use of less expensive, lighter materials that are still sufficient for the reduced thermal and chemical exposure, thereby resolving the cost contradiction.
3Reliability
If thicker wall material is used for the heat exchanger, then resistance to thermal and chemical loads is improved, but the weight increases significantly
Solution Approach 1:
By changing the flow configuration parameter to external flow along the walls, the thermal stress on the heat exchanger wall is reduced. This allows the use of thinner wall material that provides sufficient protection against the reduced thermal and chemical loads, thereby achieving the required longevity without the penalty of excessive weight.
4Weight of moving object
If thin sheet metal is used for the heat exchanger wall, then weight is reduced, but mechanical stability deteriorates under transport stresses
Solution Approach 1:
The patent employs a composite construction approach where thin sheet metal walls are combined with an internal framework or support structure. This composite design allows the thin walls to provide the necessary thermal and chemical resistance while the supporting framework provides the mechanical strength and stability required to withstand transport stresses, thereby resolving the contradiction between weight reduction and mechanical stability.
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 lightweight, mechanically stable, and cost-effective heat exchanger that efficiently transfers heat while withstanding the demands of mobile use, enabling effective heating for applications like hay drying and tent heating.
Implementation Method 1
the heat is transferred directly from the hot gas to the cooling gas
Implementation Method 2
The hot gas used is flue gas that flows from the combustion chamber into the heat exchanger
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a heat exchanger (22) for a mobile solid-fuel firing system (2) comprising a hot gas connection (38) and an inner gas duct (32), a cooling gas connection (58) and an outer gas duct (34) and a wall (30) separating the gas ducts (32, 34) and conducting heat, for producing a heat transfer from the hot gas to the colder gas. Defined gas ducting and a low weight of the heat exchanger can be achieved if the wall (30) comprises a number of interconnected corrugated sheets (74), between which both gas ducts (32, 34) run.