Indirect Rod Preheating Using Waste-Heat Liquid Heat Exchange
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Solution Overview
Problem
The existing methods for preheating rod-shaped metallic workpieces, such as aluminum rods, using exhaust gases from gas quick preheating ovens are inefficient due to low heat capacity and short contact time between gas molecules and the workpieces, resulting in low heat transfer efficiency.
Innovation Solution
A heat exchanger device is introduced between the fluid flow connection and the preheating chamber to transfer heat from the fluid flow to a heat transfer medium flow, which then preheats the workpieces indirectly, optimizing the heat transfer medium flow to enhance efficiency, particularly using a liquid medium like water that can provide better wettability and contact time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If exhaust gas flow is used directly to preheat workpieces, then the system structure is simple, but the heat transfer efficiency is low
Solution Approach 1:
A liquid heat transfer medium is introduced as an intermediary between the exhaust gas and the workpiece. The liquid medium absorbs heat from the exhaust gas through a heat exchanger and then applies heat to the workpiece surface, thereby improving heat transfer efficiency while maintaining system simplicity
Solution Approach 2:
The patent changes the physical state of the heat transfer medium from gas (exhaust gas) to liquid (heat transfer medium). This parameter change enables better heat transfer characteristics including higher heat capacity, improved wettability, and extended contact time with the workpiece surface
2Duration of action of moving object
If gas flow is used for preheating, then the contact time between heat medium and workpiece is short, but using liquid medium increases contact time and efficiency
Solution Approach 1:
The liquid heat transfer medium serves as a mediator that can be applied to the workpiece surface and remain in contact for an extended period. This intermediary approach allows the system to achieve longer contact time despite the added complexity of the heat exchanger device
Solution Approach 2:
The patent utilizes the liquid phase of the heat transfer medium to achieve prolonged contact with the workpiece surface. The liquid phase allows the heat medium to conform to and remain in contact with the workpiece geometry, thereby extending the duration of heat transfer action
3Loss of energy
If exhaust gas is used directly, then no additional heat transfer medium is needed, but heat transfer effectiveness is low
Solution Approach 1:
The patent changes the heat transfer medium from gas phase (exhaust gas) to liquid phase (heat transfer medium). This parameter change fundamentally improves heat transfer effectiveness due to the liquid's superior heat capacity, thermal conductivity, and wettability properties
Solution Approach 2:
The liquid heat transfer medium acts as an intermediary substance that bridges the exhaust gas and the workpiece. This intermediary approach significantly enhances heat transfer effectiveness, and the patent notes that the water flow can be recovered and reused, minimizing the net quantity of additional substance required
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
This approach significantly increases the effectiveness of heat transfer from the exhaust gas flow to the workpieces, achieving better preheating efficiency and economical operation by using a water flow that spreads across the workpiece surface by gravity, ensuring comprehensive surface coverage and continuous operation.
Implementation Method 1
a heat exchanger device (11) is provided between a fluid flow connection (14) and the preheating chamber (12) in a fluid flow line (15, 16) in order to transfer the heat from the fluid flow to a heat transfer medium flow
Implementation Method 2
transfer the heat from the fluid flow to a heat transfer medium flow
Implementation Method 3
the wettability which is provided by a liquid compared to a gas and which allows a corresponding residence or contact time of the liquid on the workpiece can lead to a significant increase in effectiveness
Implementation Method 4
the wettability which is provided by a liquid compared to a gas and which allows a corresponding residence or contact time of the liquid on the workpiece
Implementation Method 5
the liquid applied to the upper side of the workpiece can spread across the entire surface of the workpiece by gravity alone
Data Source
AI summary
A device for preheating rod-like, metal workpieces, in particular aluminium rods, by means of a fluid flow heated by residual heat or waste heat of a combustion process occurring in a heating device for heating the workpieces. The device has a preheating chamber for receiving at least one workpiece, wherein, in order to transfer the heat from the fluid flow to a heat transfer medium flow in a fluid flow line between a fluid flow connection and the preheating chamber, a heat-exchanger unit is provided in such a way that the workpiece is preheated indirectly via the heat transfer medium flow heated in the heat-exchanger unit by the fluid flow.