Timber Drying Method Using Inverse Temperature Gradient and Heat Recovery
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Solution Overview
Problem
Existing timber drying processes face challenges such as high energy consumption, risk of drying cracks, and growth of thermo-tolerant moulds, which can result in surface defects and discolouration in timber.
Innovation Solution
The method involves dividing the drying process into two subprocesses with inverse temperature gradients, where the first subprocess operates at a high wet temperature and the second at a low wet temperature, with heat recovery systems transferring enthalpy from the first to the second subprocess.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a preheating zone with moderate drying capacity is used, then energy consumption is reduced, but the risk of drying cracks increases
Solution Approach 1:
The patent inverts the conventional temperature gradient approach by using a high wet temperature (50-70°C) in the preheating zone followed by a lower wet temperature in the main drying zone. This reverse approach prevents drying cracks while maintaining energy efficiency, as the high initial temperature makes the wood more plastic and reduces drying tensions.
Solution Approach 2:
The patent changes the temperature parameters in a specific sequence: first maintaining high wet temperature (50-70°C) with dry temperature 5-15°C lower, then transitioning to lower wet temperature in the main drying zone. This parameter change strategy resolves the contradiction between energy efficiency and crack prevention.
2Loss of energy
If low temperature is used during initial drying phase, then energy consumption is reduced, but thermo-tolerant mould growth is promoted
Solution Approach 1:
The patent applies preliminary high temperature action in the preheating zone (50-70°C wet temperature) before the main drying phase. This preliminary high temperature treatment prevents mould spore germination and eliminates thermo-tolerant moulds, while the overall process remains energy efficient due to heat recovery.
Solution Approach 2:
The patent converts the potentially harmful high temperature requirement for mould prevention into a beneficial preheating phase that also serves to condition the wood for subsequent drying. The high temperature zone, which could be seen as energy-intensive, actually prevents mould problems that would require additional treatments.
3Object-affected harmful factors
If high wet temperature is maintained throughout the drying process, then mould growth is prevented, but energy consumption increases
Solution Approach 1:
The patent segments the drying process into two distinct zones: a preheating zone with high wet temperature (50-70°C) for mould prevention and wood conditioning, and a main drying zone with lower wet temperature for energy-efficient moisture removal. This segmentation allows high temperature to be applied only where necessary.
Solution Approach 2:
The patent applies different temperature qualities to different zones: the preheating zone receives high wet temperature locally to prevent mould and condition the wood, while the main drying zone operates at lower temperature locally to minimize energy consumption. This local quality differentiation resolves the contradiction.
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 reduces energy consumption, minimizes the risk of drying cracks and mould growth, and results in high-quality timber with reduced surface defects, while maintaining efficient drying processes.
Implementation Method 1
A heat exchanger is normally used in this case in which the ventilation is carried out in such a manner that the exhaust air (with a higher temperature) that is output from one zone is allowed to transfer part of its enthalpy to the supply air (with a lower temperature) that is input to another zone.
Implementation Method 2
The drying air is heated with the aid of an air-heating arrangement that comprises heating coils.
Implementation Method 3
Air is used as a drying medium to transfer heat and transport moisture, which air is circulated with a specific temperature, moisture content and rate of flow through the material with the aid of fans.
Implementation Method 4
The drying air is caused to pass through the material such that moisture and water evaporate from the material and are absorbed by the drying air.
Data Source
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AI summary
The invention concerns a method of drying of material, in particular timber, using warm air, where the drying process is divided into at least a first and a second subprocess (A, B), in series with each other, and the circulating flows (2) of the two subprocesses in the relevant drying chambers are conditioned to significantly different wet temperatures (TvA) and (TvB), respectively. In order to achieve a reduced energy input, the circulating air (2) in the first subprocess (A) is given a higher wet temperature (TvA) than the circulating air (2) in the second subprocess (B), and that heat in the circulating air (2) in the first subprocess (A) is recovered and transferred to the second subprocess (B).