RU2163328C1 - Method of convective drying of wood - Google Patents

Abstract

FIELD: wood- working industry. SUBSTANCE: convective drying of wood, mainly logs and bars is effected as follows: prior to starting the drying procedure, grooves are made on opposite sides along longitudinal axis of log or bar and air is admitted along these grooves whose sizes are found from the following relationships:

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Description

 The invention relates to woodworking, and in particular to a technology for drying wood and other fibrous materials, and can be used at enterprises of the woodworking industry and other industries.

 A known method of drying wood, including heating it with hot air and subsequent evacuation with the repetition of these cycles "heating - evacuation" until the wood reaches the specified moisture content (see the description of the patent of the Russian Federation N 2027126, F 26 B 3/02, 1995/1 /). The disadvantage of this method is the difficulty of implementation, since it provides for the presence of several cycles of "heating - evacuation" and the need for relatively complex drying devices capable of evacuating significant volumes.

 A known method of convective drying of wood, including its heating in the chamber at atmospheric pressure and subsequent evacuation of the chamber with the supply of atmospheric air until the wood reaches a predetermined residual moisture content (see the description of RF patent N 2045720, F 26 B 3/20, 1995/2 /). The known method should be classified as convective, since convection is used in its implementation, i.e. heat transfer, in particular, with the help of a drying agent, which is used as air (see Physical Encyclopedic Dictionary. M., SE, 1983, p. 307).

 The disadvantage of this method, as described above, is the relative complexity of the implementation, which consists in the need to use plants that provide evacuation of significant volumes.

 The closest to the claimed in its technical essence and the achieved result is a known method of convective drying of wood, including its blowing with heated air in a tunnel dryer (see the description of the patent of the Russian Federation N 2080532, F 26 B 9/06, 1997/3 /).

 The disadvantage of this method is the long drying time of wood and the resulting significant energy consumption, due to the lack of preliminary operations that contribute to the acceleration of drying processes.

 The inventive method of convective drying of wood is aimed at reducing the drying time and associated energy costs.

 This result is achieved by the fact that the method of convective drying of wood, mainly of timber or logs, involves performing grooves before drying along the longitudinal axis of the timber or log on its opposite sides.

 The specified result is also achieved by the fact that the air flow is directed along the grooves.

The specified result is also achieved by the fact that the groove in the beam is performed with the following aspect ratio:
b = (Dd) / 2 = a; l = (Ha) / 2,
where D is the thickness of the beam, mm;
d is the groove width, mm;
b is the distance from the edge of the beam to the groove wall mm;
H - beam height, mm;
l - groove depth, mm;
a is the distance between the bottom of the grooves, mm

Distinctive features of the proposed method are:
- execution in the timber being dried or a log before drying the grooves on opposite sides along the longitudinal axis;
- the direction of the air flow used to create forced convection by blowing along the grooves;
- the execution of the groove in the timber with the specified size ratio.

 Performing grooves in the bar or log to be dried allows increasing the surface of the product from which moisture will evaporate and providing the drying agent with access to the interior of the material and thereby speeding up the drying process and, therefore, reduce the energy consumption for the process.

 The implementation of the grooves along the longitudinal axis of the beam or log on its opposite sides, firstly, provides the technological preparation of the drying process, and, secondly, preserves the strength characteristics of the log or beam, as is the case in an I-beam.

 The direction of the air flow used to blow wood along the grooves also accelerates the drying process, since it eliminates the stagnation of saturated air vapor in the grooves.

 To ensure the drying process, you can use both heated air and air having an ambient temperature.

It is known that the drying time of wood t is approximately proportional to D ^1.5 , where D is the thickness of the product to be dried. Therefore, in order to dry an article having different transverse dimensions, it must be dried for a time until it dries in the widest part of the cross section. The implementation of the grooves with the specified size ratios allows you to ensure equal thickness of the elements of the cross section of the beam, which also provides an acceleration of the drying process. In this case, the drying time t due to a decrease in the widest cross section is approximately halved by a factor of 2.8 (D ^1.5 / b ^1.5 ) ≈ 2 ^1.5 ≈ 2.8).

 An additional result of performing longitudinal grooves in logs or beams is that when assembling houses, air-filled cavities automatically arise, which increases the thermal resistance of the walls.

 The essence of the proposed method of drying wood is illustrated by an example implementation and drawings. In FIG. 1 shows cross sections of logs and beams with grooves made therein. In FIG. 2 shows a cross section of a beam with an optimal groove size, which provides the most rapid drying.

 The method is implemented as follows. In the logs or beams sent for drying, grooves are made along their longitudinal axis using known woodworking equipment. Then the bars or logs are laid in a known drying device (open or closed) and blown with a drying agent (air) with the specified temperature and humidity parameters, providing high-quality drying with the direction of its flow along the grooves. The drying process is controlled by known means and when the wood reaches the set humidity values, it stops.

Claims (2)

 1. The method of convective drying of wood, mainly timber or logs, characterized in that before drying along the longitudinal axis of the timber or log on its opposite sides, grooves are made and air flow is guided along the grooves. 2. The method according to claim 1, characterized in that the groove in the beam is performed with the following aspect ratio:
b = (Dd) / 2 = a; l = (Ha) / 2,
where D is the thickness of the beam, mm;
d is the groove width, mm;
b is the distance from the edge of the beam to the groove wall, mm;
H - beam height, mm;
l - groove depth, mm;
and - the distance between the bottom of the grooves, mm

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