DE19801162C1 - Drier for stacked timber - Google Patents

Abstract

The drier applies low to the stacked wood in a chamber with a drying gas flow passing a heating register (12). There are flow ducts (17-g) positioned successively in a plane perpendicular to the flow direction of the drying gas (14) between at least two stacked rows (13a,b).

Description

The invention relates to a device for drying stacked lumber or other hygroscopic plate or rod-shaped goods with negative pressure in one vacuum-proof drying chamber with fans for circulation tion of a gaseous dry medium, its effects direction transverse to the longitudinal axis of the drying chamber runs, with a condenser for dehumidification and with one or more heating registers for convective heat transmission, with the lumber in the direction of flow of the drying medium at least two rows behind is arranged one another.

Vacuum drying with a reduced pressure in the Range of approximately 50 to 500 mbar compared to the conventional technical drying with moist air at atmospheric pressure the possibility of drying times for comparable batches (i.e. in terms of wood type and strength and initial moisture) and at comparable To significantly reduce drying qualities. this will  due to the higher mobility of the water inside the wood allows with decreasing pressure, causing on the surface evaporated water quickly supplied from the wooden core can be without drying out the wood in the Mechanical stresses arise when the core is wet hen (the so-called "cladding") that lead to cracks or Can lead to faults.

A shortening of the drying time presupposes that the convective transport of those required for drying Evaporation heat from the heating registers to the wood Using a gaseous drying medium accordingly done faster. The circulated by the fans Desiccant takes place when passing the heating control sters thermal energy, which during the flow of the Wood stack is released again by the Desiccant cools down. Accordingly arises on the way through the stack of wood a temperature gradient that changes by the temperature difference of the drying medium Mark the entry and exit of the stack and also measure leaves. Because the density of the drying medium and therefore its Heat capacity per unit volume is approximately proportional decreases as the pressure drops, because of the faster decay drying process but just a corresponding higher heat flow compared to conventional dryers a higher flow rate is necessary of the drying medium are generated to provide enough energy to be able to transport per unit of time.

Furthermore, the wood temperature in vacuum compared to other parameters have a much greater impact on the Drying progress than with conventional drying. This effect is even more evident when than Drying medium hot steam with only a small amount of residual air  sharing is used. Under "superheated steam" it becomes unsaturated ter understood water vapor, the partial pressure of which is lower is the maximum possible at a given temperature Saturation pressure according to the known state diagram of the Water (also called "boiling" or "dew point curve"). Accordingly, greater attention must be paid to the fact that local temperature differences remain as small as possible, if a lot of wood with homogeneous initial properties evenly until the desired final moisture is reached should be dried. Temperature differences can not only occur disturbingly in the direction of flow. They also result from inhomogeneities in the dry matter flow in the interstices between the stacks, as the transfer significant or transferable amount of heat, as already mentioned, from the flow velocity depends.

Known vacuum dryers, such as those from the DE 195 22 028 A1 are known, consist of a print fixed, e.g. B. cylindrical steel kettle with a gate on The End. Fans and heating coils are in the for Wood stack with a rectangular cross-section cannot be used, free chamber areas near the wall above and / or arranged to the side of the wood pile. A capacitor for Excess steam is deposited in the Inside the boiler or is external, pressure tight pipe connected to it. By means of a Vacuum pump can permanent gases, especially air, eva be selected.

The lumber to be dried preferably becomes Stan Standard stack packages with a width of 1 to 1.5 m stacked pelt, where there is no guideline for the package height of the formed rows of stacks there. By the use of  The intermediate strips between the individual layers of wood Flow through the drying medium allows. When loading The stack packages are sent to the drying chamber Lined up in the direction of the boiler axis and according to the available height if necessary also one above the other puts. This creates a so-called "standard stack series ".

With small vacuum dryers up to 3 m in diameter, that can accommodate at most one standard stack row, is the problem of convective heat transfer and the temperature inhomogeneity is not serious. However are here the relative investment costs in relation to the volume of wood dried per unit of time higher than at conventional dryers, so that only special Woods and quality requirements for this wood economy advantages.

In the case of large-capacity vacuum dryers, on the other hand, they have a through have a knife of more than 3.5 m, two or more (also correspondingly higher) standard stack rows find space next to each other so that the relative investi tion costs become cheaper with increasing size, too if additional, mostly speed-controlled venti lators to generate one for heat transport sufficiently fast desiccant flow are necessary. However, the number of fans installed Set limits. In addition, the high Stromver affects the fans strongly depend on the operating costs of such a large-capacity vacuum dryer. The for the Heat energy required for drying, however, is comparative wise cheap, for example, from combustion can be obtained from chips, bark or waste wood.  

A disadvantage of such large-capacity vacuum dryers is that that strong on the border between two rows of piles Inhomogeneities in the flow profile can occur for example due to inaccurate stacking, unedged Goods (boards with bark and sloping edges) or blockwa right (whole logs cut in parallel) so that individual layers of wood and even board areas flows around more than neighboring ones and therefore dry too quickly compared to these. Correspondingly occurs here the problem of temperature differences in the stack intensifies on. Even when installing a variety of Fans remain with large total stack widths too high a temperature difference between stacks step and exit level as well as a too high tempera turinhomogeneity in the direction perpendicular to the main flow. In reverse operation (periodic reversal of the flow direction) can be systematically averaged over time reduce the resulting wood temperature gradient by Geometric discontinuities in the stack generated perturbations the airfoil with resulting, not Estimated local fluctuations in wood temperature however remain. Another influence on the The so-called dead areas have flow homogeneity between neighboring fans or in their axis close. For these reasons, compliance is important quality characteristic of drying, namely the low Scattering of the wood end moisture, in the well-known large Room vacuum dryers are not guaranteed.

The invention is therefore based on the object To create device of the type mentioned, at the one with fast and inexpensive lumber skirt a result of high wood quality with as little as possible  scatter of the final wood moisture within one the batch rows formed batch can be achieved.

According to the invention, this object is achieved with a device of the type mentioned by at least one Plane perpendicular to the direction of flow of the drying medium currents provided between at least two rows of stacks guidance unit from a sequence of in the plane arranged flow guide elements solved. By inventing Design according to the invention is an indefinable fault of the velocity profile of the desiccant flow geometric discontinuities within individual stacks packages or stack rows and especially in the border area Adjacent rows of piles can be remedied because of the speed distribution of density within the wood piles and the Speed of the drying medium itself men will. Uneven distributions of the flow ge Speed after passing through a row of piles can by the orientation and training of the Strö Guidance elements directly influenced and corrected who the.

For the next stack or the next stack row similar flow properties can then be generated as when entering the first stack row, so that the local deviations in flow velocity are not are larger than those in a small vacuum dryer ner with only one row of piles. By arranging the Flow control elements in the plane is largely one homogeneous flow of the drying medium can be achieved.

Because not only when passing through a row of piles Disturbances regarding the speed profile of the  Desiccant flow can occur, but also inevitably a systematic cooling of the dry sea diums on the way through the first row of stacks the heat transfer to the wood to be dried is in Training provided that the flow control unit is combined with a heating unit. That way a reduction in the systematic temperature gradient largely possible in the direction of flow. Preferably the heating units are adjustable, so that by independent controlled dryer zones or areas to the local temperature differences within the Wood piles can be taken, so that at least be reduced over time. The heating units can extend horizontally or vertically.

The heating unit preferably has heating pipes, so that between two rows of piles or after each second stack row a combination of heating pipes and Flow control elements is inserted. In further training it is provided that the heating tubes are the same in parallel are moderately spaced from each other, wherein Flow control elements at least in their spaces are arranged. This allows the area between the Stack rows (= chamber length × total stack height) optimal in filled in the plane perpendicular to the direction of flow be so that in this area targeted and without exception me on the flow rate as well as the temperature difference can be influenced.

The distance between the heating pipes depends on what needs to be supplied Stack width and according to the expected heat output, the a function of drying time, type of wood, thickness and -Initial moisture is chosen because on the one hand the filling area between the rows of piles (chamber length ×  Total stack height) is relatively large and on the other hand between the rows of piles only part of that for drying of the total stack of thermal energy provided may be delivered. Commercial heating registers tightly packed finned tubes would be totally overdi dimensioned and too expensive and would be substantial Problems with a sensible regulation of the heating output cause.

The flow guide elements made of heat are advantageous ing material, for example metal, and in particular thermally connected to the heating unit, so that at for example with heating tube distances of more than 20 cm for an improved homogeneity of heat transfer to the Dry medium is taken care of. During the flow guide on the one hand, firmly with the heating unit, for example the heating pipes, it can be connected with us of finned tubes possible, for example with appropriate training between neighboring Clamp ribs so that to form a Heizre gisters of heating pipes and flow control elements none additional measures for attachment are necessary.

When inserting additional heating units between the Stack rows must have the phenomenon of vacuum drying Thermal radiation must be observed. In contrast to conventional drying at northern painting pressure with moist air, at good heat transfer through the air.

Heat radiation causes an undesirable, much stronger one local drying on the surface of the wood and thus an uneven drying of the same. The heat beam The wood register must therefore be used for vacuum drying should be reduced as far as possible. This is because  with vacuum drying due to the low moving mass vaporous air and the resulting low Absorption by the gas molecules of the dry medium the short path available from the heating unit Wood heat radiation itself has a higher impact the drying has if it is not reduced. Further are in vacuum drying due to the given here increased "room costs" the heating register near the woods arranged. Also, vacuum drying in particular re expensive, slowly drying woods that dried are temperature sensitive, especially sensitive regarding temperature difference.

For all these reasons, vacuum drying is also included additional heating units between the wood piles one Shielding of heat radiation necessary.

The heating unit that is always warmer in heating mode the radiant heat emitted by the adjacent stacking surfaces (Sum of the emitted and absorbed radiation) depends primarily from the often large temperature difference, but also on the nature of the stack surfaces and surfaces of the ribs. Is the radiant heat compared to the heat transmitted by convection negligibly small, it must be reliably reduced be decorated. This occurs especially when as Heating medium high pressure steam or thermal oil (temperatures < 100 °) is used. But also with usual preliminaries temperatures of 80 to 100 ° C can cause problems with sensitive woods, as they Quality drying does not tolerate high temperatures. In Extreme cases (depending on wood type and thickness, permissible against discolouration or surface cracks) be necessary, at least in the initial phase of the process  leading drying the wood temperature to values of 30 limit to 40 ° C, which results in a clear Temperature difference to the heating register results. For this Basically it is provided that at least part of the stream mungsleitelemente from a poor heat conductor, such as for example plastic, is made or the Connection of the flow control elements to the heating unit is heat-insulating, if it is Flow guide element is a heat conductor. It is but also possible that at least part of the flow guide elements is arranged at a distance from the heating unit. Because of the above-mentioned configurations, such is one Interruption of direct optical contact between the heating unit and adjacent stacking areas through which a complete or partial shielding the heat radiation takes place. Pass the flow guide elements made of a poor heat conductor such as plastic, so they can be directly connected to the heating unit, because there is only a small amount of warming he follows. Also take them - like not with the heater connected flow control elements - due to their small no large heat capacity due to heat radiation Amount of heat. The low heat absorbed is excluded that of the fast-flowing drying medium through effective Cooling dissipated quickly.

Another way of reducing heat radiation is the emissivity of the heating unit belittling. This can be done by using the brightest possible smooth surfaces of the heating pipes and fins as well as the Reach flow control elements.

In a preferred embodiment it is provided that the Flow guide elements profiled in the direction of flow  are trained. For example, the profiling preserved in the form of steps or shoulders. On due to such profiling is a comparative speed distribution possible, the desired turbulent flow between the layers of wood due to the high flow rate of the dry sea diums is preserved. Furthermore, a pressure dam generated for the drying medium, so that, as far as heating unit ten are provided, a good heating of the flow dry medium.

In a preferred embodiment it is provided that the Flow control elements in the form of parallel to each other arranged slats are formed. The order can be in the manner of blinds, being towards It is important to ensure that these flat streams guiding elements the surfaces approximately parallel to each other different. The slats are preferably rotatable stored so that their angle of attack relative to the horizon tal is so changeable that by oblique position len the slats with respect to the horizontal a change tion of the overflow area of the drying medium is reachable. Due to the rotatable bearing, the Slats move and oscillate, which also leads to Changing the overflow area contributes. Preferential it is intended that at least every second Slat is individually adjustable. Of course All movable slats can be adjusted together to local irregularities, for example wise with regard to the stacking of the items to be dried To be able to react specifically to wood. For example so the vaporous air is focused and aimed at that Dried goods are directed, the direction of Air or steam flow and the flow profile of the  Drying medium can be changed over time during drying is.

In another preferred embodiment it is provided that the flow control elements through openings in one flat plate are formed. By using a such perforated sheet or several perforated sheets can be shield the heat radiation as much as possible, whereby even saved space compared to the slats that is precious in the vacuum dryer. During one Flow control unit each formed by a plate can be through a group of plates be educated. The openings are preferred arranged equidistantly on the plate and can for example in the form of slots. Such pinholes can be inexpensive Achieve smoothing of the flow profile. To also here each individually influence on the flow profile of the To be able to take dry medium, it is intended that the flat plate horizontally and / or vertically in the plane is displaceable perpendicular to the direction of flow.

To go to the flow profile within the stack Reduction of the systematic temperature gradient To be able to exert targeted influence, it is envisaged that the Flow control elements together in groups, each group but are adjustable independently of each other. The groups are either next to each other by a sequence barter flow guide elements formed or in each case through an alternating sequence of flow elements, hereby forming a group by every two te to understand every third etc. flow control element is. In this way settings can then be made in groups between adjacent rows of stacks, by  which reduce the flow rate Temperature gradients can be increased locally. Example is wise by reducing or blocking the Dry medium flow in partial stack areas by ent speaking setting of the flow control elements constant fan speed necessarily the flow speed increased in the other sections. The Duration of the reduction or blocking for each of the partial areas rich can with appropriate control or Regulation can be chosen arbitrarily, so that the Teilbe range also individually, d. H. different speeds Let dry if necessary or desired is. Are the flow control elements Slats, can be adjusted accordingly the formation of relatively narrow slots (nozzles) on one Side take place, which means the conveyed drying medium zones of higher speed is imposed, which the temperature gradient along the way through the next stack row reduced accordingly. Self ver Of course, by suitable oscillation, the Slats the directions of the narrow desiccant flows be varied so that on average all layers of wood in the stack row in the same way through the drying medium be applied, otherwise there are none or only very poor drying would occur.

As the foregoing shows, is for a balanced one Drying in the dryer room, i.e. in the drying chamber, the use of individual controllable groups Heating units and flow control elements the right one Way, because this reduces the temperature according to the invention settle differences locally.

It has been shown that an important basic control variable  for the chamber temperature is the wood temperature. Additional Lich provides the actual temperature compensation for accurate wood moisture measurement and allows statements about the wood moisture itself. For this reason inventive sensor for measuring the wood temperature vorese as a control variable for controlling the drying hen. The sensors are preferably each over the rows of piles distributed in the core of selected woods arranged. To do this, dry a hole in it en Wood drilled, the sensor inserted and dipped tet. Further training is a tax and rule device for adjusting the flow guide and / or Heating units depending on the measured wood temperature temperature provided.

Of course, measuring points for the wood can also be used moisture and / or the wood moisture gradient (wood moisture difference between core and surface of the material to be dried Wood) and / or dry medium temperature and / or equal weight moisture (of steam partial pressure and drying medium temperature dependent or derivable state quantity of the Chamber climate) and / or vapor partial pressure within the Stack or in the immediate vicinity of the stack, their measured values also as criteria for the setting development or regulation of the flow control units and / or Heating units can be used. The total pressure only needs to be measured at one point because the Pressure difference within the drying chamber (between Suction and pressure side of the arranged fans) is at most a few millibars and therefore neglect is casually small.

Overall, such a device is created by means of whose reliable local tempera, at least on average  Turdifferenzen be reduced within the wood stack can.

Further advantages and features of the invention result from the claims and from the following description exercise, in the exemplary embodiments with reference to the drawing is explained in detail. It shows:

Fig. 1 shows a cross section through a dung OF INVENTION proper drying chamber of a large-capacity vacuum dryer;

Fig. 2-5 different embodiments of combined flow control and heating units in partial view;

Figs. 6a and b exemplary planar and profiled fins or lamellae;

. Fig. 7 is a view corresponding to Figure 1 of another embodiment of the invention with a arranged transversely to the direction of flow of the drying medium flow guide with different Durchtrittsöffnun gene corresponding to FIG. 8;

. Fig. 8 is a plan view of a corresponding to Figure 7 is to be arranged transversely to the flow direction of the drying medium flow guide with different union through transverse openings is a schematic representation of a heating register with Strömungsleiteinheiten;

Fig. 9 shows another embodiment of the invention in an overall view corresponding to FIG. 1 with a heating register with flow control units according to FIGS. 10 and

Fig. 10 is an enlarged schematic Dar position of the heating coil with Strö mungsleiteinheiten of Fig. 9.

The illustrated in Fig. 1 vacuum-tight drying chamber 1 for drying stacked sawn timber with spacer bars under reduced pressure consists of an elongate cylindrical vessel 2, which at at least one end face is closed by a gate not shown. The vacuum dryer does not have to be cylindrical; it could also have the cross section of a polygon of the same or different shape, in particular a rectangle. In this boiler 2 rails for rail wagons are built, which carry the stack of lumber 3 a to 3 d to be dried. In the lumber stack 3 a, individual boards are shown in cross section. May be above the timber stack 3 a-3 d is an intermediate ceiling 4, underneath the timber stack 3 a-3 d an intermediate floor 5, the subsequent example of the platforms of the cars and on the side of the boiler walls 6 bottom parts formed. Gaps then remain between the platforms and these floor parts, the task of which will be explained later.

The false ceiling 4 above the timber stack 3 a-3 d the Trock extends in length from one end of drying chamber 1 to the other end but does not reach the wall of the vessel 2 at its sides, but leaves enough space that an annular Flow of the drying medium around the longitudinal axis A of the boiler 2 is possible, as indicated by the arrows. The flow runs according to the arrows drawn through the sawn timber stacks 3 a - 3 d along the boiler wall in the room 7 above the false ceiling 4 and from there again along the boiler wall 6 in the chen Chen, the sawn timber stacks 3 a - 3 d receiving drying room 8 . The flow of the drying medium can be reversed, the direction of the flow being reversed.

Thermal insulation 9 is applied to the outside of the boiler 2 so that no uncontrolled heat exchange can take place between the drying room 8 and the surroundings.

The lower intermediate floor 5 also extends from one to the other end of the boiler 2 and extends laterally up to the boiler wall 6 . The space 10 below the intermediate bottom 5 is not herme table from the actual drying space 8 separated, rather the drying medium from the drying chamber 8 can in serving as condenser space space 10 beneath the false floor 5 eintre through said column th. In this condenser space 10 is a condenser, not shown, the space itself serves as a reservoir for the condensate obtained on the condenser.

One or more fans 11 for circulating the dry medium in the boiler 2 are arranged above the false ceiling 4 . This fan 11 is speed-regulated for both directions of rotation, wherein reversing is possible, that is, its direction of rotation can be reversed. Depending on the direction of rotation, a heating register 12 for heating the drying medium is arranged behind or in front of the fan 11 in the flow direction.

Furthermore, measuring points for the wood moisture and / or the wood moisture gradient as well as the wood temperature, the drying medium temperature, the equilibrium moisture, the steam partial pressure in the drying room 8 are provided, but not shown in the figure.

A vacuum pump is also provided, but is also not shown.

To be dried sawn timber stack 3 a to 3 d in the illustrated embodiment of the invention in the form of two rows of stacks 13 a, 13 b disposed in the drying vessel 2, wherein both of these stack rows 13 a, 13 of the boiler 2 b in the transverse direction are spaced apart. In this space between the rows of stacks 13 a, 13 b, a combination of a flow control unit 14 and a heating unit 15 is arranged in a plane perpendicular to the direction of flow of the drying medium. The heating unit 15 is formed in the exemplary embodiment shown by heating tubes 16 , on the outside of which the heating tubes 16 surrounding fins 17 are attached as flow guide elements. These slats 17 are arranged parallel to each other.

In the embodiment shown in Fig. 2, the heating tubes 16 a to Rippenheizroh re, which are each evenly spaced from one another along the longitudinal axis A of the boiler 2 is arranged. On the side of the heating tubes 16 a facing the stack rows 13 a, 13 b, fins 17 a running along the longitudinal axis A are arranged, which, as FIG. 5 a shows, are clamped between the adjacent ribs of the finned tubes 16 a. As shown in Fig. 5 also shows the blades 17 have a respectively from the finned tubes 16 a to the outside in a step 18.

In the embodiment shown in Fig. 3, the fins 17 b are each arranged in the spaces between two adjacent finned tubes 16 a and between these two each clamped. These fins 17 b of the fins 17 a can have a gradation accordingly, in this case then a saturated tellerförmi cross-sectional profile of the slats 17 is obtained b.

In the embodiment shown in Fig. 4, the heating tubes 16 b are smooth and surrounded both on both of the two rows of stacks 13 a, 13 b facing outer sides and in their spaces 19 by the lamella len 17 c. These slats 17 c, as Fig. 5b shows, in turn in the direction of the stack rows 13 a, 13 b on a gradation 20 , so that the slats 17 c are verses with a substantially plate-shaped cross-sectional profile. The heating ribs or lamella len shown in rectangular form in the above exemplary embodiments can in principle be formed in the form of circular disks.

Figs. 6a and 6b show in perspective view fins or bars 17, 17 a, where the fins 17 are flat or plane, while the ribs are formed edged 17 a corresponding to those of FIG. 5b. Any other suitable profiles are also possible. The main plane of the ribs 17 , 17 a lies in the main flow direction of the drying medium.

Fig. 7 shows a drying chamber 1 a with a flow guide element in the form of a plate to be arranged perpendicular to the flow direction of the drying medium with different shapes of the passages. There are horizontal slots 31 , circular sections 32 , vertical slots 33 , but also other passage shapes are conceivable ( Fig. 8). As a rule, the passages are not all formed in such a plate-shaped flow element, but such a rule generally has only one type of passage. However, combinations of different types of culverts are also possible.

FIG. 9 shows a drying chamber 1 b with a schematic representation of a heating register or a heating unit 15 with flow guide elements arranged on both sides in the flow direction, the. Flow takes place according to arrow A from right to left (see also Fig. 10).

The guide elements 17 d- 17 g are fixed in frames 35 and 36 .

In this embodiment, the guide elements 17 e of the frame 35 are movable, as can be seen in particular from FIG. 10; they are interconnected by linkage 35 a or the like (such as ropes) which are driven by a Stellmo gate. The guide elements 17 d are fixed. The same applies to the movable guide elements 17 g of the frame 36 with the linkage 36 a and the guide elements 17 f fixed there. From the flow profile b, a flow profile c, which is sinusoidal in space, is created in this way. The frame 35 oscillates in such a way that the uneven flow profile c is evenly distributed over the time over the stack entry level into the wood.

Due to the inclination of the flow guide elements otherwise achieved in an extremely advantageous manner that the heat radiation of the heating register compared to warming wood is shielded and therefore the heating of the woods essentially solely through the between drying medium flowing through them takes place.

Claims (29)

1.Device for drying stacked lumber or other hygroscopic plate or rod-shaped goods at negative pressure in a vacuum-proof drying chamber with fans for circulating a gaseous drying medium, the direction of which is transverse to the longitudinal axis of the drying chamber, with a condenser for dehumidification and with one or A plurality of heating registers for convective heat transfer, the sawn timber being arranged one behind the other in the flow direction of the drying medium in at least two stack rows, characterized by a flow guide unit ( 14 ) provided at least in one plane perpendicular to the flow direction of the drying medium between at least two stack rows ( 13 a, 13 b). from a sequence of flow control elements arranged in the plane ( 17 , 17 a-c; 17 d-g). 2. Device according to claim 1, characterized in that the flow guide unit ( 14 ) is combined with at least one heating unit ( 15 ). 3. Device according to claim 2, characterized in that the heating units ( 15 ) are individually controllable. 4. Apparatus according to claim 2 or 3, characterized in that the heating unit ( 15 ) heating tubes ( 16 , 16 a, 16 b). 5. The device according to claim 4, characterized in that the heating tubes ( 16 , 16 a, 16 b) are arranged parallel and evenly spaced from one another, with at least some of the flow guide elements ( 17 b, 17 c) arranged in the spaces ( 19 ) is. 6. Device according to one of claims 1 to 5, characterized in that at least part of the flow guide elements ( 17 , 17 a, 17 b, 17 c) consists of good heat-conducting material. 7. The device according to claim 6, characterized in that at least a part of the flow guide elements ( 17 , 17 a-c; 17 d-g) is connected to the heating unit ( 15 ) with good thermal conductivity. 8. Device according to one of claims 1 to 7, characterized in that at least part of the flow guide elements ( 17 , 17 a-c; 17 d-g) consists of a poor heat conductor. 9. Device according to one of claims 1 to 8, characterized in that the connection of at least part of the flow guide elements ( 17 , 17 a-c; 17 d-g) with the heating unit ( 15 ) is heat-insulating. 10. Device according to one of claims 1 to 9, there characterized in that at least part of the Flow control elements spaced from the heating unit is arranged. 11. The device according to one of claims 1 to 10, characterized in that the flow guide te ( 17 a, 17 c) in the direction perpendicular to the longitudinal direction of the stack rows ( 13 a, 13 b) are profiled. 12. The apparatus according to claim 11, characterized in that the profiling is obtained in the form of steps ( 18 , 20 ). 13. The device according to one of claims 1 to 12, characterized in that the flow guide elements te ( 17 , 17 a, 17 b, 17 c) are designed in the form of parallel to each other arranged lamellae. 14. The apparatus according to claim 13, characterized net that the slats in the manner of blinds are arranged. 15. The apparatus of claim 13 or 14, characterized ge indicates that the slats are rotatably mounted are. 16. The device according to one of claims 13 to 15, characterized in that at least every second Slat is individually adjustable.   17. The device according to one of claims 1 to 12, characterized in that the flow control elements as openings in a flat plate det. 18. The apparatus according to claim 17, characterized in net that one plate each has a flow guide unit forms. 19. The apparatus according to claim 17, characterized in net that the flow control unit through a group is formed by plates. 20. Device according to one of claims 17 to 19, characterized in that the breakthroughs are distributed equidistantly on the plate. 21. Device according to one of claims 17 to 20, characterized in that the openings in Form of slots are formed. 22. The device according to one of claims 17 to 21, characterized in that the flat plate hori zontal and / or vertical in the plane perpendicular to Flow direction of the drying medium can be shifted is. 23. The device according to one of claims 1 to 22, characterized in that the flow control elements te in groups, but each group is independent are completely adjustable.   24. The device according to claim 23, characterized in net that the groups by a sequence of each other adjacent flow guide elements are formed. 25. The device according to claim 23, characterized net that the groups alternate by one de sequence of flow guide elements are formed. 26. The device according to one of claims 1 to 25, characterized by sensors for measuring the Wood temperature as a control variable for controlling the Drying. 27. The apparatus according to claim 26, characterized in net that the sensors each over the stack rows distributed selected lumber arranged in the core are not. 28. The device according to claim 26 or 27, characterized through a control and regulating device for tax purposes tion of the flow control and / or heating units in Dependence on the measured wood temperature. 29. Device according to one of claims 2 to 28, characterized in that flow guide elements ( 17 d-g) are designed as shielding the heat radiation of the heating units ( 15 ).