Fresh-air heat exchanger and method for providing heated fresh air with the electrically heated fresh air heat exchanger

Abstract

The present invention relates to a fresh air heat exchanger (100) for heating a fresh air stream, comprising: at least one ventilator (106) for suctioning in fresh air and generating a fresh air stream; and at least one electrically heated heat transfer unit (108) for transferring thermal energy to the fresh air stream.

Description

[0001] Fresh air heat exchanger and method for providing heated fresh air with the electrically heated fresh air heat exchanger

[0002] The present invention relates to a fresh air heat exchanger and a method for providing heated fresh air with a corresponding fresh air heat exchanger.

[0003] It is known from practice that within treatment plants for workpieces, in particular within drying plants (dryers for short) for vehicle bodies, fresh air heaters are used to heat the fresh air supplied to the airlock areas of such a plant in order to avoid the formation of condensate, in particular in the airlock areas of the plant.

[0004] In general, the following two options are known for heating such fresh air heaters.

[0005] On the one hand, in dryers with recuperative thermal exhaust air cleaning (TAR), the clean gas enthalpy flow close to the dryer can be used to heat the fresh air, i.e. the thermal energy of the clean gas led from the TAR is transferred to the fresh air supplied to the dryer.

[0006] On the other hand, in the case of burner heating, the fresh air heating can be carried out either directly, e.g. by means of a gas surface burner, or indirectly by means of a combustion chamber with flue gas heat exchanger.

[0007] A corresponding fresh air heater is known to comprise the following components: an intake with a filter, where the intake is drawn, for example, directly from the dryer hall; a silencer; a heat exchanger for transferring the thermal energy of the clean gas to the supplied fresh air or a combustion chamber for combusting a burner gas with supplied fresh air; a fan; and the required fresh air and clean gas ducts. The fresh air heater can be either integrated into a housing or freestanding, with the individual components being connected by a duct system in the latter embodiment.

[0008] Such fresh air heaters can be installed on a separate steel platform above the dryer. In rare cases, they can also be installed below the dryer, in which case the dryer tunnel itself is mounted on a steel structure.

[0009] On the other hand, in the case of clean gas heating, the fresh air heater can be located at the beginning or end of the clean gas line, i.e., at the beginning or end of the dryer, particularly to reduce the temperature of the clean gas to a low level with the aid of the supplied fresh air before it is released into the atmosphere, i.e., preferably via the roof of the hall. A counterflow heat exchanger is preferably used to reduce the temperature of the clean gas by means of the supplied fresh air.

[0010] In a burner-heated dryer, the exhaust air is typically cleaned in a gas-fired regenerative thermal exhaust air treatment system, also known as regenerative thermal oxidizer (RTO). However, due to its design, typically consisting of three chambers and the associated dimensions, such a system is designed for installation outside the building, i.e., the hall. Thus, waste heat utilization to preheat the incoming fresh air is not possible in the vast majority of cases due to the required duct lengths between the RTO and the fresh air heat exchanger.

[0011] Furthermore, a compact design is not possible due to the voluminous clean gas heat exchanger or the voluminous combustion chamber.

[0012] In addition, such a system requires two insulated ducts or duct systems for the heating medium and the fresh air.

[0013] Furthermore, there are limitations regarding installation options. For example, an additional steel platform is required for an arrangement above the dryer. Regardless of the installation location, an insulated fresh air duct is always required along at least the entire length of the dryer, especially if both airlocks (inlet and outlet) must be connected from the fresh air heat exchanger.

[0014] As already mentioned, the fresh air heated in the fresh air heater is fed to the dryer, firstly to the airlock areas of the dryer and secondly to the recirculation units or recirculation modules of the sections of the dryer in which the workpieces are treated or dried.

[0015] A dryer typically has an inlet lock at the dryer's (frontal) inlet and an outlet lock at the dryer's (frontal) outlet. The dryer typically comprises several consecutively arranged sections that together form a treatment channel. Intermediate locks may also be arranged between the dryer's treatment sections.

[0016] The inlet, intermediate and outlet locks can be designed as single-stage locks, while the inlet and outlet locks can alternatively be designed as two-stage locks.

[0017] In the case of single-stage locks, a constant fresh air volume flow is fed into these locks via a duct starting from the fresh air heater.

[0018] With the help of additional ducts and corresponding branch lines to the individual recirculation units, a variable fresh air volume flow is also fed into the recirculation units.

[0019] In this context, a fresh air control damper is used to regulate the amount of fresh air in such a way that variable proportions of fresh air are supplied to the recirculation units depending on the dryer load, while a constant proportion of fresh air is always supplied to the air locks. This is because when the dryer load is low, e.g. in the case of paint dryers, fewer solvents escape from the painted surfaces of the workpiece to be dried. The total amount of fresh air fed into the dryer or the variable proportion fed to the recirculation units can be correspondingly lower. In the case of two-stage inlet and / or outlet air locks, i.e. air locks on the front of the dryer with a double, silhouette-based air curtain, the outer air curtain or the outer stage is supplied with fresh air heated in the fresh air heater via its own duct (fresh air curtain), while the inner air curtain orThe inner stage is supplied with recirculated air from the adjacent recirculation unit (recirculation curtain). Adjacent here means that the inner stage of the outlet lock is supplied with recirculated air from the last treatment section of the dryer, i.e., the last holding zone, and the inner stage of the inlet lock is supplied with recirculated air from the first treatment section of the dryer, i.e., the first heating zone.

[0020] In other words, the fresh air curtain can be considered a barrier that borders a cooler area on its outward-facing side. Thus, the fresh air curtain of an inlet lock preferably forms a barrier between the surroundings of the treatment room and the recirculating air curtain of the inlet lock, while the fresh air curtain of an outlet lock preferably forms a barrier between a cooling zone downstream of the treatment room and the recirculating air curtain of the outlet lock.

[0021] Within the framework of the fresh air / exhaust air concept already presented, in the case of two-stage airlocks, the inner stage, i.e., the respective recirculation air curtain, is not directly influenced by the damper control, meaning the supplied recirculation air portion remains constant. The air portions are therefore only adjusted for the fresh air supplied by the fresh air heater. Here, too, the portion for the outer stage, i.e., the fresh air curtain, is kept constant, whereas the portion for the recirculation air units is adjusted, or can be adjusted, by an allocating control damper depending on the dryer's load.

[0022] A disadvantage of previous variable fresh air / exhaust air control is that this approach requires two insulated fresh air ducts for both clean gas and burner heating: a lock duct for a constant fresh air portion and an insulated unit duct for the variable fresh air portion. These ducts must be routed to the other end of the dryer - usually to the inlet lock. For a 30 jph dryer, this corresponds to a duct length of 15 vehicle lengths, and for a 60 jph dryer, a duct length of 30 vehicle lengths. In addition, by supplying the variable fresh air portion to the recirculation units, this same portion of fresh air does not contribute to reducing the solvent concentration in the lock area and thus does not minimize the risk of condensation in the cold peripheral areas of the dryer, such as in the inlet area or in the cooling zones.

[0023] The present invention is therefore based on the object of creating a fresh air heat exchanger for heating a fresh air flow, which enables a more flexible and economical arrangement on the dryer level due to a more compact design.

[0024] This object is achieved according to the invention in that a fresh air heat exchanger for heating a fresh air flow is provided, which comprises the following: at least one fan for sucking in fresh air and generating a fresh air flow, and at least one electrically heated heat transfer unit for transferring thermal energy to the fresh air flow.

[0025] It is advantageous if the fresh air to be heated is preheated in a preheating device before being supplied.

[0026] This approach is particularly economical and sustainable when waste heat from the dryer or renewable energy sources are used, as this can reduce the demand for electricity with a high energy quality (exergy).

[0027] This can be achieved, on the one hand, by an electric and thus flameless system for regenerative thermal oxidation of the dryer exhaust air. Unlike a gas-fired RTO (see above), the electric RTO, due to its design (single bed), can be installed inside the building and thus close to the dryer. This approach enables fresh air preheating using a clean gas enthalpy flow downstream of the electric RTO. The electric RTO has the special feature of a low temperature rise of approximately 20 K during thermal oxidation. The enthalpy flow of the clean gas is generally not sufficient to bring the fresh air to the desired target temperature using a heat exchanger alone, which transfers the thermal energy of the clean gas to the fresh air.In contrast, the combination of preheating the fresh air and subsequent electrical temperature increase in the fresh air heat exchanger according to the invention enables the target temperature to be reached efficiently.

[0028] Alternatively, a heat pump can be used to preheat the fresh air. With this form of preheating, a small amount of unusable waste heat (e.g., cooling zone exhaust air with a temperature in the range of 40°C to 50°C, or the remaining clean gas enthalpy flow after the RTO with a temperature in the range of 60°C to 100°C, for example) is brought to a usable temperature level for preheating the fresh air using mechanical drive energy. The heat exchange between the heat pump and the fresh air or clean gas can be achieved, for example, via a water-to-air heat exchanger.

[0029] However, heat-absorbing direct evaporation on the evaporator side or heat-emitting direct condensation on the condenser side is also conceivable, whereby heat energy is supplied to or removed from the working gas via a heat exchanger and thus without an intermediate medium.

[0030] Solar thermal energy can also be used for preheating. The heat exchange between the fresh air and the solar thermal heat transfer medium (e.g., thermal oil or water) takes place, for example, via a water-to-air heat exchanger or an oil-to-air heat exchanger.

[0031] A fresh air heat exchanger according to the invention has the advantage that simplified ducting can be achieved within the treatment plant or dryer due to the elimination of the heating medium, since only the ducting for the fresh air is required. Furthermore, the depth and length of the entire heat exchanger can be reduced compared to a clean gas heat exchanger with a combustion chamber concept. The compact design advantageously allows for integrated installation in a recirculation unit or in a lock or lock module. Furthermore, the previously unused space between the dryer's outer wall and inner wall (usable space wall), for example, can be used to accommodate the fresh air heat exchanger according to the invention.

[0032] In contrast to the state of the art, the compact design of the fresh air heat exchanger makes it possible to install it at the tunnel level, i.e., at the level of the dryer's treatment sections, preferably in the niches between two recirculation units. Consequently, no additional steel construction is required.

[0033] Since the fresh air heat exchanger according to the invention no longer needs to be installed at the end of the clean gas line, it is advantageously possible to divide the heat exchanger, i.e., a separate fresh air heat exchanger for the inlet and outlet locks. Thus, an insulated fresh air duct along the entire length of the dryer is preferably not required.

[0034] In the case of an intermediate airlock, it can also be supplied with electrically heated fresh air from the fresh air heat exchanger of the inlet airlock or the inlet airlock unit. In this context, the temperature of the fresh air heated in the fresh air heat exchanger is adjusted to the intermediate airlock, the heated fresh air flow is divided, and correspondingly cold fresh air for the inlet airlock is mixed with the heated fresh air flow.

[0035] It is further provided that the at least one electrically heated heat transfer unit comprises at least one heating resistance device.

[0036] The electrically heated heat transfer unit, also known as a register, preferably comprises heating elements with a profiled tube surrounding the heating wire as a heating resistance device. This results in minimal dirt adhesion and, at the same time, easy cleaning.

[0037] Alternatively, open, electrically insulated wire coils with high temperature resistance can be used. The fresh air stream flows directly over the heating wire, thus achieving maximum heat transfer efficiency. This alternative is a cost-effective variant compared to heating rods with profile tubes. In one embodiment of the invention, the at least one electrically heated heat transfer unit is arranged downstream of the at least one fan.

[0038] Furthermore, it can be provided that the fresh air heat exchanger has at least one filter unit for filtering the fresh air taken in.

[0039] Since the fresh air is drawn in, for example, from the hall surrounding the dryer, filtering the drawn-in air is advantageous to prevent contamination, particularly of the heating element. Filtering is sufficient at this point, since the drawn-in fresh air has not yet come into contact with the dryer atmosphere.

[0040] In a further embodiment of the invention, it is provided that the fresh air heat exchanger has at least one silencer unit for reducing the noise emission of the fresh air flow.

[0041] In a further embodiment of the invention, it is provided that the at least one filter unit and / or the at least one silencer unit is arranged upstream of the at least one fan.

[0042] In a further embodiment of the invention, it is provided that the at least one filter unit and / or the at least one silencer unit is arranged at least partially above the at least one fan.

[0043] In a further embodiment of the invention, it is provided that the fresh air heat exchanger has at least two, preferably three electrically heated heat transfer units.

[0044] In a further embodiment of the invention, the electrically heated heat transfer units are arranged one after the other along the fresh air flow. This allows the fresh air flow to be heated successively, reaching the target temperature at the latest when it passes the last heat transfer unit.

[0045] In a further embodiment of the invention, it is provided that a first flow path of the fresh air flow upstream of the fan is perpendicular to a second flow path of the fresh air flow downstream of the fan.

[0046] The fresh air duct on the intake side of the fan, i.e., upstream of the fan, serves to draw in the fresh air via the filter units and through the downstream silencer units. It can be described as the first flow path, which follows a U-shape from the filter units through the silencer units to the fan. Relative to the dryer's installation plane, the fresh air flow runs horizontally from the intake through the filter units to the silencer units. The flow then runs vertically through the silencer units before flowing horizontally into the fan.

[0047] The fresh air flow on the pressure side of the fan, i.e. downstream of the fan, is directed longitudinally along the housing and thus preferably – when installed between two recirculation units on the dryer tunnel level – in or against the direction of the conveyor system or the conveying direction of the workpieces. The flow path downstream of the fan can be considered a second flow path. Here, the fresh air flows preferably in a straight line and parallel to the dryer installation level through the heat transfer units, meaning there is no repeated redirection of the fresh air as in the case of a cross-counterflow heat exchanger. This eliminates the need for redirection spaces, which would necessitate additional installation space perpendicular to this air flow direction.

[0048] The planes of the first and second flow paths or the flow paths are preferably perpendicular to each other.

[0049] Further preferably, the second flow path runs at least approximately in or opposite to the conveying direction of the treatment system or treatment chamber. In a further embodiment of the invention, the at least one fan is a radial fan.

[0050] A radial fan converts the upstream fresh air flow into a downstream fresh air flow that runs perpendicular to the first. The radial compressor thus ensures that the first flow path runs perpendicular to the second flow path.

[0051] In a further embodiment of the invention, it is provided that the fresh air heat exchanger comprises a housing in which the at least one filter unit, the at least one silencer unit, the at least one fan and the at least one electrically heated heat transfer unit are at least partially accommodated.

[0052] In a further embodiment of the invention, it is provided that the housing comprises a service side which has at least one maintenance access.

[0053] The object is further achieved by the use of a fresh air heat exchanger according to the invention as described above for heating a fresh air stream which is supplied to a treatment plant for workpieces, in particular a drying plant for vehicle bodies.

[0054] The object is further achieved according to the invention by a method for providing heated fresh air with an electrically heated fresh air heat exchanger, the method comprising the following steps:

[0055] Suction of fresh air from the environment of the fresh air heat exchanger, filtering the sucked in fresh air, reducing the noise emission of the sucked in fresh air,

[0056] Diverting the flow direction of the fresh air flow and compressing the fresh air flow,

[0057] Transferring heat energy generated by at least one heating resistor device to the fresh air stream, and discharging the heated fresh air. The fresh air from the surroundings of the fresh air heat exchanger is drawn in by a fan and cleaned of ambient air impurities on the inlet side as it flows through at least one filter unit.

[0058] The noise emission is then reduced within a silencer unit.

[0059] The fresh air flow is then passed through a fan, preferably a radial fan, which compresses the fresh air flow and deflects it in a direction perpendicular to the upstream direction of the fresh air flow.

[0060] The fresh air flow then flows around at least one electrically heated heat transfer unit, each of which has a heating resistance device.

[0061] Finally, the heated fresh air is discharged from the fresh air heat exchanger towards the dryer locks.

[0062] In a further embodiment of the invention, it can be provided that the method according to the invention comprises a step of preheating the fresh air in a preheating device, wherein the preheating device is a heat pump, a regenerative thermal, in particular purely electrically operated and flameless, oxidation device or a solar thermal device which comprises thermal oil or water.

[0063] The heated fresh air is then used in a treatment plant for workpieces, in particular a drying plant for vehicle bodies, or is made available to this plant so that the locks of this treatment plant can be supplied with heated fresh air.

[0064] A corresponding treatment system for treating workpieces, in particular vehicle bodies, comprises a treatment chamber, which itself comprises several treatment chamber sections, each assigned to one of several separate recirculation modules of the treatment system, and at least one airlock. The airlock can have a first stage and a second stage, wherein fresh air can be supplied to the first stage of the airlock, and wherein recirculation air and / or fresh air can be supplied to the second stage. It is provided that the treatment system further comprises at least one electrically heated fresh air heat exchanger according to the invention, which provides heated fresh air to the at least one airlock.

[0065] The use of a fresh air heat exchanger according to the invention allows the use of separate fresh air heat exchangers for the inlet and outlet locks, whereby the heat exchangers of the first stage (fresh air curtain or silhouette) provide a constant amount of fresh air and the second stage (recirculating air silhouette or recirculating air and fresh air silhouette) provide a variable amount of fresh air.

[0066] The advantage of this is that—especially with these double-stage airlocks—there is no longer any need for an insulated fresh air duct for the constant airlock air across the entire length of the dryer. Likewise, an insulated fresh air duct for the variable air to the recirculation units across the entire length of the dryer is no longer required, since all the fresh air in the airlock area is now utilized.

[0067] In addition, it is conceivable that at least one controllable and / or adjustable throttle device is arranged between the electrically heated fresh air heat exchanger and the first stage of the at least one lock, so that a constant volume flow of fresh air can be supplied to the first stage of the lock.

[0068] In addition, at least one further controllable and / or adjustable throttle device can be arranged between a treatment chamber section and the second stage of the at least one lock, so that a constant volume flow of recirculating air and / or fresh air can be supplied to the second stage of the lock.

[0069] The first throttle device assigned to the first stage thus ensures the volume flow to the first stage by discharging the excess fresh air into the line or duct of the second stage. The total volume flow to the second stage is regulated by the additional, second throttle device, so that the second stage is also supplied with a constant volume flow. Furthermore, a lock fan can be assigned to the second stage of the lock. The lock fan preferably comprises a frequency converter or is frequency-controlled and / or open-loop controlled.

[0070] It is also possible for the second stage of the lock to be supplied with 50%, preferably 100%, particularly preferably 200% more recirculated air than fresh air.

[0071] It can also be provided that a filter unit is assigned to each of the first and second stages of the lock.

[0072] It is also conceivable that at least one temperature sensor and at least one volume flow probe are arranged between the at least one electrically heated fresh air heat exchanger and the at least one lock and between at least one recirculation module and the at least one lock.

[0073] It is also possible that a pressure sensor is assigned to the second stage of the lock to control the lock fan.

[0074] It may further be provided that the first and second stages of the lock comprise slot nozzles for forming a silhouette-based air curtain.

[0075] In the case of an inlet lock, the fan of the fresh air heat exchanger according to the invention can thus supply the fresh air silhouette of the first stage of the lock with fresh air.

[0076] A separate airlock fan also supplies the recirculation silhouette of the second stage of the airlock with recirculated air from the adjacent treatment room section or the adjacent heating / drying zone.

[0077] The fresh air and recirculated air ducts are connected via a branch.

[0078] The two air ducts converge on the intake side of the airlock fan. This allows the airlock fan to be supplied with both fresh air and recirculated air. A motor-driven throttle device is installed in both intake-side inlets of the airlock fan (for fresh air and recirculated air). This throttle device allows the adjustment of the air flow ratios of fresh air and recirculated air for the airlock stages. It also prevents unwanted reversal of the airflow in the airlock (fresh air and recirculated air lock).

[0079] The fan speed of the fresh air heat exchanger according to the invention, and thus the amount of fresh air conveyed, depends on the volume flow required for the drying process in a dryer. Since the air volume of the two airlock stages must be kept constant in every operating state to achieve optimal airlock function, the excess fresh air volume from the first stage is fed to the second stage of the airlock, i.e., the recirculation stage, via the fresh air supply branch.

[0080] For this purpose, a volume flow probe and a temperature sensor are located or installed in the fresh air supply, which are used to calculate a standard volume flow. The calculated value serves as the control variable for the motor-driven throttle device. It is regulated so that the fresh air flow to the first airlock stage remains constant and the excess fresh air flow can be used for the second airlock stage.

[0081] To ensure a constant volume flow of the second airlock stage, the airlock fan uses the signal from the associated pressure sensor. The motor-driven throttle device is controlled so that the excess fresh air flow, combined with the recirculated air flow, results in a constant volume flow for the second airlock stage.

[0082] Optionally, the airlock fan can be equipped with a frequency converter. In this case, the volume flow can be kept constant by varying the fan speed and using the motor-driven throttle device, or preferably even without the motor-driven throttle device.

[0083] Preferably, all electrically operated heating components, such as fresh air heat exchangers, can be supplied with a medium voltage of, for example, at least approximately 3 kV and / or at most approximately 8 kV, in particular 4160 V to 6600 V, instead of the usual 400 V. Although this may require special heating elements with corresponding additional costs, it offers great savings potential, preferably in the periphery, i.e. with regard to connections, cables, etc. Furthermore, a significantly lower voltage transformation factor from the supply network is necessary, which, among other things, reduces the size of the transformer station in favor of lower investment costs and saves space. Connecting an electrically operated heating component with this type of medium voltage also results in significantly smaller cable diameters.

[0084] Further preferred features and / or advantages of the invention are the subject of the following description and the drawings of exemplary embodiments.

[0085] The figures show:

[0086] Fig. 1 is a schematic isometric view of an electrically heated fresh air heat exchanger according to the invention;

[0087] Fig. 2 is a schematic representation of an end face of the electrically heated fresh air heat exchanger according to the invention;

[0088] Fig. 3 is a schematic representation of a service side of the electrically heated fresh air heat exchanger according to the invention; and

[0089] Fig. 4 is a schematic representation of the entrance area of ​​a treatment plant with an electrically heated fresh air heat exchanger and a double lock on the entrance side;

[0090] Identical or functionally equivalent elements are provided with the same reference numerals in all figures.

[0091] A fresh air heat exchanger 100 shown schematically in Figs. 1 to 3 serves to provide a heated fresh air heat flow within a treatment plant 10 of workpieces (not shown).

[0092] The treatment system 10 is, for example, a drying system 12 for drying workpieces. The workpieces are, for example, vehicle bodies.

[0093] In particular, to simplify the description of the fresh air flow, a three-dimensional coordinate system with the axes x, y, z was introduced in Figs. 1 to 3.

[0094] The fresh air heat exchanger 100 comprises a filter unit 102, a silencer unit 104, a radial fan 106 and two electrically heated heat transfer units 108, which are together accommodated in a housing 110.

[0095] The housing 110 has a service side 112 in which two maintenance accesses 114 are provided.

[0096] The filter unit 102 and the silencer unit 104 are arranged above the radial fan 106.

[0097] In the embodiment shown in Fig. 1, the silencer unit 104 comprises four cuboid silencer elements.

[0098] In Fig. 2 it can be seen that the sucked-in fresh air 116, which is preferably sucked in from the surrounding hall, first flows through the filter unit 102 in the y-direction, ie in a horizontal direction, in order to filter out possible impurities from the sucked-in fresh air 116.

[0099] The fresh air 116 sucked in can be ambient air, ie from inside or outside the hall in which the treatment plant 10 is installed, or can also be purified exhaust air.

[0100] The sucked-in fresh air 116 describes a U-shaped, first flow path in the yz plane upstream of the radial compressor 106, ie on its suction side.

[0101] Along the first flow path 118, the fresh air flow passes the filter unit 102 and the silencer unit 104 in the z-direction, i.e., in a vertical direction. The fresh air then flows through the radial fan 106 in the y-direction, i.e., again in a horizontal direction.

[0102] Fig. 3 shows that the radial fan 106 deflects the fresh air flow into the xz plane.

[0103] Downstream of the radial fan 106, ie on the pressure side, the fresh air flows in the x-direction, ie in a horizontal direction, along a second, straight flow path 120.

[0104] After the radial fan 106, the redirected fresh air flow flows through or around the two heat transfer units 108 arranged one after the other along the second flow path 120.

[0105] In this case, the heat energy generated by means of a heating resistance device of the electrically heated heat transfer unit 108, such as preferably a heating wire, is transferred to the fresh air flow before it leaves the housing 110 or is led out of it as heated fresh air 122 or heated fresh air heat flow.

[0106] The achievement of the target temperature of the heated fresh air 122 is preferably measured or checked at the outlet of the fresh air heat exchanger 100 by means of a temperature sensor 123 and a measuring nozzle 124 (shown in Fig. 4).

[0107] Preferably, the standard volume flow at the outlet of the fresh air heat exchanger 100 is between 4250 Nm 3 / h and 12000 Nm 3 / h in the case of a split heat exchanger supplying the inlet and intermediate locks or the outlet lock. In the case of a single fresh air heat exchanger 100 supplying all locks, the standard volume flow is up to 24000 Nm 3 / h.

[0108] Fig. 4 schematically shows the entrance area of ​​a treatment system 10, for example, a drying system 12. The treatment system 10 comprises a treatment chamber 200 with several treatment chamber sections, of which a first treatment chamber section 202 or a first heating zone is shown in Fig. 1.

[0109] The first treatment room section 202 is assigned a recirculation module 204 or a recirculation unit.

[0110] The recirculation module 204 comprises a recirculation fan 206, a measuring nozzle for manual measurements 208 and a heat exchanger 210.

[0111] In the first treatment room section 202, a filter unit 212 is also arranged, which filters the recirculated air returned from the recirculation module 204 via the recirculation duct 211.

[0112] Furthermore, the treatment chamber 200 according to the embodiment in Fig. 4 comprises a two-stage lock 214, which preferably forms a silhouette-based air curtain in order, among other things, to keep the solvents in the treatment chamber 200 or to prevent them from being released into the environment.

[0113] The lock 214 has a first stage 216 and a second stage 218, wherein - with respect to a conveying direction 220 of the workpieces within the treatment chamber 200 - the first stage 216 is passed first by the workpieces, followed by the second stage 218.

[0114] Preferably, the first stage 216 and the second stage 218 are arranged directly one behind the other in the conveying direction 220, ie without an intermediate element.

[0115] However, it is also conceivable in an advantageous embodiment that a pivotable shield can be mounted between the stages 216, 218, which, in the pivoted-out state, acts as a physical barrier supporting the lock function and at the same time stabilizes the air flow of the first stage 216.

[0116] Each stage 216, 218 of the lock 214 is provided with a filter unit 222, 224 to ensure that no contaminants from the respective air supplies are applied to the workpieces via the slotted nozzles (not shown) of the stages 216, 218 of the lock 214. Each stage 216, 218 is also assigned a measuring nozzle for manual measurements 226, 228 upstream of the filter units 222, 224, via which physical variables can be manually monitored, particularly during commissioning of the lock 214.

[0117] Heated fresh air 122 is supplied to the lock 214 via a fresh air supply 230 from a fresh air heat exchanger 100, as described above in connection with Figs. 1 to 3.

[0118] The fresh air supply 230 leads the heated fresh air 122 to the first stage 216, which forms a fresh air curtain.

[0119] In the flow path of the fresh air supply 230 to the first stage 216 of the lock 214, which is supplied with a constant fresh air volume flow, preferably in the amount of 4250 Nm 3 / h, a further measuring nozzle for manual measurements 231, a compensator 232, and a throttle device 233 are arranged. The compensator 232 is an element for compensating for movements in the corresponding pipe of the fresh air supply 230, in particular in the case of thermal length changes, vibrations, wall penetrations, or settlement phenomena.

[0120] A temperature sensor 234 and a volume flow probe 236, in particular a dynamic pressure probe, are arranged upstream of the throttle device 233 and downstream of the measuring nozzle 226.

[0121] The fresh air supply 230 is further branched off at a branch 238 in the direction of the second stage 218 in order to also be able to supply the second stage 218 with fresh air.

[0122] Downstream of the branch 238, a further compensator 240 and a motor-driven throttle device 242, which is controllable and / or adjustable, are arranged. By means of the motor-driven throttle device 242, the amount of fresh air that can be supplied to the second stage 218 can be adjusted, ie, controlled and / or regulated.

[0123] The second stage 218 is generally supplied with recirculating air from the first treatment room section 202, which is sucked in by means of a lock fan 243.

[0124] In other words, the lock fan 243 supplies the recirculation silhouette of the second stage 218 with recirculation air from the adjacent first processing section 202.

[0125] The amount of recirculated air is also controlled and / or regulated by a motor-driven throttle device 244.

[0126] Downstream of the motor-driven throttle device 244, a further compensator 246 and a further measuring nozzle for manual measurements 248 are arranged before the branched fresh air flow is fed to the recirculating air flow.

[0127] The second stage 218 of the lock 214 also forms an air curtain through a constant volume flow, preferably at a level of 10000 Bm 3 / h, comprising recirculated air and fresh air.

[0128] Downstream of the fresh air supply 230 into the recirculating air flow, a further throttle device 250 is arranged for adjusting the volume flow.

[0129] Furthermore, to compensate for pipe movements in the area of ​​the lock fan 243, a further compensator 252 or 254 is arranged directly upstream and downstream of the lock fan 243.

[0130] The speed of the radial compressor 106 of the fresh air heat exchanger 100, and thus the amount of fresh air delivered or supplied, depends on the air mass flow required for the treatment or drying process. Since the fresh air volume of the first stage 216 of the lock 214, in particular, must be kept constant to achieve optimal lock function, the excess fresh air volume is supplied via branch 238 to the second stage 218, i.e., the recirculation stage.

[0131] For this reason, the temperature sensor 234 and the volume flow probe 236 are provided in the fresh air supply 230. Using these two measuring devices, the (standard) volume flow can be determined, which serves as a controlled variable for the motor-driven throttle device 242. This throttle device 242 can be controlled so that the fresh air flow to the first stage 216 is always constant and the excess fresh air portion is directed to the second stage 218.

[0132] A pressure sensor 256 is arranged upstream of the airlock slot or airlock nozzle of the second stage 218, and particularly downstream of the filter unit 224. Its pressure difference relative to the environment, such as the hall, serves as a control variable for the frequency-controlled airlock fan 243. This differential pressure also ensures that the second stage 218 is also supplied with a constant airflow. The arrangement downstream of the filter unit 224 ensures that contamination of the filter unit 224 is irrelevant for the pressure measurement.

[0133] As already mentioned, this air flow can consist of pure recirculated air or a mixture of recirculated air and fresh air.

[0134] If the drying process is carried out with a high amount of fresh air, i.e. a high dryer load, then the excess fresh air share is correspondingly high, preferably up to a maximum of 7500 Nm 3 / h. As a result, the proportion of recirculated air added for the second stage 218 is lower.

[0135] The opposite is true for low utilization, when only a few workpieces, such as vehicle bodies, are in the drying system 12, i.e., a low dryer utilization. In this case, the amount of fresh air provided by the fresh air heat exchanger is just sufficient to supply the first stage 216 of the airlock 214 with fresh air.

[0136] In this case, the motor-driven throttle device 242 is completely or largely closed and the air for the second stage 218 must be completely sucked in by means of the lock fan 243 from the adjacent first treatment chamber section 202.

[0137] The advantage of supplying the excess fresh air to the second stage 218, depending on the capacity of the treatment system 10, is that fresh air is no longer directly mixed into the recirculation modules 204 as was previously the case. This results in all fresh air being available to the lock 214, where it can help minimize the solvent content in the atmosphere of the treatment chamber 200 at its periphery. This further counteracts the risk of solvent recondensation in these cooler periphery areas.

[0138] List of reference symbols

[0139] Treatment plant

[0140] Drying system / dryer Fresh air heat exchanger Filter unit

[0141] Silencer unit radial fan

[0142] Heat transfer unit housing

[0143] Service page

[0144] Maintenance access intake fresh air first flow path second flow path heated fresh air

[0145] Temperature sensor

[0146] Measuring nozzle for manual measurements Treatment room Treatment room section / first heating zone Recirculation module / recirculation unit Recirculation fan

[0147] Measuring nozzle for manual measurements heat exchanger

[0148] Recirculation filter unit two-stage lock first stage of the lock second stage of the lock

[0149] Flow direction Filter unit Filter unit Measuring nozzle for manual measurements Measuring nozzle for manual measurements Fresh air supply

[0150] Measuring nozzle for manual measurements

[0151] compensator

[0152] Throttle device

[0153] Temperature sensor

[0154] Volume flow probe

[0155] branch

[0156] Volume flow probe motor-driven throttle device

[0157] Lock fan motor-driven throttle device

[0158] compensator

[0159] Measuring nozzle for manual measurements

[0160] Throttle device

[0161] Measuring nozzle for manual measurements

[0162] Measuring nozzle for manual measurements

[0163] pressure sensor

Claims

Claims: Fresh air heat exchanger (100) for heating a fresh air stream, comprising: at least one fan (106) for drawing in fresh air and generating a fresh air stream, and at least one electrically heated heat transfer unit (108) for transferring heat energy to the fresh air stream. Fresh air heat exchanger (100) according to claim 1, characterized in that the at least one electrically heated heat transfer unit (108) comprises at least one heating resistance device. Fresh air heat exchanger (100) according to claim 1 or 2, characterized in that the at least one electrically heated heat transfer unit (108) is arranged downstream of the at least one fan (106). Fresh air heat exchanger (100) according to any one of claims 1 to 3, characterized in that the fresh air heat exchanger (100) has at least one filter unit (102) for filtering the drawn-in fresh air.A fresh air heat exchanger (100) according to any one of claims 1 to 4, characterized in that the fresh air heat exchanger (100) has at least one silencer unit (104) for reducing the noise emission of the fresh air flow. A fresh air heat exchanger (100) according to claim 5, characterized in that the at least one filter unit (102) and / or the at least one silencer unit (104) is arranged upstream of the at least one fan (106). A fresh air heat exchanger (100) according to claim 5 or 6, characterized in that the at least one filter unit (102) and / or the at least one silencer unit (104) is arranged at least partially above the at least one fan (106). A fresh air heat exchanger (100) according to any one of claims 1 to 7, characterized in that the fresh air heat exchanger (100) has at least two, preferably three, electrically heated heat transfer units (108). A fresh air heat exchanger (100) according to claim 8, characterized in that the electrically heated heat transfer units (108) are arranged sequentially along the fresh air flow. A fresh air heat exchanger (100) according to any one of claims 1 to 9, characterized in that a first flow path (118) of the fresh air flow upstream of the fan (106) is perpendicular to a second flow path (120) of the fresh air flow downstream of the fan (106). A fresh air heat exchanger (100) according to any one of claims 1 to 10, characterized in that the at least one fan (106) is a radial fan.Fresh air heat exchanger (100) according to any one of claims 5 to 11, characterized in that the fresh air heat exchanger (100) comprises a housing (110) in which the at least one filter unit (102), the at least one silencer unit (104), the at least one fan (106), and the at least one electrically heated heat transfer unit (108) are at least partially enclosed. Fresh air heat exchanger (100) according to claim 12, characterized in that the housing (110) comprises a service side (112) which has at least one maintenance access (114).Fresh air heat exchanger (100) according to one of claims 1 to 13, characterized in that a preheating device for preheating the fresh air flow is arranged upstream of the at least one fan, wherein the preheating device is a heat pump, a regenerative thermal, in particular purely electrically operated and flameless, oxidation device or a solar thermal device comprising thermal oil or water. Use of a fresh air heat exchanger (100) according to any one of claims 1 to 14 for heating a fresh air stream which is supplied to a processing system for workpieces, in particular a drying system for vehicle bodies. Method for providing heated fresh air with an electrically heated fresh air heat exchanger (100), wherein the method comprises the following steps: The process involves drawing in fresh air (106) from the vicinity of the fresh air heat exchanger (100), filtering the drawn-in fresh air (116), reducing the noise emission of the drawn-in fresh air (106), redirecting the flow direction of the fresh air stream and compressing the fresh air stream, transferring heat energy generated by at least one heating resistance device to the fresh air stream, and discharging the heated fresh air (122). The method according to claim 16 is characterized in that the method further comprises a step of preheating the fresh air in a preheating device, wherein the preheating device is a heat pump, a regenerative thermal, in particular purely electrically operated and flameless, oxidation device, or a solar thermal device comprising thermal oil or water.

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