EP2684613B1

EP2684613B1 - Device for exchanging air with heat recovery, especially in spray booths

Info

Publication number: EP2684613B1
Application number: EP12461528.7A
Authority: EP
Inventors: Piotr Nikonczuk; Boguslaw Zakrzewski
Original assignee: Zachodniopomorski Uniwersytet Technologiczny w Szczecinie
Current assignee: Zachodniopomorski Uniwersytet Technologiczny w Szczecinie
Priority date: 2012-07-09
Filing date: 2012-07-09
Publication date: 2015-11-25
Anticipated expiration: 2032-07-09
Also published as: EP2684613A1

Description

A subject of the invention is a device for exchanging air with heat recovery, especially in the spray chambers but also in the other structures requiring similar methods of exchanging air, where removed hot air is polluted with solid particles precipitated on the walls of the ventilation ducts.
The known spray booths are operated in the three following modes - spraying mode, drying mode and ventilation mode. In the spraying mode, the air in the booth is continuously exchanged through intake and outtake ducts. The air is let through the open damper and initially cleaned using the prefilter. Next the air is heated by the burner to temperature 20 - 21°C and injected to the spraying booth through the ceiling filters. The air polluted with the spray dust is exhausted from the booth through the floor channel after cleaning in the paint stop filter. The average filtration of floor filter is 93-97%.
In the drying mode the outtake fan is off. The air in the spray booth is recirculated by closing one damper and opening another one. The first damper is not entirely closed, allowing for free exchange of 10% of the recirculated air. Temperature of the air during the drying mode is between 40 and 60°C. After the drying mode is completed the booth is ventilated to reduce the temperature inside, structural elements of the booth and a vehicle (or other details). The air circulation is the same as in the spraying mode. The difference between the ventilation and spraying modes is that during the ventilation the intaken air is not heated. There are offers of the spray booths with the devices for heat recovery, so called recuperators, in the European market. They are composed of the inlet channel connected to the chamber of the intake fan. Inlet channel 4 is equipped with the damper in the lower part for closing the channel and with the prefilter situated at the entry to the intake fan chamber. The damper is, through the heat exchanger with the burner, connected to the channel supplying the hot air to the spray booth through the ceiling filter. The spray booth has the floor filter situated in the floor. Through the floor filter the air from the spray booth is directed through the floor channel to the outtake fan chamber and further to the outlet channel. The device is equipped with the cross-flow recuperator situated to recover the heat from the air carried away from the booth and to convey the heat to the air taken from outside to the spray booth.
Application of standard recuperators in such a solution can result in damage of the recuperators. As it was previously given, the average level of filtration by the floor filter is 93-97%, so it can be assumed that the number of particles of the overspray can reach as much as 10% of pollution before filtration. Such a situation can gradually lead to blocking the micro-channels of the recuperator with the solid particles of the overspray and there is no possibility to clean the micro-channels in a simple manner. Fouling of recuperator results is increase of the air flow resistance and decrease of the efficiency of heat exchange. In Polish patent application P 323643 a method is known for organization of air circulation in the paint and spray booths with the manual hydrodynamic or pneumatic spray consisting in enforcing beneficial unidirectional air flow in the compartment which is obtained by setting the outtake openings on the whole surface of one of the walls of the rectangular prismatic compartment while on the opposite side, on the border of the entrance opening intake fans are situated fulfilling the loss of air in the compartment directing the jets rectangular to the axis of the entrance opening. In the compartment with subatmospheric pressure, two horizontal zones are separated for the air exhaust; the upper serviced by the upper zone outtake fan and the lower serviced by the lower zone outtake fan, each of the fans occupies the whole space of the barrier where it is installed. The air sucked in by the upper fan is carried away outside without reducing pollution, while the air sucked in by the lower fan carried to installation for utilization (reduction) of the solvent vapor. Passing the system of heat recovery at the air-to-air membrane exchangers, the air is carried away outside with the emitter. The air thermal energy intaken in the booth entrance opening zone is refilled using additional source of additional energy on the heaters, the intake unit is equipped with. From Polish patent description 138875 a method is known for preparing air for paint booth ventilation and a device for preparing air for paint booth ventilation employing low temperature source of exhausted paint booth ventilation air. The device for preparing air equipped with a filter, fan, heater and ventilation ducts is characterized in that the duct carrying away air from the initial heater is connected through the air distributor with two ducts, one of them being connected to the rotational heater. At the output of the heater an outlet duct is situated connected to the outlet collector connected to the by-pass duct. A temperature sensor is situated in the outlet collector controlling the position of the damper in the distributor and position of the valve controlling the amount of the thermal energy passing through the initial heater, whereas the ventilation ducts carrying air are connected to the rotational heater. From American patent description US 4422370 a method and device are known for the thermal energy recovery from the air outlet from the spray booth for painting car chassis, where the heat from relatively hot air outlet is transported to the cold air intaken to the booth. The air carried away is mixed with water or other liquid solvent, and the liquid is then separated in the separation chamber adjacent to the booth ventilation outlet, and in such a way it circulates between the chamber and heat exchanger, through which the intaken air flows.
The device for the air exchange in the present invention equipped with the spray booth, filters, fans, heat exchanger, dampers, ventilation ducts is characterized in that there are two intake ducts: a duct with heat recovery and a duct without heat recovery. Inside the duct with heat recovery the outtake duct is situated. The intake duct with heat recovery is connected to the intake duct without heat recovery before the prefilter with at least one damper and is equipped with at least one additional damper, with which the waste heat from the spray booth is recovered for heating the air in the hall. Air to the spray booth can be taken through the intake duct with heat recovery or intake duct without heat recovery, depending on the dampers settings. The outtake duct between the diffuser and confuser is equipped with a heat exchanger in the form of tubular ducts connected to the perforated bottom of the diffuser and confuser. Cross sections of the heat exchanger ducts can be of various shapes, beneficially round or square so that removing the overspray sediment from their internal walls was ensured. Numbers and cross sections of the tubular ducts must be selected to ensure the air mass flow necessary for the correct operation of the device without excessive resistance and to obtain the area of air exchange as large as possible. Amount of the air which must flow through the heat exchanger depends on the volume of the spray booth.
The device according to the invention enables heat recovery from the exhaust air what allows for reduction of energy consumption for heating fresh air, especially in winter. The heat exchanger pipes can be cleaned from the depositing solid particles of the overspray. Air intake through the intake duct, where the air is not heated, during the ventilation, allows cooling the booth and objects inside faster after drying. It reduces costs of electric energy for driving fans. The heat recovered during ventilation of the booth can be used for heating the hall.
The device according to the invention is presented on examples and in the figure, where Fig. 1 presents the device in the longitudinal section operating in the spraying mode, Fig.2 presents the device in the longitudinal section operating in the drying mode, Fig.3 presents the device in the longitudinal section operating in the ventilation mode, Fig.4 presents the device in the longitudinal section operating in the spraying mode, where the intake duct without heat recovery is connected to the intake duct with heat recovery with the use of one damper.

Example 1

The device is composed of the intake duct without heat recovery 4 which is connected to intake fan chamber 12. Intake duct 4 is equipped with damper 9 situated in the lower part enabling closing the valve and prefilter 11, situated at the inlet of intake fan chamber 12, which through heat exchanger 13 is connected to spray booth 16 with duct 14 supplying hot air to the booth through ceiling filter 15. Floor filter 17 is situated in the floor of spray booth 16. Through the filter the air from spray booth 16 is, through floor duct 18, directed to outtake fan chamber 19 and further to outtake duct 2. Outtake duct 2 is situated inside intake duct with heat recovery 1, which is adjacent to intake duct 4 and is connected with it by two dampers 5 and 6. Moreover, intake duct with heat recovery 1 is equipped with two additional dampers 7 and 8 situated on the opposite side of intake duct 4, through which, after they are opened, the air from the hall flows and is heated with the waste heat of the air exhausted from the booth in the heat exchanger. Outtake duct 2, between diffuser and confuser, has heat exchanger 3 in the form of 16 tubular ducts, which ends are connected to perforated bottom of the diffuser and confuser. Sections of the heat exchanger ducts are round with the diameter of 20 cm, what ensures removing solid particles of the overspray from their internal walls. In spraying mode dampers 5 and 6 are open, while dampers 7, 8, and 9 are closed. Air is taken to spray booth 16 through additional intake duct 1, what allows reducing energy consumption for heating air. In the drying mode, the air inside the spray booth is recirculated. Damper 10 is entirely open, while dampers 5 and 6 are slightly open to cause partial exchange of air in the booth. After finishing the drying cycle spray booth 16 is ventilated to cool a sprayed vehicle and structural elements of spray booth 16. Air to the booth is taken through intake duct 4 what allows to shorten the cooling time. Such a circulation of air is obtained closing dampers 10, 5 and 6 and opening damper 9. During this time heat from the exhausted air can be recovered for heating the hall opening dampers 7 and 8.

Example 2

The device as in Example 1, the difference is that there are 12 ducts having square cross sections with the length of the edge 20 cm in heat exchanger 3.

Example 3

The device as in Example 1 or Example 2, the difference is that there are 8 ducts having rectangular cross sections with the lengths of the edges 10 cm and 60 cm in heat exchanger 3.

Example 4

The device as in Example 1, the difference is that intake duct 4 is connected to intake duct 1 by one damper 6. Moreover, intake duct with heat recovery 1 is equipped with one additional damper 7 situated on the opposite side of intake duct 4, through which, after it is opened, the air from outside flows to the hall and is heated with the waste heat of the air exhausted from the booth in heat exchanger 3.

Claims

A device for air exchange with heat recovery, especially in spray booths composed of filters, fans, heat exchanger, dampers, ventilation ducts, characterized in that the device has two intake ducts: without heat recovery (4) and with heat recovery (1), inside which there is outtake duct (2) with heat exchanger (3), the intake duct with heat recovery being connected to duct without heat recovery 4 by at least one damper (6).
A device according to claim 1, characterized in that intake duct with heat recovery (1) is equipped with at least one damper (7).
A device according to claim 1, characterized in that outtake duct (2) between the diffuser and confuser has heat exchanger (3) in the form of tubular ducts connected to the perforated bottom of the diffuser and confuser.