CASING FOR COLD BRIDGE-FREE AIR HANDLING UNIT

Abstract: Air handling unit casing in which the circulated air is thermally conditioned, preventing the change of the thermal condition of the circulated air due to air leakage and thermal bridge. It has a modular structure which can be disassembled and is constructed from panels (1) which are made of an inner skin (15), an outer skin (16) and insulation material (9) therebetween, doors (2) and door frames (3). The embodiment of the panels do not allow the direct contact of the inner and outer skin and reduces the thermal bridge and air leakage through the unit by employing gaskets (8, 11, 17), plastic bushing (18) and heat barrier slits (28). The panels (1) can be joined to each other side by side or perpendicularly.

Description: CASING FOR COLD BRIDGE-FREE AIR HANDLING UNIT TECHNICAL FIELD The present invention relates to a particular feature of an Air Handling Unit Casing which holds various components for changing the thermal conditions of air . More particularly the present invention relates to the feature which is "the cold-bridge- free" and "air tight" construction of the casing by means of which the heat transfer between the air inside and outside of the air handling unit and the air leakage to and from the outside air are minimized. BACKGROUND ART Air handling units are widely used in both comfort and industrial process air conditioning systems for the purposes of changing the thermal conditions of air and removing the undesired particles and odors from the air. Various components such as cooling and heating coils, filters, blowers, humidifiers etc. are installed inside the air handling unit casing in order to change the thermal conditions of air and in order to circulate the air through the air handling unit casing. The function of the air handling unit casing is separating physically the conditioned and circulated air inside the unit from the environment air outside, and additionally to provide a protective cover for the inner components. The main elements which comprise an air handling unit casing are doors, panels and the fixing accessories that join these elements. The doors provide access to the inside of the casing for maintaining and repairing the components or for making amendments or adjustments on the system in case of necessity. The door is basically made of two separate sheet metal plates called inner and outer skins and a filling material in between which is used for insulation. The door is also furnished with hinges along one side through which it is fixed to the panels of the casing and with door handles on the side across, for locking the door. The panels are also constructed of two separate sheet plates and an insulation material in between similar to the doors. Since the different sizes depending on the required performance and air conditioning capacity, a different number and combination of standard panels are used to build each particular size of the casing and different techniques and methods are employed to join the panels. Due to the air temperature difference between inside and outside of the air handling unit, a heat flow occurs through the casing which has to be controlled and reduced by means of applying an insulation material between the panel skins. With the present technology and the construction outlines of air handling unit casings as described above, properties of the conditioned air are negatively affected due to occurrence of thermal-bridge and air leakage. Disadvantages or negative effects introduced by the constructions which are produced by the present technology can be listed as follows: In case there is any thermal-bridge in any part of the air handling unit casing, the heat transfer rate between inner and outer air is augmented and condensation may be formed locally on the casing surface depending on the inner and outer air temperature and humidity conditions. On the other hand in case of an air leakage through the adjoining surfaces of the panels due to the pressure difference between the inside and the outside of the casing condensation may occur alongside the edges of the panels and doors. If the condensation is formed on the inner surfaces of the air handling unit it promotes the corrosion of the material inside the casing and depending on the amount of condensation, some amount of water may be collected inside the air handler which is then carried to the other sections of the system and even to the conditioned space. Alternatively condensation formed outside the air handling unit casing causes rusting and corrosion of the outer skin and accumulation of condensed water in the machine room, where the equipment is installed, which degrades the hygiene in the environment. Besides condensation problems, air leakage through panel and door joints creates energy loss and air thermal condition inside the unit deviates from the intended quantities. Another disadvantage offered by the constructions that the comfort air which is filtered and cleaned through the filter sections is lost due to air leakage through the casing and/or similarly the unfiltered and unconditioned air from the environment enters to the unit due to slack joints on the air handling unit casing. DESCRIPTION OF THE INVENTION One purpose of the invention is; to reduce the thermal-bridge between the inner and the outer skins of the panels which are used in constructing air handling unit casings and hence to prevent deviation of the thermal conditions of the conditioned air from that of the intended for comfort. Another purpose of the invention is; to prevent formation of the condensation on the inner or the outer surfaces of the air handling unit casings which depends on the temperature and humidity conditions of inner and outer air and thus to prevent corrosion on the inner or the outer skin of the casing caused by this condensation. Another purpose of the invention is; to prevent the energy losses caused by the air leakage through panel and door joints which are in turn caused by the pressure differences between inner and outer air. Yet another purpose of the invention is to prevent loss of the filtered and cleaned air, which has already passed through filter section, through the leaking joints under the pressure differential as described above and to prevent suction of the unfiltered air inside the unit casing. The casing of the air handling unit described by the invention is mainly composed of panels, doors and door frames. Panels are made of an inner skin, an outer skin and an insulation material in between. The circumference of the outer skin is bent and a channel is formed all around the panel. The bent outer edges of the panel inner and outer skins are then furnished with plastic spacer bushings through which mounting bolts are inserted as to pass through insulation and the inner and outer skins. The joining of the panels to each other is realized by means of mounting bolts which pass through these bushings. Panels are joined to each other by two different met joined side by side i.e. at a 180° angle, a gasket is placed between the facing edges in order to prevent the conditioned air leakage from inside the air handling casing to outside when there is a positive pressure in the unit, and from outside to inside when there is a vacuum in the unit. After the panels are joined side by side another insulated and formed metal cover piece is fixed onto the channels to hide the bolts and nuts. This insulated metal cover compensates the thermal bridge due to reduced thickness of the panel around the circumference. In case the panels are joined perpendicular to each other, a special metal fixing angle and a special rubber gasket with a triangular cross-section which fills the gap between the fixing angle and panel edges, is used to prevent air leakage and occurrence of the thermal bridge. In this method, similar to side by side panel joining, the connection of the panels is performed by mounting bolts which are placed inside the channel formed in the circumference of the outer skin except that two rows of bolts are used instead of one and bolts in each row lay perpendicular to the ones in the other row. Again as in line method there is an insulated metal cover for hiding the bolts and for reducing heat transfer through the channel. Air handling unit door is also made of an inner skin, an outer skin and an insulation material in between. The door is fitted with hinges along one side for being mounted on the door frame which is already assembled on the air handling unit casing. A door handle and door lock on the reverse side helps to open and close it. Plastic spacer profiles are inserted between inner and outer skins around four sides to eliminate direct contact of these two parts and hence reduce the conductive heat transfer from inside air to outside air or vice versa. Additionally a continuous strip of gasket is fitted on the profile surfaces which meet the profile of the door frame surfaces for air tightness when the door is closed. The door frame has the same basic construction as the panels. Channels are formed around on circumferences of the four sides of the door frame and a gasket seat is made on the inner skin surfaces where they meet the adjacent panels. DESCRIPTION OF DRAWINGS The advantage of the structure of the present invention and its auxiliary elements will become better understood from the given detailed figures. Figure 1 shows a perspective view of the air handling unit casing Figure 2 shows the detail design of the panel in the scope of the invention. Figure 3 shows the detail of the air handling unit door, door frame and panel connection in the scope of the invention. Figure 4 shows the detail of side by side connection of two panels. Figure 5 shows the detail of the perpendicular connection of two panels. REFERENCE NUMBERS OF ELEMENTS IN THE FIGURES 1 Panel 18 Plastic bushing 2 Door 19 Plastic spacer 3 Door frame Profile 4 Hinge 20 Door inner skin 5 Door handle 21 Door outer skin 6 Hinge bolt 22 Door frame inner skin 7 Bolt and nut 23 Door frame outer skin 8 Door and frame gasket 24 Sheet metal screw 9 Insulation material 25 Plastic piece 26 Corner cover 10 Middle cover 27 Outer skin bend 11 Gasket 28 Heat barrier slits 12 Fixing beam 29 Channels 13 Side cover 14 Side cover fixing piece 15 Panel inner skin 16 Panel outer skin 17 Panel gasket DETAILED DESCRIPTION OF THE INVENTION The main elements of the air handling unit casing are shown in figure 1. These elements are panels (1) which can be joined side by side or perpendicularly, middle cover (10) which are placed on the channels between the panels when connected side by side, side cover (13) which are located on the channels and fixing beams when the panels are joined perpendicularly, a door (2) which provides access to the air handling unit elements e.g. in order to repair them and a door frame (3) is employed to mount the door (2) to the casing. Figure 2 shows the detail of the designed panel (1) according to the present invention. The panel (1) is formed by a panel inner skin (15), panel outer skin (16) and insulation material (9) between panel skins. The distance between panel skins (15,16) is determined such that heat transfer due to temperature difference between the inside and outside of the air handling unit is reduced to the acceptable level. Channels (29) and outer skin bends (27) are provided around the circumference of outer skin (16) for preventing any contact between panel inner skin (15) and panel outer skin (16) in any place of panels (1). After joining of the panels (1) by mounting bolts (7), the channels (29) are closed by the middle and side covers (10,13). Thus, the formation of thermal bridge at the connection region is reduced to the minimum level. Due to mounting bolt channel (29) which decrease the distance between the inner and outer skin , heat barrier slits (28) are cut around the circumference of the inner skin (15) to prevent thermal bridge formation. Thus, heat transfer through the cross section of the inner skin (15) and consequently heat transfer from the inner skin (15) to the outer skin (16) is reduced. Gaskets (17) are located in grooves parallel to the heat barrier slits (28) on the edges of the panels (1) in order to prevent air leakage between the inside and outside of the air handling unit in the case of the positive or negative interior working pressure. The detailed view of the air handling unit door is show of the door (2) is similar to the panel (1). The door (1) is also formed by an inner skin (20), an outer skin (21) and an insulation (9) therebetween. The door handle (5) is assembled on the door to open or close it. Hinges (4) are employed to connect the door (2) to the door frame (3). The inner and outer skins of the door (20,21) are inserted to the plastic spacer profile (19) in order to fix them so as to prevent them from touching each other. A door frame gasket (8) is provided on the plastic spacer profile (19) of the door (2) and door frame contact surfaces .which are tapered, for holding the gasket in position to prevent air leakage between the air handling unit and surroundings. Figure 4 shows the detail of side by side connection of two panels (1). The joining of the panels (1) to each other is performed by mounting bolts (7) located in the panel channel (29) which are formed by bending (27) of the outer skin (16). The formation of thermal bridge between the inner and outer skins (15,16) which may occur by mounting bolts (7) is prevented by using plastic bushings (18). Two arrangements are employed to prevent formation of thermal bridge due to reduced panel thickness in the channels (29): Firstly, the upper side of channel (29) is covered by middle or side covers (10,13) which are coated with an insulation material (9) on the inner surfaces. It not only prevents the formation of the thermal bridge but also hides the unpleasant appearance created by channels (9) and bolts (7) and forms a smooth outer casing surface. Secondly, heat barrier slits (28) cut along the edges of the panel inner skin reduces the area which causes conductive heat transfer and consequently thermal bridge formation. In order to prevent air leakage from the inside of the air handling unit to the surroundings and vice versa, gaskets (17) are placed below the heat barrier slits (28). The air leakage through the connection surfaces between panels (1) which are located side by side is considerably reduced by employing the gaskets (17) which are pressed on each other. The connection detail of the two panels (1) which , each other is presented in figure 5. The connection of the panels (1) to each other are performed by two sets of mounting bolts (7) whose axes are perpendicular to each other. The perpendicular connection is done by mounting bolts (7) to a fixing beam (12). The fixing beam (12) performs a task of structural integrity for the perpendicular connection of the panels (1). The air leakage is prevented by a corner gasket (11) which is located in the gap between the panels (1) and fixing beam (12). Similar to the side by side joining of panels, a side cover (13) is employed to cover the channels around the panels and the space between the legs of the fixing beam (12) and the bolts (7). A side cover fixing piece (14) is used to fix the side cover (13). The side cover fixing piece (14) is connected to the fixing beam (12) by the sheet metal screw (24). Formation of the thermal bridge which otherwise occurs between the side cover fixing piece (14) and fixing angle (12) is prevented by a plastic piece (25) inserted therebetween.

Claims: CLAIMS 1. Air handling unit casing comprising panels (1) for preventing change of the thermal condition of the circulated air due to air leakage and thermal bridge between the outer and inner surfaces of the air handling casing unit, made of a panel inner skin (15), a panel outer skin (16) and insulation material (9); and doors (2) and door frames (3) characterized in that , outer panel skin bends (27) and channels (29) are provided around the circumference of said panel outer skin (16) for preventing any contact between said panel inner skin (15) and said panel outer skin (16) in any place of said panels (1), and heat barrier slits (28) are provided for panel gaskets (17) to cut around the circumference of the panel inner skin (15) to prevent thermal bridge formation and air leakage. 2. The air handling unit panels according to claim 1 , characterized in that bolts (7) are disposed in the said channels (29) . 3. The air handling unit panels according to claim 1 and 2, characterized in that a middle cover (10) is provided on said channels (29). 4. The air handling unit panels according to claim 3, characterized in that insulation material (9) is disposed in said middle cover(10). 5. The air handling unit panels according to claim 2, characterized in that plastic bushings (18) are provided with said bolts (7). 6. The air handling unit panels according to claim 1 , characterized in that panel gaskets (17) are disposed grooves formed around the circumference of the panel inner skin (15). 7. The air handling unit panels according to claim 6, characterized in that panel gaskets (17) are positioned as to touch and press each other. 8. The air handling unit panels according to claim 1 , characterized in that at least two sets of mounting bolts (7) and a fixing beam (12) are disposed for perpendicular connections of panels (1) thereof. 9. The air handling unit panels according to claim 1 , characterized in that a gasket (11) is disposed for filling the gap between the fixing beam (12) and panel (1) edges. 10. The air handling unit panels according to claims 8 and 9, characterized in that a side cover (13) is provided on said bolts (7) and fixing beam (12). 11. The air handling unit panels according to claim 10, characterized in that said side cover (13) is connected to a side cover fixing piece (14) by a sheet metal screw (24). 12. The air handling unit panels according to claims 10 and 11 , characterized in that a plastic piece (25) is provided between said fixing beam (12) and side cover fixing piece (14). 13. The air handling unit panels according to claim 1 , characterized in that a door frame gasket (8) is disposed in door (2) and door frame (3) contact surfaces. 14. The air handling unit panels according to claim 13, characterized in that said door (1) and door frame (3) contact surfaces are tapered. 15. The air handling unit panels according to claim 10, characterized in that plastic space profiles (19) are disposed for preventing of contacting door inner skin (20), door frame inner skin (22) and door outer skin (21), door outer skin (23)

Inventors: ARKUN YILDIRIM, BESER ERKUT, UYSAL HAMDI, ARKUN, YILDIRIM, BESER, ERKUT, UYSAL, HAMDI
Applicants: ARKUN YILDIRIM, BESER ERKUT, TEBA ISITMA SOGUTMA KLIMA TEKN, UYSAL HAMDI, ARKUN, YILDIRIM, BESER, ERKUT, TEBA ISITMA SOGUTMA KLIMA TEKNOLOJILERI A.S., UYSAL, HAMDI
Application year: 2000
Main classification: F24F13
IPC codes: F24F13