IE55587B1

IE55587B1 - Vapour extraction hood

Info

Publication number: IE55587B1
Application number: IE607/84A
Authority: IE
Original assignee: Schmalhofer Markus
Priority date: 1983-03-15
Filing date: 1984-03-12
Publication date: 1990-11-07
Also published as: NO161774B; DK136484D0; IE840607L; ATE21448T1; EP0121809A1; NO840946L; DK153436C; DK136484A; NO161774C; DE3460458D1; EP0121809B1; DK153436B; DE3309208A1

Abstract

1. Fume hood with an elongate extraction chamber, with an exit air connection for discharging extracted exit air and with a fresh air supply chamber and a fresh air collection chamber, between which heat exchange elements, through which fresh air can flow, of a recuperator are arranged which is provided in the extraction chamber of the hood and around which the exit air flows, characterized in that the fresh air supply chamber (5) and the fresh air collection chamber (6) are arranged in the region of the top side of the extraction chamber (3) each along one edge of the hood and extend over at least approximately the entire length of the hood, and that the heat exchange elements (26) are arranged transversely to the longitudinal direction of the hood.

Description

3 3 a S 5 i) 7 The invention relates to a vapour extraction hood.

A vapour extraction hood is known for example from DE-A-3011 101 and is suitable in particular for use in large kitchens. The vapour extraction hood 5 disclosed comprises a housing in which an elongated suction chamber is disposed.

The suction chamber, which is arranged above the cooker or cookers producing the vapour or the like, is supplied with hot exit air for removal from the 10 kitchen for example by means of a fan to an exit air connection from whence the exit air is conducted into the surroundings. The known vapour extraction hood further comprises a recuperator having heat exchange elements which are arranged between an inlet air 15 receiving chamber and an inlet air collecting chamber. The inlet air supplied via the inlet air receiving chamber flows through the heat exchange elements and the warm exit air conveyed into the suction chamber flows around said heat exchange 20 elements, and a greater part of the heat content of the exit air can be transferred to the inlet air which after its warming is conveyed via blow-out openings of the vapour extraction hood into the kitchen.

Although the principle of the known vapour 25 extraction hood has proved itself very well in practice, the good efficiency of the heat transfer from the exit or drawn-off air to the inlet air permitting a considerable saving of energy in the heating of the kitchen, due to the heat exchange 30 elements of the recuperator disposed in the longitudinal direction of the suction chamber efficiency losses 3 occur in the heat exchange between exit air and inlet air because in the rear region of the heat exchange elements, considered in the direction of flow of the inlet air, the latter is already heated up to a great 5 extent so that the temperature difference between inlet air and exit air necessary for a heat exchange of' high efficiency is already so small that the utilization of the drawn-off or exit air flowing in the rear region of the heat exchange elements is considerably less 10 than in the front region of the heat exchange elements.

According to the invention there is provided a vapour extraction hood, suitable for use in large kitchens, comprising an elongate suction chamber to which vapour containing exit air can be drawn off, a recuperator 15 located in the suction chamber and having a number of heat exchange elements, a fresh air supply chamber from which fresh air can be supplied to flow around the heat exchange elements for heat transfer from the exit air to the fresh air, an exit air extraction chamber connected 20 to the suction chamber for carrying away exit air to be extracted and a chamber for collecting the fresh air after it has passed around the heat exchange elements, wherein the fresh air supply chamber and the fresh air collecting chamber extend substantially the entire 25 length of the hood and are arranged, in the installed condition of the hood, above the suction chamber, the fresh air collecting chamber being located adjacent to a longitudinal side of the hood and wherein the heat exchange elements are arranged transverse to the 30 longitudinal direction of the hood and define separate flow passages for the exit air and the fresh air. 4 The result is firstly that with relatively long hoods of relatively great inlet air requirement, the entry area for the inlet air is increased by providing a relatively large number of heat exchange elements running transversely of the longitudinal direction of the hood. The number of heat exchange elements provided depends on the length of the extraction hood and is chosen to achieve optimum flow conditions for the inlet air and for the exit air. 1o A further advantage is that the arrangement of the heat exchange elements transversely of the longitudinal direction of the hood permits a greater heat exchange area per meter hood length which results in a very high utilization of the heat content of the exit air and thus is a very high efficiency of the hood.

Another advantage in providing the heat exchange elements transversely of the longitudinal direction of the hood is that the temperature difference between inlet air and exit air is of the same order of magnitude 20 al°ng the longitudinal extent of the hood in all hood regions.

The particular overall advantage with the vapour extraction hood according to the invention is that the arrangement of the heat exchange elements transversely of the longitudinal direction of the hood permits 5 greater adaptability to the changes of the flow conditions due to different hood lengths on the inlet air side and on the exit air side and this in turn permits the heat transfer quantities partially also dependent on the hood length and the related changes 10 of the supplied inlet air amounts or drawn-off outlet air amounts to be set to values which give an optimum efficiency of the vapour extraction hood.

Advantageously, the heat exhange elements are constructed as plates which are ccntoined to form heat exchange modules. Accordingly, 11 it is possible to combine a plurality of heat exchange elements constructed as plates to a module, and the plate spacings can be chosen to obtain optimum flow and heat transfer conditions. It is possible with such a heat exchange module to obtain 20 a basic unit, adapted to inlet air and exit air basic values, of a heat exchanger particularly suitable for the vapour extraction hood according to the invention and to adapt hoods of different lengths for various uses with in each case different inlet air and exit 21 air displacements by providing a corresponding number 6 of heat exchange modules to the different use conditions. This enables a sort of modular system to be provided with which a prefabrication of always identical basic construction units is possible which can then be combined to obtain the vapour extraction hoods adapted to the particular purpose. This in turn permits a standardization of the individual construction units which can increase economy with corresponding reduction of production costs particularly with high production quantities.

Further details, features and advantages of the invention will be apparent from the following description of an example of an embodiment with the aid of the drawing.

The single Figure of the drawing shows diagramatically in greatly simplified perspective view a central region of a vapour extraction hood according to the invention.

In the embodiment illustrated in the Figure of the vapour extraction hood 1 according to the invention for clarity constructional details have not been illustrated so as to enable the function principle essential to the mode of operation of the vapour extraction hood according to the invention to be shown more clearly. Furthermore, the size relationships are not shown to scale, in particular as regards the dimensions of the heat exchange elements and the spacings between them because both the thickness of the heat exchange elements and the distances between them in the particularly preferred embodiment of the vapour extraction hood 1 according to the invention illustrated in Fig. 1 lie in the region of a few 7 millimeters so that a true-to-scale illustration would have considerably reduced the clarity of the drawing and unnecessarily made the explanation of the mode of operation more difficult, 5 The vapour extraction cooker hood 1 according to the invention, a central region of which is shown in the Figure, is suspended in the present example in a manner not shown on the ceiling of a kitchen. The hood comprises a housing 2 in which an elongated 10 suction chamber 3 is disposed which can be covered at the bottom for example with a grating not illustrated in the Figure and consisting for example of mesh material. Above the suction chamber 3 in the embodiment of the hood illustrated a collecting 15 chamber 4 is disposed which comprises a fresh air supply chamber 5, a fresh air collecting chamber 6 and an exit air collecting chamber 7. In the example of the embodiment illustrated the fresh air supply chamber 5 and the fresh air collecting 20 chamber 6 are each divided into two subchambers 8 and 9 and 10 and 11 respectively. The subchambers 8 and 9 of the fresh air supply chamber 5 and the subchambers 10 and 11 of the fresh air collecting chamber 6 extend substantially over the entire length of the 25 hood and are arranged on either side of the exit air collecting chamber 7 along the two edges of the hood.

The two subchambers 8 and 9 of the fresh air supply chamber 5 are directly adjacent to the exit air collecting chamber 7 and are separated by means 30 of upright side walls 12 and 13 from the exit air collecting chamber 7. On the outside towards the edges of the hood the subchambers 8 and 9 of the fresh air supply chamber 5 are bordered by the subchambers 10 and 11 of the fresh air collecting 8 chamber 6 which are also separated by upright walls 14 and 15 from the subchambers 8 and 9. The subchambers 10 and 11 of the inlet air collecting chamber 6 are connected via discharge openings 16 and 5 17 in side walls 18 and 19 to the interior of the kitchen in which the vapour extraction hood 1 according to the invention is disposed. At its upper side the collecting chamber 4 is covered by a cover wall 20 extending over the fresh air supply 10 chamber 5, the fresh air collecting chamber 6 and the exit air collecting chamber 7.

The subchambers 8 and 9 of the fresh air supply chamber 5 are connected to two distributor passages 21 and 22 which open into a central inlet air passage 15 23. The irtlet air passage 23 is connected in a manner not shown to the atmosphere and supplies inlet air to the fresh air supply chamber 5.

The exit air collecting chamber 7 is connected via an exit air connection 24 to an exit air passage 25 which 20 carries the exit air drawn off from the kitchen into the atmosphere or the like.

In the suction chamber 3 of the housing 2 of the vapour extraction hood 1 heat exchange elements 26 are disposed transversely of the longitudinal 25 direction of the hood. The heat exchange elements 26, which in the example of embodiment are made as substantially trapezoidal plates from a material particularly suitable for a good heat transfer, for example copper or aluminium, are spaced apart from each other a few millimeters, a particularly preferred spacing being about 5 mm. The spacings between the heat exchange elements 26 constructed as plates are 30 9 fixed by a spacer 27, forming between two heat exchange elements 26 in each case flow passages 28 and 29 serving respectively for conducting exit air and inlet air. In the embodiment of the vapour 5 extraction hood according to the invention illustrated the two front plates 26 in the Figure define a flow passage 28 for exit air, the area 30 between the heat exchange elements 26 at the lower side of the collecting chamber 4 in the illustration chosen is 10 partially covered for forming a passage opening 31 for exit air by means of the spacer 27.

The flow passage 28 is directly adjacent to a flow passage 29 which is again defined by two heat exchange elements 26 constructed as plates and serves to 15 conduct inlet air. The horizontal area 32 adjoining the lower side of the collecting chamber 4 and defined by the plates 26 of the flow passage 29 is partially covered by means of the spacer 27 to form an inlet opening and outlet opening 33 and 34 respectively 20 for inlet air whilst the areas 35, 36 and 37 facing downwardly in the illustration shown and defined by the plates 26 of the flow passage 29 are completely covered by means of the spacer 27.

All the flow passages 28 and 29 for exit air and 25 inlet air of the heat exchange elements 26 constructed as plates and combined by means of the spacer 27 to form a heat exchange module are constructed in the manner described above so that along the longitudinal direction of the housing 2 of the hood alternately 30 adjacent to each other in each case a flow passage 28 for exit air and a flow passage 29 for inlet air are arranged in the immediate vicinity of each other, the heat exchange elements 26 being disposed transversely ΙΟ of the longitudinal direction of the hood. The passage openings 31 for exit air formed by the partial covering of the areas 30 adjoining the lower side of the collecting chamber 4 are connected to the exit air collecting chamber 7 whilst the inlet openings 33 of the flow passages 29 for inlet air are connected to the subchambers 8 and 9 of the fresh air supply chamber 5 and the outlet openings 34 are connected to the subchambers 10 and 11 of the inlet air collecting chamber 6.

Beneath the heat exchange elements 26 filters 38 and 39 are provided which extend over the entire length of the hood and are suspended in inclined arrangement in the hood and the lower ends of which are disposed in a trap area 40 disposed horizontally in the hood.

The filters 38 and 39 are air-permeable so that the exit air sucked upwardly from the cooker can pass through the filters 38 and 39. On the other hand, the filters 38 and 39 trap the water of condensation formed by the condensation effect on the heat transfer from the exit air to the inlet air and the precipitated liquid fat particles and conduct them into the trap area 40.

In operation of the vapour extraction hood 1 according to the invention by for example a fan which is not shown hot exit air is drawn upwards from the cooker into the housing 2 and conveyed through the filters 38 and 39 into the flow passages 28 for exit air.

At the same time, via the inlet air passage 23 inlet air is conveyed into the distributor passages 21 and 2 2 which convey the inlet air into the subchambers 8 and 9 of the fresh air supply chamber 5. From the fresh air supply chamber 5 the inlet air is 11 conveyed via the inlet openings 33 into the flow passages 29 for inlet air, and in the embodiment illustrated the inlet openings 33 alternately along the longitudinal direction of the housing 2 conduct inlet air via the entry openings 33 disposed in the subchamber 8 and via the entry openings 33 disposed in the subchamber 9 into the flow passages 29. Accordingly, the inlet air heated by the heat transfer between the exit air and the inlet air emerges alternately via the outlet openings 34 in the subchambers 10 and 11 respectively into the latter, whereafter the heated inlet air is blownout via the discharge openings 16 and 17 respectively into the interior of the kitchen at least approximately parallel to the ceiling to produce a room air circulation.

The alternate arrangement chosen in the example of the embodiment illustrated of the inlet openings 33 and outlet openings 34 is necessary to obtain a hood which can blow out inlet air heated at its two longitudinal sides into the interior, for which purpose an arrangement of the subchambers 10 and 11 in the immediate vicinity of the longitudinal edges of the hood is necessary. For a hood which blows out inlet air on one side only a subdivision into in each case two subchambers 8 and 9 and 10 and 11 of the fresh air supply chamber 5 and the fresh air collecting chamber 6 respectively is not necessary so that for such a hood for example the subchamber 8 and the subchamber 10 of the fresh air supply chamber 5 and of the fresh air collecting chamber 6 respectively could be combined to form an inlet air receiving chamber, the exit openings 34 then forming the inlet openings 33 which could convey the inlet air to be heated into the fresh air supply chamber 5 which 12 would then be formed by the subchambers 9 and 11; in this inlet air receiving chamber each inlet opening 33 would then form an outlet opening 34 for inlet air.

In the embodiment illustrated of the vapour extraction hood according to the invention, however, as described above the inlet air is conducted alternately via the inlet openings 33 disposed in the subchambers 8 and 9 of the fresh air supply chamber 5 into the flow passages 29 and after heating by the hot exit air introduced via the outlet openings 34 into the subchambers 10 and 11 of the inlet air collecting chamber 6 so that a blowing out of heated inlet air via the discharge openings 16 and 17 is possible in both directions.

The exit air is introduced via the flow passages 28 and the openings 31 into the exit air collecting chamber 7 from whence the exit air is conducted via the exit air connection 24 into the exit air passage 25 and from there into the atmosphere or the like.

The arrangement of the heat exchange elements 26 transversely of the longitudinal direction of the hood has the advantage that depending on the length of the hood and the resulting inlet air and exit air quantities a corresponding number of heat exchange elements 26 and a resulting number of flow passages 28 and 29 for exit and inlet air can be chosen which permits optimum flow and heat transfer conditions.

In particular when heat exchange elements are provided in the form of heat exchange modules, as are used in the example of the embodimsnt of the hood illustrated, it is possible in simple manner to determine prior to the actual production of the vapour extraction hood 1 according to the invention the cross-sectional areas of the flow passages 28 and 29 particularly suitable for optimum flow and heat transfer conditions and fix these areas in the production of the heat exchange 13 modules. With such a basic unit it is then possible to make hoods of various lengths for various purposes, providing in accordance with the exit air and inlet air quantities to be expected a suitable number of 5 heat exchange modules to obtain the optimum flow and heat transfer conditions which permit an optimum efficiency of the vapour extraction hood 1. This thus means that for a long hood a correspondingly large number of heat exchange elements 26 for example in 10 the form of the aforementioned heat exchange modules is provided in the hood so that the cross-sectional area of the flow passages 28 and 29 necessary for conveying the large amount of inlet air and exit air corresponding to the length of the hood can be 15 increased to a value which permits maintenance of the aforementioned predetermined optimum flow and heat transfer conditions. In particular, with the vapour extraction hood 1 according to the invention the flow losses can be minimized by correspondingly large flow 20 cross-sections and relatively short flow paths and it is possible to set the heat transfer coefficients necessary for good heat transfer by corresponding arrangement of the heat exchange elements 26. This makes it possible to achieve with the vapour extraction 25 hood 1 according to the invention high efficiencies so that even the provision of an afterheat means for the inlet air can be dispensed with provided the temperatures at which the inlet air is inspired are not extremely low. On the other hand, it is of course also possible 30 to provide afterheat means in the vapour extraction hood 1 according to the invention for extreme temperatures of the inlet air.

In addition, it is possible to construct the vapour extraction hood 1 according to the invention as part 14 of a suspended ceiling in which then the side walls 18 and 19 with the discharge openings 16 and 17 in the installed condition are downwardly inclined so that on combining a plurality of vapour extraction hoods 1 along their longitudinal edges to form a suspended ceiling roof-like connecting areas in the form of joined side walls 18 and 19 of the respective vapour extraction hoods 1 can be formed.

Finally, a particular advantage of the vapour extraction hood according to the invention is that the heat exchange area of particular significance for a high efficiency in the heat exchange between exit and inlet air can be still further considerably increased by arranging the heat exchange elements transversely of the longitudinal direction of the hood enabling a particularly high efficiency to be achieved with the vapour extraction hood 1 according to the invention. Thus, with hoods of the type according to the invention efficiencies between 70 and 80% have been found and in the construction of the heat exchange elements 26 as plates plate thicknesses of about 0.3 mm and plate spacings of 5 mm have been found particularly advantageous. This gave as further advantages due to the favourable flow-in conditions due to the arrangement of the heat exchange elements 26 in the suction chamber 3 and the advantageous construction of the flow passages 28 and 29 both as regards their cross-sectional area and as regards their length that the fan powers for conveying the exit air and inlet air, if a fan is used for this purpose, can be lower than with known hoods. Furthermore, due to the high efficiency a very high condensate formation results and thus a very high fat separation from the drawn-off exit air, and it has been found with a hood of the type IS according to the invention that the degree of fat separation can be so high that additional measures for avoiding fires and explosions can be dispensed with.

A further advantage of the vapour extraction hood 1 according to the invention is to be seen in that the high efficiency can be kept constant over the entire hood length because due to the heat exchange elements 26 arranged transversely of the longitudinal direction of the hood over the entire length of the hood the high temperature difference between inlet air and exit air of particular importance for a high efficiency is retained.

Claims

1. A vapour extraction hood, suitable for use in large kitchens, comprising an elongate suction chamber to which vapour containing exit air can be drawn off, a recuperator located in the suction chamber and having a number of heat exchange elements, a fresh air supply chamber from which fresh air can be supplied to flow around the heat exchange elements for heat transfer from the exit air to the fresh air, an exit air extraction chamber connected to the suction chamber for carrying away exit air to be extracted and a chamber for collecting the fresh air after it has passed around the heat exchange elements, wherein the fresh air supply chamber and the fresh air collecting chamber extend substantially the entire length of the hood and are arranged, in the installed condition of the hood, above the suction chamber, the fresh air collecting chamber being located adjacent to a longitudinal side of the hood and wherein the heat exchange elements are arranged transverse to the longitudinal direction of the hood and define separate flow passages for the exit air and the fresh air.

2. A vapour extraction hood according to claim 1, wherein the heat exchange elements are constructed as plates which are combined to form heat exchange modules.

3. A vapour extraction hood according to claim 2, wherein the spacings between the plates of the modules are fixed by means of at least one spacer to form flow passages, one flow passage for exit air being arranged alternately in the immediate vicinity of a flow passage for inlet air.

4. A vapour extraction hood according to claim 3 wherein the surface 30 limited by the two plates forming a flow passage for exit air, in the installed condition of the hood, is located horizontally in the region of the upper side of the suction chamber and is partially covered by means of a spacer to form a passage opening. - 17 -

5. A vapour extraction hood according to claim 3 in which the surface 32 limited by two plates forming a flow passage for inlet air, in the installed condition of the hood, is situated in the region of the upper side of the suction chamber and is partially covered by a spacer to form at least one inlet opening and at least one outlet opening for inlet air and in which a surface between two plates forming a flow passage for inlet air, in the installed condition of the hood is directed downwards and is completely covered by means of a spacer.

6. A vapour extraction hood according to any one of claims 1 to 5, wherein in the installed position of the hood above the heat exchange elements at least one collecting chamber is disposed in which the fresh air supply chamber, the inlet air collecting chamber and an exit air collecting chamber are disposed.

7. A vapour extraction hood according to claim 6, wherein passage openings for exit air open into the exit air collecting chamber which is connected to the exist air connection.

8. A vapour extraction hood according to claims 6 and 7, wherein the fresh air supply chamber and the inlet air collecting chamber are each divided into two subchambers which are disposed on either side of the exit air collecting chamber, the subchambers of the inlet air collecting chamber being disposed along the longitudinal edges of the hood and in the immediate vicinity thereof.

9. A vapour extraction hood according to claim 8, wherein the inlet opening and the outlet opening for 18 inlet air along the longitudinal extent of the hood open alternately into one of the two subchambers of the fresh air supply chamber and the inlet air collecting chamber respectively.

10. ft. vapour extraction hood according to any one of claims 1 to 9, wherein a number of heat exchange modules depending on the length of the hood are provided.

11. A vapour extraction hood according to claim 2, 10 wherein the plates of the heat exchange modules have a thickness of 0.3 mm.

12. A vapour extraction hood according to any one of claims 1 to 11, wherein the distance between the heat exchange elements is a few millimeters. 15

13. A vapour extraction hood according to claim 12, wherein the distance is 5 mm.

14. A vapour extraction hood as claimed in claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. F. R. KELLY & CO., AGENTS FOR THE APPLICANTS.