GB1602190A - Natural ventilators - Google Patents

Description

(54) NATURAL VENTILATORS (71) We, H.H. ROBERTSON (U.K.) LIMITED, a British company of 27 Newgate Street, Chester Cill 1DE, and DSD DILLINGER STAHLBAU G.m.B.H., a German Company, of 6630 Saarlouis Henry-Ford-Strasse, West Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The invention relates to ventilation systems of the so called "natural" type where air flow through a building is at least principally controlled by the heat generated in the building, i.e. is not powered by fans associated with the ventilation system.

Such ventilating systems require as ventilators large, usually elongate, air-exit structures or heads above wide vents or "chimneys" through the roofs of buildings, often referred to as ridge ventilators, in order to give satisfactory ventilation in view of the large volume of air flow required at the low speeds at which it will take place. The size of the ventilator is at least partly dictated by the width of the vent or vents and the necessity to provide for weather protection, particularly from ingress of rain water. Hitherto, natural ventilators have had an elongate central ridged portion disposed above the vent or chimney and extending downwardly on each side to positions beyond but above the sides of the vent or chimney.

This ridged portion is normally located between spaced side walls that extend outwardly and upwardly, i.e. divergently, from the sides of the vent or chimney and then curve or return inwardly about and above the edges of the ridged portion. Such a ventilator structure is not very efficient in relation to air-flow by reason, it is now believed following detailed research, of turbulence at the vent or chimney exit and at the edges of the ridged portion and also the collection of air under the ridged portion. This inefficiency has been compounded where, in order to achieve a desired exit aperture between the upper edges of the side walls, it has often been necessary to provide for further weather protection by way of additional inclined shielding walls fixedly positioned between the ridged portion and the upper parts of the side walls or below the edges of the ridged portion.

It is an object of this invention to provide a natural ventilator structure that achieves a better compromise in the conflict between the need for weather protection and desirability of achieving good air-flow characteristics.

To this end, a natural ventilator is provided in the form of a structure of elongate form to service at least one building-communicating duct or passage along its length, the structure comprising outer longitudinal side walls that initially diverge from adjacent said duct or passage and then converge to upwardly spaced positions, a central longitudinal inner portion spaced from the outer side walls and of upwardly divergent sided form from a centrally interconnected longitudinal position, and exit air guidance means including elongate curving guides at upper edges of the mouth of the duct or passage and further curving baffling within spaces or airways between and spaced from both of terminations of upwardly divergent sides of the inner portion and the outer side walls.

Preferably the terminations of the upwardly divergent sides of the inner portion terminate at or near the maximum spacing of the outer sidewalls. Central disposition of the inner part gives adequate weathering where those terminations extend beyond the sides of the duct or passage to be serviced.

The guides of upper edges of the mouth or duct contribute to reducing the incidence of turbulence, and other elongate curving guides may be provided at the free edges of the inner portion for similar purposes thereat.

The baffling contributes to aiding desired directions of air-flow and smooth transitions thereof, and further curved baffling may be provided for similar purposes within the transition from the mouth of the duct or passage to the space or airway between the divergent inner portion walls and outer side walls the inner portion and the outer side walls. It will be appreciated that references to the duct or passage to be serviced should include only the throat of the ventilator structure if such is distinguishable from the duct or passage.

A preferred ventilator structure will have its curved baffling about the edges of the inner portion sized and disposed to achieve both air guidance and weather protection via a drain or gutter at its lower edge, or free-fall or water onto the lower parts of the outer side-walls.

It is preferred that the inner portion be of V-shape in cross-section for simplicity of construction and be centrally drained rather than covered with a domed or ridged arrangement.

Closing or shuttingsff of the ventilator structure from communication with the building to be served is conveniently achieved where baffling is provided between the duct or passage and the divergent air-ways past the inner portion by arranging that baffling to be adjustable between air-guidance positions and positions where parts thereof combine to close either the mouth of the duct or passage or the air-ways.

This is most advantageously done using a single baffle for each air-way that is pivotable intermediate its ends, but could be achieved by multiple baffle arrangements, say with a hinged louvre-like closure system.

Ways of putting the invention into practice will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1 and 1A are plan and isometric views of a natural ventilator installation on a ridge-roofed building; Figure 2 is an end elevation of what is shown in Figure l; Figure 3 is a diagrammatic transverse section of Figure 1; and Figure 4 is a side view of a ventilator section or module partly broken away to show interior details.

Figures 1 and 2 show a medium size industrial installation for a factory or work-shop, say a foundry, where 10 is a building of about 40 metres by 12 metres in area and some 6 metres high to its ridged roof 12. For the majority of its length the roof 12 has a central gap 14 weather-sealed at 16 to a natural ventilator structure 18 comprising a plurality of interconnected moduler sections 20. Ventilation air inlets will be provided, way by louvred grilles, at the side walls and/or end walls as shown at 22 and/or through the floor of the building.

It should be appreciated that much larger buildings could be serviced, as indeed could smaller ones, and that the proportions of the building as to area and height may vary widely.

All these factors, and also the activities performed and facilities provided within the building as it is the heat generated by them that "powers" the ventilations system will affect the air inlets and the size of the ventilator at least in relation to the width of its longitudinal vent 14 or duct forming the throat of the ventilator. In general, duct widths of 1 to 5 metres are usual and the specific illustration of Figures 1 and 2 might well have a width of metres.

Calculation of the required duct width is further dependent on the efficiency of the ventilator and the improvements obtained by use of the invention are clearly of great importance as size reductions produce massive economic advantages in respect both of the ventilator structure itself and of the reinforcing purlin requirements of the roof itself.

Characteristic features of a ventilator module embodying this invention are shown in Figures 3 and 4, though as will be made clear not all of the illustrated features are necessary for obtaining the advantages of the invention in relation to air flow improvement. An outer casing between support frames 28 for all longitudinal elements has side walls 30 of a generally convex shape extending upwards from an elongate throat 32 communicating directly with a gap 34 in the ridged roof. The side walls 30 terminate spaced from a wide ventilator exit mouth 36 and the sides 38 of the throat are bent outwardly for weathering at 40 to the roof. As can be seen, the lowermost edges 42 of the side walls 30 will drain onto the weathering parts 40 of the throat walls.

Instead of a simple ridge weathering guard over the throat in the conventional style indicated by the dashed lines 44, the roof gap 34 is weathered by a relatively inverted structure having centrally connected upwardly divergent side panels or walls 46. The structure 46 may be drained by pipes or gutters running from its central interconnection, or at least partially protected by a domed, arched or ridged cap, for example lightweight structure similar to that dashed at 44, when gulleys at or beyond the upper inner edges of the walls of structure 46 may be drained as desired, say at joints between modules.

Instead of, or as shown in addition to, sharply angled upward terminations 48 of the throat walls 38, carefully selected curving terminations or guides 50 are used to reduce or eliminate turbulence of air that passes through the throat and is split into two streams in an aerodynamically efficient manner by the lowest part of the structure 46. These terminations or guides 50 are found to be of particular value in improving efficiency of air flow.

Turbulence at the upper edges of the structure 46 may also be reduced by carefully selected curving terminations or guides 52, though these have been found to have a much less contribution compared with the throat terminations or guides 50.

It is noted that the terminations or guides 50 assist in streamlining air flow in its division and relative to the opposing surfaces of walls 30 and 46 defining permitted exit airways 54 and 56. Although both of walls 30 and 46 are divergent up to the position of curved terminations or guides 52, their relative convergence may assist in avoiding undue break-away or air flow from those surfaces, at least at higher speeds thereof, and consequent turbulence and frictional drag. Also, and at least at higher speeds of air flow, the curved terminations or guides 52 can serve to assist in the necessary redirection of air flow without turbulence as the side walls 30 return inwardly.

Specific further assistance may be given to air flow direction transitions by curved baffles.

Thus, from the throat 32 to the airways 54 and 56, this is aided by elongate curved baffles 60, 62 are shown, one for each airway, which are conveniently initially flat but slightly divergent and finally curved outwardly to optimise air flow transitions, but this has been found to have a relatively small or negligible contribution to improved efficiency. However, and more importantly for improved air flow there is shown about the edge terminations 52 of the structure 46 and in the major region or convexity of the walls 30, other curved baffles 64, 66 provided to assist air flow transitions from the airways 54, 56 to the ventilator exit.

It is observed that the baffling 64,66 also serves a weathering function in obstructing even wind-driven rain drops that might otherwise enter the throat part in spite of the relatively great width between the curved guides 52. To this end, the upper edges of the baffles 64, 66 are spaced less than the guides 52 and their lower edges are located to drop water onto the lower parts of the outer casing walls 30, or even if preferred, directly into gaps between the lower edges of those walls 30 and the guide 50.

Alternatively, of course the lower edges of the baffles may be guttered.

The baffles 60, 62 are shown as being pivotted at 68 intermediate their ends, preferably substantially centrally, and are dimensioned and configures to be mutually movable to one or, even either, of the dashed line positions 60', 62' and 60", 62" to close off the ventilator or to partially restrict its operation.

Interestingly, experiments have shown that a ventilator of or approximating the dimensions and curvatures shown in Figure 3 provides satisfactory streamlined airflow characteristics, even at higher test speeds of airflow than will occur in natural ventilation, and, most importantly is susceptible to scaling for larger and smaller size units. However, tests on the features 60,62, 60-i2 and 64-66 individually and in various combinations shown that the overall improvement in drag coefficient is not quantifiable as, i.e. does not correspond to, a summation of individual contributions.

Thus, compared with a hitherto used structure with a narrower exit mouth, a ridged structure 44 and downwardly diverging weathering plates above and across the position of the edges of 44 but with lesser inclination than the ridge structure, the widening of the exit mouth plus air flow guidance enabled and provided by the curving guidance and weathering baffles 64, 66 provides a significant drag reduction.Also, incorporation alone of the downwardly convergent airflow splitting structure 46 together with relatively large size terminating guides 52, say on an overfitting wider downwardly divergent cap, produces significant improvement, but is believed to be due to their capacity to take a significant part of the function of the baffles 64, 66. This relative significance of the guides 52 and baffling 64, 66 was found to be reversed for the guides 50 and baffling 60, 62 in that the guides 50 were made a greater contribution than the baffling 60, 62 even to the extent of making the baffling contribution more a matter of readily shutting off the ventilator than in air flow improvement.

The minimum structure in terms of provision of guides and baffling to obtain significant advantages is thus the provision of curving throat guides or terminations 50 and baffling 64,66. The extended curved guides or terminations 52 also usually assist to some extent, as does the additional provision of throat baffling 60,62 as well as providing for ventilator closure if pivotable. In summary, we believe that the relative significance of in-airway baffling and airway edge guides is opposite at the ventilator throat and at the transitions of the divided airways about the splitting structure 46, being in favour of edge guides at the throat and in-airway baffling at the transitions.

The height of the throat baffles should, of course, be sufficient to give good protection against rain ingress, despite the upper outward flaring thereof, and the end framed structure herein proposed permits achievement of a satisfactorily rigid structure without any requirement for top support of the outer side walls at edge-most positions where substantial reductions of discharge coefficient are then likely to result.

WHAT WE CLAIM IS: 1. A natural ventilator in the form of a structure of elongate form to service at least one building-communicating duct or passage along its length, the structure comprising outer longitudinal side walls that initially diverge from adjacent said duct or passage and then converge to upwardly spaced positions, a central longitudinal inner portion spaced from the outer side walls and of upwardly divergent sided form from a centrally interconnected longitudinal position, and exit air guidance means including elongate curving guides at upper edges of the mouth of the duct or passage and further curving baffling within spaces or airways between and spaced from both of terminations of upwardly divergent sides of the inner portion and the outer side walls.

2. A natural ventilator according to Claim 1, wherein said terminations of said upwardly divergent sides of the inner portion terminate at or near the maximum spacing of the outer side walls.

3. A natural ventilator according to Claim 2, wherein said terminations extend beyond sides of the duct or passage to be serviced.

4. A natural ventilator according to any preceding claim, comprising upwardly and inwardly curving elongate guides at and extending

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. redirection of air flow without turbulence as the side walls 30 return inwardly. Specific further assistance may be given to air flow direction transitions by curved baffles. Thus, from the throat 32 to the airways 54 and 56, this is aided by elongate curved baffles 60, 62 are shown, one for each airway, which are conveniently initially flat but slightly divergent and finally curved outwardly to optimise air flow transitions, but this has been found to have a relatively small or negligible contribution to improved efficiency. However, and more importantly for improved air flow there is shown about the edge terminations 52 of the structure 46 and in the major region or convexity of the walls 30, other curved baffles 64, 66 provided to assist air flow transitions from the airways 54, 56 to the ventilator exit. It is observed that the baffling 64,66 also serves a weathering function in obstructing even wind-driven rain drops that might otherwise enter the throat part in spite of the relatively great width between the curved guides 52. To this end, the upper edges of the baffles 64, 66 are spaced less than the guides 52 and their lower edges are located to drop water onto the lower parts of the outer casing walls 30, or even if preferred, directly into gaps between the lower edges of those walls 30 and the guide 50. Alternatively, of course the lower edges of the baffles may be guttered. The baffles 60, 62 are shown as being pivotted at 68 intermediate their ends, preferably substantially centrally, and are dimensioned and configures to be mutually movable to one or, even either, of the dashed line positions 60', 62' and 60", 62" to close off the ventilator or to partially restrict its operation. Interestingly, experiments have shown that a ventilator of or approximating the dimensions and curvatures shown in Figure 3 provides satisfactory streamlined airflow characteristics, even at higher test speeds of airflow than will occur in natural ventilation, and, most importantly is susceptible to scaling for larger and smaller size units. However, tests on the features 60,62, 60-i2 and 64-66 individually and in various combinations shown that the overall improvement in drag coefficient is not quantifiable as, i.e. does not correspond to, a summation of individual contributions. Thus, compared with a hitherto used structure with a narrower exit mouth, a ridged structure 44 and downwardly diverging weathering plates above and across the position of the edges of 44 but with lesser inclination than the ridge structure, the widening of the exit mouth plus air flow guidance enabled and provided by the curving guidance and weathering baffles 64, 66 provides a significant drag reduction.Also, incorporation alone of the downwardly convergent airflow splitting structure 46 together with relatively large size terminating guides 52, say on an overfitting wider downwardly divergent cap, produces significant improvement, but is believed to be due to their capacity to take a significant part of the function of the baffles 64, 66. This relative significance of the guides 52 and baffling 64, 66 was found to be reversed for the guides 50 and baffling 60, 62 in that the guides 50 were made a greater contribution than the baffling 60, 62 even to the extent of making the baffling contribution more a matter of readily shutting off the ventilator than in air flow improvement. The minimum structure in terms of provision of guides and baffling to obtain significant advantages is thus the provision of curving throat guides or terminations 50 and baffling 64,66. The extended curved guides or terminations 52 also usually assist to some extent, as does the additional provision of throat baffling 60,62 as well as providing for ventilator closure if pivotable. In summary, we believe that the relative significance of in-airway baffling and airway edge guides is opposite at the ventilator throat and at the transitions of the divided airways about the splitting structure 46, being in favour of edge guides at the throat and in-airway baffling at the transitions. The height of the throat baffles should, of course, be sufficient to give good protection against rain ingress, despite the upper outward flaring thereof, and the end framed structure herein proposed permits achievement of a satisfactorily rigid structure without any requirement for top support of the outer side walls at edge-most positions where substantial reductions of discharge coefficient are then likely to result. WHAT WE CLAIM IS:

1. A natural ventilator in the form of a structure of elongate form to service at least one building-communicating duct or passage along its length, the structure comprising outer longitudinal side walls that initially diverge from adjacent said duct or passage and then converge to upwardly spaced positions, a central longitudinal inner portion spaced from the outer side walls and of upwardly divergent sided form from a centrally interconnected longitudinal position, and exit air guidance means including elongate curving guides at upper edges of the mouth of the duct or passage and further curving baffling within spaces or airways between and spaced from both of terminations of upwardly divergent sides of the inner portion and the outer side walls.

2. A natural ventilator according to Claim 1, wherein said terminations of said upwardly divergent sides of the inner portion terminate at or near the maximum spacing of the outer side walls.

3. A natural ventilator according to Claim 2, wherein said terminations extend beyond sides of the duct or passage to be serviced.

4. A natural ventilator according to any preceding claim, comprising upwardly and inwardly curving elongate guides at and extending

from said terminations of said upwardly divergent sides of the inner portion.

5. A natural ventilator according to any preceding claim, further comprising curved baffling within the transition from the mouth of the duct or passage to the spaces or airways betweeen the divergent sides of the inner portion and the outer side walls but spaced from both.

6. A natural ventilator according to Claim 5, wherein the last-mentioned curved baffling is a single baffle for each airway that is pivotable to provide for closure of the ventilator.

7. A natural ventilator according to any preceding claim, constituting a module for end-toend interconnection or association with other modules.

8. A natural ventilator arranged and adapted to operate substantially as herein described with reference to and as shown in the accompanying drawings.