Ventilation airflow in confined spaces to inhibit the transmission of disease

Abstract

The present invention relates to a reduction in the propagation rate of airborne pathogens by an improved airflow ventilation pattern in confined spaces, such as in buildings or in vehicles. Since human beings are normally horizontally disposed with respect to each other, the optimum airflow pattern minimizes the horizontal component of the airflow velocity field. This invention addresses the fluid-mechanical requirements to achieve this goal.

Claims

1. A ventilation system configured to provide an approximately uniform, upward air flow within an enclosed volume, the system comprising: a plenum or manifold beneath the floor of the volume; a porous floor to the volume; one or more exhaust ports in or near the ceiling of the volume; and a supply of clean air pressurized to provide a volume flow rate substantially equal to or greater than the total volume flow rate of plumes and jets impinging on the ceiling from all sources of buoyancy and upward momentum.

2. The system of claim 1, wherein the enclosed volume is a room in a building.

3. The system of claim 1, wherein the enclosed volume is a cabin of an aircraft.

4. The system of claim 1, wherein the enclosed volume is the interior of a car of a train or subway.

5. The system of claim 1, wherein the enclosed volume is the interior of a bus.

6. The system of claim 1, wherein the enclosed volume is the interior of an automobile.

7. The system of claim 1, wherein the enclosed volume is the interior of an elevator car in a building.

8. The system of claim 1, wherein the exhaust port is a porous surface.

9. The system of claim 1, wherein the porous floor has a solidity of less than 43%.

10. The system of claim 1, wherein the porous floor consists of multiple layers of porous surfaces, such that the uppermost surface has a solidity less than 43%.

11. The system of claim 1 wherein the plenum or manifold has a cross section perpendicular to the flow within it that progressively decreases in the downstream direction from the plenum or manifold inlet so as to maintain an approximately constant pressure throughout the plenum or manifold.

12. The system of claim 1, wherein the porous floor has a local pressure-drop coefficient that progressively increases with distance from the plenum or manifold inlet so as to maintain an approximately constant flow speed through the porous floor.

13. The system of claim 1, wherein the vertical velocity of the ventilation airflow is varied with time.

14. A ventilation system configured to provide an approximately uniform, upward air flow within an enclosed volume, the system comprising: a plenum or manifold beneath the floor of the volume; multiple inlet ports distributed over the floor with a separation less than the design separation distance of the occupants in the volume; one or more exhaust ports in or near the ceiling of the volume; and a supply of clean air pressurized to provide a volume flow rate substantially equal to or greater than the total volume flow rate of plumes and jets impinging on the ceiling from all sources of buoyancy and upward momentum.

15. A ventilation system configured to provide an approximately uniform, downward air flow within an enclosed volume, the system comprising: a plenum or manifold above the ceiling of the volume; a ceiling consisting of a porous surface or a solid surface with discrete inlet vent nozzles; one or more exhaust ports in or near the floor of the volume; and a supply of clean air pressurized to provide a volume flow rate substantially equal to or greater than that of all plumes and jets impinging on the floor from all sources of buoyancy and downward momentum.

16. The system of claim 15, wherein the exhaust port is a porous floor.

17. The system of claim 15, wherein the porous ceiling has a solidity of less than 43%. The particulars shown herein are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of various embodiments of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of then invention, the description taken with the drawings and/or examples making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. As used herein and unless otherwise indicated, the terms “a” and “an” are taken to mean “one”, “at least one” or “one or more”. Unless otherwise required by context, singular terms used herein shall include pluralities and plural terms shall include the singular. Unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. Words using the singular or plural number also include the plural and singular number, respectively. Additionally, the words “herein,” “above,” and “below” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of the application. The description of embodiments of the disclosure is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. While the specific embodiments of, and examples for, the disclosure are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the disclosure, as those skilled in the relevant art will recognize. All of the references cited herein are incorporated by reference. Aspects of the disclosure can be modified, if necessary, to employ the systems, functions, and concepts of the above references and application to provide yet further embodiments of the disclosure. These and other changes can be made to the disclosure in light of the detailed description. Specific elements of any foregoing embodiments can be combined or substituted for elements in other embodiments. Moreover, the inclusion of specific elements in at least some of these embodiments may be optional, wherein further embodiments may include one or more embodiments that specifically exclude one or more of these specific elements. Furthermore, while advantages associated with certain embodiments of the disclosure have been described in the context of these embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the disclosure.

Description

DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 illustrates one configuration of a room with upward-flowing ventilation. Air 1 enters via a duct 2 into a plenum 3. The air flows through a porous floor 4 into an enclosure or room 5 with a vertical speed 6. Air 10 leaves the room through a porous ceiling 7 into a plenum 8 and duct 9.

[0034] FIG. 2 indicates the behavior of plumes with descending ambient air 11. Just above a person 12, the initial plume flow 13 is upward, but the plumes eventually stop and reverse 14.

[0035] FIG. 3 describes the plume behavior in an environment with upward, co-flowing air 15. The plumes 16 tend to rise.

[0036] FIG. 4 illustrates the impingement 14 of a rising plume 16 on the porous ceiling 7. All of the plume air will enter the porous ceiling at sufficient upward ambient velocity 15.

[0037] FIG. 5 shows one means of providing uniform velocity by achieving constant pressure in the floor and ceiling plenums or manifolds. The cross-sectional area of the floor manifold is progressively tapered 16 so as to maintain a constant horizontal speed and hence constant pressure within the floor manifold or plenum. The cross-sectional area 17 of the ceiling manifold is also tapered.

[0038] FIG. 6 illustrates the effect of multiple, discrete floor vents 18 on the air flow pattern in a room. Formed above each floor vent, the jets impinge on the ceiling and then descend. The descending air moves horizontally 19 as it is entrained into the turbulent jets.

[0039] FIG. 7 depicts a vertical sectional view of an aircraft cabin 20, with a porous floor 21 and a porous ceiling 22. The ventilation air 6 flows upward.

REFERENCES

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