EP1323988B1

EP1323988B1 - Ventilation system and method

Info

Publication number: EP1323988B1
Application number: EP02445193A
Authority: EP
Inventors: Per-Olov Danielsson; Lubos Bartek
Original assignee: Flaekt Woods AB
Current assignee: Flaekt Woods AB
Priority date: 2001-12-27
Filing date: 2002-12-23
Publication date: 2006-03-15
Anticipated expiration: 2022-12-23
Also published as: DE60209878D1; ATE320578T1; SE0104424D0; SE0104424L; EP1323988A1

Abstract

A system for displacement ventilation in a room (1), wherein at least one air supply means (5) is arranged to supply clean supply air to the room, and wherein at least one discharge air means (6) is arranged to remove used indoor air from the room, wherein position in the room, outflow angles from and flow of said air supply means (5) as well as position in the room and flow of said air discharge means (6) are chosen for providing a clean air zone in a specified part of the room (1). The invention also concerns a method for producing a system for ventilation. <IMAGE>

Description

FIELD OF THE INVENTION

The invention relates to a ventilation system according to the preamble of claim 1 and a method for producing a ventilation system.

DESCRIPTION OF PRIOR ART

The principle of displacement ventilation is that air is introduced into a room through one or more low-position air supply means. The velocity of the supply air through the air supply surface of the air supply means is held low which results in a low degree of turbulence.
The supply air from the supply air means is further held somewhat sub-tempered, i.e. has a temperature somewhat lower than the temperature of the air in the room, which results in that the supply air, after having left the supply air means, floats out over the floor and fills the room with clean supplied air from below. The used air, which is somewhat warmer and contains i.a. particles and possibly an undesired gas composition, will thereby be pressed upwards, above the clean air and is typically removed from the room through discharge air means being placed at a high level in the room.
In ideal displacement ventilation, the air in the room is therefore clearly stratified with clean air in the lower region of the room and used air in the upper region of the room. In practise there is, however, also in case of displacement ventilation systems, a certain vertical mix because of e.g. effect from heating radiators in the room. Such effect may cause the ventilation to work less satisfactory. Further, the lower stratum with relatively clean air may be insufficiently high, resulting in that standing persons will have their heads in relatively unclean air.
US-A-6033 303 describes a process and a system for controlling the concentration of dust levels in a room. Air is withdrawn from the room by way of ceiling vents. This is coordinated with the flow of fresh air directed into the room so that a controlled air migration pattern is established.

THE AIM AND THE MOST IMPORTANT FEATURES OF THE INVENTION

It is an aim of the present invention to provide a system for ventilation, which provides an improvement of previously known displacement ventilation systems. In particular it is an aim to provide a system for the achievement of improved environment for persons in the room.
These aims are achieved according to the invention in a system of the above mentioned kind through the features of the characterising portion of claim 1. Corresponding advantages are achieved through an inventive method.
Hereby it is achieved that the ventilation may be arranged such that specified portion or portions of the room, where there are particular demands with respect to air purity are set, may be provided with a clean air zone, through the inventive system. The portions in question are primarily areas where persons dwell, whereby it is also to be considered that the clean air zone or zones also has sufficient vertical dimension.
It should be stressed that it has proved that today's system with displacement ventilation will in practice not result in the formation of the ideal condition, which is discussed above. On the contrary, stratification will occur, not only in the vertical direction of the room, but also in portions of the room as seen in its extension in the plane. Where clean air could have been expected in a room, according to agreed practice, it may very well happen that instead there is relatively impure air.
A method of producing a system for providing said clean air zones in a room is accomplished according to the invention by mapping the prevailing conditions in the room such as at least certain of the parameters: room description with general measurements, positions and measurement of windows, positions and measurement of interior structures and furniture, dimensions of and heat emitted from heat sources and potential impurity sources and sizes of working spaces. Further, consideration is made to the positioning of supply air means, discharge air means and circulation air means, their flow geometry and flows. Starting out from these facts, according to the invention, temperatures, air velocities and concentrations of impurities may be calculated and displayed for different parts of the room.
Hereby the indoor environment as regards ventilation may be custom-made with respect to the use and the need in the respective room, since the positioning of the cleanest zones in the room may be controlled by choice of positions, flows etc. of the respective ventilation means so that an optimal indoor environment may be obtained in the desired position in the room. The calculations according the above are made through a computer program or physical measurements are made in a test room, which simulates the room in question, whereby positioning of different air means, flows from air means, furnishing, sources of impurities etc., are variable in order to make it possible to calculate an arrangement, which gives the best result for the specific application of the room.
In particular filtered circulating air from the room is fed back through the air supply means. This gives the possibility of increased filtering effect with reduced energy consumption because the circulation results in reduced need of air heating, central air treatment and air transport. Further, central aggregates and channels may be given smaller dimensions. In this connection it may be mentioned that use of air circulation means with adjustable flow increases the freedom to adapt the clean air zone with respect of its dimensions.
It could also be mentioned that the invention is particularly useful and preferable if air supply means as well as air discharge means and air circulation means include so called HEPA-filters, i.e. high effective particle filtering filters.
Further aspects of the invention result in further advantages, which will be evident from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described at the background of an embodiment and with reference taken to the annexed drawing, wherein the only figure diagrammatically shows a system according to the invention in connection with a nursing-room.

DESCRIPTION OF EMBODIMENT

In the only figure a nursing-room 1 is shown intended for a patient with particular demands for clean air. The room is connected to a diagrammatically shown ventilation system according to the invention. The system includes a central air treatment unit 2 having a sub unit 3 for air supply including an inlet conduit I for outside air, a supply air filter F_i and a supply air fan 20.
In the system there is also included a sub unit 4 for air discharge including an incoming air conduit 23, which sucks air from a number of air discharge means (see below reference No. 6), a filter F_u and an air discharge fan 21 as well as an conduit U for outlet to the surroundings.
The sub unit 3 for air supply supplies air to a central air supply channel into which a number of room units corresponding to the room 1 in the figure are connected. The corresponding goes for the sub unit 4 for air discharge. An air supply means 5 which is positioned in the room, in a manner which will be described in more detail below, is connected to the central air supply channel 22 in the room.
The air supply means 5 provides an outflow angle α, as seen in a horizontal plane, and operates in a manner which is per se known in air supply means for displacement ventilation, i.e. it has a large outflow area resulting in a low outflow velocity of the supply air. Further, the air supply means 5 preferably includes a filter chamber with a HEPA filter.
An air discharge means 6 is positioned at a high level in the room 1 and it is connected to the sub unit 4 over a discharge air channel 23. The flows of the supply air means 5 and the air discharge means 6 are controlled through a control unit 24 which is placed locally in the room and which controls the flows of the air supply means 5 and the air discharge means 6. This is indicated through reference No. 8. The control may be based on sensed temperature, gas composition, degree of impurities etc.
Further, it is suitable that a central computing unit 7 controls the fans of the central air treatment unit and supply air temperature. In a modified version of the system according to the invention the unit 7 may also be envisaged to control the air means in the rooms belonging to the system.
In operation of the ventilation system different zones will be formed in the room 1 where the indoor air has different degree of purity. Thus, in general in the outflow directions from the air supply means within the outflow angle α there will be a zone with the highest degree of purity of the air, in this application called clean air zone. The extension of this zone, however, depends highly of the geometry of the room, the sizes of impurity sources etc. which is described in the general portion of this description.
Further, according to the principle of displacement ventilation, at a low level in the room as a whole there will be found air of relatively high degree of purity, however, outside the clean air zone not with the highest degree of purity, whereas at a higher level, and in principle in particular at the largest distances from the clean air zone, the most impure air will be found.
According to the invention this knowledge is considered in such a way that a custom-made air environment may be created inside the specific room, whereby it is arranged that the clean air zone is positioned where there is the greatest demand of such a zone, as for example at the working space for a human, at a sleeping place, a place for socialising etc.
In places where the highest degree of impurities may be expected or be observed and also be tolerated, in a corresponding manner one or more air discharge means are positioned so that it is continuously provided for the most impure air in the room to be removed.
In the figure No. 9 concerns a clean air zone. This is also where the largest extension in a vertical direction of clean air can be found. Reference No. 10 indicates zones having relatively high air purity. Zone 11, however, concerns a zone with most impure air.
Only as an example it is shown in figure 1 that a nursing-bed 12 is placed in the clean air zone 9 in room 1.
An important condition to consider when choosing positions for different air means, calculations of flows etc. is the presence of different types of sources of impurities in the room.
Hereby humans are considered to comprise sources of impurities through constant emission of skin particles, textile particles etc., comprising load on the air in the room. Besides, humans produce carbon dioxide.
Further, office machines such as copiers and printers create impurities through emission of paper particles, ink particles etc. Further, heat sources such as heat radiators, machines, lamps etc. affect the air conditions by creating air streams affecting the extension of the different zones in the room. Equipment including movable parts and fans may essentially affect the extension of the zones by creating and maintaining air streams. A phenomenon promoting the conditions in displacement ventilation is that impurity sources are normally also heat sources which results in that impurities in a natural way are brought upwards through the upward air stream which is created by that source of impurities by its heat emission.
In a method wherein a custom-made environment is to be created, at least most of these factors affecting the positioning and extension in the room of the different zones should be considered.
According to the invention, the evaluation may be made by using a model, which preferably is a computer program for simulating how air purity etc. is affected by positioning of air supply means, air discharge means and occasionally air circulating means, their flows etc. according to the above. The program further takes into account factors that affect the position and extension of said zones when dimensioning the installation, positioning of the air means and adjustment of air flows emanating from and being drawn into (concerns air discharge means), respectively, the air means, and matches that with the demands for air purity prevailing in the room in question and in particular for certain parts of the room where particular high demands of air purity prevails.
Alternatively, and this is not preferred, positioning in the room, flow of and at occasional out-flow angles from said means may be chosen starting from measurements of parameters describing air purity in different places in a test room which simulates the room in question.
The invention may be modified within the scope of the following claims and for example the air supply means in figure 1 may be supplemented with an air circulating means, which may be connected to the air supply means 5. Preferably the air circulating means may have a shape corresponding to the air supply means and be positioned upwardly this at a chosen vertical height. A circulation fan, which is controllable by the control unit 24 ensures adjustability of the circulation flow. By having a HEPA filter in the air circulating means, unnecessary contamination of the inside of the air supply means is avoided as well as of a HEPA filter positioned in the air supply means.

Claims

System for ventilation of a room (1) through displacement ventilation, wherein at least one air supply means (5) is arranged to supply clean supply air to the room, and wherein at least one air discharge means (6) is arranged to remove used indoor air from the room, characterised in
- that in order to provide a clean air zone in a specified part of the room, the position in the room (1), outflow angles from and air flow of said supply air means (5) as well as position in the room and flow of said air discharge means (6) are determined based on previous simulation in a computer or previous measurements taken of parameters describing air purity in a test room simulating the room (1),

- that the air supply means (5) is arranged to be supplied with filtered circulation air from the room (1),

- that at least the air supply means (5) is equipped with a high effective particle filter,

- that a control unit (24) is provided for controlling the magnitude of the flow of supply air and/or at occasions of circulation air and thereby the size of the clean air zone, and

- that the position in a vertical direction in the room of intake of an air discharge means (6) and/or at occasions of an air circulation means is chosen for adjusting the dimension of the clean air zone in vertical direction.
Method for producing a system for displacement ventilation in a room (1), wherein at least one air supply means (5) is arranged to supply clean supply air to the room, and wherein at least one discharge air means (6) is arranged to remove used indoor air from the room, characterised in that position in the room, outflow angles from and flow of said air supply means (5) as well as position in the room and flow of said air discharge means (6) are adapted for providing a clean air zone in a specified part of the room (1), wherein position in the room, flow of and at occasions outflow angles of said means (5;6) are chosen based of any out of the group: simulation in a computer; measurements taken of parameters describing air purity in different positions in a test room simulating the room (1).
Method according to claim 2, wherein the air supply means (5) besides supply air also is supplied with filtered circulation air from the room (1).
Method according to claim 2 or 3, wherein at least the air supply means (5) is equipped with a high effective particle filter.
Method according to claim 2, 3 or 4, wherein magnitude of flow of supply air and/or at occasions of circulated air and thereby the dimension of the clean air zone is controlled (7).
Method according to any of the claims 2 - 5, wherein position in the vertical direction in the room of intake of air discharge means (6) and/or at occasions of circulation air is chosen for controlling the dimensions of the clean air zone in a vertical direction.