EP3992536B1 - Method and device for determining the air flow volume through a ventilation pipe of a ventilation system - Google Patents

Description

The invention relates to a method and a measuring device for determining the air flow volume through a ventilation pipe of a ventilation system, wherein the ventilation pipe has a cross-section and is arranged between an air inlet and an air outlet.

In building engineering, ventilation is a very important system and its sizing is not always easy. Depending on various parameters, such as the type of ventilation system installed, the distribution system, the size of the rooms and the number of people to be supplied with fresh air, there are different methods for measuring the air flow in or between building zones.

To determine and verify the optimal design of such a system, complex procedures are often used, such as the blower door test or the gas trace test.

The blower-door test includes a calibrated fan, a door panel system, and a pressure gauge. The gauge compares the pressure inside the building or room to the outside pressure and converts the pressure difference into an airflow rate.

In the tracer gas test, a gaseous tracer is distributed in a room or building and the air flow can be determined by tracking the movement or concentration of the tracer gas.

However, both of the above techniques involve a high level of technical and mechanical effort and are not easily feasible in the context of a large building complex.

In modern buildings, ventilation systems are often dimensioned based on experience, and fine-tuning of the system, such as after commissioning, is usually carried out by facility management.

This optimization phase often involves adjusting settings ("trial and error"), and performance usually improves over time.

Additional factors such as interdependence with other systems, such as heating, and adjustments due to seasonal operating modes also complicate fine-tuning of the ventilation system.

The document CN111 380 145 A discloses a generic method for determining the air flow volume through a ventilation pipe of a ventilation system.

It is an object of the invention to provide a method with which it can be determined in a simple manner whether the existing air flow volume of a ventilation system of a building is sufficient to ventilate the building accordingly.

ermittelt wird, mit

Q

... Flussvolumen,

Δp

... Anlagen-Druck-Differenz, und

ρ0

... Luftdichte.

The object of the invention is achieved by a method according to claim 1, in which a system pressure difference between the air inlet and the air outlet is measured, and with the help of an air density the flow volume is determined according to the relationship $$Q\left(A,\mathrm{\Delta }p\right)=\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="imgf0001.png"\; state="\{\{state\}\}">A</figure-callout>}\sqrt{\frac{2\cdot \mathrm{<figure-callout\; id="0"\; label="\Delta \; p\; \rho "\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">\Delta </figure-callout>}p}{{\rho }_{}}}$$

is determined with

Q

... flow volume,

Δp

... system pressure difference, and

ρ0

... air density.

This ensures that a sufficiently accurate estimate of the existing ventilation capacity for the ventilation system can be made in relation to a given ventilation load, taking into account particularly easy to collect measured values.

It is only necessary to record measured values for the supply air and exhaust air of the system using appropriate measuring equipment.

A standard value can be applied for the air density, since constant ambient conditions can be assumed over a recording period.

The ventilation load can be determined from relevant ventilation standards, especially for a given maximum room occupancy, for example by children and adults.

According to the invention, it is provided that the determination of the system pressure difference takes place in that a first pressure difference is detected before and after a first fan arranged in the air inlet by a corresponding first means, and a second pressure difference is detected before and after a second fan arranged in the air outlet by a corresponding second means, and the system pressure difference is formed from the first and second differences.

The air supply is understood to be the area between the interface to the outside air and the interface to the ventilation load, such as a room or a building area.

The air outlet is the area between the interface of the ventilation load and the interface to the exhaust air.

One or more fans can be arranged in the air inlet and outlet areas to support air circulation.

Therefore, measuring devices are installed to determine an air pressure difference before and after the respective fan, which are used in accordance with the invention and determine measured values particularly reliably and, moreover, allow particularly simple integration into the ventilation system.

This makes it particularly easy to determine the system pressure difference.

In a further development of the invention, it is provided that the air flow volume is determined continuously over a recording period, and the ventilation load of the ventilation system is recorded by the occupancy of the rooms ventilated by the ventilation system in the recording period, and from the ventilation load and the air flow volume it is determined whether sufficient ventilation has taken place.

This makes it particularly easy to carry out a load-dependent and dynamic check or validation of a ventilation system.

The object according to the invention is also achieved by a device according to claim 3, which carries out the method according to the invention.

Fig. 1

ein Ausführungsbeispiel einer erfindungsgemäßen Messvorrichtung mit einer Gebäudebelüftungsanlage,

Fig. 2

ein erstes Diagramm mit einem zeitlichen Verlauf für ein ermitteltes Luft-Flussvolumen in einem ersten Raum,

Fig. 3

ein zweites Diagramm mit einem zeitlichen Verlauf für ein ermitteltes Luft-Flussvolumen in einem zweiten Raum,

Fig. 4

ein drittes Diagramm mit einem zeitlichen Verlauf für ein ermitteltes Luft-Flussvolumen in einem dritten Raum.

The invention is explained in more detail below using an embodiment shown in the accompanying drawings. In the drawings:

Fig.1

an embodiment of a measuring device according to the invention with a building ventilation system,

Fig.2

a first diagram with a time course for a determined air flow volume in a first room,

Fig.3

a second diagram with a time course for a determined air flow volume in a second room,

Fig.4

a third diagram with a time course for a determined air flow volume in a third room.

It is clear that other parts not shown are necessary for the operation of a building ventilation system, such as assembly parts, electrical drives and controls. For better understanding, these parts are not shown or described.

The invention is not limited to the specific embodiments described in detail here, but includes all variants, combinations and modifications thereof that fall within the scope of the appended claims.

Fig.1 shows an embodiment of a measuring device according to the invention with a building ventilation system.

The ventilation system has an air inlet (AUL) and an air outlet FOL.

The air inlet AUL is connected to the air outlet FOL via a ventilation pipe LR with a cross-section A.

In ventilation and air conditioning technology, air types characterize the different air flows with regard to their use.

Outside air, one of the types of air in ventilation and air conditioning technology, is the air drawn in from the environment. This is the air as it occurs on the outside of the building.

However, it should not be confused with fresh air. The outside air can be improved by two measures for ventilation and air conditioning technology: firstly, choosing the intake location in the building where the outside air is least polluted, such as sunlight, car exhaust fumes, exhaust air outlets, etc., and secondly, cleaning the outside air.

The term room air or indoor air describes the air in rooms. In construction, the term is used primarily in the air conditioning and air technology to separate the air inside rooms in buildings from other types of air, such as supply and exhaust air or outside air.

In air conditioning technology, exhaust air is the exhaust air that is blown outside. This means that the air can no longer be used for air conditioning technology. However, energy can be extracted from the air using heat or cold recovery and fed back into the process.

In general, exhaust air is the air that flows freely or forcibly out of a room.

The figure also shows an AUL temperature sensor 1, which measures the temperature of the outside air.

A shut-off damper 2 can block the ventilation pipe LR in the area of the air inlet AUL.

A shut-off valve 3 can block the ventilation pipe LR in the area of the air outlet FOL.

A defrosting flap 4 can temporarily connect the ventilation pipe LR in the area of the air inlet AUL with the area of the air outlet FOL.

A bypass flap 5 can reduce or prevent air backflow in the ventilation pipe LR.

A corresponding differential pressure sensor 6 can detect such a case and signal it to a control device.

Various shut-off dampers 7, 8, 9 and 10 for the outside air, the exhaust air and the recirculated air can be used, for example, to specifically redirect the air path during maintenance.

An evaporator 11 can be inserted into the ventilation pipe LR to increase the humidity in the ventilation system.

A supply air fan 12 is used to suck in outside air and supply fresh air.

A differential pressure sensor 13 in the supply air fan 12 is provided to detect the pressure difference before and after the supply air fan 12 and to signal this to a control device. Additional shut-off valves 14 and 15 for the supply air and the exhaust air can be used, for example, to specifically close the air path during maintenance.

A capacitor 16 can be inserted into the ventilation pipe LR to reduce the humidity in the ventilation system.

An ABL fan 17 is used to suck in room air and to exhaust exhaust air.

A differential pressure sensor 18 in the ABL fan 17 is provided to detect the pressure difference before and after the ABL fan 17 and to signal this to a control device. A supply air temperature sensor 19 can detect the temperature of the supply air and signal this to a control device.

An ABL temperature sensor 20 can measure the temperature of the exhaust air and signal it to a control device.

A room temperature sensor 21 can detect the ambient room temperature and signal it to a control device.

By means of a room thermostat 22, a target temperature can be set for a heating system, which can be integrated into the ventilation system.

A supply temperature sensor 23 can be used for the room thermostat 22 to display a corresponding temperature value.

ermittelt wird.The figure also shows an example of the measuring device MV according to the invention, by means of which pressure differences p ₁ and p ₂ are recorded by the differential pressure sensors 13 and 18 respectively, and the system pressure difference Δ p between the air inlet AUL and the air outlet FOL is measured, and using an air density ρ ₀ the flow volume Q is determined according to the relationship $$Q\left(A,\mathrm{\Delta }p\right)=A\sqrt{\frac{2\cdot \mathrm{<figure-callout\; id="0"\; label="\Delta \; p\; \rho "\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">\Delta </figure-callout>}p}{{\rho }_{}}}$$

is determined.

The pipe diameter of the ventilation pipe LR of 50 cm results in a cross-section A of the ventilation pipe LR of approximately 0.2 m ² , which results in an ideal average air flow of approximately 15,000 m ³ /h.

Due to the complexity of the school's ventilation system, we derive these standard measures1 for all eligible pipes in the classroom ventilation system. However, this assumption can easily be adapted to the realities of a concrete building. Second,

The temperature of the supply and exhaust air is not subject to major fluctuations.

The annual average is usually between 20 °C and 25 °C.

For the air density ρ ₀ , a constant standard value of 1.21 km/m ³ at 20°C can therefore be used.

The system pressure difference (Δp) is determined by first detecting a first pressure difference p ₁ before and after the first fan 12 arranged in the air inlet AUL by a corresponding first means 13.

Furthermore, a second pressure difference p ₂ before and after the second fan 17 arranged in the air outlet FOL is detected by a corresponding second means 18.

The system pressure difference Δ p is formed from the first and second differences p ₁ , p ₂ .

The air flow volume Q is determined continuously over time t over a recording period.

The ventilation load of the ventilation system is recorded by the occupancy of a room R ventilated by the ventilation system during the recording period.

The ventilation load and the air flow volume Q are used to determine whether there is sufficient ventilation.

Factors relating to a ventilation duct configuration or an installation of the LR ventilation pipe, a pipe length, a pipe friction coefficient and changes in the geometry or material can lead to flow losses.

However, including these factors would make the estimation of the ventilation function more complex.

However, the invention is intended to enable a very simple form of estimation taking into account measurement values that are particularly easy to collect, without limiting the fundamental quality of the estimate.

From the above formula, not only can the air flow volume Q be determined, but the air flow per second or per hour can also be easily derived.

For further considerations, the load of the ventilation system must be taken into account, which may result from the occupancy of room R.

For example, for a school class, room R can have a maximum occupancy of 25 children and two adults.

Alternatively, a small group room such as Room R can have a maximum occupancy of ten children and one adult.

With the help of ANSI/ASHRAE Standards 62.1-2019 (American Society of Heating and Air-Conditioning Engineers, 2019, Ventilation for Acceptable Indoor Air Quality ) a required air flow volume Q or a corresponding air flow can be determined.

The ASHRAE standard suggests 0.283 m ³ /min per child (9-10 years) and 0.43 m ³ /min per adult as ideal ventilation for acceptable indoor air quality.

Fig.2 shows the air flow volume Q over a recording period t in a first room with a first room size.

Fig.3 shows the air flow volume Q over a recording period t in a second room with a second room size.

Fig.4 shows the air flow volume Q over a recording period t in a third room with a third room size.

In the Fig. 2 to Fig. 4 The time courses of air flow volume Q shown show both the air inflow and outflow.

Furthermore, the limit values specified in the ASHRAE 62.1-2019 standard for optimal ventilation with different room occupancy are recognizable.

Line L11 indicates 100% occupancy of the first room, line L12 indicates 80% occupancy, line L13 indicates 60% occupancy, line L14 indicates 40% occupancy and line L15 indicates 20% occupancy of the first room.

It can be seen from the figure that the ventilation system can handle 100% occupancy with large reserves and that the ventilation system is therefore optimally dimensioned.

This makes it clear that the method according to the invention allows a simple and efficient validation of a ventilation system in which only the air pressure conditions on the fans in the supply air and exhaust air area of the ventilation pipe.

In other words, the Fig. 2-4 that the ventilation systems in the respective rooms in the example building seem to correspond to the air demand profile of these building zones under ideal conditions.

When comparing a calculated airflow volume for supply and exhaust air to the ideal ventilation volume according to ASHRAE Standard 62.1-2019 at different occupancy conditions represented by limit lines L11-L15, L21-L24, L31-L34, enough air is moved through the school's ventilation system to maintain an acceptable indoor climate for the occupants.

Therefore, under-dimensioning of the ventilation system cannot be confirmed.

The statements apply to Fig.3 and Fig.4 accordingly.

Reference number:

1

AUL temperature sensor

2

Butterfly valve AUL

3

Butterfly valve FOL

4

De-icing flap

5

Bypass valve

6

Differential pressure sensor

7

AUL flap

8th

FOL flap

9, 10

UML flap

11

Evaporator

12

Supply fan

13

Differential pressure sensor supply fan

14

Shut-off valve ZUL

15

Butterfly valve ABL

16

capacitor

17

ABL fan

18

Differential pressure sensor ABL fan

19

Supply temperature sensor

20

ABL temperature sensor

21

Supply temperature sensor for display

22

Room temperature sensor

23

Room thermostat, emergency thermostat

A

Cross section of the ventilation pipe

ABL

Exhaust air

AUL

Outside air

FOL

Exhaust air

UML

circulating air

PERMISSION

Supply air

MV

Measuring device

LR

Ventilation pipe

L11-L15,

L21-L24,

L31-L34

Line for standard limit

Δp

System pressure difference

Q

Air flow volume

Q1

ABL air flow volume

Q2

Supply air flow volume

R

Space

ρ0

Air density

t

Time

Claims (3)

1. Method for determining the air flow volume (Q) through a ventilation pipe (LR) of a ventilation system, wherein the ventilation pipe has a cross-section (A) and is arranged between an air inlet (AUL) and an air outlet (FOL), wherein a system pressure difference (Δp) between the air inlet (AUL) and the air outlet (FOL) is measured and with the aid of an air density (ρ ₀) the flow volume (Q) is determined according to the relationship $$Q\left(A,\mathrm{\Delta }p\right)=A\sqrt{\frac{2\cdot \mathrm{\Delta }p}{{\rho }_0}}$$

   

   characterised in that
   the system pressure difference (Δp) is determined by a first pressure difference (p ₁) being detected upstream and downstream of a first ventilator (12) arranged in the air inlet (AUL) by means of a corresponding first means (13) and a second pressure difference (p ₂) being detected upstream and downstream of a second ventilator, arranged in the air outlet (FOL), by means of a corresponding second means (18), and the system pressure difference (Δp) is formed from the first and second difference (p ₁,p ₂).
2. Method according to the preceding claim, wherein the air flow volume (Q) is determined continuously over a detection time period (t) and the ventilation load (VR) of the ventilation system is detected by occupying the rooms (R) ventilated by the ventilation system in the detection time period and it is determined from the ventilation load (VR) and the air flow volume (Q) whether adequate ventilation takes place.
3. Measuring apparatus (MV) with a processor and a memory for determining the air flow volume (Q) through a ventilation pipe (LR) of a ventilation system, which ventilation pipe (LR) has a cross-section (A) between an air inlet (AUL) and an air outlet (FOL) and with the air inlet (AUL) and the air outlet (FOL) means (13, 18) for measuring a respective air pressure are provided in each case, characterised in that the means have a first means (13) for measuring a first pressure difference (p1) upstream and downstream of a first ventilator (12) arranged in the air inlet (AUL) and a second means (18) for measuring a second pressure difference (p2) upstream and downstream of a second ventilator (17) arranged in the air outlet (FOL) and the measuring apparatus (MV) is designed to carry out the method of the preceding claims.

Images