H to calculate air cHange rates according to tHe in typical rooms … · 2019. 7. 9. · How to calculate air change rates according to the activity in typical rooms and buildings

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How to calculate air cHange rates according to tHe activit y in t ypical rooms and buildings

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Determination of necessary air-flow ...................................................................................

Air renewal per hour (DIN 1946) .......................................................................................

Example of air renovation calculation in a warehouse .....................................................

Ventilation in stabling farms ...............................................................................................

Example of calculation of renovation in a hen farm for laying ..........................................

Calculation of fresh air needed per person .........................................................................

Possible facilities to generate environmental renewal ...........................................................

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How to calculate air change rates according to the activity in typical rooms and buildingsCalculation tables for correct ventilation (renovation per hour) of a room with activity


DETERMINATION OF NECESSARY AIR-FLOW

At the moment that we must choose a fan for the air renovation of a room, several factors should be taken into account:1. The air-flow or air volume needed to ventilate the premise, measured in m3/h.2. The necessary pressure to overcome the resistance offered by the installation, measured in mmca.

To ventilate or renovate the air of a room, we must supply new air on one side and extract it on the other. This air contribution will depend on the activity developed in the premises, the air alterations and dismissed head depending on the activity (mainly in the industrial sector).

AIR RENEWAL PER HOUR (DIN 1946)

Depending on the factors that affect the air supply, you can determine the number of renewals per hour required by a specific location. It is called R/H (number of precise renewals per hour).

The DIN 1946 standard indicates the advisable number of renovations in premises as described below:

TYPE OF ROOMAIR RENEWALS PER

HOURSECTOR

Armored cameras 3-6

TERT

IARY

Auditoriums 6-8Casinos 8-12Changing rooms 6-8Classrooms 5-7Clubs 10-12Conference rooms 6-8Garages 5 aprox.Gyms 4-6Hotel rooms 3-8Laundries 10-20Libraries 4-5Meeting desks 6-8Meeting rooms 5-10Offices 4-8Professional kitchens 15-30Restaurants 8-12Shops 4-8Swimming pools 3-4Tertiary toilet 8-15Theaters and cinemas 5-8Waiting room 4-6


HOURSECTOR

Airbrush stores 10-20

IND

UST

RIA

L

Assembly workshops 4-8Dry cleaners 5-15Foundries 8-15Industrial kitchens 15-30Industrial toilet 8-15Laboratories 8-15Laminators 8-12Machinery rooms 10-40Paint booths 25-50Photocopy rooms 10-15Pickling premises 5-15Soaking ≤ 80Warehouses 5-10Welding workshops 20-30Workshops with great alterated air 10-20Workshops with little alterated air 3-6


HOURSECTOR

Bathrooms 5-7

RESI

DEN

TIA

L O

R D

OM

ESTI

C

Residential kitchens 10-15Residential rooms 3-8Residential toilet 4-5Showers 15-25Wardrobes 4-6

How to calculate air change rates according to the activity in typical rooms and buildingsCalculation tables for correct ventilation (renovation per hour) of a room with activity

Air supply according to:• use of premise• air alteration• dismissed heat


EXAMPLE OF AIR RENOVATION CALCULATION IN A WAREHOUSE

Taking into account that in the previous table it is indicated that in a warehouse we recommend between 5 and 10 reno-vations per hour, we will take on average 7 renovations.

Then we will calculate the volume of the room (V) in cubic meters (m3) with the formula V= A·B·C

We obtain that the volume of this warehouse is 1.000m3; multiplying it by the 7 renovations/hour it will give us a necessary flow of 7.000m3/h. We will need the fans to provide a recommended flow rate (Q) of 7,000m3/h in this warehouse.

C = 20m

A= 5m

B = 10m

V = 5 · 10 · 20 = 1.000m3

Q = 1.000m3 · 7R/H = 7.000m3/hQ = V · R/H

VENTILATION IN STABLING FARMS

The activity that takes place in the premises is complicated when it includes the animals. Seeking your well-being, the ventilation must be appropriate to the type of animal that is in farms, mainly if they are in a closed housing regime. The animals are sensitive to temperature (both cold and heat) but also to air currents and humidity in the environment.

The ventilation should provide an adequate environment for the welfare and development of the animals that are on the farm. The following table shows the values that must be taken into account for the proper calculation of ventilation in each case:

Animals Age or Weight Kg Temperature ºC Humidity %Necessary air flow m3/h Air speed at the

animal height. Max admissible m/sWinter Summer

Hens for laying

1 - 1,5 Kg 18 - 23ºC 70-60 0,3 - 0,5 8 - 10 0,3 - 0,5

1,5 - 2 Kg 17 - 20ºC 0,3 - 1 9 - 12 0,4 - 0,6

2 - 3 Kg 15 - 18ºC 0,5 - 2 12 - 15 0,5 - 0,75

Laying hens - 21ºC 65 - 60 0,5 - 2 10 - 15 0,5 - 0,75

Boars - 11 - 13ºC 85 - 55 36 360 0,4 - 4,5

Calves3 weeks 20 - 27ºC 75 - 65 5 - 10 50 0,5 - 0,75

17 - 23ºC 80 - 70 10 - 25 100

Bobbin fattening - 10 - 16ºC 80 - 70 15 - 50 150 0,75 - 1

Cows - 10 - 16ºC 80 - 70 40 - 60 175 - 200 1,5 - 2

Poultry fattening

1 day 35ºC 80 - 700,1 - 0,2 1 - 3 0,2

2 days 31ºC

75 - 652 - 3 weeks 27ºC

0,2 - 0,35 - 8

0,33 - 4 weeks 22ºC

4 - 7 weeks 18 - 22ºC

More than 7 weeks 15 - 19ºC 70 - 60 0,3 - 0,5 0,3 - 0,5


Animals Age or Weight Kg Temperature ºC Humidity %Necessary air flow m3/h Air speed at the

animal height. Max admissible m/sWinter Summer

Pigs piglets

5 Kg 23 - 25ºC

85 - 55

4 8 0,2 - 0,5

10 Kg 23 - 24ºC 5 16 0,2 - 0,8

15 Kg 22 - 24ºC 6 24 0,2 - 1

20 Kg 22 -23ºC 7 32 0,2 -1,5

25 Kg 22 -23ºC 8 40 0,2 - 1,5

Fattening pigs

25 Kg 22 -23ºC

85 - 55

4 30 0,2 - 1,5

30 Kg 21 - 23ºC 5 36 0,2 - 1,5

40 Kg 21 - 22ºC 6 48 0,2 - 2

50 Kg 20 - 21ºC 7 60 0,3 - 2,5

60 Kg 19 - 21ºC 9 72 0,3 - 3

70 Kg 18 - 20ºC 10 84 0,3 - 3

80 Kg 18 - 19ºC 11 96 0,4 - 3,5

90 Kg 17 - 18ºC 13 108 0,4 - 4

100 Kg 16 - 18ºC 14 120 0,4 - 4

SowsBreeding 15 - 17ºC

85 - 55

17 180 0,4 - 4

For breeding 10 - 13ºC 23 240 0,4 - 4,5

Pregnant 12 - 15ºC 25 250 0,3 - 2

Sow with litter Litter of 10 piglets 12 - 15ºC 85 - 55 28 375 0,2 - 1

Fattening lambs 20 - 25Kg 15 - 20ºC 80 - 70 10 - 15 90 - 100 0,5 - 0,75

Breeding rabbits 3 - 4Kg 12 - 14ºC 60 - 50 1 - 1,5 20 - 25 0,3 - 0,5

Fattening rabbits 1 - 2Kg 15 - 18ºC 60 - 50 0,3 - 0,5 8 - 10 0,2 - 0,4

EXAMPLE OF CALCULATION OF RENOVATION IN A HEN FARM FOR LAYING

We suppose a case of an exploitation farm of 500 chickens for laying of about 2Kg each chicken, with an ambient temperature of 16ºC and a humidity of 65%.

According to the previous table for the calculation of the ventilation in farms, we obtain that in winter the air-flow that must be contributed is of 1 m3/h, and in summer of 13 m3/h. With these parameters we ensure that the air speed is between 0.5 and 0.75 m/s, admissible limit for this kind of hens. Maintaining the appropriate air speed for each type of animal is important to prevent them from catching colds and diseases.

To know the flow rate that must be provided in this farm of 500 chickens for laying, we must multiply the number of chickens by the neces-sary air flow in winter and summer. Thus, in winter we will have to provide a flow of 500m3/h, and 6,500m3/h in summer.

In winter 1m3/h · 500u = 500m3/hIn summer 13m3/h · 500u = 6.500m3/h


These tables are based on empirical, non-scientific, safety and hygiene criteria in order to avoid harmful environmental po-llution for those who live or work in the premises. The number of people or pollution produced by industrial activities is not taken into account, in which case the number of renewals per hour must be higher.

The experience of the technician is the one that will be able to determine more accurately the number of renovations ne-cessary to achieve a clean and pollution-free environment, mainly in large enclosures.

CALCULATION OF FRESH AIR NEEDED PER PERSON

When an activity with people takes place in a room or premise, the demands for renewal of air are even greater.The more vitiated the environment, there is pollution, smoke or heat evacuation is necessary, the renewal values will be even higher. The following table indicates an approximation of flow rate m3/h should be provided per person in a premise depending on its nature:

TYPE OF ROOM AIR FLOW PER PERSON m3/h

Bedrooms 40-80Entertainment halls 50Meeting rooms 50-100Offices 50-100Ordinary hospitals * 70Schools 50Warehouses 60-100Workshops, factories 60-100Workshops, unhealthy factories 100-150* In the case of clean rooms there is a specific regulation


POSSIBLE INSTALLATIONS TO GENERATE ENVIRONMENTAL AIR RENEWAL

To achieve a correct environmental renovation of a room we have different ways of installation.

From an air supply and/or forced extraction (fan) and natural openings in walls or ceiling, the following installations can be made:

EXHAUST FANVENTILADOR EXTRACCIÓN







NATURAL APERTUREABERTURA NATURAL



SUPPLY FAN OR NATURALAPERTURE

APORTACIÓN VENTILADOR OABERTURA NATURAL

SUPPLY FANVENTILADOR APORTACIÓN

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H to calculate air cHange rates according to tHe in typical rooms … · 2019. 7. 9. · How to calculate air change rates according to the activity in typical rooms and buildings