AIR CONDITIONING VENTILATION DESIGN

AIR CONDITIONING VENTILATION

VENTILATION IS A PROCESS WHICH ADD OXYGEN CONTENT AFTER REMOVING THE FOUL GASES FROM THE CONDITIONED SPACE.

As we know in the fast growing world , the standard of living of humans have immensely grown up .

Hence it is important that we make good choice towards healthy environment within the surrounding, hence it is possible if we make smart choice with regards to smart resource which generate clean environment around you.

Yes I am talking about ventilation which is underrated under air conditioning.

Well air conditioning is important parameter but with the presence of ventilation it won`t make any better option to work with the conditioning of the surrounding.

If ventilation is absent in the system than it would require lot of energy to be consumed by the system along with low rate result of unhealthy ,sleepy, sick , etc behaviour pattern in humans.

What is ventilation and why do you need it?

Well ventilation is a process which provide a comfortable environment to surrounding by pushing out the unwanted ,foul ,oily, gases or air residues vanishing out from the space which is to be conditioned and most importantly issuing oxygen content which is necessity of humans.

Well as we know, this system provides oxygen content in the space which is having cut off,of oxygen.

without oxygen we human have tendency to almost die ,from this criteria we can say ventilation plays a vital and remarkable presence in the comfort conditioning of the humans.

As we know human comfort is about maintaining a 76°F temperature and 50%RH , so in order to maintain this objectives we have a greater helping hand from ventilation.

Lets take a simple example for better understanding, if you are person who like to cook food and while cooking if the exhaust fan is not working will we be comfortable to cook..?????

Many of must be but many must be not too….

So during this period of cooking we require a ventilation fan which removes the unwanted and non inhalable gas and provides oxygen required for human.

According to the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE), an HVAC system should “heat, cool, clean, ventilate, humidify and dehumidify as needed to provide health and HVAC comfort.”

According to ASHRAE’s definition ,ventilation is one of the most important jobs of an HVAC system.

Why?

Because without it, in the best case your space lacks fresh air and becomes stagnant and uncomfortable.

In the worst case, you can be trapping in toxins and contaminants that can make people sick.

VENTILATION IS A PROCESS IN WHICH AIR IS REPLACED OR EXCHANGED AIR FOR PARTICULAR AREA TO CONTROL ODOUR, MOISTURE, SMOKE , HEAT , DUST, AIR BORNE BACTERIA, CARBON DIOXIDE AND MAINTAING OXYGEN CONTENT.

THERE ARE TWO TYPE OF VENTILATION

1) NATURAL VENTILATION: Natural ventilation are the ventilation which takes place naturally irrespective of any presence of mechanical or electrical or in short without an external agency.

Natural forces (e.g. winds and thermal buoyancy force due to indoor and outdoor air density differences) drive outdoor air through purpose-built, building envelope openings. Purpose-built openings include windows, doors, solar chimneys, wind towers and trickle ventilators. This natural ventilation of buildings depends on climate, building design and human behaviour.

2)FORCED VENTILATION: well forced ventilation are which provide the process of ventilation with the presence of some external medium. Which used mechanical fan or it may also called as artificial ventilation process.

Mechanical fans drive mechanical ventilation. Fans can either be installed directly in windows or walls, or installed in air ducts for supplying air into, or exhausting air from, a room.

Lets see different type of ventilation fan which are used within different ventilation application

WALL MOUNTED PROPELLER FAN

INLINE CENTRIFUGAL FAN

AXIAL FAN

JET FAN

]

This are some data which is important to know.

VENTILATION DESIGN

Well has we are aware of what actually is ventilation, now you must be curious about how we design a space which is to be design.

Designing a ventilation system is very important ,as we are aware of the importance of ventilation .Calculating the amount of heat and unwanted residues to overcome it ,for the application of a ventilation system is called as a ventilation design.

Before designing it is necessary to have some data which will promote our designing i.e air change per hour

Well air change per hour is a value according to the application ,which resembles the changes or replacement of new air or fresh air in a space which is to be designed from a known design data book.

Well I have made some data accordingly with respect to different application

Design data ACPH( air change per hour)

So using the following data we will design some of the application .

TOILET VENTILATION

Let take an example of toilet which is common for every one.

As we know toilet is compulsory is a space which has to be ventilated either continuously or non continuous .

So depending upon the types of toilet and on process of exhausting we have some data in CFM .

PRIVATE TOILETS

CONTINUE EXHAUST FAN ( 25 CFM)

NON CONTINUE EXHAUST FAN( 50 CFM)

PUBLIC TOILETS

CONTINUE EXHAUST FAN ( 50 CFM)

NON CONTINUE EXHAUST FAN( 70 CFM)

Well there two method through which one can calculate the amount CFM which has to be exhausted or ventilated from a space to maintain a comfortable environment.

METHOD 1

Formula to find CFM

CFM=ft³ x ACH/ 60 (English system)

CFM = meter³ x ACH/1.7 (metric system)

ACH =10(residential),15(commercial)

METHOD 2

1WC =CFM according to location and type.

NO. Of toilet= no. x CFM

Passing area = 1 sq. ft =1 cfm ( according to ashrae)

Total CFM =no. of toilet CFM + passing area CFM

So lets take an example which will clear all the doubts

EXAMPLE METHOD 1

CFM=ft³ x ACH/ 60 (English system)

Let take the following data or measurement requirement for room to be ventilated,

Length :25FT, width :12FT , height :15FT and taking application to be commercial having 15 ACPH

CFM =(25FTX12FTX15FT)=4500CUB.FT X 15( COMMERCIAL) / 60=1125 CFM

EXAMPLE METHOD 2

1WC =50CFM ( COMMERCIAL)

NO. Of toilet=4 no. x 50CFM=200CFM

Passing area = 1 sq. ft =1 cfm =(12FT X 6FT)=72SQ.FT=72CFM( according to ashrae)

Total CFM =no. of toilet CFM + passing area CFM=72CFM+200CFM=272CFM

PARKING VENTILATION

Well this space is very important to be ventilated, as the gases which are been released by automobiles are very toxic and hazardous which must be ventilated to avoid comfortless to human health.

Basically there are two ways through which we can ventilate either by using ducting or by using jet fan .

So lets have look at the calculational formulae….

FOR DUCTING SYSTEM

EXHAUST / FRESH AIR=M^3 X ACH/1.7=CMH
EXHAUST / FRESH AIR=FT^3 X ACH/60=CFM

FOR EXHAUST AIR=10000CUB. FT X 12/60=2000CFM

FOR FRESH AIR=10000CUB. FT X 6/60=1000CFM

DUCTLESS

JET FAN AT 3000SQ.FEET
NO.OF FANS= AREA OF SPACE / 3000SQ.FEET
=10000/3000=3NOS

DEPENDING ON THE CALCULATION THE EXHAUST VENTILATION FAN IS PLACED OPPOSITE TO RAMP WITH TWO FANS. IN NORMAL MODE SINGLE FAN RUNS WHILE EMERGENCY BOTH FAN RUNS TO EVACUATE THE UNWANTED GASES WITH AN ARRANGE TEMP.SENSORS CARBON MONOXIDE SENSORS .THE FRESH AIR FAN IS PLACED NEAR TO RAMP TO PROVIDE FRESH AIR SUPPLY.

SMOKE DETECTOR IS PROVIDE AT 5 METRE DISTANCE.

JET FAN AT 3000SQ.FEET

NO.OF FANS= AREA OF SPACE / 3000SQ.FEET

Kitchen ventilation

Kitchen ventilation is the branch of ventilation specialising in the treatment of air from kitchens. It addresses the problems of grease, smoke and odours not found in most other ventilation systems.

Kitchen ventilation equipment includes an extractor hood or canopy, and a filtering system. The system's fan may be located in the kitchen or in its ducts.

TYPES OF HOOD

BASICALLY EXHAUST HOOD ARE BASICALLY A PATH THROUGH WHICH GREASE ,SMOKE,VAPOUR AND HEAT ARE RELEASED .

WALL MOUNTED CANOPY HOOD

SINGLE ISLAND HOOD

DOUBLE ISLAND HOOD

WALL MOUNTED CANOPY HOOD

3`` GAP BETWEEN HOOD AND WALL.

THREE FINISHED SIDE

MINIMUM 6`` OVERHANG REQUIRES ON SIDE AND 6`` TO 12 `` IN FRONT.

SINGLE ISLAND HOOD

IT IS PALCED IN CENTRE HAVING FOUR FINISH SIDE.

6`` TO 12 `` OVERHANGE ON ALL SIDE

BAFFLE FITLER V CONFIGURATION

DOUBLE ISLAND HOOD

IN THIS TWO STOVE EQUIPMENT ARE ARRANGED BACK TO BACK ALONG WITH TWO WALL MOUNTED HOOD.

6`` TO 12`` OVERHANGING ON ALL 4 SIDES.

So following are the design formulae which present the required value of CFM to be ventilated.

PH=2LH + WH ( WALL MOUNTED)

PH = 2LH + 2 WH( SINGLE AND DOUBLE ISLAND)

LH=LS + 0.8H

WH=WS + 0.8H

PH= PERIMETER OF HOOD

LH = LENGHTH OF HOOD

WH= WIDTH OF HOOD

H= DISTANCE BETWEEN STOVE AND HOOD

LS = LENGTH OF STOVE

WS = WIDTH OF STOVE

CFM=200PH FOR HEAVY COOKING

CFM = 150PH FOR MEDIUM COOKING

CFM=100PH FOR LIGHT COOKING

FOR EXHAUST CFM = 150 X PH

FOR FRESH AIR CFM =EXHAUST CFM X 0.8

PH=2LH+WH

LH=LS+0.8 H =1.7 + 0.8(1)=2.5MTR

WH=WS+0.8H=1.5+0.8(1)=2.3MTR

PH=2(2.5)+(2.3)=7.3MTR= 7.3 X 3.28=23.944FT

EXHAUST CFM=150X23.944=3592CFM
FRESH CFM=3592X0.8=2874 CFM

hope this article was useful .......

I hope we are clear with all details of ventilation

thanks for reading

About HVAC Groomingminds

HVAC INTRODUCTION,APPLICATION,DESIGNING,EXECUTION,ENGINEERING,HEAT LOAD CALCULATION,PIPE SIZING,CHILLED WATER SYSTEM,AC,CONTROL ,DUCT DESIGN,etc