theory and calculation of our project and final result

7/31/2019 theory and calculation of our project and final result

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CHAPTER-1


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AIR CONDITIONING SYSTEM

The air conditioning is that branch of engineering science which deals with the

study of conditioning of air i.e. supplying and maintaining desirable internalatmospheric for human comfort, irrespective of external conditions

Fig no-1


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AIR CONDITIONING WORK

Heres how air conditioning works, there are the key steps to a functional

Air conditioning system.

Compress, heat, cool, condense, dry, expand and cool. Evaporate.

DETAILED OPRATION:

COMPRESSOR: Its primary function is to compress and pressurize gaseous

refrigerant. It takes in cool gas its suction port and pressurizes it at its dischargeport. The compressor is powered by a drive belt from the engine. The compressor

has electrically operated engagement clutch to either turn the refrigeration

operation off or on. Output = high pressure (hot) gas.

CONDENSER: The condenser is located in front of cool air flow (and kind of

looks like a radiator too) Through the use of cool air flow provided by the engine

fan, the condenser cools the hot gas and converts it to liquid. The liquid is still

under considerable pressure and is warm, but not as hot or as high pressureconsiderable pressure and is warm, but not as hot or as high pressure as when it

exited the compressor. Output = high pressure (warm) liquid

EXPANSION VALVE SYSTEM : The exiting liquid is sent through a small

tube (liquid line) to a receiver/drier (applies only to an expansion valve system).

The drier is a can with a desiccant bag inside. It looks about the size of a soda can,

and is usually located very near the condenser outlet pipe .There is no pressure/temperature change at the receiver/drier.

Output = same as condenser, but moisture is removed by desiccant.


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Now comes the magic : As the high pressure, warm liquid exits the drier , it

passes through an expansion device. It can be either be an expansion value (which

modulates refrigerant flow in an expansion valve/drier system), or a fixed

expansion orifice tube in a cycling clutch/orifice tube system (which slight

functional differences, mainly in how the low temperature is maintained. Well any

way, for illustration, the pressurized liquid passes through the expansion device,

the pressure is reduced considerably; hence the temperature drop also . Output =

Cold Liquid.

EVAPORATOR: As the cold liquid exits the expansion device, it is fed to a heat

exchanger type device under the dash that blows warm air from the car interior

across it. The cold liquid refrigerant is what cools the air you feel coming out of

the ducts. As the air is cooled in the heat exchanger, the liquid refrigerant is heatedin the other side of the heat exchanger and then it evaporates

ACCUMULATOR: Only used in orifice tube system. It contains a desiccant bag

also. The accumulator provides a similar function as the drier in the expansion

valve system, but is located in the evaporator outlet instead. This positioning

allows the accumulator to collect any un-evaporated refrigerant from liquid lock

damage.

The evaporated gas then returns through the tube to the compressor suction port

to begin this whole process again.


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FACTOR AFFECTING COMFORT AIR CONDITIONING

1. Temperature of air : Inair conditioning, the control of temperature meansthe maintenance of any desired temperature within an enclosed space even

through the temperature of the outside air is above or below the desired

room temperature . This is accomplished either by the addition or removed

of heat from the enclosed space as and when demanded. It may be noted that

a human being feels comfortable when the air is at 21 degree Celsius with 56

percent relative humidity.

2. Humidity of air: The control of humidity of air means the decreasing orincreasing of moisture contents of air during summer or winter respectively

in order to produce comfortable and healthy conditions.

3. Purity of air: It is an important factor for the comfort of a human body. Ithas been noticed that people do not feel comfortable when breathing

contaminated air, even if it is within acceptable temperature and humidity

range. It is thus obvious that proper filtration, cleaning and purification of air

is essential to keep it free dust and other impurities.

4. Motion of air: The motion of circulation of air is another important factorwhich should be controlled, in order to keep constant temperature

throughout the conditioned space. It is therefore , necessary that there should

be equi - distribution of air throughout the apace to be air conditioned.


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EQUIPMENT USED IN AIR CONDITIONING SYSTEM

Following are the main equipments used in air conditioning system :

1. Circulation fan: The main function of this is to move air to and fromthe room.

2. Air conditioning unit : It is a unit, which of cooling dehumidifyingprocesses for summer air conditioning or heating and humidification process

for winter air conditioning.

3. Supply duct : Itdirects the conditioned air from the circulating fan to thespace to be air conditioned at proper point

4. Supply outlets: These are grills, which distribute the conditioned air evenlyin the room .

5. Return outlet: These are the opening in a room surface which allow theroom air to enter the return duct.

6. Filters: The main function of the filters is to remove dust, dirt and otherharmful bacteria are from the air.


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TYPES OF AIR CONDITIONING SYSTEMS

The air conditioning system can be broadly classified as follows-

1.According to the purpose

(a)Comfort air conditioning system

(b) Industrial air conditioning system

2. According to season of the year

(a)Winter air conditioning system

(b) Summer air conditioning system

(c) yearround air conditioning system

3. According to the arrangement of equipment

(a)Unitary air conditioning system

(b) Central air conditioning system


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COMFORT AIR CONDITIONING SYSTEM

In comfort air conditioning system, the air is brought to the required dry bulb

temperature and relative humidity for the human health , comfort and efficiency. If

sufficient data of the required condition is not given, then it is assumed to be 21degree Celsius DBT and 50% RH

The comfort air conditioning may be adopted for homes. Office. Shops,

restaurants, theater, hospitals, schools etc

INDUSTIAL AIR CONDITIONING SYSTEM

It is an important system of air conditioning these days in which the inside dry bulb

temperature and relative humidity of the air is kept constant for proper working of

the machine and for the proper research and manufacturing processes. Some of the

sophisticated electronic and the other machine need a particular dry bulb

temperature and relative humidity. Sometimes, these machine also require a

particular method of psychometric processes. This type of air conditioning system

is used in textile mills, paper mills, machine-part manufacturing plants, tools

rooms, photo-processing plants etc.


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WINTER AIR CONDITIONING SYSTEM

In winter air conditioning , the air is heated, which is generally accompanied by

humidification. The outside air flow through a damper and mixes up with the

recirculated air (which is obtained from the conditioned space). The mixed airpasses through a filter to remove dirt .dust and other impurities. The air now passes

through a preheat coil in order to prevent the possible freezing of water and to

control the evaporation of water in the humidifier.

After that, the air is made to passes through a reheat coil to bring the air to the

designed dry bulb temperature. Now the conditioned air is supplied to the

conditioned space by a fan . From the conditioned space, a part of the used air is

exhausted to the atmosphere by the exhaust fans or ventilators.

The remaining part of the used air is again conditioned

The outside air is sucked and made to mix with recirculated air, In order toMake up for the loss of conditioned air through exhaust fans from the conditioned

space.

Fig no-2


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SUMMER AIR CONDITIONING SYSTEM

It is most important type air conditioning, in which the air is cooled and generally

dehumidified. The outside air flows through the damper, andMixes up with recirculated air (which is obtained from the conditioned space. ) .

The mixes air passes through a filter to remove dirt, dust and other impurities. The

air now passes through cooling coil . The coil has a temperature much below the

required dry bulb temperature of the air in the conditioned space . The cooled air

passes through a perforated membrane

And losses its moisture in the condensed from which is collected in sump.

After that, the air is made to pass through a heating coil which heats up the air

slightly. This is done to bring the air is designed dry bulb temperature

and relative humidity .

Now the conditioned air is supplied to the conditioned space by fan . From the

conditioned space, a part of the used air is exhausted to the atmosphere by the

exhaust fans or ventilators. The remaining part of the used air is again

conditioned. The outside air is sucked and made to mix with the

Recirculated air in order to make up for loss of conditioned air through exhaust fan

or ventilation from the conditioned space .

Fig no-3


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YEAR ROUND AIR CONDITIONING SYSTEM

The year round air conditioning system should have equipment for both the

summer and winter air conditioning. The out side air flow through the damper and

mixes with the recirculated air . The mixed air is passes through a filter to remove

dirt, dust and other impurities. in summer air conditioning, the cooling coil

operates to cool the air to the desired value .

The dehumidification is obtained by operating the cooling coil at a temperature

lower than the dew point temperature. In winter, the cooling coil is made

inoperative and the heating coil operates to heat the air

Fig no-4


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CHAPTER-2


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PSYCHROMETRY

1) The art of measuring the moisture content of air is termedPSYCHROMETRY

2) The science which investigates the thermal properties of moist air ,

Consider the measurement and control of the moisture content of air,

And studies the effect atmospheric on material and human comfort may properly

be termed PSYCHROMETRY.

PSYCHROMETRY TERMS:-

1. Dry air :-The pure dry air is mixture of a number of a gases such as nitrogen,

Oxygen, carbon dioxide Hydrogen, argon , neon, helium, etc . but the

Nitrogen and oxygen have the major portion of the combination.

2. Moist air :-It is mixture of dry air and water vapour . the amount of water

Vapour , present in the air, depends upon the absolute pressure and

Temperature of the mixture.

3. Saturated air :-

It is the mixture of dry air and water vapour, when the air has diffused

The maximum amount of water vapour into it . The water vapour.

Usually . occur in the form of superheated steam as an invisible gas.

However when the saturated is cooled, the water vapour in the air

Start condensing, and the same may be visible in the air starts

Condensing, and the same may be visible in Condensation on cold surfaces.


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4. Degree of saturation :-

It is the ratio of actual of mass of water in a unit mass of dry air to the mass

of water vapour in the same mass of dry air when it is saturated at the same

temperature

5. Humidity :-

It is the mass of water vapour present in 1 kg of dry air, and is generally

expressed in terms of gram per kg of dry air. It is also called specific humidity

or humidity ratio

6. Absolute humidity:-It is the mass of water vapour present in m3 of dry air, and generally expressed in

term of gram per cubic-meter of dry air

7. Relative humidity:-

It is ratio of actual mass of water vapour in a given volume of moist air to the

mass of water vapour in the same volume of saturated air at the same

temperature and pressure. It is written as RH

8. Dry Bulb Temperature of Air (DBT)It is the temperature of air recorded by a thermometer, when it is not affected by

the moisture present in the air. The dry bulb temperature is denoted by td.

9. Wet Bulb Temperature of Air (WBT):

The wet bulb temperature of air is also measured by the ordinary thermometer, but

the only difference is that the bulb of the thermometer is covered by the wet cloth.

Temperature of the ordinaryair measured by the thermometer when it is coveredby wet cloth or wick is called as the wet bulb temperature, commonly referred to as

WBT. When the air comes in contact with the wet cloth it absorbs some moisture

and gives up some heat, sue to which the temperature of the air reduces. This

reduced temperature measured by the thermometer is called as the wet bulb

temperature.


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If the moisture content of the air is very low, it will give up more heat to the cloth

and the wet bulb temperature of air will also be comparatively lower. On the other

hand, if the moisture content of air is high it will loose lesser heat to the air and wet

bulb temperature will be higher. The more is the moisture or water vapor content

of the air more is the wet bulb temperature. Thus the wet bulb temperatureindirectly indicates the moisture content present in the air or we can say that it is

affected by the relative humidity of the air.

10.Wet bulb depression:-

It is the difference between dry bulb temperature and wet bulb temperature any

point

11.Dew Point Temperature of Air (DPT)

When the temperature of the air is reduced, the temperature of the water vapor

present within the air also reduces. The water vapor within the air is similar to the

superheated steam in the vapor condition, but at much lower pressure. When we

reduce the temperature of the superheated steam, its sensible heat content starts

reducing and at some particular temperature (100 degree C) it starts condensing. In

a similar manner, when the temperature of the air is reduced continuously, the

point comes when the water vapor within the air starts getting converted into dews.

The temperature at which the water vapor within the air at some temperature starts

condensing is called as the dew point temperature of the air or DPT. When the dewis formed the air is said to be in saturated condition.

When any object is cooled below the dew point temperature of the air, we can see

the formation of sweat on its surface. A glass of water filled with chilled water is

an example.

The dew point temperature of air depends upon its moisture content. Higher the

moisture content of the air, higher is the dew point temperature. For the saturated

air, the dry bulb temperature, the wet bulb temperature and dew point temperature

are same.

12.Dew point depression

It is the difference between the dry bulb temperature and dew point temperature of

air


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PSYHROMETRIC CHART

It is graphical representation of the various thermodynamic properties of moist air.

The psychometric is very useful for finding out the properties of air (which are

required in the field of conditioning ) and eliminate the calculations.

Fig no-5

Through the psychometric chart has a number of details, yet the following lines are

important :-


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1. Dry bulb temperature lines :- The dry bulb temperature lines areVertical i.e. parallel to the ordinate and uniformly spaced. The temperature

range of these lines on chart is form -6 to 45 degree centigrade . The dry

bulb temperature lines are drawn with difference of 5 degree centigrade and

up to the saturation curve.

Fig no-6


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2. Specific humidity or moisture content lines:- The lines are horizontal i.e.parallel to the abscissa and uniformly spaced . Moisture content range of these

lines on chart is form o to 30 g/kg of dry air. Moisture content lines are drawn

with a difference of every 1 g and up to saturation curve

3. Dew point temperature lines:- These are lines are horizontal to abscissa andnonuniformly spaced . At any point on the saturation curve, the dry bulb anddue point temperature are equal .

Fig no-7


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4. Wet bulb temperature lines :- These lines are inclined straightLines are inclined straight lines and non- uniformly spaced. At any

Point on the saturation curve , the dry and wet bulb temperature are equal

Fig no-8


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5. Enthalpy (total heat) lines:- These lines are inclined straight lines anduniformly spaced. These lines are parallel to the wet bulb temperature lines,

and are drawn up to saturation curve. Some of these lines are coincide with

the wet bulb temperature lines also

Fig no-9


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6. Specific volume line:- These lines are obliquely inclined straight lines anduniformly spaced . these lines are drawn up to the saturation curve

Fig no-10


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7. Vapour pressure lines:- These lines are horizontal and uniformly spacedgenerally the vapour pressure line are drawn in the main chart . but a scale

showing vapour pressure in mm of hg is given on the extreme left side of

chart

8. Relative humidity lines:- These lines are curved lines and fallow thesaturation curve. These lines are drawn with value 10%, 20%, 30%. Etc. and

up to 100% . The saturation curve represent 100% relative humidity

Fig no-11


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PSYCHROMETRIC PROCESS:-

The various psychometric process involved in air conditioning to vary the

psychometric properties of air according to the requirement as follow:-

1) Sensible heating and cooling2) Dehumidification by cooling3) Adiabatic humidification (Evaporative cooling)4) Adiabatic dehumidification

1) Heating or Cooling:-

Fig no-12The addition or removal of heat, without any change in the moisture content (AH),

resulting in the change in DBT. The status point will move horizontally to the left

(Cooling) or to the right(Heating) . Note that while the AH does not change, the

change in temperature means the relative humidity (RH) change. It increase if the

temperature lowers and vice versa.


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2) Dehumidification by cooling :-

If as a result of cooling, the point moving towards the left reaches the saturation

line, some condensation will start. The DBT corresponding to this point is referred

to us the dew-point temperature of the original atmosphere. if there is a further

cooling , the status point will move along the saturation line and condensation will

occur . The reduction in the vertical ordinates (on the AH scale) represents the

amount of moisture precipitated, i.e. condensed out. This process will reduce the

absolute humidity, but will always end 100% RH.

Fig no-13


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3) Adiabatic humidification (Evaporative cooling):-

Fig no-14

If moisture is evaporated into an air volume without any heat input or removal

(this is the meaning of term adiabatic the latent heat of evaporation is taken

from the atmosphere. The sensible heat content thus the DBT is reduce, but

the latent heat content is increased. The status point move up and to the left,

along a WBT line. This is the process involved in evaporating cooling . By this

process , the relative humidity is increased . it increased only until it hits the

saturation line , at which it become 100% . Beyond it no decrease in sensible

temperature . This is the reason why during hot and humid months, evaporative

cooling is ineffective and uncomfortable.


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4) Adiabatic dehumidification

Fig no-15

If the air is passed through a chemical sorbent material (e.g., silica gel), some ofthe moisture is removed and the latent heat of evaporation is released. There will

be an increased in sensible heat content , thus in the system (i.e. if the process is

adiabatic) . the state point down and towards the right along an enthalpy line . This

process, in effect is the reverse of the previous one .


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CHAPTER-3


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COMFORT CONDITIONING

The human comfort depends upon physiological and psychological condition

.thus it is difficult to define the human comfort .these are many definition give

for this term out the most accepted definition Is given by the American society ofheating. Refrigeration and air conditioning engineers (ASHRAE) which states

Human comfort is that condition of mind, which express satisfaction with the

thermal environment.

COMFORT CHART

Fig no-16


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FACTOR AFFECTING HUMAN COMFORT:-

In designing winter or summer air conditioning system, the designer should be

well conversant with a number of factors which physiologically human comfort.

The important factors are follows:

1) Effective temperature

2) Heat production and regulation in human body

3) Heat and moisture losses from the human body

4) Moisture content of air

5) Quality and quantity of air

6) Air motion

7) Hot and cold surfaces

8) Air stratification

1)EFFECTIVE TEMPERATURE:- There degree of warmth or cold felt

by a human body depend mainly on the following three factors

Dry bulb temperature Relative humidity Air velocity

In order to evaluate the combined effect of these factors, the term effective

temperature is employed. It is define as that index which correlates the combine

effect of air temperature, relative humidity and Air velocity on the human body.

The practical application of the concept of the effective temperature is presentedby the comfort chart. This chart is the result of research made on different kinds of

people subjected to wide range of environmental temperature, relative humidity

and air movement by ASHRAE. It is reasonably still air (5 to 8 m/min) to

situations where the occupants are seated at rest or doing light work and to


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for different type of activity. spaces whose enclosing the surfaces are at a mean

temperature equal to air dry bulb temperature.

The most desirable relative humidity lies between 30 and 70 percent. When the

relative humidity is much below 30% the mucous membranes and the skinsurfaces become too dry for comfort and health.

For summer condition the chart indicates that a maximum of 98% people felt

comfort for an effective temperature of 21.6 degree centigrade

For winter condition the effective temperature was 20 degree centigrade desired

by 97.7% people.

1)Effective tempreture:-The human body acts like a heat engine which gets

energy from the combustion of food within the body, the process of

combustion (called metabolism) produces heat and energy due to oxidation of

products in the body by oxygen obtained from inhaled air. The rate of heat

production depends upon the individuals health, the physical activity and is

environment. The rate at which body produces heat is termed as metabolic rate.

The heat production from a normally a healthy person when a sleep is about 60

watts and it is about 10 times more for a person for carrying out sustained very

hard work.

2)Heat and moisture losses from human body:- The heat is given off

from the human body as either sensible or latent heat or both. In order to

design any air conditioning system for spaces which human bodies are to

occupy. It is necessary to know the rate at which these forms of heat are given

off under different condition of air temperature for different type of activity


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3)Moisture content of air:- The moisture of content of outside air during

winter is generally low and it is the average during the summer, because the

capacity of air to carry moisture is depend upon its dry bulb temperature.This

mean that in winter, if the cold outside air having low moisture content leaks

into the conditioned space, it will cause a low relative humidity unless

moisture added is dry to the air by the process of humidification.In summer,

the reserve will take place unless moisture is removed from the inside air by

dehumidification process.

4)Quality and Quantity:- The air in occupied space should, at all times, be

free from toxic, unhealthful or desirable fumes such as carbon dioxide it should

be free from dust and odor.The concentration of odor in a room depend upon

many factors such as dietary and hygienic habits of occupants, type an amountof outdoor air supplied, room volume per occupants and type of odor sources.

In general when there is no smoking in the room, 1m^3/min per person out

side air will take care of all condition. But when smoking takes place in a

room, 1.5m^3/min per person of out side air is necessary.

5)Air motion:- The air motion which include the distribution of air is veryimportant to maintain uniform temperature in the condition space. No air

conditioning system is satisfactory unless the air is handled is properly

circulated and a distributed. Ordinary, the air velocity in occupied zone should

not exceed 8 to 12 m/min. The air motion without proper distribution produces

local cooling sensation known as draft.

6)Cold and hot surfaces:- The cold and hot objects in a conditioned space

may cause discomfort to the occupants. In the designing of an air conditioning

system, the temperature of the surfaces to which the body may exposed must

be given considerable importance.

7)Air satisfaction:- when air is heated, its density decreases and thus it is rises

to the upper part of the confined space. This result in a considerable variation


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in the temperature between the floor and ceiling is termed as air satisfaction. In

order to achieve comfortable conditions in the occupied space, the air

conditioning system must be designed to reduce the air satisfaction to a

minimum.

8)Safety controls

Following are some safety controls which are required for refrigeration and

air conditioning system.

1.Heating thermostat: is one which opens on a rise in temperature or closes acircuit on a fall in temperature. It has single pole single Throw action.

2.Cooling Thermostat : is one which opens a circuit on a fall in temperatureor closes a circuit on a rise in temperature.

3.High Pressure Switch : is one which opens a circuit on a in pressure orcloses Circuit on a fall in pressure .it has a SPST action.

4.Low pressure switch: is one which opens a circuit on fall in pressure orcloses circuit on a rise in pressure.

5.Differential oil pressure switch: this protective device is used forstopping A compressor whenever the differential oil pressure falls below the

predetermined set point. By differential oil pressure we mean the gauge

pressure of the oil minus the gauge pressure of the gas the crankcase .it isdifferential oil pressure which is the criteria for protecting the system.

6.Low Temperature Cut-out: is a low temperature thermostat which isspecifically used in chilled water system for tripping the compressor when the

temperature falls below a pre set value. such a thermostat Is also refereed to

anti-freeze thermostat when used in chillers to trip compressor when water

temperature approaches the freezing point.

7.Fusible Plug :is used in water cooled condenser or in receivers oil air cooledcondensers to release the gas from these vessels and whenever the pressure inthe vessel exceeds a predetermined value.

8.Rapture discs : are used in chillers of centrifugal water chilling units. Theirfunction is the same as that of fusible plugs. they have a thin membrane which

will burst open when the pressure exceeds the pre determined value .


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Case study


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Estimation of cooling load


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What is cooling load:

The total heat required to be removed from the space in order to bring

It at the desired temperature by the air conditioning and refrigeration

Equipment is known as cooling load.

The purpose of load estimation is to determine the size of the air

Conditioning and refrigeration equipment that is required to maintain inside

Design conditions during periods of maximum outside temperature.

The design load is based on inside and outside design conditions and it is air

Conditioning and refrigeration equipment capacity to produce and maintain

satisfactory inside condition.

Components of cooling load:-The two main components of a cooling load imposed on an air conditioning

Plant operating during hot weather are as follows:

1) Sensible heat gain:- when there is a direct addition of heat to the enclosed

space, a gain in the sensible heat is said to occur. This sensible heat is to be

removed during the process of summer air conditioning.

The sensible heat gain may occur due to any or all of the following sources of

heat transfer:- |

a) the heat flowing into the building by conduction through exterior walls,

floors, ceiling ,doors and window due to the temperature difference on

the two sides.

b) The heat received from solar radiation. It consist of:

The heat transmitted directly through glass of window, ventilator doorsand

The heat absorbed by walls and roofs exposed to solar radiation and lateron trasferred to the room by conduction

c) The heat conducted through interior partition from rooms in the same

building which are not conditioned.


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d)The heat gain of off by lights, motors, machinery.

e) The heat librated by the occupants.

f) The heat carried by the outside air which leaks in(infiltrating air)

through their frequent unit.

g) The heat gain from the fan work.

2) Latent heat gain:- when there is a addition of water vapour to the air of

enclosed space, a gain in latent heat is said to occur. This latent heat is to be

removed during the process of summer air conditioning. The latent heat gain

may occur due to nay one or all of the following sources:

a) The heat gain due to moisture in the outside air entering by infiltration

b)The heat gain due to condensation of moisture from occupants.

c) The heat gain due to moisture passing directly in to the conditioned space

through permeable walls or partitions from the outside or from the

adjoining regions where the water vapour pressure is higher


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Seminar Hall Parameter:

Seminar Hall Dimension

Length13.2m Width11.6m Height2.9m Thickness (wall)0.20m

Door Dimension

Width1.1m Height2.1m

Total no of door is two.

Door Window Dimension

Height0.65m Width1.2m

Total no of door window is two.

Window Dimension

Height1.85m Width-2.28m

Total no of window is six.


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Seminar Hall Include

Computer-1

Sitting-185

CFL-28

Projector-1

Amplifire-1

Speaker-6

CPU-1

Monitor-1

Rating

CPU-70 Watt

Monitor-100-240 V,50-60 Hz,1.5A

Projector-210 Watt

Amlifire-240V,50Hz,750VASpeaker-18W

CFL- 18W,250V


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TEMPERATURE MEASUREMENT

TIME EAST WALL WEST WALL NORTH WALL SOUTH WALL

DBT WBT DBT WBT DBT WBT DBT WBT

10:20 27 23

10:35 28 24

10:50 26 23.5

11:05 26 24

11:50 34 32

12:05 29 26.5

12:20 25.5 24

12:35 27 2302:05 36 33

02:20 31 27

02:35 27 24

02:50 27 24

03:05 30 26.5

03:20 26.5 23.5

Table-1

Maximum temperature of east wall = 27 C

Maximum temperature of west wall = 31 C

Maximum temperature of north wall = 27 C

Maximum temperature of south wall = 36 C


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CALCULATION

Design a central plant for air conditioning temp.DBT 22C; 50% RH for Seminar

hall located in our college gives following data -

Area =153.12m2

Height =2.9m

Total Volume =444.048m3

Area of wall including window:

1- Area of East wall = Height*Width=2.9*11.6

=33.64 m2

2- Area of West wall = Height*Width=2.9*11.6

=33.64 m2\

3- Area of North wall =Length*Height=13.2*2.9

=38.28 m2

4- Area of South wall = Length*Height=13.2*2.9

=38.28 m2

5- Area of Door = Height*Width=2.1*1.1

=2.31 m2

Total area = 2*2.31

=4.62 m2


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6- Area of Door Window = Height*Width=0.65*1.2

=0.78 m2

Total area = 2*0.78=1.56 m2

7- Area of Window = Height*Width=1.85*2.28

=4.218 m2

Total area of window (west wall)

=2*4.218

=8.436 m2

Total area of window (south wall)

=4*4.218

=16.872 m2

Area of West wall without window

=Total area - area of window

= 33.648.436

= 25.204 m2

Area of South wall without window

=Total areaarea of window

= 38.2816.872

=21.408 m

2

Area of North wall without door and door window

=Total areaarea of doorarea of door window

=38.284.62 -1.5=32.1m2


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HEAT LOAD CALCULATION

1-Heat gain through glasses =

(a) transmitted solar radiation+ (b)heat flow by convection and radiation between

glass and indoor surface

A- transmitted solar radiation , It = Tt * IS

where

Tt = transmittance for Transmitivity

=0.8-0.93(for window glass )from HMT data book

IS = incident solar radiation

Total emissive power Eb =AT4

Incident solar radiation, IS = Eb/ = AT4

/

For sun side glasses( West wall) IS = AT

4/

=5.67*10-8 *8.436 * 3044/

=1301.02 Watt

Transmitted solar radiation , It = Tt * IS

=0.88 *1301.02

=1144.89 W

(South wall) IS = AT4

/

=5.67*10-8 *16.872 * 3094/

=2777.48W


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=0.88 * 2777.48

=2444.18 W

For dark side glasses, IS = AT4

/

=5.67*10-8 * 1.56 * 3004/

=228.17 W


=0.88 *228.17

=200.789 W

B- Heat Flow by Convection &Radiation

Q COND. = Q CON. + Q RAD.

= h A (TSTF ) +F A ( TS4TF

4)

h = Coeff. of Conv. Heat Transfer=100w/m2k

A = Area exposed to Heat Transfer

TS = Surface temp.

TF = Fluid temp.

F = Form factor=0.92 &

= Stefan Boltzmann constant. (5.67*10-8 w/m2k4 )


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Hence,

sensible heat is-

For sun side glasses(West wall) Q COND. = Q CON. + Q RAD.


4)

=100 *8.436 *(304295) + 0.92 * 5.67*10-8 *8.436*

( 3044295

4)

=8018.09 W

(South wall) Q COND. = Q CON. + Q RAD.


4)

=100 *16.872 *(309295) + 0.92 * 5.67*10-8

*16.872

*( 3094295

4)

=24979.04 W

For dark side glasses(North wall) . Q COND = Q CON. + Q RAD.


4)

=100 *1.56 *(300295) + 0.92 * 5.67*10-8 * 1.56*

( 3004295

4)

=822.85 W

Total sensible heat gain from sun side glasses=36586.2 W

Total sensible heat gain from dark side glasses=1023.63 W


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2-Sensible heat gain through building structure

Q = U A (TOTi)

Where,

U = Overall coeff. Of heat transmission of wall

= 2.38 w/m2

A = area of wall

TO,Ti = outside & inside temperature

Overall coefficient of heat transmission (U) for brick wall of thickness 20 cm for

both side plaster=2.38 W/m2

Heat gain through wall

Q = U A (TOTi)

East Wall =2.38 * 33.64 * (300-295)

=400.316 W

West Wall =2.38 * 25.204 * (304-295)

=539.869 W

North Wall=2.38 * 32.1 *(300-295)

=381.99 W

South Wall =2.38 * 21.408 *(309-295)

=713.31 W


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3- Internal Load

A) Heat gain from occupants

Heat gain from occupants

= No of occupants * heat gain by single person

(for very light work)

sensible heat = 185 * 53 =9805 W

latent heat = 185 * 44 =8140 W

B) Heat gain from light source

Q=total wattage*use factor*allowance factor

=(18 * 28) * 1 * 1.25

=630 W

C) Heat gain from appliances

1- Heat gain from CRT monitor=(1*360) *1 *1.25=450 W

2- Heat gain from CPU =(1 *70) *1 *1.25=87.5 W

3- Heat gain from amplifier =(1 *750) *1*1.25=937.5 W

4- Heat gain from speaker =(6 *18) *1 *1.25=135 W

5- Heat gain from projector = (1 *210) *1 *1.25=262.5 W

Total Heat gain from appliances

= Sensible heat

=1872.5 W


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D-Out Side Air

A-Ventilation load :-

Volumetric flow = no. of person*outside air(m3/min/persion)

v1 =185 * 0.45

=83.25 m3/min

Outside Air Condition (at point 1)

DBT = 36C

.WBT = 29C

Inside Air Condition (at point 2)

= 22C DBT & 50% R


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Fig no-17

From psychometric chart -:

Specific volume of air, vs1 =0.89

Enthalpy h1 = 94 KJ/kg Enthalpy h2 = 44 KJ/kg

Enthalpy hA = 58 KJ/kg

Mass = volumetric flow/specific volume

m1 = v1 / vs1

=83.25/0.89


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=93.54 kg/min

Sensible heat gain due to ventilation = m1 * (hA-h2)

= 93.54 *(58-44)

=1309.56 KJ/min

=21.826 KW

=21826 W

Latent heat gain due to ventilation = m1 * (h1-hA)

=93.54 * (94-58)

=3367.44 KJ/min

=56.124 KW

=56124 W

B-Infiltration load (by crack length method)

Amt. of infiltrated air through windows and wallsv1 = ( L*W*H*AC ) / 60

Where,

L= room length in meter

W=width in meter

H=height in meter &

AC = air changes per hour = 2 for three wall exposed

Hence, v1 = (13.2 *11.6 *2.9 *2)/60

= 14.80 m3/min

m1 = v1 / vs1


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= 14.80/0.89

=16.62 kg/min

Sensible heat gain = m1 * (hA-h2)

=16.62 *(58-44)

=232.68 KJ/min

=3.878 KW

=3878W

Latent heat gain = m1 * (h1-hA)

=16.62 *(94-58)

=598.32 KJ/min

=9.972 KW

=9972 W

Total Internal load:

Sensible heat =34133.5 WLatent heat =64264 W

Total Sensible heat = 73778.824 W

Total Latent heat = 74236 W


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Safety factor (10% TSH, 5% TLH)

Sensible heat =7377.883 W

Latent heat = 3711.8 W

Total effective sensible heat = 81156.707 W

Total effective latent heat = 77947.8 W

Grand total heat:-

= Total effective sensible heat + Total effective latent heat

= 81156.707 + 77947.8

= 159104.507 W

=159.105 KW

1 KW =1 KJ/s

159.105 KW= 159.109*60 KJ/min

=9546.28 KJ/min

1 TR = 210 KJ/min

9546.28 KJ/min = 9546.28/210 TR

=45.45 TR

Result:-

We need 45.45 TR of refrigeration.


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Advantage

1. Refrigerated air conditioner changes the inside room condition acoording tothe human comfort .

2. Help full with Asthma : Refrigerated air conditioner dry out the air. Thosewho suffer from asthma tend to have difficulty breathing very moist air. So

refrigerated air conditioning is very helpful.

3. Dampness: humidity can give an uncomfortable and damp feeling that therefrigerated air conditioner do not produce .

4. Great cooling potential.5. With the help of cooling load we can estimate the exact size of air

conditioning and refrigeration equipment, which is use full for maintaining

desired temp.


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Application

1. Air Conditioning / Refrigeration Market2. Comfort and Commercial Air Conditioning3. Building and Facility air conditioning4. Transport Refrigeration5. Water cooler6. Ice manufacture


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ABBREVIATIONS

W- Watt

m- Meter

min- Minute

KJ- Kilo Joule

Kw- Kilo Watt

temp- Temperature


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CONCLUSION

The refrigeration and air conditioning systems are now widly used in industries

and home for maintaining the the inside tempreture of the respective area for the

human comfort . there are many technology which are improve the previous air

conditioning system with increase the COP .

From our case study we make conclude the capacity of air conditioner that can be

use to give effective cooling for particular area by the estimation of cooling load.

From our study and calculation we found that nearly a 45 tones of AC is required

for a total surface volume of 444.48 cubic meter. Hence we can estimate the

requirement of AC unit for given area..

This estimation minimize energy resources needed for cooling the specific area and

hence we can save the energy. This also save our capital requirement and energy

resources and electricity requirement for the system.

There are so mny opportunity in this field as we work further we can increase the

coefficient of performance of refrigeration and air conditioning system , minimize

the cost of air conditioner, increase the quality of metal required and increase the

cooling effect by further study and researcher .

We dont think this project work had been completed yet because as there is

further scope of research work that should go on. But we have given our best to

complete the whole work within a specific period and we will continue work in

this field in coming future.


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BIBLIOGRAPHY

BOOKS:

R.S. Khurmi, ( Refrigeration and Air Conditioning )

R.K. Rajput, ( Refrigeration and Air Conditioning )

R.K. Rajput, ( Heat and Mass Transfer)

C.P. Arora , ( Refrigeration and Air Conditioning )

Dmkundwar & domkundwar , HMT Data book

WEBSITES:-

www.wikipedia.com

www.housetuffworks.com

www.google.com
http://www.wikipedia.com/http://www.wikipedia.com/http://www.housetuffworks.com/http://www.housetuffworks.com/http://www.google.com/http://www.google.com/http://www.google.com/http://www.housetuffworks.com/http://www.wikipedia.com/

theory and calculation of our project and final result

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