Chapter-1

Introduction

o Introduction

o Need

1

1.1 INTRODUCTION

Fig 1.1: Automobile Air-Conditioning System

The vapour absorption refrigeration system is one of the oldest methods of producing

refrigerating effect. The principle of vapour absorption was first discovered by Michael

Faraday in 1824 while performing a set of experiments to liquefy certain gases. The first

machine was based on Vapour Absorption Refrigeration machine was developed by a

French scientist, Ferdinand Carry, in 1860. This system may be used in both the domestic

and large industrial refrigerating plants. The refrigerant commonly used in vapour

absorption system is Ammonia.

This system uses Heat energy instead of mechanical energy as in vapour compression

system, in order to change the condition of refrigerant required for the operation of the

refrigeration cycle.

2

This idea of refrigeration system is being utilized in our project for the purpose of air

conditioning. Like other air conditioner systems, the automobile air conditioner must

provide adequate comfort cooling to the passenger in the conditioned space under a wide

variety of ambient conditions. In automobile air conditioning load factors are constantly

and rapidly changing as the automobile moves over highways at different speeds and

through different kind of surroundings. As the car moves faster there is greater amount of

infiltration into the car and the heat transfer between the outdoor air and the car surface is

increased. The sun baking down on a black top road will raise its temperature to 350C –

450C approximately and thus increases the amount of heat transmitted into car. When

driving through a grassy terrain, much less radiant heat is experienced than when passing

through sandy flats or rocky hills. Therefore, the car is subjected to varying amounts of

heat load when its orientation changes during the journey.

An automobile engine utilizes only about 35% of available energy and rests are lost in the

form of heat and mechanical losses to cooling and exhaust system. If one is adding

conventional air conditioning system to automobile, it further utilizes about 4-5% of the

total energy. Therefore automobile becomes costlier, uneconomical and less efficient.

The conventional air conditioning system in car decreases the life of engine and increases

the fuel consumption, further for small cars compressor needs 3 to 4 bhp i.e. a significant

ratio of the power output. Keeping these problems in mind, a car air conditioning system

is proposed which is using exhaust heat. The advantages of this system over conventional

air-conditioning system are that it does not affect designed efficiency life and fuel

consumption of engine.

3

1.2 NEED

An automobile engine utilizes only about 35% of available energy and rests are lost to

cooling and exhaust system. If one is adding conventional air conditioning system to

automobile, it further utilizes about 5% of the total energy. Therefore automobile

becomes costlier, uneconomical and less efficient. Additional of conventional air

conditioner in car also decreases the life of engine and increases the fuel consumption.

For very small cars compressor needs 3 to 4 bhp, a significant ratio of the power output.

Keeping these problems in mind, a car air conditioning system is proposed using exhaust

gases. The advantages of this system over conventional air-conditioning system are that it

does not affect designed efficiency life and fuel consumption of engine. And hence

makes the running of the engine efficient and economical.

Thus to have the more economical air conditioning and more efficient engine in the

automobile the need of this system arises.

4

Chapter-2

Mechanism Details

o Working Principle

o Operational Stages

5

2.1 WORKING PRINCIPLE

Fig 2.1: Vapour Absorption Cycle

The underlying principle is the “Practical Vapour Absorption System” that uses a

Generator, instead of compressor (i.e. used in vapour compression system). This

Generator requires a Heat Source to generate Ammonia vapours from Aqueous Ammonia

Solution received from Absorber. The above heat requirement is served by the exhaust

heat of the engine.

Some power is also required to run the Pump, which is used to raise the pressure of

Aqueous Ammonia Solution as well as to transmit it from Absorber to Generator. As the

pump consumes very less amount of power in comparison to Compressor, it is quite

comfortable to drive it from battery power or directly from crank-shaft.

Using the above setup, we can relieve the crank-shaft from excess load of compressor;

this will help in decreasing the fuel requirement of engine. Thus, increases the fuel

efficiency.

6

So, without using any other equipment or source of energy besides the vehicle itself, it is

possible to introduce this air-conditioning system in existing automobiles/vehicles. Also

it uses Ammonia as refrigerant, which do not affect the ozone layer as well as it does not

contribute to the greenhouse effect, and it’s LCCP (Life-Cycle Climate Performance) is

also highly favorable.

7

2.2 OPERATIONAL STAGES

Fig 2.2: Vapour Absorption Cycle

Stage 1-2:

-The low pressure ammonia vapour leaving the evaporator enters the absorber where it is

absorbed by the cold water in the absorber.

-The water has the ability to absorb very large quantity of ammonia vapour and the

solution thus formed, is known as aqua-ammonia.

Stage 2-3:

-The strong solution thus formed in the absorber is pumped to the generator by the liquid

pump to increase the pressure of the solution up to 10 bar.

8

Stage 3-4:

-The strong solution of ammonia is heated by some external source, in our system by the

exhaust heat of automobile.

-During the heating process the ammonia vapour is driven off the solution at high

pressure leaving behind the hot weak ammonia solution in the generator.

Stage 4-5:

-The weak ammonia solution flows back to the absorber at low pressure after passing

through the pressure reducing valve.

Stage 6-7:

-The high pressure vapour from the generator is condensed in the condenser to high

pressure liquid ammonia.

Stage 7-8:

-The condensed liquid ammonia from the condenser is stored in a vessel known as

receiver valve, from where it is supplied to the evaporator through the expansion valve.

Stage 8-9:

-The liquid ammonia is passed to the expansion valve in which its high pressure and

temperature is reduced at a controlled rate after passing through it.

Stage 9-1:

-The liquid vapour ammonia at low pressure and temperature is evaporated and changed

into vapour refrigerant. In evaporator, the liquid vapour ammonia absorbs its latent heat

of vaporization from the medium to be cooled.

9

Chapter-3

Pros & Conso Advantages

o Disadvantages

o Comparison

10

3.1 Advantages

Uses Engine heat as source of energy hence enhances the efficiency of engine.

Moving parts are only in the pump, which is a small element in the system hence

operation becomes smooth and also wearing and tearing is reduced.

The system works at low evaporator pressures without affecting the COP of the

system.

Environmental friendly, no release of CFC derivatives.

Helps in protecting OZONE layer from depletion.

Helps engine to cool, as it extracts heat from engine.

Low running cost.

Higher engine power efficiency.

11

3.2 Disadvantages

1) Initial capital cost

Though the running cost of the absorption refrigeration system is much lesser than the

vapor compression system, its initial capital cost is much higher.

2) Corrosive nature

In case of the ammonia system, ammonia is corrosive to copper. In the vapor

compression system copper is used with the halocarbon refrigerants and they are quite

safe thus ensuring long life of the refrigeration system. As such the vapor compression

system with reciprocating or centrifugal compressor has longer life than the absorption

refrigeration system.

3) Low working pressures

The working pressures of the absorption refrigeration cycle are very low. Due to this the

refrigeration system should be sealed thoroughly so that no atmospheric gases would

enter the refrigeration system. As such the system of the compression refrigeration should

also be packed tightly, but this is to prevent the leakage of the refrigerant to the

atmosphere.

4) Coefficient of Performance (COP)

The coefficient of performance of the absorption refrigeration systems is very low

compared to the vapor compression systems. Thus the absorption refrigeration system

becomes competitive only if the ratio of the electricity to fuel (oil, gas or coal used to

generate the steam in the boiler) becomes more than four. If this ratio is lesser there are

chances that excess fuel would be required to generate the steam. However, if there is

excess steam in the industry, this ratio may not be given importance.

12

3.3 Comparison of Vapor Absorption Air Conditioning over Vapor

Compression Air Conditioning

1) Method of compression of the refrigerant: One of the most important parts of any

air conditioning cycle is the compression of the refrigerant since all the further operations

depend on it. In the vapor compression air conditioning system the compression of the

refrigerant is done by compressor which can be of reciprocating, rotating or centrifugal

type. In the vapor absorption air conditioning system, the compression of the refrigerant

is done by absorption of the refrigerant by the absorbent. As the refrigerant is absorbed, it

gets converted from the vapor state to liquid state so its volume reduces.

2) Power consumption devices: In the vapor compression cycle the compressor is the

major power consuming device while in the vapor absorption cycle the pump used for

pumping refrigerant-absorbent solution is the major power consuming device.

3) The amount of power required: The compressor of the vapor compression cycle

requires large quantities of power for its operation and it increases as the size of the

system increases. In case of the vapor absorption system, the pump requires very small

amount of power and it remains almost the same (or may increase slightly) even for

higher capacities of air conditioning. Thus the power consumed by the vapor absorption

system is less than that required by the vapor compression system.

4) Type of energy required: The vapor absorption system runs mainly on the waste or

the extra heat in the plant. Thus one can utilize the extra steam from the boiler, or

generate extra steam for the purpose and also use the hot available water. Similarly the

waste heat from the diesel engine, hot water from the solar water heater, etc. can also be

utilized. In case of the vapor compression system, the compressor can be run by electric

power supply only; no other types of energy can be utilized in these systems.

5) Running cost: The vapor compression air conditioning system can run only on electric

power, and they require large amount of power. These days the electric power has

13

become very expensive, hence the running cost of the vapor compression air conditioning

system is very high. In case of the absorption air conditioning system only small pump

requires electric power and it is quite low. In most of the process industries, where the

absorption refrigeration is used, there is some extra steam available from the boiler,

which can be used for running the system. Thus in absorption air conditioning system no

extra power in the pure electric form is required and the energy that would have

otherwise gone wasted is utilized in the plant. Thus the running cost of the absorption air

conditioning system is much lesser than the vapor compression system.

14

Chapter-4

Construction Details

o List of Components

o Component Details

15

4.1 LIST OF COMPONENTS

Evaporator

Condenser

Absorber

Receiver-Drier

Pump

Glass Cloth Tape

Insulation Foam Tube

Globe Valves

Heating Coil

Drier

Generator

Connection Tubes

16

4.2 COMPONENT DETAILS

4.2.1 EVAPORATOR

Fig 4.1: Evaporator

EVAPORATOR is a device used to turn (or allow to turn) the liquid form of a refrigerant

into its gaseous form. An evaporator is used in an air conditioning system to allow the

compressed cooling refrigerant (ammonia) to evaporate from liquid to gas while

absorbing heat in the process. It is installed in the low pressure side of the cycle.

How it works?

Air conditioning evaporator works by absorb heat from the area (medium) that need to be

cooled. It does that by maintaining the evaporator coil at low temperature and pressure

than the surrounding air.

17

As the liquid refrigerant enters the evaporator at low pressure and flows through it

continually and absorbs heat through the coil walls, from the medium being cooled

during this the refrigerant continues to boil and evaporate.

Why evaporators remain cold?

The evaporator remains cold because of the following two major reasons:

The temperature of the evaporator coil is low due to the low temperature of the

refrigerant inside the coil.

The low temperature of the refrigerant remains unchanged because any heat it

absorbs is converted to latent heat as boiling proceeds.

18

4.2.2 CONDENSER

Fig 4.2: Condenser

The condenser is a device used to change the high-pressure refrigerant vapour to a liquid.

It is mounted in front of the engine's radiator, and it looks very similar to a radiator. The

vapour is condensed to a liquid because of the high pressure that is driving in it, and this

generates a great deal of heat. The heat is then in turn removed from the condenser by air

flowing through the condenser on the outside.

It is installed in the high pressure side of the cycle whose function is to remove the heat

of the hot vapour refrigerant discharged, which consists of heat absorbed by the

evaporator .The heat from the hot vapour refrigerant in a condenser is removed first by

transferring it to the wall of condenser tubes and then from the tubes to the condensing or

cooling medium which may water, air or combination of both.

19

4.2.3 ABSORBER

Fig 4.3: Absorber

Absorber is the part of the system where vapour ammonia at low pressure and weak

solution from the generator comes through pressure reducing valve and get accumulated.

20

Here the vapour ammonia gets dissolved into the water as per the solubility ratio of water

and ammonia. This water and ammonia vapour solution is known as aqua ammonia

solution or strong solution which is pumped to the generator at high pressure where it is

heated from some external source of heat. Thus, Ammonia vapour gets evaporated and

the cycle continues.

21

4.2.4 RECEIVER-DRIER

Fig 4.4: Receiver-Drier

- The receiver-drier is used on the high side of systems that use a thermal expansion

valve.

- This type of metering valve requires liquid refrigerant. To ensure that the valve

gets liquid refrigerant, a receiver is used.

- The primary function of the receiver-drier is to separate gas and liquid.

- The secondary purpose is to remove moisture and filter out dirt.

22

Fig 4.5: Schematic Diagram of Receiver-Drier

- The receiver-drier usually has a sight glass in the top. This sight glass is often

used to charge the system. Under normal operating conditions, vapor bubbles

should not be visible in the sight glass.

- This is a small reservoir vessel for the liquid refrigerant, and removes any

moisture that may have leaked into the refrigerant.

- Moisture in the system causes havoc, with ice crystals causing blockages and

mechanical damage.

23

4.2.5 PUMP

Fig 4.6: Pump

- A pump is a device used to move fluids, such as liquids, gases or slurries.

- A pump displaces a volume by physical or mechanical action.

- Pumps fall into three major groups: direct lift, displacement, and gravity pumps.

Their names describe the method for moving a fluid.

Pump converts the mechanical energy from a motor to energy of a moving fluid; some of

the energy goes into kinetic energy of fluid motion, and some into potential energy,

represented by a fluid pressure or by lifting the fluid against gravity to a higher level

24

Fig 4.7: Schematic Diagram of Pump

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the

pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pump

used to move liquids through a piping system. The fluid enters the pump impeller along

or near to the rotating axis and is accelerated by the impeller, flowing radially outward or

axially into a diffuser or volute chamber, from where it exits into the downstream piping

system. Centrifugal pumps are typically used for large discharge through smaller heads.

25

4.2.6 GLASS CLOTH TAPE

Glass cloth tube is an electrical insulator and the heat conductor i.e. it enables the heat to

be transmitted but insulate the system electrically. It is made from high grade heat

resistant glass cloth coated with special silicone backing.

Characteristics:

Highly conformable and easy to install

Very flexible accommodating angles and turns

Aggressive adhesive system

Removes easily without leaving residue

High tensile strength and abrasion resistant

Repositionable

Excellent performance in temperatures up to 500°F (260°C)

Can be single-sided or double-sided

Fig 4.8: Glass Cloth Tape

26

4.2.7 INSULATION FOAM TUBE

Insulation is a product that blocks transfer of heat, thus helps in maintaining the desired

temperature by obstructing the flow of heat.

Characteristics:

Low thermal conductivity (K value) makes it highly efficient and effective in the

insulation of cooling or heating systems.

The thermal blister close cell structure forms as impermeable layer which is in

itself a good vapour barrier.

It is suitable for application within the temperature range of -40°C to 125°C.

The material has been specially compounded to self-extinguishing in nature.

It is CFC, asbestos, chlorine and fiber free and does not cause skin allergy.

It is inert to most chemical agent and neutral to pipe metals.

The extreme flexibility of the materials makes installation fast, easy and

economical.

Fig 4.9: Insulation Foam Tube

27

4.2.8 GLOBE VALVE

Fig 4.10: Globe Valve

A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a

movable disk-type element and a stationary ring seat in a generally spherical body.

28

Globe valves are named for their spherical body shape with the two halves of the body

being separated by an internal baffle. This has an opening that forms a seat onto which a

movable plug can be screwed in to close (or shut) the valve. The plug is also called a disc

or disk. In globe valves, the plug is connected to a stem which is operated by screw

action using a hand wheel in manual valves. Typically, automated globe valves use

smooth stems rather than threaded and are opened and closed by an actuator assembly.

Although globe valves in the past had the spherical bodies which gave them their name,

many modern globe valves do not have much of a spherical shape. However, the term

globe valve is still often used for valves that have such an internal mechanism. In

plumbing, valves with such a mechanism are also often called stop valves since they don't

have the global appearance, but the term stop valve may refer to valves which are used to

stop flow even when they have other mechanisms or designs.

29

4.2.9 HEATING COIL (NICHROME)

Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a

resistance wire. Patented in 1905, it is the oldest documented form of resistance heating

alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many

others to accommodate various applications. It is silvery-grey in colour, is corrosion-

resistant, and has a high melting point of about 1400 °C. Due to its relatively high

electrical resistivity and resistance to oxidation at high temperatures, it is widely used in

electric heating elements, such as in hair dryers, electric ovens, soldering iron, toasters,

and even electronic cigarettes. Typically, Nichrome is wound in coils to a certain

electrical resistance, and current is passed through to produce heat.

Fig 4.11: Heating Coil (NICHROME)

30

The properties of Nichrome vary depending on its alloy. Figures given are representative

of typical material and are accurate to expressed significant figures. Any variations are

due to different percentages of nickel or chromium.

Material property Value Units

Modulus of elasticity 2.2 × 1011 Pa

Specific gravity 8.4 Dimensionless

Density 8400 kg/m3

Melting point 1400 °C

Electrical resistivity at room temperature 1.0 × 10−6 to 1.5 × 10−6 Ωm

Specific heat 450 Jkg−1°C−1

Thermal conductivity 11.3 Wm−1°C−1

Thermal expansion 14 × 10−6 °C−1

Table No 4.1: Properties of NICHROME

31

4.2.10 DRIER

Fig 4.12: Drier

Filter-driers play a pivotal role in the operation of air conditioning and

refrigeration systems. At the heart of the unit is the desiccant held in its

cylindrical metal container. As important as the filter-drier is, many actually

do not understand how it works. Here are some details.

The word desiccate means to dry out completely and a desiccant is a material or

substance that accomplishes the moisture removal. Moisture in the mechanical

refrigeration cycle is detrimental to the operation and life of the system. The filter-drier is

an accessory that performs the functions of filtering out particles and removing and

holding moisture to prevent it from circulating through the system.

32

Moisture in a System

Consider a chemist working with chemical elements to create new substances. The

chemist combines atoms of selected elements to cause them to bond or link together to

form new combinations of molecular structures. These new molecular structures are

called compounds. Chemists perform such creations in the process of developing new

synthetic oils, refrigerants, glues, rubbers, metal alloys, and a host of other products that

are useful in many ways.

Some combinations of atomic elements create molecular structures that can be either

useful or harmful. Acids are formed when the right combination of elements are linked

together chemically. If we have a use for the acid and use it for its intended purpose, all is

well. However, in some cases unwanted chemical combinations occur where we least

want them and where they cause serious harm. Under certain circumstances, hydrochloric

and hydrofluoric acids chemically form in the mechanical refrigerant system. This, of

course, is what we want to prevent.

Again, let us consider how the chemist facilitates the chemical bonding process. The

chemist wants certain chemical reactions to take place in an effort to create new

substances that hopefully have special properties that are useful. Perhaps the chemist is

attempting to create a new refrigerant to replace another that is being phased out. The

chemist combines particular elements to form bonds or links that when complete meet all

the qualities of a suitable refrigerant. A catalyst is anything that hastens, encourages, or

helps bring about a result. Heat is one of chemistry’s most active catalysts. A chemist

may purposely add heat to a beaker of chemicals to cause them to combine to form a new

substance.

Keep It Clean

The case has been made as to how important it is to prevent chemical reactions from

taking place in a system. It almost seems from what we have described up to this point

that it could be difficult to prevent chemical breakdown from occurring. Fortunately, the

installation crew and service technician can prevent system failure due to a chemical

reaction.

33

It is imperative that installation and service technicians prevent foreign materials, air,

moisture, brazing flux, carbon created during brazing, and insulation powder from

entering or remaining in a system. Good piping practice includes bleeding a small amount

of dry nitrogen through the system while brazing. Pipe ends need to be sealed prior to

sliding pipe insulation over the piping. A good 500-micron evacuation should be reached

to remove air and moisture before charging with refrigerant. And, the addition of a

properly sized filter-drier is important on both new systems as well as anytime a system

is opened for service.

The filter-drier is designed to both remove any particulates that may circulate as well as

collect and hold any moisture that may be present in the system. The use of a filter-drier

containing a good desiccant has become even more important with the advent of R-410A

systems, which utilize the highly hygroscopic synthetic polyolester oils.

Capacity

Capacity refers to the amount of moisture the desiccant in the filter-drier can hold.

Capacity is measured in parts per million (ppm). One ppm is one part of water per million

parts of refrigerant. In practical terms, this would be approximately equal to one drop of

water in a 125-pound drum of refrigerant. Desiccant capacities are rated at 75 and 125

degrees F. The older desiccant, activated alumina, had a moisture holding capacity of 4

grams of moisture per 100 grams of desiccant. Silica gel had a moisture holding capacity

of 3 grams of moisture per 100 grams of desiccant. Modern zeolite molecular sieve

desiccants have a capacity of approximately 16 grams of moisture per 100 grams of

desiccant.

The capacity of a desiccant is temperature dependent. The colder the desiccant, the more

moisture it can hold. Therefore, locating a filter-drier in a cooler location is an advantage.

Removing a brazed filter-drier with a torch flame causes moisture to be driven out of the

desiccant and into the system. Generally, it is better to cut the filter-drier out with a

tubing cutter.

34

Location

The desiccant works better at removing and holding moisture when it is placed in a

refrigerant line where the refrigerant is in the liquid state. The filter-drier is often called a

“liquid line filter-drier” for this reason.

Suction Line Filter-Driers

The desiccant is still able to absorb moisture when applied to the suction line but not

quite as effectively. Special suction line filter-driers are made for cleaning up a system

after a compressor burnout. A larger shell is used to minimize pressure drop on suction

line driers. Suction line filter-driers marked as “HH” driers contain carbon filter material

in addition to the zeolite desiccant. The carbon and zeolite are capable of capturing and

holding acids as well as moisture. Suction line filter-driers used to clean up a system after

a burnout should be replaced until the system is known to be clean and no longer tests

positive for acids in the system.

A suction line filter-drier with an excessive pressure drop across it should not be left in a

system. An excessive pressure drop in the suction line reduces the volumetric efficiency

of the compressor, thus reducing system operating capacity. Many suction line filter-

driers have a pressure tap on the inlet end so the pressure on the inlet of the drier can be

compared to the pressure at the suction service valve at the compressor. Still other

suction line filter-driers have pressure taps on both the inlet and outlet.

35

4.2.11 GENERATOR

Fig 4.13: Generator

o It is a kind of heat exchanger.

o Collects Heat from Exhaust and Coolant to vaporize Ammonia from strong solution

of Aq. Ammonia.

o Supplies Vaporized Ammonia to Condenser.

o

36

Chapter-5

Calculations

o Engine Heat Data

o Phase Diagrams Used

o Calculations

o Bill of Materials

37

5.0 ENGINE HEAT DATA

5.0.1 EXPERIMENTAL DATA OF FOUR CYLINDER FOUR STROKE PETROL ENGINE

S. No.

Voltag

e

(V)

Curren

t

(A)

Speed

(RPM

)

Fuel to 10

cc Time

Manomete

r Reading

T1

(oC)

T2

(oC)

T3

(oC)

T4

(oC)

T5

(oC)

T6

(oC)

Rotameter Reading

Engin

e

Jacke

t

Calorimete

r

1 230 7/7.3 1595 11.16 17-9 23 52 38 603 164 40 92 57

2 230 14 1550 10.13 17.6-8.4 21 52 38 607 168 40 92 57

3 208 21.2/21 1548 9.31 18.8-7.2 20 53 38 622 180 40 92 57

4 198 28 1523 8.31 18.8-6.2 19 52 39 630 189 40 92 57

5 195 31 1524 8.21 19.7-6.4 18 51 37 614 189 41 92 57

Table 5.1: Engine Heat Data Sheet

T1= Temp of water inlet to engine & calorimeter

T2= Temp of water outlet of engine jacket

T3= Temp of water outlet of calorimeter

T4= Temp of Exhaust Gas inlet to calorimeter

38

T5= Temp of Exhaust gas outlet of calorimeter

T6= Ambient Temp

39

Fig 5.1: Four Stroke Four Cylinder Engine Test Rig

40

5.0.2 Phase Diagram of Water

Fig 5.2: Phase Diagram of Water

41

5.0.3 p-h Chart of Ammonia (R-717)

Fig 5.3: p-h Chart of Ammonia (R-717)

42

5.1 CALCULATIONS

Design Consideration of Automobile Air Conditioning Unit based on Vapour Absorption Refrigeration System (CAPACITY=1TR)

Temperature

(oC)

Temperatur

e (K)

Pressure

(bar)

Specific Enthalpy

(kJ/kg)Specific Entropy (kJ/kg K)

Enthalpy

(kJ/kg)

Liquid

(hf)Latent (hfg) Liquid (sf) Vapour (sg) (hg)

Absorber (T_A) 0 273 4.29586 181.20 1263.25 0.7151 5.3405 1444.45

Generator (T_G)# 100 373 11.66896 323.08 1145.79 1.2037 4.9842 1468.87

Condenser (T_C) 30 303 11.66896 323.08 1145.79 1.2037 4.9842 1468.87

Evaporator (T_E) 0 273 4.29586 181.20 1263.25 0.7151 5.3405 1444.45

For design considerations we have to take assumptions which are based on the basis of normal summer ambient

weather/temperature conditions as well as the temperature to be maintained at Evaporator Coil is also assumed to be maintained for

human comfort.

Table 5.2: Data Table for Calculation

(For ease of calculation and compactness of the model we have made all of our calculations, taking Capacity = 1TR)

Coefficient of Performance (COP )=[ T e

T c−T e

×T g−T a

T g] ¿ [ 373

303−273×

373−273373 ]

¿2.4397

43

W input=Capacity ×210 kJ /min

COPkJ /min

¿ 1× 2102.4397

kJ /min

¿86.0769 kJ /min

¿1.4346 kW

Mass of Refrigerant Flowing= Hgc−HfcCapacity ×210

kg /min

¿ 1468.87−323.081 ×210

kg /min

¿5.4561 kg /min

¿0.0909 kg /sec

Volumeof Refrigerant Flowing= Mass Flow RateDensity

¿ 5.4561640.10

m3/min

¿0.0085 m3/min

¿0.0001 m3/sec

Power Required ¿Drive Suction Pump=Volume flow Rate ( m3

sec )× ( Pg−Pa ) ×105

ηpump

¿0.0001× (11.66896−4.29586 )× 105

0.85W

¿260.1531 W

44

Amount of Heat Required∈Generator=(W ¿×1000−Ppump) Watts

¿ (1.4346 ×1000−260.1531 ) W

¿1174.4623W

¿1174.4623×60

1000kJ /min

Amount ofHeat Rejectedby Refrigerant=Mass of Refrigerant Flowing∈Cycle × Sp . Heat of Refrigerant ×(Temp .Condenser−Temp . Absorbe r)

¿5.4561 ×4.635 × (30−0 )kJ /min

¿758.6767 kJ /min

¿12.6446 kJ /sec

45

Volume & Mass Database for Refrigerant (Excluding Water in Absorber & Generator)

 Pressure

(bar)

Temperature

(oC)

Temperature

(K)

Mass Flow Rate

(kg/min)

Mass Flow Rate

(kg/sec)

Mass Flow Rate

(gm/sec)

Absorber 4.29586 0 273 5.4561 0.0909 90.9357

Generator 11.66896 100 373 5.4561 0.0909 90.9357

Condenser 11.66896 30 303 5.4561 0.0909 90.9357

Evaporato

r4.29586 0 273 5.4561 0.0909 90.9357

 

 

 Temperature

(oC)

Density

(kg/m3)

Density

(gm/cm3)Volume (m3/min) Volume (m3/sec) Volume (cm3/sec)

Absorber 0 640.1000 0.6401 0.0085 0.1421 142.0649

Generator 100 594.5303 0.5945 0.0092 0.1530 152.9539

Condenser 30 594.5303 0.5945 0.0092 0.1530 152.9539

Evaporato

r0 640.1000 0.6401 0.0085 0.1421 142.0649

Table 5.3: Volume & Mass Data Sheet

46

Solubility Matrix of Ammonia & Water

Temperature Mass (gm) Solubility Factor (SF)

(oC) (K) Gas Water Gas/Water (SFgw) Water/Gas (SFwg)

0 273 900 1000 0.9000 1.1111

10 283 700 1000 0.7000 1.4286

20 293 525 1000 0.5250 1.9048

30 303 410 1000 0.4100 2.4390

40 313 315 1000 0.3150 3.1746

50 323 215 1000 0.2150 4.6512

60 333 175 1000 0.1750 5.7143

Mass of Water Required in Absorber as a Solvent= 101.0397 gm/sec Water

Gross Mass of Refrigerant Flowing Between Absorber & Generator= 191.9754 gm/sec

Gross Mass of Refrigerant Flowing Between Absorber & Generator= 11.5185 kg/min

Gross Mass of Refrigerant Flowing Between Absorber & Generator= 0.1920 kg/sec

Table 5.4: Solubility Matrix of Ammonia & Water

47

Volume & Mass Database for Refrigerant (Including Water in Absorber & Generator)

 Pressure

(bar)

Temperature

(oC)

Temperature

(K)

Mass Flow Rate

(kg/min)

Mass Flow Rate

(kg/sec)

Mass Flow Rate

(gm/sec)

Absorber 4.29586 0 273 11.5185 0.1920 191.9754

Generator 11.66896 0 273 11.5185 0.1920 191.9754

 Temperature

(oC)

Density

(kg/m3)

Density

(gm/cm3)Volume (m3/min) Volume (m3/sec) Volume (cm3/sec)

Absorber 0 640.1000 0.6401 0.0180 0.0003 299.9147

Generato

r100 594.5303 0.5945 0.0194 0.0003 322.9026

Table 5.5: Volume & Mass Database for Refrigerant (including water)

Calculation of Diameter of Tubes

 Length of Tube (L) Volume Flow Rate Radius of Tube Diameter of Tube

(m) (cm) (m3/sec) (cm3/sec) (m) (cm) (m) (cm) (mm)

Absorber 0.80 80.00 0.0003 299.9147 0.01 1.09 0.02 2.18 21.84

Generator 0.80 80.00 0.0003 322.9026 0.01 1.13 0.02 2.27 22.67

Condenser 8.00 800.00 0.1530 152.9539 0.08 0.25 0.16 0.49 4.93

Evaporator 10.00 1000.00 0.1421 142.0649 0.07 0.21 0.13 0.43 4.25

48

Table 5.6: Calculation of Diameter of Tubes

49

5.2 BILL OF MATERIALS

S. No.Material Particulars as per Cycle Quantity

Price (in 

INR)

1 GI Pipe (2") Absorber 80cm 100

2 Sockets (2") Sealing Purpose 4 160

3 End Nuts (2") Sealing Purpose 4 40

4 Centrifugal Pump (1/2 HP) Pump 1 1100

5 GI Pipe (2") Generator 80cm 100

6 Stop Valve (1/2") Flow Control Valve 1 150

7 PVC Pipe (1/2") Connecting Hose 1 60

8 Nipple Pipes Connecting Hose 2 20

9 Pipe Bends Connecting Hose 2 40

10 Copper Pipe (1/4") Connecting Hose + Evaporator 18 ft 450

11 Copper Pipe (1/2") Connecting Hose 10 ft 70

12 Drier (1/2 by 1/2) Drier 1 200

13 Condenser (Car A/c) Condenser 1 1200

14 Receiver Valve Receiver Valve 1 700

15 Expansion Valve Expansion Valve 1 20

16 Insulation Foam Insulation Purpose 1 30

17 1/4" to 1/4" Connector Connections on Generator &

Absorber

2 40

18 1/4" to 1/2" Connector Connections on Generator &

Absorber

4 160

19 1/2" Nut Connections on Generator &

Absorber

6 150

20 1/4" Nut Connections on Generator &

Absorber

2 20

21 3/8" Pipe Connecting Hose 1 ft 45

22 3/8" Nut Connection Purpose 2 70

50

23 Threading/Drilling on

Generator & Absorber

Connections on Generator &

Absorber

- 150

24 Ply board (3'X3') Base for Equipment 1 360

25 Glass Tape (40m) Electrical Insulation Purpose 1 90

26 Heating Element (1000W) Heating Coil 1 10

27 Heating Element (500W) Heating Coil 1 10

Gross Total= 5545

Table 5.7: Bill of Materials

51

Chapter-6

Conclusion & References

o Conclusion

o Further Improvement Possible

o References

52

6.1 CONCLUSION

As per our analysis and references, we have found that, it is possible to design an

automobile air conditioning system using engine heat based on Vapour Absorption

Refrigeration System.

Also from the Environmental point of view this system is Eco-friendly as it involves the

use of Ammonia as a refrigerant which is a natural gas and is not responsible for OZONE

layer Depletion. Furthermore, it also saves the power of engine as it replaces the

compressor by the four components i.e. Absorber, Pump, Generator & Pressure Reducing

Valve out of which only the pump consumes some power that too is very feeble as

compared to that of the Compressor, and thus helps in saving of fuel.

Also this system can be employed to commercial heavy vehicles including those which

are involved in the transportation of refrigerated products, as this system can easily

provide the refrigeration/air-conditioning of cabin as per the requirements by using the

exhaust heat of the vehicle’s engine (which is in abundance in such vehicles) thus will

not add any additional engine to run the air-conditioning/refrigerating unit in vehicle and

hence reduces the operational cost.

All in all, it can be a very well and economical asset for the automobile and can

completely change the scenario of Automobile Air-Conditioning System.

53

6.2 FURTHER IMPROVEMENT POSSIBLE

As the major limitation of the system is the use of ammonia which is a life causing gas if

inhaled in large amounts, so to overcome this problem it can be suggested to couple this

system electronically by the use of various ammonia detecting sensors, which when

detect any leakage (which is hardly possible) will bring down the closed windows of the

vehicle so the possibility of any damage will be eliminated, and will enable the driver to

get aware of any problem and will release the leaked gas in to the atmosphere and thus

the impeding danger will be eliminated.

54

6.3 REFRENCES

[1] Alam Shah (2006), A Proposed Model for Utilizing Exhaust Heat to run Automobile

Air-conditioner, The 2nd Joint International Conference on “Sustainable Energy and

Environment (SEE 2006)” 21-23 Nov; 2006, Bangkok, Thailand.

[2] G Vicatos, J Gryzagoridis, S Wang, Department of Mechanical Engineering,

University of Cape Town, A car air-conditioning system based on an absorption

refrigeration cycle using energy from exhaust gas of an internal combustion engine.

“Journal of Energy in Southern Africa (Vol 19 No 4), November 2008”

[3] M. Hosoz , M. Direk, Department of Mechanical Education, Kocaeli University,

Umuttepe, 41100 Kocaeli, Turkey, Performance evaluation of an integrated

automotive air conditioning and heat pump system “Received 5 November 2004;

accepted 18 May 2005 Available online 14 July 2005.” Energy Conversion and

Management 47 (2006) 545–559

[4] Khurmi R S, Gupta J K, Refrigeration and Air Conditioning- 2010, Vapour

Absorption Refrigeration (Pg 238-249).

[5] Ganeshan V, Internal Combustion Engine- 2010, Heat Rejection & Cooling (Pg 445-

467)

[6] Domkundwar & Domkundwar, Refrigeration & Air-Conditioning Data book

55