experiment no. : 1 - rajiv gandhi college of engineering...

RCERT / Mech. / Model Journal-EC-II 1

EXPERIMENT NO. : 1

TITLE : Vapour Absorption System

AIM : To deal with Vapour Absoption System

THEORY : Refrigeration :

It may be defined as artificial withdrawal of heat producing in a substance or within a

space a temperature lower than that which exists under the natural influence of

surroundings. According to ASHRAE, it is defined as science of providing and

maintaining temperatures below that of surroundings.

Non- cyclic processes :

The use of evaporative cooling using porous pots or bags is an application of

refrigeration in olden days. When certain salts such as sodium chloride ,calcium

chloride salt petre etc are dissolved in water they absorb heat. This property has been

used to produce refrigeration.

If a substance such as ice is used to cool certain space, heat will flow from ice to space.

The space will be cooled. However ice will melt and cannot be used again. Thus

process would become non cyclic.

Cyclic processes :

The various cyclic processes used are

1. Air refrigeration system

2. Simple Vapour compression refrigeration system

3. Vapour absorption refrigeration system


Applications of refrigeration :

The various Applications of refrigeration are

1. Preservation of food

2. Food processing and candy manufacturing

3. Bakery product storage

4. In chemical and process industries

5. Petroleum refineries

6. Paper & pulp industries

7. Precision parts & clean room

8. Cold storage

9. De-salting of sea water

10. Tempering &hardening of metals

11. Environmental laboratories

12. Ice ceam manufacturing & beverage storage

Unit of refrigeration :

In refrigeration industry the unit used is ton i.e tonnage of refrigeration (TR).One TR is

defined as refrigeration effect produced by melting one American ton of ice from and at

0 0 C in 24 hours.

1 TR =1000x336/24 =210KJ/min =3.5 KW

Coefficient of performance:

It is defined as the ratio of magnitude of desired commodity to the magnitude of

expenditure. The Coefficient of performance of a refrigerator is ratio of heat extracted in

the refrigerator to the work done on the refrigerant.

COP =Useful refrigeration/Net work

This is also known as theoretical COP.

Relative COP= actual COP/ theoretical COP.


Vapour Absorption Refrigeration System :

There is peculiar property of some substances to have more affinity for another

substance at some temperature and pressure conditions. This is the idea generated for

working of vapour absorption refrigeration system.

In a vapour absorption refrigeration system,the compressor is replaced by an absorber

,pump, generator &pressure reducing valve. These components in vapour absorption

refrigeration system perform same function as that of compressor in vapour

compression refrigeration system.

Aqua Ammonia Absorption System :

In this system, the low pressure ammonia vapour laving the evaporator enters the

absorber where it is absorbed by the cold water in absorber .The water has ability to

absorb very large quantities of ammonia vapours. The absorption of ammonia vapour

inwater lowers pressure in absorber which in turn draws more ammonia vapours from

the evaporator &thus raise temperature of solution. Some form of cooling

arrangement(usually cooling water) is employed in the absorber to remove the heat of

solution evolved there.This is necessary to increase absorption capacity of water. The

pump increases the pressure of solution upto 10 bar.

The strong solution of ammonia in the generator is heated by some external source

such as gas or steam. during the heating process the ammonia vapour is driven off the

solution at high pressure leaving behind the hot weak ammonia solution. This weak

ammonia Solution flows back to the absorber at low pressure after passing through the

pressure reducing valve. The high pressure ammonia vapour from the generator is

condensed in the condenser to a high pressure liquid ammonia.this liquid ammonia is

passed to the expansion valve through the receiver & then to evaporator.

In order to make the system more practical it is fitted withan analyzer ,a rectifier& two

heat exchangers.

COP = Heat absorbed in evaporator/(Work done by pump+heat supplied in generator)


Lithium Bromide Absorption Refrigeration System : The weak solution of water –lithium bromide is pumped into the generator .Heat transfer

to the generator causes separation of water vapour Thereby pure vapour flows into the

condenser while the strong solution of lithium bromide returns into absorber. Water

from condenser is throttled to evaporator pressure. The vapourisation of water at low

pressure causes cooling i.e refrigeration effect. The vapour from evaporator is

reabsorbed, completing the cycle. It works under high pressure i.e 6.35 mm of Hg. At

this pressure the boiling point of water is 4.40 C.

Advantages of vapour absorption refrigeration system :

1. The only moving part of the entire system is a pump which has a small motor. Thus

the operation of the system is quiet and is subjected to little wear.

2. The vapour absorption system uses heat energy to change the condition of

refrigerant from the evaporator.

3. The load variations does not affect the performance of vapour absorption

refrigeration system.

4. The vapour absorption refrigeration system can be built in any capacity well above

1000 TR .

5. The space requirements &automatic control favour the absorption system more as

the designed evaporator pressure drops.

6. In the vapour absorption refrigeration system, the liquid refrigerant leaving the

evaporator has no bad effect on system except that of reducing th refrigerating

effect.

Dis–advantages of vapour absorption refrigeration system :

1. COP of the system is less.

2. It takes more time to produce refrigerating effect.

3. Charging of the refrigerant is difficult


EXPERIMENT NO. : 2

TITLE : Study & demonstration on household refrigerator.

AIM : 1. To list out various parts

2. To observe the working of household refrigerator

3. To note down the technical data

PRINCIPLE OF OPERATION: A household refrigerator works on vapour compression refrigeration cycle

Various parts of refrigerator : The various parts of a refrigerator are listed below:

1. Freezer

2. Condenser

3. Compressor

4. Refrigerant

5. Capillary tube

6. Chill tray

7. Trays

8. Crisper

9. Magnetic doors

10. General compartment

Freezer (evaporator) is held at - 180 C & is used for frozen food. The general

compartment is held at 00 C to 40 C for fresh food. Frozen food includes fish, meat,

chicken .Freezer is provided at the top position and occupies 1/10th to 1/3rd of

refrigerator volume. Refrigerator may be single door ,double door or multidoor. Magnetic

doors are most common.


Description :

Evaporator coil is wrapped around the freezer. The cooling of lower space is

accomplished by free convection. A tray is provided below freezer is known as chill tray

to collect .the space below freezer is divided by trays to accommodate various food

items. Cold drinks, butter, eggs are kept in refrigerator doors having proper packets &

partition .fruits & vegetables are kept in crisper. Items like milk, dough etc are kept on

trays in general compartment.

WORKING :

The working of household refrigerator depends on following five essential parts.

1. Compressor : It uses a hermetically sealed compressor .The low pressure and

temperature vapour refrigerant from evaporator is drawn into compressor through the

inlet or suction valve where it is compressed to high pressure & temperature &

discharged through discharge valve.

2. Condenser : The condenser consists of coils of pipes given on back side of

refrigerator in which the high pressure and temperature refrigerant is cooled by natural

convection.

3. Receiver : The condensed liquid refrigerant from the condenser is stored in a

vessel known as receiver from where it is supplied to evaporator through expansion

valve. Receiver is an optional part of a refrigerator.

4. Expansion valve: The expansion valve used in a household refrigerator is a

capillary tube. It is used to decrease the pressure of liquid refrigerant through throttling.

5. Evaporator : An evaporator consists of pipes o coils of pipe in which the liquid

refrigerant of low pressure & temperature is evaporated by taking the heat fom the

inside of refrigerator. Usually evaporator coil is wrapped around the freezer.


Defrosting :

One of the simplest methods of defreezing is by manually putting OFF the refrigerator

&restarting only after complete defrosting of the evaporator. Nowadays .the refrigerator

are provided with push button defrost thermostats. A push button is provided in the

center of thermostat knob which puts OFF the refrigerator & returns to normal

functioning automatically, once the defrosting is complete.

Refrigerator also consists of starting relay, overload protector & a thermostat for

controlling various functions. The controls are very essential for satisfactory &

economical working of any refrigeration. Thermostat is used for changing internal

temperature of refrigerator depending upon the needs of the operator.

TECHNICAL DATA : Compressor : 1/8th to 1/6th HP

Capillary diameter : 0.8mm

Power consumption : 3-4 KW/hr,286 litre capacity

2-3 KW/hr,165 litre capacity

Minimum evaporator temperature : -17+2 0C

Suction pressure : 0.7 to 0.85 bar

Discharge pressure : 12 to 13 bar

Refrigerant used : freon –12

CONCLUSION : 1. Different parts of the household refrigerator were observed critically.

2. The dimensions of household refrigerator were i.e h x w x d

3. It was working

4. The capacity of refrigerator was

5. The model name & nomenclature was


EXPERIMENT NO. - 3

TITLE : Solar dryer.

AIM : Study & demonstration on solar applications.

APPARATUS: Solar dryer, Anemometer, Stop watch, Psychrometer, Temperature

indictor, Pyranometer.

EXPERIMENTAL SET UP : The experimental set up consists of flat plate collector & a drying chamber as shown in

figure. The flat plate collector is a rectangular box of aluminium covered with a glass

frame. Inside the frame, there are two plates arranged along the glass frame known as

Absorber. These plates coated with black point which absorb light radiation incident on

it. Air absorber enters the collected space through holes between the absorber plates.

As air enters the collector it absorbs heat from the plates & gets heated & flows to the

drying chamber due to low density & rises up.

There are trays arranged one over the other in the chamber. The air flows over these

grates ( having good kept over it) & heats it. The air then moves out.

PROCEDURE : 1. Measure solar radiation by pyranometer.

2. Measure wind velocity by Anemometer.

3. Measure dry bulb temperature & wet bulb temperature by

psychrometer.

4. Note various temperatures.

5. Measure humidity (relative) at inlet and exit.


OBSERVATION TABLE :

Different parameters

Ambient temp. T1

Wind velocity

Relative humidity in (φ1 )

Relative humidity out ((φ2 )

Glass temp. (T2)

Observer temp.

(T3)

(T4)

(T5)

(T6)

Air space inlet temp. (T7)

Air space exit temp. (T8)

Insulation temp. (T9)

Drying chamber air temp. (T10)

1st tray temp. (T11)

Air space temp. (T12)

2nd tray temp. (T13)

Air space temp. (T14)

3rd tray temp. (T15)

Air space temp.(T16)

Exit (T17)

Tdb

Twb


CALCULATIONS : 1. Solar declination

δ= 23.45 sin [ 360( n+284)/365]

2. Equation of time

EOT = - [ 9.87 sin 2B –7.53 cosB – 1.5 sin B]

Where B = 360(n- 81)/364

EOT =

3. Standard time

ST = IST –EOT –4 (ϕ std -ϕloc)

Where

IST = hours x60 =

4. Hour angle

ω=15(12 –ST)=

5. cosθ =cosδcosω=cos (-18.79) cos17.25 =

6. cosθz =sinφ sinδ +cosφ cosδ cosω

7. Ibn = A e{-B/cosθz} =

8. Ib = Ibn cosθz=

9. Id =CxIbn =

10. Ig= Ib +Id=

11. rb= cosθ/ cosθz=

12. rd =(1+cosβ)/2 =


13. rr =ρ( 1-cosβ)/2 =

14. It = Ib rb +Id rd+ Ig rr

15. It loc=0.972 It =

16. Velocity of air =(final reading –initial reading)/time

17. Mass flow rate of air =ρAC=

ρ=p/RT=

A=

18. Useful heat gain

Qu=m Cp (Tfo- Tfi)=

19. Efficiency of solar dryer = Qu/ItxArea of solar air heater=

CONCLUSION : 1. Sensible heat of air is used to evaporate the moisture from agricultural products.

2. Efficiency of the dryer is 74.00 %.

3. Dryer is used for number of agricultural products.


EXPERIMENT NO. - 4

TITLE : Energy Conservation.

AIM : Study of Energy conservation opportunities preferably in industries.

THEORY : What is Energy? - Capacity for vigorous activity.

- An exertion of power.

- Capacity of matter to do physical work.

- Capacity converted into heat.

- Sources of energy – Solar, Wind, Wave, Geothermal.

What is Energy Conservation? Wise and efficient use of energy in order to ensure that for a given amount of energy

maximum activity, productive work & profitability is achieved.

Why? - Due to energy gap.

Resources will deplete & hence energy conservation is necessary.

Alternatives : 1. More power through hydel.

2. Nuclear.

3. Renewable.

4. Comercing energy – Cheapest

- Environmentally clean alternative.


INDUSTRY CONSUMPTION

Cement 11.14 %

Paper 2.96 %

Aluminium 4.78 %

Steel 34.49 %

Fertilizer 5.87 %

Petrochemical 7.86 %

The industrial sector is the largest energy consuming sector & also most extensive in

terms of energy conservation potential.

1. Lighting : Lumens/Watt Consumed.

5 % of electricity consumption.

- Storage & non working areas; Reduce illumination.

- Intermittent lighting load : Install timers.

- Roads / open areas : Install photo cell controlled switches.

- High ceiling buildings : Height of light fixtures should be less.

- High intensity of light work spots : Resort to spot lighting.

- North roof structures : Clean glasses.

- Mounting heights – 3 m → Tube lights

- 3 – 4 m → Mercury vapour / Sodium vapour lamp

- 5 m & above → High bay fitting.

- Control of luminance by dimmers.

- Use of electronic ballasts.

- Compact fluorescent lamps ( CFL )

9 W → 40 W incandescent lamp




2. Power :

Electric Motor : 75 % of electricity.

Selection of motor properly matched with load survey indicates more than 50 % of

motors work out at loads less than 50%.

Preparation of replacement programme.

- Minimising idle running, maintenance, rewinding.

- M⁄C tools are not stopped in recess.

- Conveyors continue to run without load.

- Auxiliaries: exhaust fan, cooling tower fans/ pump continue to work even

when process M/C have stopped.

- Regular m/c ; cleaning → good ventilation.

- Rewinding : smaller wire size : efficiency decreases.

Increased wire size : efficiency increases

3. Efficiency of driven equipment : Better design of fans

Trimming of impellers

Proper size of distribution lines

4. High efficiency motors More copper / aluminium in starter & rotor to reduce copper loss

Improved quality of stampings to reduce iron losses

Improved design of fans & ventilation circuit

Improved electromagnetic design & manufacturing methods to reduce stray losses

Furnaces

Heat balance

Energy input

Useful energy

Radiation losses

Losses through insulation

Thermal inertia

Burners : clean


Flame : avoid direct impingement of flame on charge /refractory lining

Pressure lines : Provide pressure gauges

Skin temperature of furnace : Not more than 60 0 C

Capacity : full

Air level : excess

Recuperators : Air preheating

Temperature measurement : Pyrometers

Opening of furnace lids,doors : Minimised

Boilers :10 to 20 % savings possible

Scale formation : Clean

Stack temperature : !50 - 200 0 C: adjust burner

Excess Air : check :20 to 25 %

Oil : Preheat oil -100 0 C –burner

Leakage of steam: check

Steam traps : check for leaks

Waste heat : Recuperators : preheat air

Insulation of steam pipe lines

Proper sizing of steam & condensate lines

Boiler load fluctuation : avoid through proper regulated use of steam

Compressed Air KWH/m 3

Leakage in air lines ,fittings &pneumatic tools - eliminate

Filters : Clean /replace regularly

Air intake location : cool air is taken in

Speed regulators : Vary compressor rpm to meet demand

Portable small compressor : Use occasional /limited

Switches : Pressure switches to switch off to prevent non –essential high pressure build

ups

Load : match compressor to load

Reduce compressed air use : only 5% of input electric energy –useful energy

Water

Leakages : detect & stop

Overflow : Stop by providing float valves

Recycle treated water


CONCLUSION : Energy saved through conservation measures is energy produced

Substantial quantity of energy can be saved through conservation measures without

sacrificing production. It is high time that old energy intensive manufacturing units

should adopt measures to save energy by revamping & retrofitting the energy

consuming equipments in their units. Energy conserved will therefore bring down cost of

production.


EXPERIMENT NO.- 5

TITLE : Experiment on Desert Cooler

AIM : 1. To determine cooling efficiency of desert cooler

2. To plot process on psychrometric chart

APPARATUS & EQUIPMENTS : Sling psychrometer, Thermometer, Anemometer, Stop watch, Desert cooler test rig

THEORY : There are coolers of two types

A. Fan in vertical plane

B . Fan in horizontal plane

SET UP : The components are

1. Fan

2. Pump

3. Switches

4. Pads

5. Divertor

6. Electronic regulator

7. Connecting cable & supply cable

8. Junction box

9. PVC pipes

WORKING :

The pump pumps the water from bottom tank to top & water trickles through holes

provided on top tank & falls passing through the pads to the bottom tank.The air is

sucked by fan from all three sides & gets cooled passing through pads .The cool air is

discharged by fan in the vertical plane.The direction of air is controlled with the help of

louvers.


OBSERVATION TABLE :

Sr. No.

Details 1 2 3 4 5

Outside

1. Dry bulb Temp

(°C)

2. Relative

Humidity %

(Digital meter )

3. Wet bulb temp.

(°C)

4. Inlet tank water

temp.

5. Final tank

water temp.

Inside

1. Dry bulb temp.

(°C)

2. Relative

humidity %

3. Wet bulb temp

(°C)

4. Air velocity of

grill 30 sec.

CALCULATION : DBTout - DBTin

Cooling η = ------------------------

DBTout - WBTout

CONCLUSION :

1. The test on desert cooler was performed

2. The cooling efficiency comes out to be 32.04%

3. Psychrometric chart is drawn using DBT &RH of inside & outside


EXPERIMENT NO. - 6

TITLE : Pneumatics

AIM : Study & demonstration of pneumatics.

Basic Pneumatic Circuit : Air is used as working fluid. The operation is simple but noisy. Air compressor is

necessary as compressed air is used to perform the work. It dose not require any return

line as air is abundantly available, so it is thrown out at the end of circuit without being

circulated. Because of compressibility of air & its friction the dynamic response is slow.

There is no possibility of shocks & water hammer. Sometime air contains moisture so it

can not be used in sever temperature variations. In extreme cold conditions, the

condensation in the line would freeze and make the system inoperative. It is safe in the

volatile atmosphere as there are no fire hazards. It can provide very high speed of

operation at low costs.

Basic Pneumatic Circuit for Single Cylinder : Figure 2 (a) & 2 (b) shows a simple pneumatic circuit diagram of a single acting cylinder

being controlled by a 3 way 2 position direction control valve.

As shown in figure, the single acting cylinder with its in-built spring is in its retracted

position & the 3/2 D.C. valve is exhausting the used compressed air from the cylinder.

No air moves to the cylinder as the P port of the DC valve is blocked at this position, the

valve position being determined here by the valve spring. But if the push button of the

D.C. valve is manually pressed (i.e., actuated) as shown in figure 2 (b), the valving

element gets shifted against the valve spring, opening thereby the P port to the A port of

the valve, shifting the valving element and thus the single acting cylinder is fed with the

compressed air. The cylinder advances, compressing its spring in the process. But the

actuating force from the push button is released, the valve spring resets the valving

element and air stops moving to the cylinder as the port P gets blocked to port A as


shown in figure due to resetting of the valving element. The port A thus opens to port R.

Therefore all the air from the cylinder gets exhausted through the R port of the valve &

the compressive force of the spring pushes the piston rod of the cylinder & the cylinder

is back to its retracted, or original position. This is so far the as the single acting cylinder

is considered.

3/2 Spool Type valve :- It consists of an inbuilt air reservoir, an inbuilt non-return flow control valve and a pilot

controlled spring return 3-way 2-position direction control valve. The valve is used in

pneumatics system to initiate a delayed signal.

When the compressed air is supplied to the port P of the valve, it is prevented from

flowing to port A from port P, as this is blocked by the spring actuated spool. Air is

accumulated in an inbuilt reservoir of the valve from the pilot control port Z, the control

passage of the same being controlled by the needle of the inbuilt throttle valve.

Pressure starts building up here. When the pressure needed to push the spool is built

up in reservoir, the pilot spool of the 3/2 direction control valve shifts, thus opening port

P of the main valve to A & closing R. With further increase of pressure, the built check

valve open, the air from the reservoir gets exhausted and the valve spool returns to the

original position.

Shuttle Valve : Figure shows a shuttle valve which consists of a valve body and a synthetic ball or a

cuboid valving element moving inside the bore in the valve housing.

There are three openings P1, P2, & A. If an air signal is fed to port P1, the ball moves,

closing port P2 and air passes to A. If the air is fed to port P2, port P1 is closed and air

moves to A. If the air is fed simultaneously to port P1 & P2, then air moves to A either

from P1 or P2 or from both. This element is also called as OR GATE.

CONCLUSION : The study of basic pneumatic circuit, single acting cylinder, 3/2 spool valve & shuttle

valve is performed successfully.


EXPERIMENT NO. – 7

TITLE : Air preparatory unit.

AIM : To study air preparatory unit.

THEORY : The air preparatory unit is also called FRL unit.

The three main elements of the unit are:

1. Air Filter.

2. Pressure Regulator &

3. Lubricator.

AIR FILTER :

Air filters are used.

1. To prevent entrance of solid contamination to the system

2. To condense & remove water vapour present in air.

3. To arrest any submicron particles that may pase problem in system component.

WORKING OF AIR FILTER: The air following in panes the filter cartridge through a zig-zag passage due to deflector

the major part of the bigger foreign (solid) particles gets separated from the air & collect

at the bottom of the bowl. The remaining finer foreign particles move along with the air &

pass through cartridge where these are arrested. The size of solid particles arrested will

depend on the pore size provided in filter media. The water vapour gets condensed

inside the filter & collect at the bottom of the plastic bowl. The on-off drain valve is

provided at the bottom of the plastic bowl. It is manually opened to drain of the plastic

bowl. It is manually opened to drain off the accumulated water & other solid particles.


PRESSURE REGULATOR : The main function of pressure regulator is to regulate incoming pressure so that desired

air pressure is capable of flowing at a steady state. The valve of pressure regulator has

metallic body & has two openings, one is primary & other secondary. Pressure regulator

is achieved by opening poppet valve and creating opening to allow air to move from

primary to secondary side.

Opening of valve is pressure of air flowing through is directly proportional to

compression of spring. Higher compression, opening increases, pressure increases of

spring.

LUBRICATOR : Lubricator is a form of equipment which forms mist of oil and air. All lubricators follow

the principle of venturimeter. The compressed air passes through narrow construction

inside lubricator. Air flows inside plastic bowl containing oil & also inside small siphon

tube. Slowly a pressure difference sets in between air siphon & bowl. Oil is naturally

pressed upwards & passes at top of sight and feed dome through oil controlling valve.

The oil drops are made to fall at main constricted passage where air will have high

velocity & thereby oil drops are broken to form a mist of air & oil flows out of the system.

CONCLUSION : Air preparatory unit was studied thoroughly.


EXPERIMENT NO.- 8 TITLE : Visit to ice plant

AIM : To go through various equipments &processes of an ice plant

Name of factory : “ Fakri Ice Plant”

Owner : Mr. Fakhruddin

Finished product : Icecubes or slabs of weight 50 kg to150 kg

Equipments installed : compressor ,condenser, agitator, Accumulator, ice

cans

Raw materials : Water,oil,ammonia gas ,salt

Production per day : 15 tons

Dimension ice manufactured :

Time taken for ice formation : 72 hours

Minimum temperature of : -16 0 Cto –32 0C

ammonia required

MANUFACTURING PROCESS :

An ice plant consists of an ice box having insulation to prevent heat transfer from surroundings

into system. The insulation is of glass wool or fibre.

Water level in the can should be around 20 to 30mm below the brine level. A suitable clearance

should be provided between the top of ice can & the cover of ice box. The tank is provided with

piping for air blowing into ice cans to create agitation. The drain pipe for brine is provided at the

bottom to remove brine.

Heat transfer between water & brine is by either free convection or combined free & forced

convection .Latter is caused by a suitable number of agitators. In medium size ice tank two

agitators are mounted diagonally to create churning equivalent to about 8 to 10 m/min of brine

speed.

REFRIGERATION SYSTEM:

Cooling in the tank is achieved by brine circulation. The brine solution is usually prepared from

commercial calcium chloride having appropriate concentration. It consists of a refrigeration

system usually having ammonia compressor .The compressed refrigerant vapour is cooled in

the water cooled condenser before throttling. The condensate is throttled to evaporator

pressure where brine from the ice tank is cooled. The cold brine circulates around cans causing

ice formation .Usual brine temperature for ice formation is –160C to -300C.

experiment no. : 1 - rajiv gandhi college of engineering...

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