ABSTRACT

This work investigates the result of an experimental study carried out to

determine the performance of domestic refrigerator when a propane-butane mixture is

liquefied petroleum gas (LPG) which is locally available and comprises 24.4%

propane, 56.4% butane and 17.2% isobutene which is very from company to company.

The LPG is cheaper and possesses an environmental friendly nature with no ozone

depletion potential (ODP). It is used in world for cooking purposes. The various

methods of refrigeration on the basis of standard refrigerant discussed. He refrigerator

used in the present study is of medium size with a gross capacity of 125 litre and is

designed to work on LPG. The performance parameters investigated is the

refrigeration effect in certain time. The refrigerator worked efficiently when LPG was

used as refrigerant instead of CFC 12. The evaporator temperature reached -5 ºC with

and an ambient temperature of 12 ºC. Also from the experiment which done in

atmospheric condition, we can predict the optimum value of cooling effect with the

suitable operating condition of regulating valve and capillary tube of the system. The

results of the present work indicate the successful use of this propane-butane mixture

as an alternative refrigerant to CFC 12 in domestic refrigerant.

1

CHAPTER 1:- REFRIGERATION

1.1 INTRODUCTION

The term ‘refrigeration’ in a broad sense is used for the process of removing heat

(i.e. cooling) from a substance. It also includes the process of reducing and

maintaining the temperature of a body below the general temperature of its

surroundings. In other words, the refrigeration means a continued extraction of heat

from a body, whose temperature is already below the temperature of its surroundings.

For example, if some space (say in cold storage) is to be kept at -2 ºC, we

must continuously extract heat which flows into it due to leakage through the walls

and also the heat, which is brought into it with the articles stored after the temperature

is one reduced to -2 ºC. Thus in a refrigerator, heat is virtually being pumped from a

lower temperature to a higher temperature. According to second law of

thermodynamics, this process can only be performed with the aid of some external

work. It is thus obvious, that supply of power (say electrical motor) is regularly

required to drive a refrigerator. Theoretically, the refrigerator is a reversed heat

engine, or a heat pump which pumps heat from cold body and delivers to a hot body.

The substance which works in a heat pump to extract heat from a cold body and to

deliver it to a hot body is called refrigerant.

When people hear the word refrigeration they immediately think of the

refrigerator in their kitchen. However there are actually quite a few different kinds of

refrigeration out three and they each have their own methods of functioning. One

particular type of refrigeration is industrial refrigeration. This type of refrigeration is

typically used for cold storage, food processing, and chemical processing.

The equipment is very large and made of industrial stainless steel. Industrial

refrigeration, which frequently uses ammonia refrigeration to maintain temperature, is

2

necessary for computer, foodstuffs, blood, vaccines, and quite a few other goods that

must maintain a constant and steady temperature at all times. Temperatures that are

too high or too low may spoil certain goods or ruin them. As a result industrial

refrigeration is especially important maintaining temperature is as well. Since

temperature is so important into industrial refrigeration companies offering this

service must pay attention at all times to the temperature of the industrial refrigerators.

1.2 HISTORY OF REFRIGERATION

The refrigeration system is known to the man, since the middle nineteenth

century. The scientist, of the time, developed a few stray machines to achieve some

pleasure. But it paved the way by inviting the attention of scientist for proper studies

and research. They were able to build a reasonably reliable machine by the end of

nineteenth century for the refrigeration jobs. But with the advent of efficient rotary

compressors and gas turbines, the science of refrigeration reached its present height.

Hebrews, Greeks, and Romans placed large amounts of snow into storage pits

dug into the ground and insulated with wood and straw. The ancient Egyptians filled

earthen jars with boiled water and put them their roofs, thus exposing the jars to the

night’s cool air. In India, evaporating cooling was employed. When a liquid vaporises

rapidly, it expands quickly. The rising molecules of vapour abruptly increase heir

kinetic energy and this increase is drawn from the immediate surroundings of the

vapour. These surroundings are therefore cooled.

The intermediate stage in the history of cooling foods was to add chemicals like

sodium nitrate or potassium nitrate to water causing the temperature to fall. Cooling

wine via above method was recorded in 1550, as were the words “to refrigerate”.

3

Cooling drinks came into vogue by 1600 in France. Instead of cooling water at

night, people rotate long-necked bottles in water in which saltpetre had been dissolved.

This solution could be used to produce very low temperature and to make ice. By the

end of the 17th century, iced liquors and frozen juices were popular in French society.

The first known artificial refrigeration was demonstrated by William Cullen at

the University of Glasow in 1748.

Beginning in the 1840, refrigerated cars were used to transport milk and butter.

By 1860, refrigerated transport was limited to mostly seafood and dairy products. The

refrigerated railroad car was patented by J.B.Sutherland of Detroit, Michigan in 1867.

He designed an insulated car with ice bunkers in each end. Air came in on the top,

passed through the bunkers, and circulated through the car by gravity, controlled by

the use of hanging flaps that created differences in air temperature.

Brewing was the first activity in the northern states to use mechanical

refrigeration extensively, beginning with an absorption machine used by S.

Liebmann’s Sons Brewing Company in Brooklyn, New York in 1870.

commercial refrigeration was primarily directed at breweries in the 1870 and 1891,

nearly every brewery was equipped with refrigerating machines.

Natural ice supply became an industry unto itself. By 1879, there were 35

commercial ice plants in America, more than 200 a decade later, and 2,000 by 1909.

No pond was safe from scraping for ice production, not even Thoreau’s Walden Pond,

where 1,000 tons of ice was extracted each day in 1847.

However, as time went on, ice, as a refrigeration agent, became health problem.

Says Bern Nagengast, co-author of Heat and Cold: Mastering the Great Indoors

(published by the American Society of Heating, Refrigeration and Air-conditioning

Engineers), “Good sources were harder and harder to find. By the 1890’s, natural ice

became a problem because of

pollution and sewage dumping.” Signs of a problem were first evident in the brewing

industry. Soon the meatpacking and dairy industries followed with their complaints.

4

Refrigeration technology provided the solution: ice, mechanically manufactured,

giving birth to mechanical refrigeration.

Carl (Paul Gottfried) von Linde in 1895 set up a large scale plant for the

production of liquid air. Six years later he developed a method for separating pure

liquid oxygen from liquid air that resulted in widespread industrial conversion to

processes utilizing oxygen (e.g. in steel manufacture).

1.3 TYPES OF REFRIGERATION

The difference types of refrigeration systems are given below.

1.3.1 Cyclic Refrigeration

In the cyclic process of refrigeration the heat is removed from the low

temperature reservoir and is thrown to high temperature. As per the second law of

thermodynamics the natural flow of heat is from the high temperature to low

temperature reservoir. In the cyclic refrigeration process since the flow of heat is

reversed, the external work has to be done on the system. The cyclic process of

refrigeration is also reverse of the thermodynamic power cycle or Carnot cycle in

which the heat flows from high temperature reservoir to low temperature reservoir;

hence the cycle of refrigeration is also called as Reversed Carnot Cycle.

There are two types of cyclic process of refrigeration:

» Vapour cycle and

» Gas cycle.

The vapour cycle is classified into

5

» Vapour compression cycle and» vapour absorption cycle.

1.3.1.1 Vapour Compression Cycle

In a vapour compression system, an evaporator and a gas-liquid separator are

received in a common casing, so that the gas-liquid separator and the evaporator are

placed close to each other. Thus, it is possible to limit heart absorption of the liquid

phase refrigerant from the atmosphere to reduce the heat loss upon discharge of the

refrigerant from the gas-liquid separator. Also, it is possible to reduce pressure loss in

refrigerant passage between the gas-liquid separator and the evaporator

1.3.1.2 Vapour Absorption Cycle

Before the development of the vapour compression system of refrigeration,

vapour absorption system was very widely used. The vapour compression system

replaced vapour absorption system because it has high coefficient performance (COP).

The vapour absorption system requires very less amount of electricity but large

amount of heat; hence it can be used very

effectively in industries where very large stocks of excessive stem are available. In

such cases there is not only effective utilization of steam, but also lots of savings in

electricity costs.

1.3.1.3 Gas Cycle

Just as the vapour are used for cooling in the vapour compression cycle and

vapour absorption cycle, the gas is used cooling in gas refrigeration cycle. When the

gas is throttled from very high pressure to lower pressure in throttling valve, its

temperature reduces suddenly while its enthalpy remains constant. This principle is in

gas refrigeration system.

6

In the system instead of using Freon or ammonia as the refrigerant, the gas is

used as the refrigerant. Throughout the cycle there are no phase changes of the gas,

which are observed in the liquid refrigerant. Air is the most commonly used gas, also

called as refrigerant in this case, in the gas refrigeration cycles.

1.3.2 Non Cyclic Refrigeration

In these methods, refrigeration can be accomplished by melting ice or by dry ice. These methods are used for small-scale refrigeration such as in laboratories and workshops, or in portable coolers.

1.3.3 Thermoelectric Refrigeration

A refrigeration effect can also be achieved without using any moving parts by

simply passing a small current through a closed circuit made up of two dissimilar

materials. This effect is called Peltier effect, and a refrigerator that works on this

principle is called a thermoelectric refrigerator.

7

Fig : 1.1 Thermoelectric refrigeration

Under steady-state operating conditions, heat will be transferred from the refrigerated

space to the cold junction. The other junction will be at a temperature above the

ambient, and heat will be transferred from the junction to the surrpundings.

1.3.4 Magnetic Refrigeration

Magnetic refrigeration is a cooling technology based on the magneto caloric

effect. This technique can be used to attain extremely low temperatures (well below

1K), as well as the ranges used in common refrigerators, depending on the design of

the system.

8

1.3.5 Other Methods

Other methods of refrigeration include the air cycle machine used in aircraft; the

vortex tube used for spot cooling, when compressed air is available; and thermo

acoustic refrigeration using sound waves in a pressurised gas to drive heat transfer and

heat exchange.

1.4 UNITS OF REFRIGERATION

Domestic and commercial refrigerators may be rated in kj/s, or Btu/h of cooling.

Commercial refrigerators in the US are in tons of refrigeration, but elsewhere in kw.

One ton of refrigeration capacity can freeze one short ton of water at 0 ºC (32 ºF) in 24

hours.

Latent heat of ice (i.e. heat of fusion) = 333.55 kj/kg

≈ 144 Btu/lb

One short ton = 2000lb

Heat extracted = (2000)*(144)/24 hr = 288000 Btu/24 hr

= 12000 Btu/hr

= 200 Btu/min

1 tonne of refrigeration = 200 Btu/min

= 3.517 kj/s

= 3.517 kw

9

The practical unit of refrigeration is expressed in terms of ‘tonne of refrigeration’

(briefly written as TR). A tonne of refrigeration is defined as the amount of

refrigeration effect produced by the uniform melting of one tonne (1000 kg) of ice

from and 0 ºC in 24 hours. Since the latent heat of ice is 335 kj/kg, therefore one

tonne of refrigeration,

1 TR = 1000 * 335 kj in 24 hours

= (1000) * (335) / (24) * (60)

= 232.6 kj/min

In actual practice, one tonne of refrigeration is taken as equivalent to 210 kj/min

or 3.5 kw (i.e. 3.5 kj/s).

1.5 COEFFICIENT OF PERFORMANCE OF A REFRIGERATOR

The coefficient of performance (briefly written as C.O.P.) is the ratio of heat extracted in the refrigerator to the work done on the refrigerant. It is also known as theoretical coefficient of performance. Mathematically,

Theoretically C.O.P. = Q/W

Where Q = Amount of heat extracted in the refrigerator ( or the amount of refrigeration effect produced, or the capacity of a refrigerator), and W = Amount of work done.

1.6 Application

1.6.1 Food processing, preservation and distribution

10

1. Storage of Raw Fruits and Vegetables

2. Fish

3. Meat and poultry

4. Dairy Products

(a). Ice cream

(b). Butter

(c). Cheese

(d). Buttermilk

5. Beverages

6. Candy

7. Processing and distribution of frozen food

1.6.2 Chemical and process industries

1. Separating of gases

2. Condensation of gases

3. Dehumidification of Air

4. Storage as liquid at low pressure

5. Cooling for preservation

1.6.3 Special application of refrigeration

1. Cold Treatment of Metals

2. Medical

3. Ice Skating Rinks

4. Construction

5. Desalination of water

11

6. Ice manufacturer

It is also widely used for the cooling of storage chambers in which perishable

food, drinks and medicines are stored. The refrigeration also has wide

applications in sub-marine ships, rockets and aircrafts.

12

CHAPTER 2 :- REFRIGERATION PROCESS

2.1 REFRIGERATOR

Refrigerator keep things cold because of the nature of the heat. Thermodynamics

essentially starts that if a cold object is placed to a next to a hot object, the cold object

will become warmer and the hot object will become cooler. A refrigerator does not

cool items by lowering their original temperature; instead, an evaporating gas called a

refrigerant draws heat away, leaving the surrounding area much colder. Refrigerators

and air conditioners both work on the principle of cooling through evaporation.

Fig 2.1 : Refrigerator

13

A refrigerator consists of two storage compartment – one for frozen items and

the other for items requiring refrigeration but no freezing. These compartment are

surrounded by a series of heat-exchanging pipes. Near the bottom of the refrigerator

unit is a heavy metal device called a compressor. The compressor is powered by an

electric motor. More heat-exchanging pipes are coiled behind the refrigerator. Running

through the entire system is pure ammonia, which evaporates at -27 ºF. this system is

closed, which means nothing is lost or added while it is operating. Because liquid

ammonia is a powerful chemical, a leaking refrigerator should be repaired or replaced

immediately.

The refrigeration process begins with the compressor. Ammonia compressed

until it becomes very hot from the increased pressure. This heated gas flows through

the coils behind the refrigerator, which allows excess heat to be released into the

surrounding air. This is why users sometimes fill warm air circulating around the

fridge. Eventually the ammonia cools down to the point where it become a liquid. This

liquid form of ammonia is then forced through a device called an expansion valve or

capillary tube. Essentially, the expansion valve has a small opening or the capillary

tube has a very small diameter of copper tube that the liquid ammonia is turned into a

very cold, fast-moving mist, evaporating as it travels through the coils in the freezer.

As the evaporating ammonia gas absorbs more heat, its temperature rises.

Coils surroundings the lower refrigerator compartment are not as compact. The cool

ammonia still draws heat from the warmer objects in the fridge, but not as much as the

freezer section. The ammonia gas is drawn back into the compressor, where the entire

cycle of pressurization, cooling and evaporation begins anew.

2.2 REFRIGERATION CYCLE

14

The refrigeration cycle uses a fluid, a called a refrigerant, to move heat from

one place to other. We will begin with the cool, liquid refrigerant entering the indoor

coil, operating as the evaporating during cooling. As the name implies, refrigerant in

the evaporator “evaporator”. Upon entering the evaporator, the liquid refrigerant’s

temperature is between 40 and 50 ºF and without changing its temperature, it absorbs

heat as it changes state from a liquid to a vapour. The heat comes from the warm,

moist room air blown across the evaporator coil. As it passes over the cool coil, it

gives up some of its heat and moisture may condense from it. The cooler, drier room

air is re-circulated by a blower into the space to be cooled.

The vapour refrigerant now moves into the compressor, which is basically a

pump that raises the pressure so it will move through the system. The increased

pressure from the compressor causes the temperature of the refrigerant to rise. As it

leaves the compressor, the refrigerant is a hot vapour, roughly 120 to 140 º F.

It now flows into the refrigerant-to-water heat exchanger, operating as the condenser

during the cooling. As it condenses, it gives up heat to the loop, which is circulated by

a pump

Fig 2.2 : Refrigeration Cycle

.

15

As the refrigerant leaves the condenser, it is cooler, but still under pressure

provided by the compressor. It then reaches the expansion valve or capillary tube. That

the high pressure refrigerant to “flash” through becoming a lower pressure, cooled

liquid. When pressure is reduced, as with spraying an aerosol can or a fire

extinguisher, it cools. The cycle is complete as the cool, liquid refrigerant re-enters

evaporator to pick up room heat.

2.3 HOW REFRIGERATOR WORKS

In the summertime, have you ever gotten out of a swimming pool and then felt

very cold standing in the sun? that’s because the water on your skin is evaporating.

The air carries off the water vapour, and with it being taken away from your skin.

This is similar to what happens inside older refrigerators. Instead of eater,

through, the refrigerator uses chemicals to do the cooling.

There are two things that need to be known for refrigeration.

1. A gas cools on expansion.

2. When you have two things that are difference temperature that touch or

are near each other, the hotter surface cools and the colder surface warms

up. This is a law of physics called the Second Law of Thermodynamics.

16

2.4 TYPES OF DOMESTIC REFRIGERATOR

There are two types of domestic refrigerator.

1. Single door fresh food refrigerator

2. Double-door refrigerator-freezer

Most domestic refrigerator are of two types – either a single door fresh food

refrigerator or a two-door refrigerator-freezer combination, with the freezer

compartment on the top portion of the cabinet, or a vertically split cabinet (side-by-

side), with the freezer compartment on the left side of the cabinet. They are completely

self-contained units and are easy to install. Most refrigerators use R-22 refrigerant,

normally maintaining temperatures of 0 ºF in the freezer compartment and about 35 ºF

to 45 ºF in the refrigerator compartment.

There are some pictures of different types of refrigerators as shown.

Fig 2.3 : Single Door Fig 2.4 : Single Door

Refrigerator Refrigerator

17

Fig 2.5 : Single Door

Refrigerator

Fig 2.6 : Double Door Refrigerator

18

2.5 TEMPERATURTE ZONE AND RATING

Some refrigerators are now divided into four zones to store different types of

food:

» -18 ºC (0 ºF) (freezer)

» 0 ºC (32 ºF) (meats)

» 5 ºC (49 ºF) (refrigerator)

» 10 ºC (50 ºF) (vegetables)

The capacity of a refrigerator is measured in either litres or cubic feet (US).

Typically the volume of a combined fridge-freezer is split to 100 litres (3.53 cubic

feet) for the freezer and 140 litres (4.94 cubic feet) for the refrigerator, although these

values are highly variable.

Temperature settings for refrigerator and freezer compartments are often given

arbitrary numbers (for example, 1 through 9, warmest to coldest) by manufacturers,

but generally 2 to 8 ºC (36 to 46 ºF) is idle for the refrigerator compartment and -18 ºC

(0 ºF) for the freezer. Some refrigerators require a certain external temperature 16 ºC

(60 ºF) to run properly. Thus can be an issue when placing a refrigerator in an

unfinished area such as a garage.

2.6 REFRIGERANT

Refrigeration application Short description Typical HFCs

19

used

Domestic Refrigeration Appliances used for keeping food in

dwelling units.

HFC-134a

Commercial

Refrigeration

Holding and displaying frozen and fresh

food in retail outlets

R 404A, R 507,

HFC-234a

Food processing and cold

storage

Equipment to preserve, process and store

food from its source to the wholesale

and cooling

R410A,

R407C,R 507,

HFC-134a

Industrial Refrigeration Large equipment, typically 25 kW to 30

MW, used for chemical processing, cold

storage, food processing and district

heating and cooling

HFC-134a, R-

404A, R-507

Transport refrigeration Equipment to preserve and store goods,

primarily foodstuffs, during transport by

road, rail, air and sea

R410A, R407C,

HFC-134A

2.7 VAPOUR COMPRESSION CYCLE

2.7.1 Introduction

The vapour compression cycle is the mostly widely used method of refrigeration in

the modern application. Your household refrigerator, water cooler, deep freezer, air-

conditioner etc, all run on vapour compression cycle. The cycle is called as vapour

compression cycle, because the vapours of refrigerant are compressed in the

compressor of the system to develop the cooling effect.

20

2.7.2 Working

Here are the various process of vapour compression cycle (refer the figure).

(1) Compression: The vapours of refrigerants enter the compressor and get

compressed to high pressure and high temperature. During this process the

entropy of the refrigerant ideally remains constant and it leaves in

superheated state.

(2) Condensation: The superheated refrigerant then enters the condenser

where it is cooled either by air or water due to which its temperature

reduces, but pressure remains constant and it gets converted into liquid

state.

(3) Expansion: The liquid refrigerant then enters the expansion valve or

throttling valve or capillary tube when sudden expansion of the refrigerant

occurs, due to which its temperature and pressure falls down. The

refrigerant leaves expansion valve or capillary tube in partially liquid state

and partially in gaseous state.

(4) Evaporation or cooling: The partially liquid and partially gaseous

refrigerant at very low temperature enters the evaporator where the

substance to be cooled is kept. It is here where the refrigeration effect is

produced. The refrigerants absorbs the heat from tge substance to be cooled

and gets converted into vapour state.

21

Fig 2.7 : Simple VCR System T-S diagram of VCR System

Fig 2.8 : P-V diagram of VCR System

2.7.3 Advantages

» Capable of large refrigerating loads at lower initial

purchase and operating cost.

» Very efficient

» Very compact system for small to very large heat loads.

22

» Cycle can be reversed for heat pump operation.

2.7.4 Disadvantages

» Parts can wear out.

» Noise.

» Potential refrigerant leaks.

» Operates in limited orientation.

2.7.5 Application

» Household refrigerator,

» Air-conditioners,

» Water coolers,

» Ice and Ice cream maker,

» Deep freezers,

» Large industrial refrigeration and

» Air-conditioning systems,

2.8 VAPOUR ABSORPTION CYCLE

2.8.1 Introduction

The various processes of the vapour absorption cycle are similar to the one in

vapour compression cycle, only the method of compression of the refrigerant is

different. In vapour absorption system ammonia is used as the refrigerant, which has

23

very high affinity to dissolve in water. Here are various processes of vapour

absorption cycle;

2.8.2 Working

(1) Compression or absorption of the refrigerant: in vapour absorption

system there is no traditional compressor, instead there is absorber. The absorber

consists of water, as a absorbent, in which the refrigerant, ammonia, dissolves.

This mixture of water and ammonia is then pumped and heated thus increase in

temperature and pressure of the ammonia occurs. Ammonia leaves the absorber at

high pressure and high temperature. Some work has to be provided to the pump

and heating is carried out by the steam. The amount of electricity required by the

pump is much lesser than that required by the compressor hence there is lots of

saving of electricity, however, the additional source of heat in the form of steam

has to be provided.

(2) Condensation: The refrigerant at pressure and temperature then enters

condenser where it is cooled by water and its temperature and pressure reduces.

(3) Expansion: Thereafter the expansion of refrigerant occurs in throttling

valve or capillary tube due to which the temperature and pressure of the ammonia

refrigerant reduces drastically and suddenly.

(4) Evaporation: Finally the refrigerant enters the evaporator where it produces

the cooling effect. It leaves the evaporator in vapour state and then enters absorber,

where it is absorbed by absorbent, water and compressed by the pump. This

process repeats again and cycle continues.

There are different types absorbents like water and lithium bromide that

can be used with refrigerant ammonia. These systems are called water absorption

system.

24

2.8.3 Advantages

» No moving parts.

» No vibration or noise on small system.

» Small systems can operate without electricity using only

heat, large systems require power for chemical pumps.

» Can make use of waste heat.

Fig 2.9 : Vapour Absorption System

25

2.8.4 Disadvantages

» Potential refrigerant leaks.

» Operates under limited vibration and orientations.

» Complicated and difficult to service and repair.

» Stalls in a hot ambient

» Very bulky.

» Poor efficiency.

26

CHAPTER 3 :- LPG REFRIGERATION

3.1 INTRODUCTION

In India, more than 80% of the domestic refrigerator utilize HFC 134a as

refrigerant, due to its excellent thermodynamic and thermo physical properties. But,

HFC 134a has a high global warming potential (GWP) of 1300. There is a need of

assess various refrigerant option considering the existing refrigerators in the field and

for the future market.

CFC’s are principally destroyed by ultraviolet radiations in the stratosphere; the

chlorine released in the high stratosphere catalyzes the decomposition of ozone to

oxygen; and ultraviolet radiations penetrates to lower altitudes. Credible calculations

of the magnitude of the effect (Hoffman 1987) and his team predicted 3% global

ozone emissions of 700 thousand tonnes/year after a hundred years. The ozone impact

of car air conditioners also can not be ignored. Hydrofluorocarbons (HFC’s) can be

thought of as a replacement, but unfortunately the radiation properties of HFC’s like

R-134a make them powerful global warming agents. HFC 134a and the HC blend

have been reported to be substitutes for CFC 12, but they have their own drawbacks in

energy efficiency, flammability and serviceability aspects of the systems. HFC 134a is

not miscible with mineral oil, and hence, polyol ester oil is recommended, which is

highly hygroscopic in nature. This hygroscopicity demands stringent service practices,

which otherwise results in moisture entry into the system.

27

Thus, hydrocarbon refrigerants; particularly LPG serves as the best contender to

replace CFC’s from domestic refrigerator as well as car air conditioners.

LPG consists mainly of propane (R-290) and butane (R-600), and LPG is

available as a side product in local refineries. In Cuba for already several decades LPG

is used as a drop-in refrigerant. LPG mixtures have composition of a commercial LPG

mixture suitable as ‘drop-in’ replacement for R-12 was calculated crudely as 64%

propane and 36% butane by mass. Liquefied petroleum gas (LPG) of 60% propane

and 40% commercial butane has been tested as a drop-in suitable for R 134a in a

single evaporator domestic refrigerator with a total volume of 10 ft3.

The revival of LPG refrigerants in domestic and small commercial application in a

happy accident (Vidal 1992). Engineers had known since the 1920’s that LPG

refrigerants performed well and in the 1980s refrigerators manufacturers again tested

them (Kuijpers et al. 1988). Fear of a flammability campaign from the chemical

industry deterred any manufacture.

In march 1989, the Institute of Hygiene in Dortmund Germany needed a new

cold storage room. The young idealistic director, Dr Harry Rosin, could not consider

using a CFC refrigerant and so tried propane and iso butane.

Greenpeace Australia imported a Foron refrigerator in February 1993 and in

December 1993 Email Ltd, Australia’s largest appliance manufacturer, displayed

prototype LPG refrigerators. In 1994, German manufacturer announced one by one

their intention of switch to LPG refrigerants.

OZ Technology Inc, a start up company in Idaho, introduced OZ-12 a mixture

of commercial propane and butane in 1992. they sold over 50,000 170 g cans the first

summer. The Mobile Air-Conditioning Society made flammability hazard claims

including ‘a bomb in the passenger compartment’ (Keebler 1993, MACS 1993). The

US EPA refused to approve OZ-12 on flammability grounds. OZ then introduced

another LPG refrigerant HC-12a, which has already sold over 100,000 cans. The US

EPA may not approve this either but OZ’s petition (OZ 1994) is convincing,

comprehensive and technically sound especially on safety. Calor released Care 30 in

28

June 1994. Care 30 is a high purity mixture of R-290 and R-600a and is a drop- in

replacement for R-12 and R 134a. it has been very successful in vehicle refrigeration

and air-conditioning.

3.2 PROPERTIES

» Colourless.

» Odourless. (It’s normal to odorise LPG by adding an

odorant prior to supply to the user, to aid the detection

of any leaks).

» Flammable.

» Heavier than air.

» Approximately half the weight of water.

» Non toxic but can cause asphyxiation.

» LPG expands upon release and 1 litre of liquid will form approximately 250 litres

of vapour.

A good mixture : LPG is mainly Propane (C3H8), Butane (C4H10) or a mix of

Propane/Butane. Since LPG has such a simple chemical structure, it is among the

cleanest of any alternative fuel.

Boiling point : LPG’s boiling point ranges from -42 ºC to 0 ºC depending on its

mixture percentage of Butane and Propane.

29

Combustion : The combustion of LPG produces carbon dioxide (CO2) and water

vapour but sufficient air must be available. Inadequate appliances flueing or

ventilation can result in the production of carbon monoxide which can be toxic.

Vapour pressure : LPG is a stored as a liquid under pressure. It is almost colourless

and its weight is approximately half that of an equivalent volume of water. The

pressure inside a closed container in which LPG is stored is equal to the vapour

pressure of the liquid and corresponds to its temperature.

Ignition temperature : The temperature required to ignite LPG in air is around 500

ºC.

Calorific value : The calorific value of LPG is about 2.5 times higher than that of

main gas so more heat is produced from the same volume of gas.

Toxicity : LPG is a colourless, odourless and non-toxic gas. It is supplied

commercially with an added odorant to assist detection by smell.

LPG is an excellent solvent of petroleum and rubber product and is generally

non-corrosive to steel and copper alloys.

Safety : LPG is just as safe as any other fuel. In fact, it is safer than most fuels

because neither LPG itself nor the end products that are produced by burning LPG in a

suitable appliance, are poisonous to inhale. Since LPG cannot burn without air, there

can never be a ‘Flash-back’ into the cylinder.

You can feel safe with LPG as the most through precaution are taken to

ensure your safety. All you have to do is to handle it correctly whilst adhering to the

simple instructions provided.

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3.3 APPLICATION

Application of LPG as refrigerant that divides in two categories:

1. Processes that uses LPG

2. Industries that uses LPG

3.3.1 Processes that use LPG

LPG’s high calorific value makes it a key gas for:

» Heating appliances :- used because of its case of

combustion, portability and clean burning characteristics

and compatibility with almost all water and space heating

appliances. The best product depends the climate.

» Propane :- suitable for use in all conditions. It is the only

LPG product suitable for cold climates (such as the UK and

Canada) because of its low boiling point of -43.6 ºF

(-42 ºC).

» Butane :- suitable for use in hot climate only because of its

higher boiling point of 22.9 ºF (-5 ºC).

» Propane/Butane mixtures :- suitable for use in moderate

climates

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» Cooking :- preferred to electricity by professional chefs.

» Oxy-Fuel application :- LPG performs well in large-scale

oxy-fuel burner application.

LPG’s clean burning characteristics make it a good gas for:

» Transport fuel :- for forklift and other trucks that operate

inside warehouses and factories because it provides no

noxious exhaust gases and give more power than batteries.

LPG is also increasingly used as a clean automotive fuel in

countries with serious air pollution problems.

» propane and butane’s low boiling points also give them good closed cycle

refrigerants characteristics (similar to Freon’s).

3.3.2 Industries that use LPG

LPG’s calorific and clean-burning characteristics are used across many industries such

as:

» Automotive :- as a forklift truck fuel and in some countries as a private car or

public transport fuel.

» Hospitality and Leisure :- as a heating and cooking gas in restaurant, cafes and

mobile catering vans.

» Agriculture :- for crop drying, heating greenhouses and animal sheds and for

flame weeding and pest control.

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» Construction :- LPG’s portability allow its use for general space heating to enable

work on projects during winter months, and for road heating in bitumen replacement

work.

» Chemicals and petrochemicals :- LPG surplus is used as feedstock when prices

are low.

3.4 THE LPG REFRIGERATION CYCLE

(1). LPG Gas Cylinder:

From the LPG gas cylinder, LPG flows through the pipe and reaches to the capillary

tube. LPG gas pressure is approximate 80-100 psi.

(2). Capillary Tube:

As the capillary tube, capillary tube downs the pressure up to less then 1 psi.

(3). Evaporator:

In the evaporator LPG is converted into the vapour from with low pressure. After

passing through the evaporator low pressure and temperature LPG vapour absorbs heat

from the chamber system.

(4). Gas Burner:

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After performing the cooling effect, low pressure LPG gas goes into the burner where

the burns.

3.5 PARTS OF REFRIGERATORS

3.5.1 LPG Gas Cylinder

LPG is Liquefied Petroleum Gas. This is general description of Propane (C3H8) and

Butane (C4H10), either stored separately or together as a mix.

This is because these gases can be liquefied at a normal temperature by

application of a moderate pressure increases, or at normal pressure by

application of LPG using refrigeration. LPG is used as a fuel for

domestic, industrial, horticultural, agricultural, cooking, heating and

drying processes. LPG can be used as an automotive fuel or as

propellant for aerosol, in addition to other specialist applications. LPG

can also be used to provide lighting

through the use of pressure lanterns.

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3.5.2 Capillary Tube

The capillary tube is the commonly used throttling device in the domestic

refrigeration.

The capillary tube is a copper tube of very small internal diameter. It is

of very long length and it is coiled to several turns so that it would

occupy less space. The internal diameter of the capillary tube used for

the refrigeration applications varies from 0.5 to 2.28 mm (0.020 to 0.09

inch). The capillary tube is shown in picture. When the refrigerant

enters in the capillary tube, its pressure drops down suddenly due to very small

diameter. The decrease in pressure of the refrigerant through the capillary depends on

the diameter of capillary and the length of capillary. Smaller is the diameter and more

is the length of capillary more is the drop in pressure of the refrigerant as it passes

through it.

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3.5.3 Evaporator

The evaporators are another important parts of the refrigeration systems. It through the

evaporators that the cooling effect is produced in the refrigeration system.

It is in the evaporators when the actual cooling effect takes place in the

refrigeration systems. For many people the evaporator is the main part of the

refrigeration system, consider other part as less useful. The evaporators are heat

exchanger surface that transfer the heat from the substance to be cooled to the

refrigerant, thus removing the heat from the from the substance. The

evaporators are used for wide variety of diverse application in

refrigeration and hence the available in wide variety of shape, sizes and

36

designs. They are also classified in different manner depending on the method of

feeding the refrigerant, construction of the evaporator, direction of air circulation

around the evaporator, application and also the refrigerant control.

In the domestic refrigerators the evaporators are commonly known as freezers since

the ice is made in these compartment.

In the evaporators the refrigerant enters at very low pressure and temperature

after passing through the capillary tube. This refrigerant absorbs the heat from

the substance that is to be cooled so the refrigerant gets heated while the substance

gets cooled. Even after cooling the substance the temperature of the refrigerant leaving

the evaporator is less than the substance.

In the large refrigeration plants the evaporator is used for chilling water. In such

cases shell and tube type of heat exchanger are used as the evaporators. In such plants

the evaporators are classified as:

(1). Dry expansion type of evaporators

(2). Flooded type of the evaporators

The evaporators are classified based on the construction as:

(1). Bare tube evaporators

(2). Plate surface evaporators

(3). Finned evaporators

(4). Shell and tube evaporator

(5). Shell and coiled evaporator, and

(6). Tube-in-tube evaporator

The evaporators are classified based on mode of heat transfer

(1). Natural convection evaporator, and

(2). Forced convection evaporator

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The evaporators are classified based on operating conditions

(1). Frosting evaporator,

(2). Non-frosting evaporator, and

(3). Defrosting evaporator

3.5.4 Pressure gauges

Many techniques have been developed for the measurement of pressure and

vacuums. Instruments used to measure pressure are called pressure gauges or vacuum

gauges.

A manometer could also referring to a pressure measuring instrument, usually

limited to measuring pressures near to atmospheric. The term manometer

is often used to refer specifically to liquid column hydrostatic instruments.

Stainless steel pressure gauge

38

Catering to the requirements of to power and allied Industry, we offer quality

array of stainless steel, weatherproof pressure gauges. Renowned for offering

resistance in corrosive environments and modes, these find wide application in power

generation, pollution control equipment, chemicals and petrochemicals and

also exploration. These gauges are available in 63mm, 100mm, and 150mm sizes and

can be customized as per client.

Bourdon gauge

A Bourdon gauge uses a coiled tube, which, as it expands due to pressure increases

cases a rotation of an arm connected to the tube.

39

In 1849 the Bourdon tube pressure gauge was patented in France by Eugene

Bourdon. The pressure sensing element is a closed coiled tube connected

to the chamber or pipe in while the pressure is to be sensed. As the gauge

pressure increases the tube will tend to uncoil, while a reduced gauge pressure

will patented France by Eugene Bourdon.

The pressure sensing el cause the tube to coil more tightly. This motion is

transferred through a linkage to a gear train connected to an indicating needle. The

needle in presented in front of a card face inscribed with the pressure indications

associated with particular needle deflections. In a barometer, the Bourdon tube is

sealed at both ends and the absolute pressure of the ambient atmosphere is sensed.

Differentials Bourdon gauges use two Bourdon tubes and a mechanical linkage that

compares the readings.

3.5.5 High Pressure pipes

The range of high pressure pipes covers most application where there is a

requirement to transfer gas at high pressure. They consist of a steel pipe with a

steel ball fitted to both ends. Two swivelling connection nipples press

these balls against the seating of the connecting hole and thus sealing

against gas leakage.

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» Wide range of pipes.

» All pipes are pressure tested to 100 M Pa (14,500 psi) over

recommended working pressure.

3.6 CONSTRUCTION OF THE LPG REFRIGERATOR

The LPG refrigerator shown in figure. We make the one box of the plywood. The

plywood sheet size is 12mm for used the LPG refrigerator. The size of the refrigerator

is 724*457*381 mm3. The evaporator is fitted on the upper portion of box inside.

Inside the refrigerator, we also put the thermo-coal sheet, because of the cold air can

not the transfer from inside to outside of refrigerator.

Fig 3.1 :- Construction of the LPG refrigerator

The schematically diagram of the LPG refrigeration system is shown in next page. The

gas tank is connect by pipes to the capillary tube. The capillary tube is fitted with

evaporator. The evaporator coiled end is connect to the stove by another gas

circulation pipe. When two pressure gauge is put between capillary tube and gas tank,

and another is put the end of the evaporator.

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3.7 WORKING LPG REFRIGERATOR

The basic idea behind LPG refrigeration is to use the evaporation of a LPG to

absorb heat. The simple mechanism of the LPG refrigeration working is shown in

figure.

Fig 3.2 Working of LPG Refrigerator

» LPG is stored in the LPG cylinder under high pressure.

When the gas tank of regulators is opened then high

pressure LPG passes in gas pipe. This LPG is going by

high pressure gas pipe in capillary tube.

» High pressure LPG is converted in low pressure at

capillary tube with enthalpy remains constant.

» After capillary tube, low pressure LPG is passed through

evaporator. LPG is converted into low pressure and

temperature vapour from and passing through the

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evaporator which absorbs heat from the chamber. Thus

the camber becomes cools down. Thus we can achieve

cooling effect in refrigerator.

» After passing through the evaporator low pressure LPG

is passed through pipe by burner. And we can uses the

low pressure of LPG is burning processes.

3.8 CAUSES AND PRECAUTION

» Explosion in space Any refrigerant with vapour pressure above ambient can

flash to a larger volume. The potential increase in volume is greater if combustion of

lubricant or refrigerant occurs. Explosion venting may be necessary to limit pressure

rise to what the space can safely withstand. 2 kPa can blow window glass off a

building.

» Fire Combustible lubricant and refrigerant must be discharged safely outside a

building when a fire occurs especially it the heat of combustion exceeds 200 MJ.

» Asphyxiation or poisoning All refrigerants except air and oxygen are

asphyxiations. Ventilation must prevent serious injury or death on a sudden total

release of refrigerants. The quantity of ventilation necessary varies greatly between

refrigerants.

» Flying metal System must comply with piping and pressure vessels codes.

» Corrosion or chemical reaction LPG refrigerants are non-reactive and chemically

stable at refrigeration temperature.

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» Chemical or cold burns Accidental contact between skin and cold metal must be

prevented by insulation. Accidental releases of liquid refrigerant must drain safely.

3.9 ADVANTAGE OF LPG

The advantages of LPG are as follows :

» Clean burning.

» Effects of corrosions are greatly reduced.

» Instantly control the flame temperature.

» Avoids scaling and decarburising of parts.

» Environmentally friendly fuel, with minimal sulphur

content and sulphur-free emissions.

» Very high efficiency with direct firing system instant heat

for faster warm-up and cool-down.

» LPG is easily liquefied and stored in pressure containers. It

can be easily transported in cylinder or tanks.

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CHAPTER 4:- ANALYSIS OF LPG REFRIGERATOR

» Size of Refrigerator :-724*457*381 mm3

» Atmospheric temperature :- 40 ºC

» Initial water temperature :- 35 ºC

» Inlet pressure of LPG :-80 psi

» Outlet pressure of LPG :- less than 1psi

4.1 :- OBSERVATION TABLE AND CHART

The experiment of this project was done on May 15, 2010 at 1.45p.m. and reading

were taken under ten minute’s interval which are under as follow:

Time Pressure

in

bar

Inlet

Temp.

(ºC)

Outlet

Temp.

(ºC)

Water

Temp.

(ºC)

Freezer

Temp.

(ºC)

Chamber

Temp.

(ºC)

10 6.7 0.2 10 30.0 1.0 37.9

10 6.4 0.01 8.2 24.2 -1.1 33.8

10 6.8 -0.09 7.6 19.7 -2.0 29.4

10 6.7 -0.90 5.2 15.8 -4.1 25.5

10 6.6 -1.25 4.1 11.2 -6.0 23.1

10 6.7 -2.20 3.1 8.3 -6.9 19.9

10 6.7 -3.74 2.2 5.1 -7.5 17.9

10 6.8 -4.90 1.8 3.2 -7.9 15.7

10 6.6 -5.90 1.1 1.02 -8.9 14.2

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10 6.7 -7.10 0.5 0.30 -9.3 10.3

Chart no. 4.1 :- Freezer Temperature Vs Time Period

X axes : Time Period in minute.

Y axes : Freezer surface temperature in ºC.

-10

-8

-6

-4

-2

0

2

0 20 40 60 80 100 120

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Chart No. 4.2 :- Water Temperature Vs Time Period

X axes : Water temperature in ºC.

Y axes : Time Period in minute.

0

5

10

15

20

25

30

35

0 20 40 60 80 100 120

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Chart No 4.3 :- Chamber Temperature Vs Time Period

X axes : Time Period in minute.

Y axes : Chamber Temperature in ºC.

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120

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4.2 ADVANTAGES

» The cooling capacity of LPG is 10% higher than R-12

and the vapour pressure is appropriate.

» LPG is naturally occurring and non-toxic.

» Use of LPG as a refrigerant also improves the overall

efficiency by 10 to 20%.

» The ozone depletion potential (ODP) of LPG is 0 and

Global warming potential (GWP) is 8 which is

Significantly negligible as compared to other

refrigerant.

» Apart from environment friendly, use of also LPG gives

us lot of cost advantages.

» LPG does not form acids and thereby eliminates the

problem with blocked capillaries.

» There is 60% reduction in weight of the system due to

higher density of LPG.

» The fridge works when electricity off.

» It is efficient to save fuel.

» No pollution

» The units are effectively silent in operation.

» Running cost is zero.

» Eliminates the compressor and condenser.

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4.3 DISADVANTAGES

» LPG is explosive in nature.

» Do not maintain constant pressure in LPG cylinder.

» Put the LPG cylinder is inverted position.

» After the refrigeration processes, the exhaust of LPG is

burn into burner. Because of the exhausted vapour LPG

can not converted again liquid phase , because the this

process is very costly.

» The prevention of leakage of the LPG is the major problem in LPG

refrigeration system. Because of the LPG is highly flammable.

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CHAPTER 5 :- CONCLUSION OF LPG REFRIGERATION

5.1 CONCLUSION

After performing this project “LPG Refrigeration”, we conclude that refrigeration effect is produced with the use of LPG.

From observation table, we conclude that, the regulating valve is fully open that, we achieve the chamber temperature down from 38ºC to 10ºC in a 100 minute. We achieve the evaporator temperature down from 1ºC to -9.3ºC in a same time interval.

We put the water in one plastic bottle in the evaporator. The initial temperature of water is 35 ºC. From observation table, we conclude that, the condition of regulating valve is fully opened, the same time period we achieve the temperature of water is 0.30 ºC.

We also conclude that, the capillary tube is maximum pressure of gas cylinder is reduces the less then of 1 psi. The capillary tube is more suitable throttling device in LPG refrigeration system.

This system is cheaper in initial as well as running cost. It does not require an external energy sources to run the system and no moving part in the system so maintenance is also very low.

We also conclude that, we try the burnt to the exhaust LPG, the pressure of exhaust gas is less than 1 psi, the small flame produce by the burner.

This system most suitable for hotel, industries, refinery, chemical industries where consumption of LPG is very high.

Picture of Project

51

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BIBLIOGRAPHY

» http://www.hychill.com.au/pdf/pasolpgr.pdf

» www.e-lpg.com

» http://www.google.com/g

» www.dynatempintl.com

» www.lpgforyou.com

» http://www.brighthub.com/engineering/mechanical.aspx

» http://coolingdevice.net/4.html

» http://howstuffworks.com/refrigerator.htm

» http://www.google.com/gwt/x?site

» www.indiamart.com

» “A Textbook of Refrigeration and Air Conditioning” by R.S.KHURMI &

J.K.GUPTA

» “Performance and safety of LPG Refrigerant ”, The Univercity of New South

Wales, Australia.

» “Applications of Refrigeration & Air Conditioning”, Lesson 3, Version 1 ME, IIT

Kharagpur 1

» “A Textbook of Thermal Engineering”, By R.S.KHURMI & J.K.GUPTA

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