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Nov 29, 2013 (3 years and 8 months ago)

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Refrigeration


History


In prehistoric times, man found that his game would last during times when food was not
available if stored in the coolness of a cave or packed in snow. In China, before the first
millennium, ice was harvested and stored.

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 on their roofs, thus exposing the jars to the night’s cool ai
r.

In
India,

evaporative cooling was employed.

When a liquid vaporizes rapidly, it expands
quickly.

The rising molecules of vapor abruptly increase their kinetic energy and this increase is
drawn from the immediate surroundings of the vapor.

These surr
oundings 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 this
method was recorded in 1550, as were the wo
rds
"to refrigerate”.

Cooling drinks came into vogue by 1600 in France.

Instead of cooling water at night,
people rotated long
-
necked bottles in water in which saltpeter had been dissolved.

This
solution could be used to produce very low temperatures and

to make ice.

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

Inventors

The first known artificial refrigeration was demonstrated by
William Cullen

at the
University of Glasgow in 1748.

Cullen let ethyl ethe
r boil into a partial vacuum; he did
not, however, use the result to any practical purpose.

Ice was first shipped commercially out of Canal Street in New York City to Charleston,
South Carolina in 1799.

Unfortunately, there was not much ice left when the
shipment
arrived.

New Englanders
Frederick Tudor and Nathaniel Wyeth

saw the potential for
the ice business and revolutionized the industry through their efforts in the first half of
the 1800s.

Tudor, who became known as the
“Ice King”
, focused on shippin
g ice to
tropical climates.

He experimented with insulating materials and built icehouses that
decreased melting losses from 66 percent to less than 8 percent.

Wyeth devised a method
of quickly and cheaply cutting uniform blocks of ice that transformed t
he ice industry,
making it possible to speed handling techniques in storage, transportation and distribution
with less waste.

In 1805, an American inventor,
Oliver Evans
, designed the first refrigeration machine that used
vapor instead of liquid.

Evans ne
ver constructed his machine, but one similar to it was built by
an American physician,
John Gorrie
.

In 1842,

the American physician
John Gorrie
, to cool sickrooms in a Florida hospital,

designed
and built an air
-
cooling apparatus for treating yellow
-
fever
patients.

His basic principle
--
that of
compressing a gas, cooling it by sending it through radiating coils, and then expanding it to
lower the temperature further
--
is the one most often used in refrigerators today.

Giving up his
medical practice to engag
e in time
-
consuming experimentation with ice making, he was granted
the first U.S. patent for mechanical refrigeration in 1851.

Commercial refrigeration is believed to have been initiated by an American businessperson,
Alexander C. Twinning
, in 1856.

Shor
tly afterward, an Australian,
James Harrison
, examined
the refrigerators used by Gorrie and Twinning and introduced vapor
-
compression refrigeration to
the brewing and meatpacking industries.

Ferdinand Carré of France

developed a somewhat more complex syste
m in 1859.

Unlike
earlier compression
-
compression machines, which used air as a coolant, Carré's equipment
contained rapidly expanding ammonia.

(Ammonia liquefies at a much lower temperature than
water and is thus able to absorb more heat.)

Carré's refr
igerators were widely used, and vapor
compression refrigeration became, and still is, the most widely used method of
cooling.

However, the cost, size, and complexity of refrigeration systems of the time, coupled
with the toxicity of their ammonia coolants
, prevented the general use of mechanical
refrigerators in the home.

Most households used iceboxes that were supplied almost daily with
blocks of ice from a local refrigeration plant.


Beginning in the 1840s, 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 cam
e 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. The first refrigerated car
to carry fresh fruit was built in 1867 by Parker Earle of

Illinois, who shipped strawberries
on the Illinois Central Railroad.

Each chest contained 100 pounds of ice and 200 quarts
of strawberries.

It was not until 1949 that a refrigeration system made its way into the
trucking industry by way of a roof
-
mounte
d cooling device, patented by Fred Jones.

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.

Com
mercial refrigeration was
primarily directed at breweries in the 1870s and by 1891, nearly every brewery was
equipped with refrigerating machines.

Natural ice supply became an industry unto itself.

More companies entered the business, prices
decreased, an
d refrigeration using ice became more accessible.

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 ton
s
of ice was extracted each day in 1847.

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

Says
Bern Nagengast
, co
-
author of Heat and Cold: Mastering the Great Indoors (published by
the American Society of Heating, Refriger
ation 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 meatpackin
g and dairy industries followed with their
complaints.

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 pro
duction 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).


Though meat
-
packers were slower
to adopt refrigeration than the breweries, they
ultimately used refrigeration pervasively.

By 1914, the machinery installed in almost all
American packing plants was the ammonia compression system, which had a
refrigeration capacity of well over 90,000 to
ns/day.


Despite the inherent advantages, refrigeration had its problems.

Refrigerants like sulfur dioxide
and methyl chloride were causing people to die.

Ammonia had an equally serious toxic effect if
it leaked.

Refrigeration engineers searched for acc
eptable substitutes until the 1920s, when a
number of synthetic refrigerants

called halocarbons or CFCs (chlorofluorocarbons)

were
developed by
Frigidaire
.

The best known of these substances was patented under the brand
name of Freon.

Chemically, Freon
was created by the substitution of two chlorine and two
fluorine atoms for the four hydrogen atoms in methane (CH
4
); the result,
dichlorodifluoromethane (CCl
2
F
2
), is odorless and is toxic only in extremely large doses.

Though ice, brewing, and meatpacking
industries were refrigeration’s major
beneficiaries, many other industries found refrigeration a boon to their business.

In metalworking, for instance, mechanically produced cold helped temper cutlery and
tools.

Iron production got a boost, as refrigerati
on removed moisture from the air
delivered to blast furnaces, increasing production.

Textile mills used refrigeration in
mercerizing, bleaching, and dyeing.

Oil refineries found it essential, as did the
manufacturers of paper, drugs, soap, glue, shoe pol
ish, perfume, celluloid, and
photographic materials.

Fur and woolen goods storage could beat the moths by using refrigerated
warehouses.

Refrigeration also helped nurseries and florists, especially to meet seasonal
needs since cut flowers could last longe
r.

Moreover, there was the morbid application of
preserving human bodies.

Hospitality businesses including hotels, restaurants, saloons,
and soda fountains, proved to be big markets for ice.

In WWI, refrigeration in ammunition factories provided the requ
ired strict control of
temperatures and humidity.

Allied fighting ships held carbon
-
dioxide machines to keep
ammunition well below temperatures at which high explosives became unstable.

In 1973,

Prof. James Lovelock

reported finding trace amounts of refri
gerant gases in the
atmosphere.

In 1974,
Sherwood Rowland and Mario Molina

predicted that chlorofluorocarbon
refrigerant gases would reach the high stratosphere and there damage the protective mantle of the
oxygen allotrope, ozone.


In 1985 the
"ozone hole
"

over the Antarctic had been discovered and
by 1990
Rowland and Molina's

prediction was proved correct.




The basic components of today’s modern vapor
-
compression refrigeration system are a
compressor; a condenser; an expansion device, which can be a val
ve, a capillary tube, an engine,
or a turbine; and an evaporator.

The gas coolant is first compressed, usually by a piston, and
then pushed through a tube into the condenser. In the condenser, the winding tube containing the
vapor is passed through either

circulating air or a bath of water, which removes some of the heat
energy of the compressed gas.

The cooled vapor is passed through an expansion device to an
area of much lower pressure; as the vapor expands, it draws the energy of its expansion from its

surroundings or the medium in contact with it.

Evaporators may directly cool a space by letting
the vapor come into contact with the area to be chilled, or they may act indirectly
--
i.e.

by
cooling a secondary medium such as water. In most domestic refri
gerators, the coil containing
the evaporator directly contacts the air in the food compartment.

At the end of the process, the
warmed gas is drawn toward the compressor.



Source:
http://www.rogersr
efrig.com/history.html


Uses and Types of Commercial R
efrigerator units


Whenever the word refrigeration is mentioned, the first thing that comes to most people’s minds
is the type of refrigerators that we have at home. The truth is,

there is also a huge demand for
commercial refrigeration that ranges in form from display freezers to blast chillers and fish
fridges. Below are the different types of commercial refrigeration units, with little specifics on
each type.


First on the list
are
blast chillers
. These chillers come in a number of sub
-

types that are
available for a wide range of applications. However, all of them serve one primary purpose: to
get food down to a low temperature as fast as possible in order to seal in the freshne
ss. Majority
of the blast chillers that are available claim that they can drop food temperature from a high of
21°C to about
-
16°C in just an hour and a half. This type of equipment is particularly important
in order to remain compliant with the various st
ringent regulations when it comes to food safety
and storage standards. There are a lot of choices in terms of blast chillers and it is very important
that you determine the appropriate unit that meets all of your requirements.


Other types of

commercial refrigeration

units that your business may require are display
fridges
and
display freezers
. The display fridge is not only used for presentation purposes but it is also
used to minimize food poisoning caused by
improper handling and storage. Display fridges and
freezers are usually the ones that you will find in your local grocery store or in convenience
stores. With the use of the display fridge and freezer, customers can see the food items that are
on sale with
out opening the doors. You can also choose from a variety of display fridges where
the doors are not included. This type is also a common fixture in food stores and offers the
convenience of being able to reach down into the food compartment in order to se
lect the item
that you want. Both display fridges and freezers come in smaller versions which grocery stores
keep upfront so they can display bottled water and other drinks along counters where customers
can easily reach for their choice.


On the other hand, if you intend to run a fish store, you're going to need a
fish fridge
. This is just
a just a commercial fridge that is specifically crafted for handling fish, typically organized on
sliding trays. But before you get one, remember that th
e size of the fridge will largely depend on
how much of the demand you have for fish in your store. There are plenty of design options that
are available for this type of refrigerator. The particular subtype that you decide to procure must
be able to maint
ain the optimum temperature setting when handling and storing the fish in your
store. You can also opt for fish cases that are refrigerated so you can display the fish where your
customers can see it but still maintain the required level of temperature at
the same time.


Source:
http://www.articlesbase.com/sales
-
articles/uses
-
and
-
types
-
of
-
commercial
-
refrigeration
-
units
-
1331775.html


How t
o take care of Refrigerator?


Run and maintain your refrigerator and freezer at maximum efficiency:

• For food safety maintain your refrigerator temperature between 36° and 40°F/2
-
5°C and your
freezer between 0° and 5°F/
-
18 and
-
15°C; colder settings than

this can waste up to 25 percent
more energy.


• When defrosting food, plan ahead and put the frozen food in the refrigerator compartment
where it will help keep the fridge cold while it thaws and thus save on electricity.


• Gently brush or vacuum the dus
t that can accumulate on the condenser coils located on the
back of the refrigerator or freezer; this can sometimes save as much as 30 percent in electric
consumption. Clean the outer and inner walls regularly with mild cleaning liquid.



• Clean and check

the door seals to make sure they are tight. If there are cracks or gaps in the
seal, replace it. An easy test for the seal is to close the door on a standard sheet of paper. The
paper should not slide around or fall out, and you should feel some resistanc
e when you pull it
out. If not, replace the seal immediately; you're wasting at lot of money and energy.


• Leave enough space between your refrigerator and the walls or cabinets so air can circulate
around the condenser coils at the back. Trapped heat fro
m the coils and motor will needlessly
increase your electric consumption.


• Keep the refrigerator full (but not packed, which prevents air from circulating). This allows the
temperature to recover quickly after the door is opened and closed.




• If your
refrigerator is more than 5 years old, replace it with a new energy efficient model,
showing the Energy

Star label orrated 'A' in energy efficiency. Buying a new high
-
efficiency
model will pay for itself in the long term and carries a big benefit for the e
nvironment.


• Get rid of those old refrigerators or freezers out in the garage or basement that you might be
using as second appliances. These are energy hogs that waste energy and money
-
.

Source(s):
http://kyotoaction.com/main_electricity2…

Features of Modern Refrigerator

Refrigerators are a great invention for house wives. These units can help people save food for a
long time without worrying about the quality of the food products. Even those f
ood items that do
not last for long and perishable products can be safely stored in these coolers. Beside the
optimum temperature that is maintained within these coolers, you can also get a new age anti
bacterial coating inside that gives an added protecti
on to your food products.

You should make sure that the best
refrigerator that you buy caters

to everyone's need in the
family. The size of the machine is essential. It is always better to go for bigger machines as
family sizes increase over time. There are some typical features that one can expect in a
refrigerator like de
-
frosting system, humidi
ty control technology and complete frost free option.
Also there are many sizes available in the market. With more and more brands coming into this
industry now the market provide lots of options for the buyer. He can now choose from a wide
array of produc
ts and variations available. It is better to go for more divisions and drawers in
your fridge. This makes sure that you can separate the products from one another and hence you
can maintain the quality of each product intact.

Most refrigerators also have a
n interior light, even inside the freezers. This makes it easy for
people to search for item at the nook and corner even at night. Also the lights are powerful and
automatic, so once you open the door the light stays on until you close it again. So now you

do
not have to grope in the dark for you favorite ice cream at the dead end of night, if suddenly you
are besieged by a desire to taste them!

You can easily control the temperature within the machine easily. There is an adjustable
thermostat that you can
control easily. Also there is a reversible door which is an added
attraction. Plus the fridge does not make any noise unlike the models of the past. If you are
worried about huge electricity bills then let us assure you that there is nothing to worry about
.
Most modern machines are environmental friendly and are does not burden you with excessive
electricity bills. But it is better to compare the different models before you buy a product. It is
also important to compare a new model with the existing one to
see the difference in energy
conservation levels.

You can directly go for free standing machines which are conventionally used or those in the
shape of a chest. These are shallow but have enough space in them hold the food items for all the
family members.

If you are trying to save wines and other costly liquors then it is advisable to go
for specialized fridges that can maintain the wines at the exact temperature. However, with
development of technologies one can expect a combination of a regular fridge an
d a wine cooler.

As An Informed Consumer If You Are Keen To Purchase

Best Refrigerators

But Not Sure How
To Go About It Then We Have The Perfect Solution For You And It Will For Sure Help You
Ma
ke An Informed Choice. You Need To Know

Refrigerator Ratings

And Select The Model
Which Best Suits You. To Know About Best Refrigerators Simply Log On To Refrigerator
-
Select.Com. The Fantastic W
ebsite Will Tell You All You Need To Know About Refrigerator.
So Visit It And Take An Informed Decision.

Article Source:

http://EzineArticles.com/?expert=Deven_Jerry

II. What Science/Physics
concepts are found / used in an Air Conditioner?

1. 1
st

Concept (with details)

Refrigeration cycle

In the refrigeration cycle, a heat pump transfers heat from a lower
-
temperature

heat
source into a higher
-
temperature
heat sink
. Heat would naturally flow in the opposite
direction. This is the most common type of air conditioning. This cycle takes advantage
of the

way
phase changes

work, where
latent heat

is released at a constant temperature
during a
liquid
/
gas

phase change, and where varying the
pressure

of a pure substance also
v
aries its
condensation
/
boiling point
.

2. 2
nd

Concept (with details)

Humidity

Air conditioning equipment usually reduces the
humidity

of the air processed by the
system. The relatively cold (below the
dew point
) evaporator coil condenses
water vapor

from the processed air. The water is drained, removing water vapor from the cooled space
and thereby lowering its
relative humidity
. The comfort air conditioner is designed to
create a 40% to 60% relative humidity in the occupied space. In food retail
establishments, large, open chiller cabinets act as highly effective
dehumidifiers
. Some
air conditioning units dry the air without cooling it. These work like a normal air
conditioner, except that a
heat exchanger

is placed between th
e intake and exhaust. In
combination with
convection

fans
, they achieve a similar level of comfo
rt as an
air cooler

in humid
tropical climates
, but only consume about one
-
third the energy.

3. 3
rd

Concept (with details)

Refrigerants

The key element of the air conditioner is a refrigerant, most often a fluorocarbon that
flows constantly through the air conditioner’s mechanisms, becoming a liquid and giving
off heat when it is compressed, and becomin
g a gas and absorbing heat when the pressure
is removed. The mechanisms that evaporate and compress the refrigerant are divided into
two areas: those on the room inside (air filter, fan, cooling coil) and those on the outside
(compressor, condenser coil, f
an). "
Freon
" is a
trade name

for a family of
haloa
lkane

refrigerants manufactured by
DuPont

and other companies. These refrigerants were
commonly used due to their superior stability and safety properties. However, it has been
shown that

these
chlorine
-
bearing refrigerants

reach the
upper atmosphere

when they
escap
e. Once the refrigerant reaches the
stratosphere
,
UV radiation

from the
Sun

cleaves

the chlorine
-
carbon

bond
, yielding a chlorine
radical
. These chlorine atoms
catalyze

the
breakdown of
ozone

into
diatomic

oxygen
, depleting the
ozone layer

that shields the
Earth's surface from strong UV radiation. Each chlorine radical remains active as a
catalyst unless it binds with another chlorine radical, forming a stable
molecule

and
breaking the
chain reaction
.

III. On
-
going Studies about Air Conditioner

Ongoing Research Relevant for Solar
Assisted Air Conditioning Systems

Overview:
Solar
-
assisted air conditioning offers opportunities to meet the increasing
cooling demand in buildings all over the world in an energy
-
efficient way. This report
presents an overview of ongoing and recently comp
leted R&D work, relevant for solar
-
assisted air conditioning. The structure of the report reflects the solar
-
assisted air
conditioning system itself, which consists of solar collectors on the one hand, and a heat
-
driven chiller/dehumidifier on the other.