for engineering student

1. CONTENTS
 History
 Freezer
 Commercial and domestic refrigerators
 Styles of refrigerators
 Production by country
 General technical explanation
 Features
 Types of domestic refrigerators
 Energy efficiency
 Effect on lifestyle
 Temperature zones and ratings

2. Refrigerator
A refrigerator (colloquially fridge) is a common household appliance that
consists of a thermally insulated compartment and a heat pump (mechanical,
electronic, or chemical) that transfers heat from the inside of the fridge to its
external environment so that the inside of the fridge is cooled to a temperature
below the ambient temperature of the room. Refrigeration is an essential food
storage technique in developed countries. Lower temperatures in a confined
volume lowers the reproduction rate of bacteria, so the refrigerator reduces the
rate of spoilage.
A refrigerator maintains a temperature a few degrees above the freezing point of
water. Optimum temperature range for perishable food storage is 3 to 5 °C
(37 to 41 °F).[1] A similar device that maintains a temperature below the
freezing point of water is called a freezer. The refrigerator replaced the icebox,
which was a common household appliance for almost a century and a half prior.
For this reason, a refrigerator is sometimes referred to as anicebox.
History
Before the invention of the refrigerator, icehouses were used to provide cool
storage for most of the year. Placed near freshwater lakes or packed with snow
and ice during the winter, they were once very common. Natural means are still
used to coolfoods today. On mountainsides, runoff from melting snow is a
convenient way to cooldrinks, and during the winter one can keep milk fresh
much longer just by keeping it outdoors.

3. Schematic of Dr. John Gorrie's 1841 mechanical ice machine.
In the 11th century, Persian physicist and chemist Ibn Sina (Latinized
name: Avicenna) invented the refrigerated coil, which
condenses aromatic vapors. This was a breakthrough in distillation technology
and he made use of it in his distillation process, which requires refrigerated
tubing, to produce essential oils.
Collective refrigerators in the Alblasserwaard, Dutch newsreel 1956
The first known artificial refrigeration was demonstrated by William Cullen at
the University of Glasgow in 1748.[5] The American inventor Oliver Evans,
acclaimed as the "father of refrigeration," invented the vapor-compression
refrigeration machine in 1805. Heat was removed from the environment by
recycling vaporized refrigerant, where it moved through
acompressor and condenser, where it eventually reverted to a liquid form to
repeat the process. However, Evans built no such refrigeration unit.[6] In
1834, Jacob Perkins modified Evans' original design, building the world's first
refrigerator and filing the first legal patent for refrigeration using vapor-
compression.[7] John Gorrie, an American doctor from Florida, invented the first
mechanical refrigeration unit in 1841—based on Evans' original invention to
make ice in—to cool air for yellow fever patients. Gorrie's mechanical

4. refrigeration unit received a patent in 1851.[8] American professor Alexander C.
Twining of Cleveland, Ohio patented an early vapor-compression refrigerator in
1853 that was fully capable of producing a ton of ice per day.[9]
In 1856, James Harrison, an immigrant from Scotland living in Australia,
developed an ice making machine using ammonia and an ether compressor.[10] It
was used in the brewing and meat packing industries of Geelong,
Victoria. Ferdinand Carré of France developed a somewhat more complex
system in 1859. Unlike earlier compression-compression machines, which used
air as a coolant, Carré's equipment contained rapidly expanding ammonia. In
1867, Andrew Muhl, an immigrant from France, built an ice-making machine in
San Antonio, Texas, to help service the expanding beef industry before moving
it to Waco in 1871.[11] In 1873, the patent for this machine was contracted by the
Columbus Iron Works,[12] a company acquired by the W. C. Bradley Co., which
produced the world's first commercial ice-makers
Carl Paul Gottfried Linde, ennobled in 1897 as Ritter von Linde, was
a German engineer who developed refrigeration and gas separation

5. technologies. In 1890, Carl von Linde moved back to Munich where he took up
his professorship once more, but was soon back at work developing new
refrigeration cycles. In 1892, an order from the Guinness brewery in Dublin for
a Carbon Dioxide liquefaction plant drove Linde's research into the area of low
temperature refrigeration, and in 1894 he started work on a process for the
liquefaction of air. In 1895, Linde first achieved success, and filed for patent
protection of his process (not approved in the US until 1903). In 1901, Linde
began work on a technique to obtain pure oxygen and nitrogen based on the
fractional distillation of liquefied air. By 1910 coworkers including Carl's son
Friedrich had developed the Linde double-column process, variants of which are
still in common use today.
These home units usually required the installation of the mechanical parts,
motor and compressor, in the basement or an adjacent room while the cold box
was located in the kitchen. There was a 1922 model that consisted of a wooden
cold box, water-cooled compressor, an ice cube tray and a 9-cubic-foot
(0.25 m3) compartment, and cost $714. (A 1922 Model-T Ford cost about
$450.) By 1923, Kelvinator held 80 percent of the market for electric
refrigerators. Also in 1923 Frigidaire introduced the first self-contained unit.
About this same time porcelain-covered metal cabinets began to appear. Ice
cube trays were introduced more and more during the 1920s; up to this time
freezing was not an auxiliary function of the modern refrigerator.
The first refrigerator to see widespread use was the General Electric "Monitor-
Top" refrigerator introduced in 1927, so-called because of its resemblance to the
gun turret on the ironclad warshipUSS Monitor of the 1860s. The compressor
assembly, which emitted a great deal of heat, was placed above the cabinet, and
surrounded with a decorative ring. Over a million units were produced. As the
refrigerating medium, these refrigerators used either sulfur dioxide, which is
corrosive to the eyes and may cause loss of vision, painful skin burns and
lesions, or methyl formate, which is highly flammable, harmful to the eyes, and

6. toxic if inhaled or ingested. Many of these units are still functional today. These
cooling systems cannot legally be recharged with the hazardous original
refrigerants if they leak or break down.
The introduction of Freon in the 1920s expanded the refrigerator market during
the 1930s and provided a safer, low-toxicity alternative to previously used
refrigerants. Separate freezers became common during the 1940s, the popular
term at the time for the unit was a deep freeze. These devices, or appliances, did
not go into mass production for use in the home until after World War II. The
1950s and 1960s saw technical advances like automatic defrosting and
automatic ice making. More efficient refrigerators were developed in the 1970s
and 1980s, even though environmental issues led to the banning of very
effective (Freon) refrigerants. Early refrigerator models (from 1916) had a cold
compartment for ice cube trays. From the late 1920s fresh vegetables were
successfully processed through freezing by the Postum Company (the
forerunner of General Foods), which had acquired the technology when it
bought the rights to Clarence Birdseye's successful fresh freezing methods.
The first successful application of frozen foods occurred when General Foods
heiress Marjorie Merriweather Post (then wife of Joseph E. Davies, United
States Ambassador to the Soviet Union) deployed commercial-grade freezers in
Spaso House, the US Embassy in Moscow, in advance of the Davies’ arrival.
Post, fearful of the USSR's food processing safety standards, fully stocked the
freezers with products from General Foods' Birdseye unit. The frozen food
stores allowed the Davies to entertain lavishly and serve fresh frozen foods that
would otherwise be out of season. Upon returning from Moscow, Post (who
resumed her maiden name after divorcing Davies) directed General Foods to
market frozen product to upscale restaurants.
Home freezers as separate compartments (larger than necessary just for ice
cubes), or as separate units, were introduced in the United States in 1940.
Frozen foods, previously a luxury item, became commonplace.

7. Freezer
Freezer units are used in households and in industry and commerce. Food
stored at or below −18 °C (−0 °F) is safe indefinitely.[16]Most household
freezers maintain temperatures from -23 to -18 °C (-9 to -0 °F), although some
freezer-only units can achieve −34 °C(−29 °F) and lower. Refrigerators
generally do not achieve lower than −23 °C (−9 °F), since the same coolant loop
serves both compartments: Lowering the freezer compartment temperature
excessively causes difficulties in maintaining above-freezing temperature in the
refrigerator compartment. Domestic freezers can be included as a separate
compartment in a refrigerator, or can be a separate appliance. Domestic freezers
are generally upright units resembling refrigerators or chests (upright units laid
on their backs). Many upright modern freezers come with an ice dispenser built
into their door. Some even more upright and new models include exact
temperature changing devices and even a built in clock.
COMMERCIAL AND DOMESTIC REFRIGERATORS
Commercial refrigerator and freezer units, which go by many other names, were
in use for almost 40 years prior to the common home models. They used gas
systems such as anhydrous ammonia (R-717) or sulfur dioxide (R-764), which
occasionally leaked, making them unsafe for home use and industrial purposes.
Practical household refrigerators were introduced in 1915 and gained wider
acceptance in the United States in the 1930s as prices fell and non-toxic, non-
flammable synthetic refrigerants such as Freon-12® (R-12) were introduced.
However, R-12 damaged the ozone layer, causing governments to issue a ban
on its use in new refrigerators and air-conditioning systems in 1994. The less
harmful replacement for R-12, R-134a (tetrafluoroethane), has been in common
use since 1990, but R-12 is still found in many old systems today.

8. STYLES OF REFRIGERATORS
Frigidaire Imperial "FrostProof" model FPI-16BC-63, top refrigerator/bottom
freezer with brushed chrome doorfinish made byGeneral Motors Canada in
1963
Most households use the freezer-on-top-and-refrigerator-on-bottom style, which
has been the basic style since the 1940s.
 Traditional style — 1940s to present. Freezer top/refrigerator bottom
(although most of the earlier models, some of the cheaper later models, and
still some mini-fridges use the freezer chest, or what is known as the freezer-
in-the-fridge). A separate freezer compartment — not located within the
larger refrigerator compartment — became the industry standard during the
early- to mid-1960s.
 Side-by-side style — introduced by Amana in 1949 but not popular until
1965–present; left side is freezer and the right is refrigerator.
 Top-refrigerator/bottom-freezer style — mid-1950s to present.
 French-doorstyle — late 1990s-present. Two French doors for refrigerator
and bottomfreezer.

9.  Four-doorFrench-doorstyle - mid-2000s-present. Two French doors for
refrigerator and bottom freezer plus an extra doorabove the freezer which
can function as a refrigerator or freezer.
 Door and drawer, similar in conceptto drawer style ovens, whereby the
entire contents of the freezer are pulled out on gliders.
 Four doorstyle-2013–present-four-door style fridge with a french-door
refrigerator section and a lower section divided into a freezer on the left and
an area that can be converted between fridge and freezer spaceon the lower-
right.
GENERAL TECHNICAL EXPLANATION
Process and Components of a Conventional Refrigerator
Vapor Compression Cycle – A: hot compartment (kitchen), B: cold
compartment (refrigerator box), I: insulation, 1: Condenser, 2: Expansion valve,

10. 3: Evaporator unit, 4: Compressor
An Embraco compressorand fan-assisted condensercoil
A vapor compression cycle is used in most household refrigerators, refrigerator–
freezers and freezers. In this cycle, a circulating refrigerant such
as R134a enters a compressor as low-pressure vapor at or slightly above the
temperature of the refrigerator interior. The vapor is compressed and exits the
compressor as high-pressure superheated vapor. The superheated vapor travels
under pressure through coils or tubes comprising the condenser, which are
passively cooled by exposure to air in the room. The condenser cools the vapor,
which liquefies. As the refrigerant leaves the condenser, it is still under pressure
but is now only slightly above room temperature. This liquid refrigerant is
forced through a metering or throttling device, also known as an expansion
valve (essentially a pin-hole sized constriction in the tubing) to an area of much
lower pressure. The sudden decrease in pressure results in explosive-like flash
evaporation of a portion (typically about half) of the liquid. The latent heat
absorbed by this flash evaporation is drawn mostly from adjacent still-liquid
refrigerant, a phenomenon known as auto-refrigeration. This cold and partially
vaporized refrigerant continues through the coils or tubes of the evaporator unit.
A fan blows air from the refrigerator or freezer compartment ("box air") across
these coils or tubes and the refrigerant completely vaporizes, drawing further
latent heat from the box air. This cooled air is returned to the refrigerator or
freezer compartment, and so keeps the box air cold. Note that the cool air in the
refrigerator or freezer is still warmer than the refrigerant in the evaporator.
Refrigerant leaves the evaporator, now fully vaporized and slightly heated, and
returns to the compressor inlet to continue the cycle.
An absorption refrigerator works differently from a compressor refrigerator,
using a source of heat, such as combustion of liquefied petroleum gas, solar

11. thermal energy or an electric heating element. These heat sources are much
quieter than the compressor motor in a typical refrigerator. A fan or pump might
be the only mechanical moving parts; reliance on convection is considered
impractical.
The Peltier effect uses electricity to pump heat directly; this type of refrigerator
is sometimes used for camping, or where noise is not acceptable. They can be
totally silent (if they don't include a fan for air circulation) but are less energy-
efficient than other methods.
Other uses of an absorption refrigerator (or "chiller") include large systems used
in office buildings or complexes such as hospitals and universities. These large
systems are used to chill a brine solution that is circulated through the building.
Many modern refrigerator/freezers have the freezer on top and the refrigerator
on the bottom. Most refrigerator-freezers—except for manual defrost models or
cheaper units—use what appears to be two thermostats. Only the refrigerator
compartment is properly temperature controlled. When the refrigerator gets too
warm, the thermostat starts the cooling process and a fan circulates the air
around the freezer. During this time, the refrigerator also gets colder. The
freezer control knob only controls the amount of air that flows into the
refrigerator via a damper system.[19] Changing the refrigerator temperature will
inadvertently change the freezer temperature in the opposite direction. Changing
the freezer temperature will have no effect on the refrigerator temperature. The
freezer control may also be adjusted to compensate for any refrigerator
adjustment.
This means the refrigerator may become too warm. However, because only
enough air is diverted to the refrigerator compartment, the freezer usually re-
acquires the set temperature quickly, unless the door is opened. When a door is
opened, either in the refrigerator or the freezer, the fan in some units stops
immediately to prevent excessive frost build up on the freezer's evaporator coil,
because this coil is cooling two areas. When the freezer reaches temperature, the

12. unit cycles off, no matter what the refrigerator temperature is. Some
people[who?] recommend setting the refrigerator to maximum and the freezer to a
point where one's refrigerated food won't freeze. Modern computerized
refrigerators do not use the damper system. The computer manages fan speed
for both compartments, although air is still blown from the freezer.
A few manufacturers, such as Sub Zero and Sun Frost, offer dual compressor
models. These models have separate freezer and refrigerator compartments that
operate independently of each other, sometimes mounted within a single
cabinet. Each has its own separate compressor, condenser and evaporator coils,
insulation, thermostat, and door. Typically, the compressorsand condenser coils
are mounted at the top of the cabinet, with a single fan to cool them both.
This design, where no air passes between the two compartments, provides for
more appropriate humidity levels and much tighter temperature control in each
compartment. It also requires much less energy to operate, since each
compressor& coolant system can be optimized for a specific temperature range.
Further, opening the doorof one compartment does not affect the temperature of
the air or humidity level in the other compartment. Thus, it avoids many of the
disadvantages of the much more common single compressor designs described
above, although at a higher initial cost. Manufacturers of such designs argue
that the increased cost is compensated over time due to reduced energy use and
less food waste due to reduced spoilage
DRIEMS POLYTECHNIC