Principles of

Refrigeration
Group 1 (BSME 2-4)
 History of
Refrigeration
Chinese

❖ Chinese harvested ice from rivers and

lakes as early as 1.000 BC

❖ They even had religious ceremonies for

filling and emptying ice cellars.
Storage pits and
Snow pits

❖ Hebrews, Greeks, and Romans

placed large amounts of snow into
storage pits and covered it with
insulating materials

❖ Snow pits were practical buildings

that were built to preserve and
save the snow collected during the
winter and then distribute it
accordingly all year round.
Egyptian & ancient
people of India

❖ They would moisten the outside of the

jars and the resulting evaporation would
cool the water that was inside of the jars.
The Persians

❖ The first group of people to use cold

storage to preserve food

❖ They invented Yakhchal, a type of ice pit

18th Century

❖ In 18th century England, servants

collected ice in the winter and were
putting it into icehouses.

❖ Icehouses were places where the

sheets of ice were packed in salt,
wrapped in flannel, and stored
underground to keep them frozen
until summer.
19th Century

❖ The first ice boxes started appearing in England.

❖ The first commercial ice started appearing with

the spreading of ice storehouses and iceboxes.
Modern Refrigeration

❖ The concept of mechanical refrigeration began

when William Cullen, a Scottish doctor,
observed that evaporation had a cooling effect
in the 1720s. He demonstrated his ideas in 1748
by evaporating ethyl ether in a vacuum.
Modern Refrigeration

❖ Oliver Evans, an American inventor,

designed but did not build the
refrigeration machine that used
vapor instead of liquid in 1805.

❖ In 1820, English scientist Michael

Faraday used liquefied ammonia to
cause cooling.
Modern Refrigeration

❖ Jacob Perkins, who worked

with Evans, received a patent
for a vapor-compression cycle
using liquid ammonia in 1835.
For that, he is sometimes called
the "father of the refrigerator."
Modern Refrigeration

❖ Refrigerators were considered essential in

homes by the 1920s, according to History
magazine, and more than 90 percent of
American homes had a refrigerator.

❖ Kelvinator produced the first automatic

refrigerator for the American market. The
first of the sealed or hermetic automatic
refrigerator units was introduced by
General Electric in 1928.
Modern Refrigeration

❖ In 1927, the first absorption

automatic refrigeration was
introduced by Electrolux
 Review of
Important Terms
Thermodynamics

Thermodynamics is a branch of
physics that deals with heat, work,
and temperature, and their relation to
energy, entropy, and the physical
properties of matter and radiation.
Properties of a
Substance

❖ Density ❖ Specific weight

= m/v y = w/v

❖Specific volume ❖ Specific gravity/

v = v/m relative density
Zeroth Law of
Thermodynamics
First Law of
Thermodynamics

Directly related to the Law of

Conservation of Energy, which states
that energy cannot be created nor
destroyed, it can only be transferred.
Second Law of
Thermodynamics

Heat transfers from a warm area to a cooler

area. The higher the degree of difference of
temperature of two objects, the faster the
heat transfer. For two objects with the same
range of temperature, no transferring of
heat will occur.
❖Temperature
- Hot
- Cold
❖Absolute zero
❖Sensible Heat
❖Latent Heat
❖BTU (British Thermal Unit)
❖Kilojoule
❖Pressure
Four Major Terms
Related To
Refrigeration Cycle

❖ Compressor ❖Condenser
- Reciprocating compressor ❖ Expansion valve
- Scroll compressor ❖ Evaporator
- Rotary compressor
Refrigeration
System
Four Refrigeratioan
System:

❖ Evaporator ❖ Condenser

❖ Compressor ❖ Expansion valve

Two Pressure side
of Refrigerator System
❖ Low-Pressure Side
❖ High-Pressure Side
Refrigerant
- It is a fluid that circulates inside the Refrigerator System
- it absorbs heat from the evaporator and discharges heat
to condenser
- R134a – is usually used in the Domestic Refrigeration
Compressor
It is called the heart of the system.

Two main function of the Compressor:

❖ It pumps the refrigerant to circulates in the

system
❖ It compresses refrigerant from low pressure
to high pressure refrigerant.
❖ Evaporator
- a coil of tubes where heat is being absorb by refrigerant.

❖ Condenser
- a coil of tubes where heat that had been absorbed in the
evaporator is being discharges to the atmosphere.

❖ Expansion valves
- the monitoring device that control the flow of refrigerant.
Different Types of
Refrigeration System
❖ Evaporating ❖Absorption
Cooling
❖ Thermoelectric
❖ Mechanical
Compression
Refrigeration
Cycle
Refrigeration
Cycle
 ❖ Latent Heat of
Evaporation
- The amount of heat that has to be
given to a unit mass of material to convert it
from the liquid to the vapor phase without a
change in temperature.

❖ Latent Heat of
Condensation
- The amount of heat that has to be
released by a unit mass of material to convert
it from the vapor to the liquid phase without a
change in temperature.
 ❖ Saturation
Temperature
- The temperature at which vaporization
(boiling) starts to occur for a given pressure. It
is also called the Boiling Point.

❖ Superheating
- Superheat is measured as the
difference between the actual temperature of
the refrigerant vapor and the saturation
temperature of the refrigerant.

❖ Subcooling
- Subcooling is any temperature of a
liquid below its saturation temperature.
Refrigeration
Cycle
At the exit of expansion valve, low pressure/ low temperature liquid will flow to the
evaporator wherein the refrigerant will absorb the heat of everything inside the refrigerator
cabinet ( fish, meat, vegetable, water, cream, etc. ). This will turn the liquid refrigerant into
gas, low pressure/low temperature.

It will enter the suction line of compressor, inside the compressor, the cylinder-
piston of the compressor will compress the refrigerant turning it to high pressure / high
temperature refrigerant flowing out of the discharge line of compressor.

It will enter the condenser wherein the high pressure/ high temperature refrigerant
will discharge heat, changing it into a high pressure/ high temperature refrigerant liquid.

It will flows to expansion valves where-in it will be controlled and expanded at the
exit, thus becoming low pressure/ low temperature liquid refrigerant.
Ph Diagram

Ts Diagram
Safety Tips
Safety tips:
❖ ALWAYS wear eye protection when servicing air conditioning systems
or handling refrigerant.

❖ Avoid breathing refrigerant and lubricant vapor or mist. Exposure

may irritate eyes, nose and throat. If accidental discharge occurs,
ventilate the work area.

❖ Do not allow refrigerants to come in contact with open flames and

high-temperature surfaces.
Safety tips:
❖ HFC-134a is not flammable at normal ambient temperatures and
atmospheric pressure.

❖ PAG lubricant is hygroscopic.

❖ PAG lubricant can be a skin irritant. Protective impervious gloves are

required to prevent lubricant contact with the skin.
Safety tips:
❖ PAG lubricants can cause damage to paint, plastic parts, engine drive
belts and coolant hoses.

❖ Failure to follow instructions provided by A/C system service

equipment manufacturers could result in personal injury or equipment
damage.

❖ To prevent refrigerant cross-contamination, use separate service

equipment for each refrigerant.
Safety tips:
❖ NEVER transfer refrigerants to a cylinder or tank unless it is
Department of Transportation approved for refilling.

DOT approval is indicated by the designation “DOT 4BA” or “DOT 4BW”

stamped on a tank’s collar

Collar

Neck Usage

Material Pressure

Foot ring Certificate Date

Manufactured
Model
Number
Safety tips:
❖ If a refrigerant tank is overfilled, it may explode.

❖ NEVER perform service on recovery/recycling/recharge equipment

without first consulting authorized service personnel.

❖ NEVER perform maintenance or service on recovery/recycling/recharge

equipment with the unit plugged into electric power unless directed
otherwise.
 Safety tips:
❖ Avoid using extension cords with recovery/recycling/recharge equipment.

❖ Recovery/recycling/recharge equipment often contains parts that may

produce arcs or sparks.

❖ Fuel injection systems on vehicles contain a service port the same size as
one of the CFC12 A/C system service ports. Be careful not to attach A/C
service equipment to a vehicle’s fuel injection system.
Thank you for
listening!
BSME 2-4 <3