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Learn about the mechanical refrigeration process and how to diagnose and troubleshoot refrigerant side, air side, and electrical side problems. Learn the basics and then develop your troubleshooting skills on various types of refrigeration and air conditioning systems. Learning air conditioning and refrigeration is fun with this comprehensive and easy to use interactive training software program.

 

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Part 1

This section explains in basic terms the principals that are used to create the refrigeration effect. Graphics and animation's are used in an attempt to make it easy to understand the concepts involved.

First of all, did you know that there is no such thing as cold? You can describe something as cold and everyone will know what you mean, but cold really only means that something contains less heat than something else. All there really is, is greater and lesser amounts of heat. The definition of refrigeration is The Removal and Relocation of Heat. So if something is to be refrigerated, it is to have heat removed from it. If you have a warm can of pop at say 80 degrees Fahrenheit and you would prefer to drink it at 40 degrees, you could place it in your fridge for a while, heat would somehow be removed from it, and you could eventually enjoy a less warm pop. (oh, all right, a cold pop.) But lets say you placed that 40 degree pop in the freezer for a while and when you removed it, it was at 35 degrees. See what I mean, even "cold" objects have heat content that can be reduced to a state of "less heat content". The limit to this process would be to remove all heat from an object. This would occur if an object was cooled to Absolute Zero which is -273º C or -460º F. They come close to creating this temperature under laboratory conditions and strange things like electrical superconductivity occur.

How do things get colder?

The latter two are used extensively in the design of refrigeration equipment. If you place two objects together so that they remain touching, and one is hot and one is cold, heat will flow from the hot object into the cold object. This is called conduction. This is an easy concept to grasp and is rather like gravitational potential, where a ball will try to roll down an inclined plane. If you were to fan a hot plate of food it would cool somewhat. Some of the heat from the food would be carried away by the air molecules. When heat is transferred by a substance in the gaseous state the process is called convection. And if you kicked a glowing hot ember away from a bonfire, and you watched it glowing dimmer and dimmer, it is cooling itself by radiating heat away. Note that an object doesn’t have to be glowing in order to radiate heat, all things use combinations of these methods to come to equilibrium with their surroundings. So you can see that in order to refrigerate something, we must find a way to expose our object to something that is colder than itself and nature will take over from there. We are getting closer to talking about the actual mechanics of a refrigerating system, but there are some other important concepts to discuss first.

The States of Matter

They are of course; solid, liquid and gas. It is important to note that heat must be added to a substance to make it change state from solid to liquid and from liquid to a gas. It is just as important to note that heat must be removed from a substance to make it change state from a gas to a liquid and from a liquid to a solid.

The Magic of Latent Heat

Long ago it was found that we needed a way to quantify heat. Something more precise than "less heat" or "more heat" or "a great deal of heat" was required. This was a fairly easy task to accomplish. They took 1 Lb. of water and heated it 1 degree Fahrenheit. The amount of heat that was required to do this was called 1 BTU (British Thermal Unit). The refrigeration industry has long since utilized this definition. You can for example purchase a 6000 BTUH window air conditioner. This would be a unit that is capable of relocating 6000 BTU's of heat per hour. A larger unit capable of 12,000 BTUH could also be called a one Ton unit. There are 12,000 BTU's in 1 Ton.

To raise the temperature of 1 LB of water from 40 degrees to 41 degrees would take 1 BTU. To raise the temperature of 1 LB of water from 177 degrees to 178 degrees would also take 1 BTU. However, if you tried raising the temperature of water from 212 degrees to 213 degrees you would not be able to do it. Water boils at 212 degrees and would prefer to change into a gas rather than let you get it any hotter. Something of utmost importance occurs at the boiling point of a substance. If you did a little experiment and added 1 BTU of heat at a time to 1 LB of water, you would notice that the water temperature would increase by 1 degree each time. That is until you reached 212 degrees. Then something changes. You would keep adding BTU's, but the water would not get any hotter! It would change state into a gas and it would take 970 BTU's to vapourize that pound of water. This is called the Latent Heat of Vapourization and in the case of water it is 970 BTU's per pound.

So what! you say. When are you going to tell me how the refrigeration effect works? Well hang in there, you have just learned about 3/4 of what you need to know to understand the process. What keeps that beaker of water from boiling when it is at room temperature? If you say it's because it is not hot enough, sorry but you are wrong. The only thing that keeps it from boiling is the pressure of the air molecules pressing down on the surface of the water. When you heat that water to 212 degrees and then continue to add heat, what you are doing is supplying sufficient energy to the water molecules to overcome the pressure of the air and allow them to escape from the liquid state. If you took that beaker of water to outer space where there is no air pressure the water would flash into a vapour. If you took that beaker of water to the top of Mt. Everest where there is much less air pressure, you would find that much less heat would be needed to boil the water. (it would boil at a lower temperature than 212 degrees). So water boils at 212 degrees at normal atmospheric pressure. Lower the pressure and you lower the boiling point. Therefore we should be able to place that beaker of water under a bell jar and have a vacuum pump extract the air from within the bell jar and watch the water come to a boil even at room temperature. This is indeed the case!

A liquid requires heat to be added to it in order for it to overcome the air pressure pressing down on its' surface if it is to evaporate into a gas. We just learned that if the pressure above the liquids surface is reduced it will evaporate easier. We could look at it from a slightly different angle and say that when a liquid evaporates it absorbs heat from the surrounding area. So, finding some fluid that evaporates at a handier boiling point than water (IE: lower) was one of the first steps required for the development of mechanical refrigeration.

Chemical Engineers spent years experimenting before they came up with the perfect chemicals for the job. They developed a family of hydroflourocarbon refrigerants which had extremely low boiling points. These chemicals would boil at temperatures below 0 degrees Fahrenheit at atmospheric pressure. So finally, we can begin to describe the mechanical refrigeration process.

 

 

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Here are Some of the Topics Covered in the

Refrigeration Basics Interactive Training Course:

Index

3 Phase
4 way reversing valve
AB
Absolute Zero
AC
access valves
accessories
accumulator
Accurator
Add On Heat Pump
adiabatic
AEV
AFUE
AHU
air (components of)
Air Conditioning
air (conditions of)
air filtration
alkylbenzene oil
All Electric Heat Pump
Alternating Current
amperage,  also
Annual Fuel Utilization Efficiency
anti-short-cycling device
anticipation
ASHRAE
atom
Automatic Expansion Valve
Azeotrope
Back Seated
Balance Point
barometer
bi-metal disk
Bourdon
Boyle's Law
British Thermal Unit
BTU
bull headed tee
burn outs
capacitor
Capacitor Start Capacitor Run Motor
Capacitor Start Induction Run Motor
capillary line
Celsius
centrifugal compressor
ceramic capacitor
charging
Charle's Law
check valve
Close Coupled
Class 1 conversion
Class 2 conversion
coalescing oil separators
compressors
compressor driver
Compressor Efficiency Test
condensate line
condensate pan
Condenser Dampers
condensing medium
Condensing Unit
conduction (electrical)
conduction (thermal)
conductor (thermal)
controls
Constant Cut In Control
convection
cooling anticipation
cooling load
cooling tower
COP,    also
Coulomb
CPRV
cracked
crankcase heater
CSIR
CSCR
current relay
cut in
cut out
Daulton's Law
DC
Defrost Termination Thermostat
design temperature
Dew Point
Defrost Termination Stat
dielectric
Direct Current
Discharge Service Valve
discharge temperature
distributor
drop in replacement
DSV
EER
EEV
electric defrost
Electro-Magnetism
electrolytic capacitor
Electromotive Force
Electronic Expansion Valve
EMF
energy
Energy Efficiency Ratio
enthalpy
enthalpy controls
entropy
EPRV
evacuation,  also
Evaporative Condenser
Fahrenheit
fan cycling
Fan Delay Thermostat
fan rotation
fan speed controller
filters (air)
filters (refrigerant)
Fixed orifice
flash gas
flammability
Fresh Air
Free Cooling
front seated
gases
Gas Laws
gauge
gauge manifold set
Hand Operated Expansion Valve
hand valve
Head Pressure Control
heat
heat anticipation
Heat of Compression
Heat Pumps
Heating Seasonal Performance Factor
helical oil separators
HEPA
hermetic compressor
Hertz
High Side Float
High Side Restriction
holding circuit
Hop Scotch Method (troubleshooting)
Hot Gas Bypass Regulator
hot gas defrost
Hot Wire Relay
HSPF
hygroscopic
hydrostatic pressure
human comfort zone
humidity
impedance
impingement oil separators
incremental unit
insulation (electrical)
insulation (thermal)
Kelvin
King Valve
Latent Heat
ladder schematic
lead-lag
Line Tap Valve
liquid/vapour interface
Liquid Line Filter/Drier
Liquid Line Solenoid Valve
liquid slugging
LLSV
lock out circuit
Locked Rotor Amperage
Low Side Float
low voltage controls
LRA
magnetism
MAT
Mechanical Cooling
MegOhm
Mercury
mercury bulb thermostat
Metering Device
MFD
micron
micron gauge
Mid Seated
migration
mineral oil
Minimum Fresh Air
Mixed Air
MO
molecule
Mollier Charts
motor theory
motor types
muffler
multiple stages
Non-Recycling Pump Down
OAT
ODS
ODS conversions
OEM
off cycle defrost
Ohm
Ohm's Law
oil failure controls
oil separator
oil slugging
open compressor
ORD
ORI
OROA
Ozone Depleting Substance
Packaged Systems
PAG
Parallel Drop
Permanent Split Capacitor Motor
phosgene
piping
POE
polyalkylglycol oil
polyolester oil
potential relay
pressure
pressure control
Pressure-Enthalpy Diagrams
Pressure Temperature Relationship
PSC
PSIG
Psychometrics
P-Trap
PTC
PT Charts
PTCR
pump down
Radiation
Rankine
receiver
reciprocating compressor
reclaim
recover
recycle
refractometer
refrigerant leaks
refrigerant oils
refrigerants
Refrigerant Side Head Pressure Control
Refrigeration (definition of)
Refrigeration loop
relay
resistance
retrofitting ODS
reuse
reverse cycle defrost
rotary compressor
rotor
run capacitor
running burn out
safety
safety controls
saturated conditions
Schraeder Valve
screw compressor
scroll compressor
Seasonal Energy Efficiency Ratio
Secondary Refrigerant
SEER
semi-hermetic compressor
Sensible Heat
Service Valves
set back
Shaded Pole Motor
short cycling
sight glass
Specific Heat
Split Phase Motors
Split Systems
Squirrel Cage
Start Capacitor
stator
Subcooling
Suction Cut-Off
suction filter
suction/liquid heat exchanger
Suction Service Valve
Superheat
SSV
tackifed
Temperature
TEV
TD (Temperature Difference)
Thermal Starting Relays
Thermostatic Expansion Valve
thermostat - low voltage
three phase motors
time delay fuses
time delay relays
Ton
toxicity
transformer
troubleshooting
TXV
unloader
vacuum
vibration absorber
vibration loop
voltage
wall mounted thermostats
water cooled condensers
water cooled system
water regulator valve
Zeotrope

 

Refrigeration Basics Interactive Training Course

Price $135

Special Offer Only $95!

(Limited Time Special Pricing Promotion)

Easy to Understand Concepts

Large Animated Graphics

Interactive Refrigerant Side Diagnostics

Troubleshoot Electrical Circuit Problems

Review Questions with Links to Answers

Automatic Self-Grading Exam

Easy to Use Software - No Installation Required

Accept Credit Cards

Contact Us at Staff@LearnAC.com

LearnAC.com - 4232 Ella Blvd - Suite 128 - Houston, TX  77018

713-481-0781

Copyright 2008 LearnAC.com - All Rights Reserved -

Sample lesson text and graphics are property of Seaside Computing and may not be reproduced in any manner.