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Refrigeration 101 (PDF) Refrigeration 101 Rusty Walker, Corporate Trainer Hill PHOENIX Compressor Basic Evaporator Condenser / Refrigeration Receiver Cycle Expansion Device Vapor Compression Cycle The MOVEMENT Cooling by the of HEAT from a removal of heat place where it is not wa nted to a place where it is unobjectionable How Heat is Removed What is heat? A form of energy What is cold? Absences of heat. How does heat High heat to low heat flow? Does cold NO flow? How is heat British Thermal Unit (BTU) measured? Heat is a form of energy and is measured British in BTU’s. Thermal Unit (BTU) A BTU is the quantity of heat required to raise the tempp,erature, of one p ound of water, one degree Fahrenheit. 1. Heat flows from high energy levels to a lower energy level. 1 2. Heat will n ot fl ow wi th out a 2 temperature difference 3 3. The greater the temperature difference, the faster the energy will flow. Radiation HtHeat Flows Three Ways Convection Conduction Conduction The transfer of heat Example: from molecule to Heating one end of molecule through a copper tube , will a substance by cause the other chain collision end to get hot. Convection Heat transfer by the Example: movement of •Convection oven molecules from •Forced air furnace one place to another. Radiation The transfer of heat Example: by passing from a Sunlight – goes source to an through a window absorbent surface without heating the without heating glass but heats the the space in su rface in the room between. it is shinning on. Temperature Temperature indicates the average velocity of the molecules of a substance. As the heat energy in a substance increases, it’ s molecules vibrate more intensely A thermometer measures the iiintensity of this vibrat ion. Thermometers do not measure heat, they measure the effect of heat. Temperature Animation The amount of heat (measured in BTU’s) required to raise one pound of a substance one degree Fahrenheit. Specific Heat Temp Rise (Deg F) Substance (BTU/LB/Deg F) (From 1 BTU Addition) Water (Liquid) 1.00 1.00 Ice 0.50 2.00 Steam 0480.48 2082.08 Aluminum 0.22 4.54 Brass 0.09 11.11 Physical State of a Substance Gas Adding heat Changing the energy in any of state of a the three states substance will Liquid will increase the require a larger temperature. quantity of heat energy. Solid Heat Energy There are two types of Heat 1. 2. Energy Sensible Heat Latent Heat 1. Is the energy of molecular motion 1 2. Causes a change in temperature, with 2 No change in state. 3. Sensible heat causes an increase in 3 molecular motion. 4 4. The addition or removal of sensible heat is measurable with a thermometer 1. Is the energy of molecular separation and arrangement. 1 2. Causes a ch an ge in state, whil e tteehere 2 is no change In temperature. 3 3. It can not be measured with a thermometer. Mechanical refrigeration The majority of heat is The majority of the works by changing the removed from the absorbed heat is state of the refrigerant. temperature controlled removed from the space as the refrigerant refrigeration system in absorbs heat when it the condenser as the changes state from a refrigerant changes liquid to a gas in the state from a gas back to evaporator. a liquid. Vapor Compression Cycle Example (Deg. F.) ( Deg. C.) 970 BTU’sNo are requiredmeasurable to changetemperature the water 250 to Latentsteam.Boilingchange Heat Water MeasurableSensibleSteam 212 100 200 tttHeatemperature 152 change 180MblMSiblSenseasura BTUibl’s e blare e 100 Liquid Heat Energy is addddded to requiredtemperatureHeat to reach Boiling 50 change 32 °F. (0°C) Water (liquid) 32 0 Point 25 100 200 400 600 800 1000 1100 1200 BTU’s The temperature Add Heat = Liquid to Vapor (Vaporization) at which a substance will change state from a liquid to a vapor or a vapor to a Remove Heat = Vapor to Liquid liquid (()Condensation) At a temperature Addition of Heat = Boiling equal to it’s boiling point or condidensing point, a substance can be both vapor and Removal Heat = Condensing liquid. 100% Liquid, no vapor present At a temperature blbelow i’it’s bo iling point, a substance is: 1lb. Of water @ 200o F. What is the state of water? - Sub-cooled liquid - Sub-cooled by 12o F. 100% vapor, no liquid present At a temperature above it’s boiling point, a substance is: 1lb. Of water @ 220o F. What is the state of water? - Super heated vapor (steam) - Super heated by 8o F. Example (Deg. F.) ( Deg. C.) A mixt ure of vapor 250 Temperature at 212 ° F. (100°C) Sensible = Saturatedand liquid. Mixture Temperature100MeasurableSteam % vapor Above 212 100 Heat212° F. (100°C) = 200 Su-temThereppperheatedperature is Va nopor 152 liquid.change Temperature100 % liquid below 100 212 °F. (100°C) = Saturation Temperature of Water -ThereSub-cooled isLiquid no is 212 °F. (100°C) at Sea Leve l 50 vapor. (0 PSIG / 14.7 PSIA) 32 0 25 100 200 400 600 800 1000 1100 1200 BTU’s Pressure: Defined as a force per unit of area PSI Bars KPA How does pressure flow? High To Low What would happen if you take Refrigerant flows two refrigerant from the tank tanks, one with with refrigerant to refrigerant and the the tank that is in other in a vacuum a vacuum, until and connect a the pressures hose between equalize. them? As the pressure on a substance increases, boiling temperature will increase. As pressure decreases, boiling temperature will also decrease. Pressure and boiling temperature follow each other At the boiling point we have both Liquid and Vapor . As the pressure increases, saturation temperature will increase. As pressure decreases, saturation temperature will also decrease. Pressure and boiling temperature follow each other At the saturation temperature we have a saturated mixture (both liquid and vapor are present). Atmospheric Pressure • At Sea Level, the atmospheric pressure on our bodies is 14.7 PSIA. • A column of air, one inch square and 60 miles high weighs 14.7 pounds. Pressure Scales Gauge Scale Absolute Scale ATMOSPHERE 0 PSIG 14.7 PSIA (Pressure @ Sea Level) 0 in Hg 29.92 in Hg Hg is the symbol for Mercury. VACUUM 29. 92 in Hg 0 in Hg Compound Gauge Gauge Scale: Positive Pressure Scale Vacuum Scale (Reference Only!) Vacuum Gauge Absolute Pressure in microns of Hg. Mercury Barometer Vacuum Atmospheric Pressure at Sea Level Column of mercury supporte77606d bcmy mm atmospheric29.92 in pressure. Hg 1 inch of Hg =25,400 microns Mercury A medium to move heat A substance that absorbs heat by evaporating at low temperatures What is a and pressures. refrigerant? And ggpives up heat by condensing at high temperatures and pressures Refrigerants No Longer Available R‐12 CFC R‐11 CFC R‐500 CFC R‐502 CFC • 100% Ozone • 100% Ozone • 66% Ozone • 28% Ozone depletion depletion depletion depletion potential • Used in • Used in • Used in • Used in centrifugals 50hz deep freezers every thing • Med. Temp • Med. - Low • Low. Temp • Med. – Low Te m p temp. Production Production Production Production ceased in 1995 ceased in 1995 ceased in 1995 ceased in 1995 RefrigerantsCurrently in Use R22HCFC RR134aHFC R507HFC 404AHFC • • 5% Ozone • 0% Ozone • 0% Ozone 0% Ozone depletion depletion depletion depletion • potential • Used in • Used in Used in • Used in auto A/C freezers deep freezers • every thing • Med. - Low •Low Temp Med. – Low • Med. – Low Te m p Te m p temp. Production phase out Replaced R-12 Replaced R-502 Compressor Refrigeration Evaporator Condenser / System Receiver Components Expansion Device Compressors Compressors Additional Compressor Types Example Mechanical Center Condensers CdCondensers Air Cooled Water Cooled Tube and fin Shell and tube Plate Evaporative Superheated Sub-cooled Vapor In Liquid Out Evaporative Plate Metering Device TXV and Electronic Evaporators Display Case Evaporators WalkWalk--InIn Evaporators Plate to Plate Heat Exchanger Questions.
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