Refrigeration Basic for Dummies [R1 Fundamentals on Refrigeration - Technical Services] .ppt
- 1. R1 Fundamentals of Refrigeration #2 Introduction to Refrigeration Systems
- 2. 2 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Example of Elementary Refrigeration Place a tank of refrigerant inside a closed box. The box and refrigerant are the same temperature (equilibrium).
- 3. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 3 Elementary Refrigerator Equilibrium R22 tank inside 80 80 80 Equilibrium 145 psig
- 4. 4 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Begin elementary refrigeration Release refrigerant outside the box. (Note: this is theoretical, EPA regulations do not allow releasing refrigerant into the atmosphere.) What do you suppose happens to the: 1. Pressure in the tank? 2. Temperature of the refrigerant? 3. Temperature in the box?
- 5. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 5 Pressure drops, temperature drops Pressure Drop R22 tank 80 145 psg 70 100 psig 80 80 60 60 As pressure drops, temperature drops, box cools. Release Pressure Vent outside box Tank pressure falls Refrigerant starts boiling Tank cools Box cools Tank absorbs box heat
- 6. 6 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Refrigerant is too expensive to waste How can we recover the refrigerant?
- 7. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 7 Vapor captured in outside tank R22 tank 70 100 psig 60 60 100 psig 80 80 Vapor rises to ambient temperature Vapor pressure rises with ambient 145 psig 60 Check valve
- 8. 8 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Changing vapor back to a liquid 1. Increase the vapor pressure Example: 100 psig to 225 psig 2. This increases the vapor‘s temperature Example: 80° to 110° 3. 80° ambient air is cooler than the vapor 4. The vapor condenses to a liquid
- 9. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 9 Increase pressure to condense vapor to liquid R22 tank 70 60 100 psig 145 psig 80 80 225 psig 110 Cooler ambient air condenses vapor to liquid Increased pressure = increased temperature
- 10. 10 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Return liquid to original tank Higher pressure liquid will returned to the original tank. The hose acts as a metering device, lowering the liquid pressure and temperature.
- 11. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 11 Return liquid to original tank R22 tank 70 60 100 psig 80 225 psig 110 110
- 12. 12 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Names for Components & Piping 1.Compressor Discharge line 2.Condenser Liquid line 3.Metering Device 4.Evaporator Suction line
- 13. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 13 Basic Components and Piping Compressor Metering Device Condenser Discharge Line Liquid Line Suction Line Evaporator
- 14. 14 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Refrigeration System “Baseball Diamond” There are 4 basic components Pipes connects them Half the system is high pressure Half the system is low pressure
- 15. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 15 Basic Components Low Side H igh Side “Baseball Diamond” Compressor Metering Device Condenser Evaporator Discharge Line Suction Line Liquid Line
- 16. 16 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 • A compressor + two tanks + metering device The following simple system illustrates: – High pressure refrigerant temperatures drop as: • discharge gas cools, • then condenses as heat is rejected, • then subcools before entering the TEV. – Low pressure refrigerant temperatures rise as: • Liquid vaporizes as it absorbs heat in the evaporator • Then superheats after all refrigerant has evaporated Simple A/C System Illustration:
- 17. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 17 165o 125o 125o 115o 50o 40o RETURN AIR 75o AMBIENT AIR 95o 278 psig 69 psig Simple A/C System 105o 40o 40o 175o 60o
- 18. 18 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 • Compressor discharges hot gas • Gas condenses to liquid • Metering device lowers pressure • Refrigerant vaporizes • Returns to compressor “Standard” A/C System
- 19. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 19 AMBIENT AIR 95o Standard A/C System R-22 RETURN AIR 75o 40º 40º 69 psig 278 psig 115º 50º EVAPORATOR CONDENSER 125º 125º 175º 60º
- 20. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 20 AMBIENT AIR 95o Standard A/C System R-22 RETURN AIR 75o 40º 40º 69 psig 278 psig 115º 50º EVAPORATOR CONDENSER 125º 125º 175º Condensing Starts Sub-Cooled Liquid Fully Condensed Liquid Super Heated Vapor Evaporation Starts Coil Superheat 10° 60º Total Superheat 20° Fully Evaporated
- 21. 21 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 Commercial Refrigeration System • Compare A/C to refrigeration: • Different “high side”? • Why or why not? • Different “low side”? • Why or why not
- 22. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 22 AMBIENT AIR 95o Typical Walk-In Refrigerator (R22) BOX TEMPERATURE 35 25º 25º 50 psig 280 psig 115º 35º EVAPORATOR CONDENSER 125º 125º 175º 45º TEV
- 23. © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2 23 AMBIENT AIR 95o Typical Walk-In Refrigerator (R22) BOX TEMPERATURE 35 25º 25º 50 psig 280 psig 115º 35º EVAPORATOR CONDENSER 125º 125º 175º 45º TEV Condensing Starts Sub-Cooled Liquid Fully Condensed Liquid Super Heated Vapor Evaporation Starts Coil Superheat 10° Total Superheat 20° Fully Evaporated
- 24. 24 © 2004 Refrigeration Training Services - R1Subject 2 Introduction to Refrigeration Systems v1.2
Editor's Notes
- #17: This is a simplified Air Conditioning system. Suppose we have a tank of R22 on the right and release it into a room. The tank drops in pressure and temperature, absorbing heat from the air surrounding the tank. The loss of refrigerant can be prevented by using a compressor to suck the heated refrigerant into itself. Because we need to have refrigerant return to a liquid state before it can be used for cooling we must compress it first. This raises the temperature of the vapor well above the room temperature. The room air passing over the left tank will condense the hot vapor into a liquid. The liquid then goes through a metering device dropping the pressure and temperature below that of the room. The right tank can absorb the heat of the room, starting the cycle all over again. NOTE: The compressor and the metering devices are the dividing lines between the high pressure and low pressure sides of the system.
- #19: Refrigeration Cycle for a Typical R22 A/C System High Side: High pressure vapor leaves the compressor at a high temperature. When it enters the condenser it first gets rid of the sensible heat of compression and motor heat it picked up in the compressor. This is known as de-superheating. Once it gets rid of that sensible heat it reaches its condensing temperature. In our example, when the vapor has reached 125º it starts condensing into a liquid (changes state) as it rejects the latent heat it picked up in the evaporator. Any additional cooling of the liquid before it leaves the condenser without a change of state is called subcooling. It often picks up additional subcooling in the liquid line before the metering device. Low Side: As it passes through the metering device the high temperature liquid drops in pressure and temperature as it changes to a dense vapor containing tiny droplets of liquid. About 25% of the liquid flashes off dropping the temperature of the remaining liquid from 115º to 40º. That temperature (evaporating temperature) remains the same through the evaporator absorbing latent heat from the refrigerated space as it boils off. When all the refrigerant is boiled off, or vaporized, it is now a “saturated vapor”. Any additional heat it picks up after that is called superheat because only sensible heat can be absorbed when there is no change of state. The vapor continues through the suction line picking up superheat until it gets to the compressor where the cycle starts all over.
- #22: Refrigeration Cycle for a walk-in refrigerator using R22 Note: the main difference between A/C and refrigeration is the evaporator temperature. The condensing temperatures are the same, except freezers and high efficiency A/C units. High Side: High pressure vapor leaves the compressor at a high temperature. When it enters the condenser it first gets rid of the sensible heat of compression and motor heat it picked up in the compressor. This is known as de-superheating. Once it gets rid of that sensible heat it reaches its condensing temperature. In our example, when the vapor has reached 125º it starts condensing into a liquid (changes state) as it rejects the latent heat it picked up in the evaporator. Any additional cooling of the liquid before it leaves the condenser without a change of state is called subcooling. It often picks up additional subcooling in the liquid line before the metering device. Low Side: As it passes through the metering device the high temperature liquid drops in pressure and temperature as it changes to a dense vapor containing tiny droplets of liquid. About 25% of the liquid flashes off dropping the temperature of the remaining liquid from 115º to 25º. That temperature (evaporating temperature) remains the same through the evaporator absorbing latent heat from the refrigerated space as it boils off. When all the refrigerant is boiled off, or vaporized, it is now a “saturated vapor”. Any additional heat it picks up after that is called superheat because only sensible heat can be absorbed when there is no change of state. The vapor continues through the suction line picking up superheat until it gets to the compressor where the cycle starts all over.