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RDI Product Training

RDI Product Training. Refrigeration 101. Table of Contents. Refrigeration 101 3-68 What is Refrigeration? 4 BTU 5 Latent & Sensible Heat 6 Latent Heat 7-12 Saturation Temperature 13 Superheat 14 Sub-cooled Liquid 15 Refrigerants 16-17

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RDI Product Training

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  1. RDI Product Training

  2. Refrigeration 101

  3. Table of Contents Refrigeration 101 3-68 What is Refrigeration? 4 BTU 5 Latent & Sensible Heat 6 Latent Heat 7-12 Saturation Temperature 13 Superheat 14 Sub-cooled Liquid 15 Refrigerants 16-17 Refrigeration Capacity 18 Pressure to Control 19 Refrigeration Cycle 20-68 Compression System 21 Basic System 22 Heat Rejection 23 Compressors 25-29 Oil Separator 30-31 Condenser 32-33 Headmaster Valve 34-36 Liquid Receiver Tank 37-38 Filter/Drier 39-40 Sight Glass 41-42 Solenoid Valve 43-44 Pump-Down 45 TXV 46-49 Superheat 50-52 Evaporators 53-56 EPR & CPR Valve 57-62 Suction Accumulator 63-65 Suction Filter 66-67

  4. What is Refrigeration? • Process of Heat Removal • Heat ALWAYS travels from a warm object to a colder object • Heat travels from the air or product inside a walk-in to the refrigerant inside the evaporator • Heat travels from the refrigerant in the condenser to the air surrounding the condenser

  5. BTU British Thermal Unit • Energy required to increase temperature of 1 pound of water 1 degree Fahrenheit • Approximately equal to energy of one wooden match

  6. Latent Heat & Sensible Heat Latent Heat • Heat that has the effect of changing the state of a substance without changing its temperature • Hidden heat; heat that cannot be sensed with a thermometer Sensible Heat • Heat that causes a change in the temperature of a substance • A rise in temperature that can be sensed with a thermometer

  7. Latent Heat Latent Heat of Vaporization • Liquid to Vapor • The amount of heat that must be added to 1 lb. of liquid at its boiling point to change it into 1 lb. of vapor Latent Heat of Condensation • Vapor to Liquid • The amount of heat that must be released by 1 lb. of vapor at its boiling point to change it into 1 lb. of liquid This is the Essence of Modern Refrigeration

  8. Latent Heat

  9. Latent Heat

  10. Latent Heat

  11. Latent Heat

  12. Latent Heat • When one pound of water boils it absorbs 970 BTU’s at a constant temperature of 212° F • When one pound of steam condenses into water, 970 BTU’s must be extracted constant temperature of 212° F

  13. Saturation Temperature • A saturated liquid or vapor is one at its boiling point; for water at sea level, the saturation temperature is 212° F • At higher pressures, the saturation temperature increases, and with a decrease in pressure, the saturation temperature decreases

  14. Superheated Vapor • The amount of sensible heat over a vapors evaporation point • Water At Sea Level at 220° F has 8° F of Superheat

  15. Sub-cooled Liquid • Any liquid which has a temperature lower than the saturation temperature corresponding to its pressure is said to be sub-cooled • Water at any temperature less than its boiling temperature (212°F at sea level) is sub cooled

  16. Refrigerants • The ability of liquids to absorb enormous quantities of heat as they vaporize is the basis of the mechanical refrigeration system R-22 • Liquid at +25°F and 48.8 psig has a Latent Heat of Vaporization of 90.3 BTU/lb. R-404A • Liquid at -20°F and 16.3 psig has a Latent Heat of Vaporization of 81.6 BTU/lb

  17. Alternative Refrigerants We are constantly looking for new technology and continue to pursue alternative refrigerants Look for possible refrigerant modifications in the future

  18. Refrigeration Capacity • Measured in BTUs or in Tons Not HP • Ton= energy needed to freeze one ton of ice • Each pound of water has a latent heat of fusion of 144 BTU • Ton = 2000 (LBS)*144 (LHF) = 288,000 BTU • 288,000/24 = 12,000 BTU/HR

  19. Pressure to Control State • At Sea Level Water Saturation Point 212° • At 10,000 Feet Water Saturation Point 193°

  20. The Refrigeration Cycle

  21. Compression System • There are two pressures existing in a compression system • Evaporating or low pressure • Condensing or high pressure • The refrigerant acts as a transportation medium to move heat from the evaporator to the condenser where it is given off to the ambient air • The change of state from liquid to vapor and back to liquid allows the refrigerant to absorb and discharge large quantities of heat efficiently

  22. Basic System High Pressure Liquid High Pressure Gas Flow Flow Flow Low Pressure Liquid Low Pressure Gas Flow

  23. Heat Rejection • The condenser is the exit door for the heat that the refrigerant has absorbed in the evaporator and compressor

  24. Refrigeration System Components

  25. Compressor

  26. Compressor • Forces (pumps) the refrigerant through the refrigeration system • Compresses the refrigerant from a low pressure gas to a high pressure gas • First it removes the refrigerant vapor from the evaporator and reduces the pressure in the evaporator to a point where the desired evaporating temperature can be maintained • Second, the compressor raises the pressure of the refrigerant vapor to a level high enough so that the saturation temperature is higher than the temperature of the cooling medium (air or water) used for condensing the refrigerant vapor to a liquid refrigerant We use Reciprocating and Scroll Compressors

  27. Hermetic Compressor Most Prevalent in Smaller Systems Costs Less Refrigerant Acts as Coolant Simple Replacement Cannot be Repaired in Field

  28. Semi-Hermetic Compressor More Robust The “Old Standard” Reputation of Quality More Expensive

  29. Scroll Hermetic System Different Compression System More Expensive than Standard Hermetic Less Expensive than Semi-Hermetic Limited to Larger Systems

  30. Oil Separator

  31. Oil Separator

  32. Condenser

  33. Condenser As heat is given off by the high temperature high pressure vapor, its temperature falls to the saturation point and the vapor condenses to a liquid, hence the name condenser Air Cooled vs. Water Cooled

  34. Headmaster Valve

  35. Headmaster Valve • Designed to maintain head pressure during low ambient conditions • Limits the flow of liquid refrigerant from the condenser while at the same time regulating the flow of hot gas around the condenser to the receiver • The two primary controlling pressures are the dome pressure, opposed by the discharge pressure which bleeds around the pushrods to the underside of the diaphragm

  36. Headmaster Valve Pressure Pre-Set Not Adjustable Gas Mixture Maintains High Pressure Liquid

  37. Liquid Receiver Tank

  38. Liquid Receiver Tank • Liquid storage tank for refrigerant which is not in circulation • Contain high pressure liquid refrigerant and some high pressure refrigerant gas • CVD Technology uses the gas here for defrost mode

  39. Filter/Drier

  40. Filter/Drier • The liquid line filter/drier absorbs moisture, acid and sludge/varnish • It also filters (collects) small foreign particles from the system

  41. Sight Glass

  42. Sight Glass • Also know as the “liquid level moisture indicator” • Provides a visual means to determine if the refrigerant charge is low • Bubbles or foaming in the sight glass indicate a shortage in the flow of refrigerant • Provides a visual means to determine the approximate moisture level within the system • GREEN – Moisture level should be at acceptable range • YELLOW – Moisture level too high. The sight glass should be located in the liquid line after the liquid line filter drier

  43. Solenoid Valve

  44. Solenoid Valve • Located in the liquid line just before the expansion valve inside the evaporator housing • Used in conjunction with the thermostat (temperature control) and a low pressure control in order to achieve an automatic pumpdown

  45. Pump-Down Sequence • The thermostat senses that the interior walk-in temperature has become cool enough. The thermostat opens, de-energizing the normally closed liquid solenoid valve • The solenoid valve closes (stops the flow of refrigerant at the valve). The compressor continues to run. The pressure in the low side of the system is reduced and all remaining liquid in the evaporator changes to vapor • When the low-side pressure has dropped to satisfy the low pressure control setting, the electrical circuit through the low pressure control opens and turns off the compressor Purpose • It removes the refrigerant from the low side, making it impossible for the oil to become diluted with liquid refrigerant. (Refrigerant vapor will always migrate to the coldest point of the system) • It prevents the compressor from having to start-up with a high suction pressure that could overload the compressor motor

  46. TXV

  47. TXV • The Thermostatic Expansion Valve (TXV) controls the flow of refrigerant to the evaporator and also reduces the high pressure liquid to a low pressure liquid and gas • Intelligent device that modulates in order to allow the correct amount of refrigerant to enter the evaporator • Senses the pressure and the temperature of the refrigerant leaving the evaporator, and determine the number of degrees of superheat

  48. TXV Sensing Superheat Liquid Liquid (Starting to Boil)

  49. TXV Sensing Superheat

  50. Superheated Vapor • The amount of sensible heat over a vapors evaporation point • Water At Sea Level at 220° F has 8° F of Superheat

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