R 1 Fundamentals of Refrigeration 1 Temperature Pressure

R 1 Fundamentals of Refrigeration #1 Temperature, Pressure, & Heat Transfer © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2

Heat and Cold is the absence of heat. Heat migrates to cold. Insulation slows the transfer of heat, not stop it. © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 2

Summer Heat Gain Heat Transfer 75 95 hot to cold Heat flows from © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 3

Winter Heat Loss Heat Transfer 70 0 Heat flows from hot to cold © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 4

Heat Rises, Cold Falls Warm air rises, cooler air falls. In a multistory house; – the heat tends to rise upstairs, – the cold falls downstairs. © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 5

Summer in a 3 -Story. Townhouse 75 95 75 75 Fan running © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 6

Summer in a 3 -Story. Townhouse Cold air falls 80 75 95 75 70 Fan running Fan stops © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 7

Winter in a 3 -Story Townhouse 70 0 70 70 Fan running © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 8

Hot air rises Winter in a 3 -Story Townhouse 75 70 0 70 Fan running Fan stops 68 70 70 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 9

Temperature measurement Celsius 100°C Fahrenheit Water boils °F = (9/5 x °C) + 32 °F = (1. 8 x 100) + 32 °F = (180) + 32 °F = 212 Water freezes 212°F 32°F Convert °C to °F: °C =. 55 x (°F – 32) °C =. 55 x (32 -32) °C = 0 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 10

Barometer Atmosphere pushes down Inches 30 25 20 15 29. 92 In. Hg 10 5 0 Mercury (Hg) © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 11

Elevation and boiling temperatures 1. 0” 25. 0” At 30, 000’ elevation water boils at 100 F At 5000’ elevation water boils at 203 F 29. 9” At sea level water boils at 212 F © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 12

Evacuation & Boiling Points Microns Boil Point 29. 92 10. 00 2. 00 1. 00. 20. 10. 04. 02. 01 760, 000 258, 000 52, 000 25, 000 2, 500 1, 000 500 250 212°F 162°F 102°F 80°F 35°F 20°F 5°F 0°F -3°F 30 80 25 DROP in. Hg In. Hg 20 15 10 5 Water Mercury Vacuum Pump © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 13

Pressure and Boiling Points 0 psig 30 psig At 0 psig water boils at 212° At 30 psig water reaches 271° before boiling © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 14

Absolute (psia) vs. Barometric (In. Hg) PSI Absolute 15 12. 5 10 7. 5 5 2. 5 14. 7 PSIA Atmosphere pushes down In. Hg. 0 30 25 20 15 29. 92 In. Hg 10 5 0 Mercury (Hg) © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 15

Low Side Gauge (Compound Gauge) 60 50 40 20 30 30 20 40 70 10 90 50 90 10 R-134 a 55 40 R-22 50 R-404 a 0 10 20 30 350 psi 0 12 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 7. 4 psia 15 in. Hg 0 psia 11 0 30 95 0 60 25 50 20 30 50 10 20 10 40 65 10 80 0 20 0 psig 14. 7 psia 29. 92 in. Hg 40 30 60 50 80 10 0 30 psig 44. 7 psia 70 0 in. Hg 16

Low Side & High Side Gauges • “Low Side” (suction) gauge Blue for cold Compound gauge • Both positive pressure and vacuum • “High Side” (discharge) gauge Red for hot © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 17

Pressure Gauges High Side 90 0 11 10 0 120 13 0 90 190 50 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 R-404 a psi 0 0 0 20 150 60 90 65 95 0 80 10 30 10 25 350 1 10 400 30 psi 0 50 20 10 20 R-134 a R-22 150 30 140 20 0 10 20 70 0 40 R-404 a 0 120 130 150 160 40 180 50 0 10 55 40 R-22 0 100 9 50 60 80 70 100 50 30 10 20 30 50 1 120 35 90 40 10 20 10 50 R-134 a 10 1 70 80 0 20 40 1 13 40 50 50 30 60 11 160 0 00 0 14 70 1 0 20 80 10 30 70 40 20 300 250 70 45 60 50 160 Low Side 0 50 18

Low Side Gauge • Read suction pressure • Read suction temperature • Read vacuum © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 19

Reading the Low Side Gauge 49 psig 70 40 20 10 30 30 60 50 40 70 10 40º (R 22) 90 50 40 30 0 20 69 psig 80 25 90 10 R-134 a 55 40 R-22 50 11 0 30 95 0 50 20 30 50 10 20 10 40 65 10 80 0 20 60 25º (R 22) 60 50 R-404 a 0 10 20 30 350 psi 0 12 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 20

High Side Gauge • Read condensing pressure • Read condensing temperature © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 21

Reading the High Side Gauge 210 psig 110 160 0 125º (R 22) 120 90 120 0 0 120 190 0 20 10 0 R-134 a 45 70 30 160 10 50 0 10 20 R-22 10 400 60 40 50 150 90 100 70 50 70 140 80 150 90 13 0 80 160 0 150 17 0 14 0 11 130 13 105º (R 22) 0 20 35 10 0 278 psig 300 250 R-404 a psi 50 50 0 0 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 22

Pressure / Temperature (PT) Charts • From the system pressure You can find its temperature • If you know the evaporator temperature You can find the suction pressure • If you know the condensing temperature You can find the discharge pressure © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 23

Pressure PSIG 180 185 190 195 200 210 220 230 240 250 260 270 280 290 300 325 350 375 400 425 450 475 Temperatures 134 a 123 125 127 128 130 134 137 140 143 146 149 152 155 22 94 96 98 100 101 105 108 111 114 117 120 123 126 128 131 137 143 149 155 404 A 82 84 86 88 89 92 95 99 102 104 107 110 113 115 118 124 129 134 139 144 149 154 If the condensing temperature is 125°, What is the head pressure of: R 134 a 185 psig R 22 278 psig R 404 A 333 psig If the head pressure of R 22 is 210 psig, The condensing temperature would be? 105° © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 24

Pressure Temperature PSIG 134 a 22 404 A 48 52 24 14 49 53 25 15 50 54 26 16 52 56 28 17 54 57 29 19 56 58 31 20 58 60 32 22 60 62 34 23 62 63 35 25 64 65 37 26 66 66 38 27 68 68 40 29 70 69 41 30 What is the suction pressure if, the evaporator temperature is: 40° for R 22 A/C 68 psig 25° for R 22 Walk-in 49 psig 25° for R 404 Walk-in 62 psig What is the evaporator temperature of R 404, if the suction pressure 50 psig? 16° © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 25

Understanding Latent & Sensible Heat by Heating Ice From 0ºF to Steam @ 212ºF Latent Heat of Vaporization 212º t le ib ea H s en S 32º le 0º ib ns Se He 16 BTUH at Latent Heat of Fusion 144 BTUH 970 BTUH 180 BTUH 160 340 1310 Heat requiredraise 0ºF iceor change to 32ºFice 1ºF? to raise much heat to 1#212ºF water 32ºF ice? of a water? How much heat to heat isof 1 lb. of 32ºF ice statesteam? How much changerequiredfrom 32ºF to 212ºF? to changetemperature to raise 1 lb. of substance: water to 212ºF Weight 144 BTU =(Specific Temperature 1ºFfusion) 1 lb. ice. X 970(212º-32º)heat. X heat of ice) X Difference = BTU water 1 lb. X Specific 144 BTU X (32 -0)ºF vaporization) water. 50 (specificheat of ice) X X BTU =970 180 (Latent heat of = =. 5 BTU = BTU (Latent heat of 16 BTU ice X. 5 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 26

Refrigeration effect of ice • Ice melts by absorbing heat, Cools surrounding air. • Ton of refrigeration = Latent heat of Ton of ice = 2000 lbs. (ton) x 144 BTU (latent heat of ice) = 288, 000 Btu (to melt a ton of ice in 24 hours) = 12, 000 Btu per hour. © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 27

U-Tube Manometer Air flow causes pressure in the duct Pressure moves water column 6 5 4 3 2 1 0 1 2 3 4 5 6 5 WC Pressure is measured in inches of water column (WC) © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 28

Three States of Substance Boiling Above freezing Gases exert pressure equally in all directions Liquids exert pressure on the surfaces of their container Solids exert pressure on their base © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 29

Summary: Forces Exerted by Three States of a Substance SOLID VAPOR LIQUID © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 30

Pascal’s Law “Pressure applied upon a confined fluid is transmitted equally in all directions. ” First used in the development of hydraulic brakes. Refrigerant is a pressurized confined fluid. Whether liquid, vapor, or a combination the pressures are the same within its part of the system. The high side of the system maintains the same pressure throughout, as does the low side. © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 LIQUID VAPOR 31

Dalton’s Law The total pressure of a confined mixture of gases is the sum of the pressures of each of the gasses in the mixture. 30 psig Oxygen 40 psig Nitrogen 70 psig Mixture of Oxygen and Nitrogen © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 32

Density Specific Gravity: IRON The density of a substance relative to the density of water. Water = 62 ÷ 62 = 1. 0 Wood = 38 ÷ 62 =. 6 (Floats) Iron = 480 ÷ 62 = 7. 7 (Sinks) Turtle Density of ? ? ? Wood Density 38 lb/ft 3 Water @ Density of 62 lb/ft 3 Iron Ball Density of 480 lb/ft 3 © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 33

Specific Heat (SH): The amount of heat (Btu) required to raise (or lower) 1 pound of a substance 1° F. SH of water = 1 SH of ice =. 5 How much heat is needed to raise 1 lb. water 1° Q = W x SH x ∆T Q =1 lb. x 1° = 1 Btu 1 Btu raises 1 lb. of water 1° F. © 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 34

© 2004 Refrigeration Training Services - R 1 Subject 1 Temperature, Pressure & Heat Transfer v 1. 2 35