Psychrometry A Trane Air Conditioning Clinic American Standard

Psychrometry A Trane Air Conditioning Clinic © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometry period one The Psychrometric Chart © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometric Chart © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Properties Of Air s Dry-bulb temperature s Wet-bulb temperature s Dew-point temperature s Relative humidity s Humidity ratio © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Dry-Bulb Thermometer © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Wet-Bulb Thermometer © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Condensation Occurs At Dew Point © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Fog Occurs When Air Is Saturated © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Relative Humidity …describes the degree of saturation Relative Humidity = © American Standard Inc. 1999 Amount of moisture that a given amount of air is holding Amount of moisture that a given amount of air can hold Air Conditioning Clinic TRG-TRC 001 -EN

Relative Humidity …compares moisture content to saturation 50% © American Standard Inc. 1999 100% (saturated) Air Conditioning Clinic TRG-TRC 001 -EN

Humidity Ratio …compares water vapor to dry air, by weight © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Knowing Two Properties …lets you determine the remaining three s Dry-bulb temperature s Wet-bulb temperature s Dew-point temperature s Relative humidity s Humidity ratio © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Summer Design Conditions s 95°F DB (dry bulb) s 78°F WB (wet bulb) A X E © American Standard Inc. 1999 E L P M Air Conditioning Clinic TRG-TRC 001 -EN

40 % 78°F 50 % “X Marks The Spot”… 72°F 95°F © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Saturated Air …grains of moisture per pound of dry air DB Temp. Humidity Ratio 25°F 19. 14 60°F 77. 61 30°F 24. 19 65°F 92. 89 35°F 29. 94 70°F 110. 82 40°F 36. 51 75°F 131. 83 45°F 44. 34 80°F 156. 38 50°F 53. 63 85°F 185. 03 55°F 64. 63 90°F 218. 42 © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Plotting Saturation Points 220 218. 42 200 185. 03 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 160 156. 38 140 131. 83 120 110. 82 100 92. 89 80 77. 61 60 64. 63 53. 63 40 44. 34 36. 51 20 19. 14 0 25 24. 19 30 29. 94 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Saturation Curve 220 200 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 100% Relative Humidity Curve 160 140 120 100 80 60 40 20 0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

relationship between… Dry Bulb, Wet Bulb And Dew Point 220 A 200 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 160 140 B C Dry Bulb 60°F 62°F 75°F Wet Bulb 60°F 60. 8°F 65. 2°F Dew Point 60°F Rel Humidity 100% 92% 60% D 90°F 70°F 60°F 37% 120 100 60°F Dew Point 60°F A Wet Bulb 80 B 60 C D 40 20 0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

moisture content doesn’t change by… Adding Sensible Heat 220 200 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 100% Saturation 160 140 120 100 60°F Dew Point 60°F Wet Bulb 80 60 40 20 0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Relative Humidity Curves 220 200 Relative Humidity 160 140 10 0 90 % % Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 120 100 80 60 % 80 % 70 % 60 % 50 % 40 30% 40 20% 20 0 25 10% 30 35 40 45 50 55 60 65 70 75 80 85 0% 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

intersection represents… Three Air Properties 220 200 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 160 140 120 100 Humidity Ratio 80 60 40 0 25 Dry Bulb Relative Humidity 20 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Wet-Bulb Lines 220 200 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 160 140 120 100 BI 80 AI 60 40 CI DI A B C D 20 0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

intersection of two known air properties… Determines The Remaining Three 220 200 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 160 140 120 100 Dew Point 80 Humidity Ratio 60 Wet Bulb 40 Dry Bulb 20 0 25 Relative Humidity 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

A Final Property…Specific Volume 220 200 160 140 5 14. Specific Volume Lines (cubic feet / pound of dry air) 120 100 80 25 0 0 20 0 5 13. 40 14. 60 13. Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Adding Sensible Heat © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Removing Sensible Heat © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Adding Moisture © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Removing Moisture © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

effect of changing… Sensible Heat And Moisture Content © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

effect of changing… Sensible Heat And Moisture Content © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometry period two Air Mixtures © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Entering Air Conditions Air Conditioner Mixture C Outdoor Air (OA) B Supply Fan Cooling Coil A Recirculated Air (RA) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Entering Air Conditions Outdoor Air B A Recirculated Air © American Standard Inc. 1999 80°F 95°F Air Conditioning Clinic TRG-TRC 001 -EN

Determining Entering Air Conditions C 4, 000 cfm Mixed Air 1, 000 cfm= 0. 25 4, 000 cfm OA = 25% RA = 75% Mixture =100% © American Standard Inc. 1999 B 1, 000 cfm OA A 3, 000 cfm RA Air Conditioning Clinic TRG-TRC 001 -EN

Determining Entering Air Conditions Mixed Air Temperature 95°F × 0. 25 = 23. 75°F 80°F × 0. 75 = 60. 00°F Mixture = 83. 75°F © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Entering Air Conditions 70°F B C A 95°F 83. 75°F 80°F © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometry period three Sensible Heat Ratio © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Removing Sensible Heat © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Removing Latent Heat © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

effect of… Removing Sensible And Latent Heat © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

supply air conditions determine… Heat And Moisture Transfer Supply Air Return Air Sensible Heat Latent Heat © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

sensible and latent heat… Effects Of Improper Removal Cooler & Damper Warmer & Drier © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

A Look At “Heat Gain”. . . © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

determining the… Sensible Heat Ratio (SHR) Sensible Heat Gain SHR = Sensible Heat Gain + Latent Heat Gain © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Sensible Heat Ratio Scale 78°F DB 65°F WB Index Point © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Drawing An SHR Line 0. 80 SHR Line A Index Point © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Room SHR dictates… Supply Air Conditions A Line o i t a R t ble Hea Sensi © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

drawing an SHR line for… Other Room Conditions D B Line R H. 60 S 0 C Index Point © American Standard Inc. 1999 80°F Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometry period four Air Quantity © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Coil Curves …show changes in air properties through a cooling coil Curves © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Supply Airflow STEP 1: Calculate the sensible heat ratio (SHR) 80, 000 Btu/hr sensible heat gain 20, 000 Btu/hr latent heat gain 80, 000 Btu/hr SHR = 100, 000 Btu/hr = © American Standard Inc. 1999 0. 80 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Supply Airflow Design Conditions: Room — 78°F DB, 50% RH OA — 95°F DB, 78°F WB Ventilation — 25% OA © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Supply Airflow STEP 2: Plot room, outdoor, and entering conditions 95°F × 0. 25 = 23. 75°F 78°F × 0. 75 = 58. 50°F Mixture = 82. 25°F B C A © American Standard Inc. 1999 0. 80 SHR Air Conditioning Clinic TRG-TRC 001 -EN

Determining Supply Airflow STEP 3: Identify supply air conditions B C A D 56. 5°F © American Standard Inc. 1999 0. 80 SHR 78°F Air Conditioning Clinic TRG-TRC 001 -EN

Determining Supply Airflow STEP 4: Solve the supply airflow equation Sensible Heat Gain 1. 085 × (Room DB – Supply DB) © American Standard Inc. 1999 = Supply Airflow Air Conditioning Clinic TRG-TRC 001 -EN

Determining Supply Airflow STEP 4: Solve the supply airflow equation 80, 000 Btu/hr 1. 085 × (78°F – 56. 5°F) © American Standard Inc. 1999 = 3, 430 cfm Air Conditioning Clinic TRG-TRC 001 -EN

Determining Supply Airflow B C A D 56. 5°F SA D 3, 430 cfm 56. 5°F DB 55. 2°F WB C 82. 2°F DB 68. 6°F WB Mixture RA © American Standard Inc. 1999 B OA A Air Conditioning Clinic TRG-TRC 001 -EN

effect of… Arbitrarily Using 55°F Supply Air 47, 000 Btu/hr sensible heat gain 20, 000 Btu/hr latent heat gain 47, 000 Btu/hr SHR = 67, 000 Btu/hr = © American Standard Inc. 1999 0. 70 Air Conditioning Clinic TRG-TRC 001 -EN

effect of… Arbitrarily Using 55°F Supply Air B AI C DI A D 51°F © American Standard Inc. 1999 0. 70 SHR 55°F Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometry period five Tons Of Refrigeration © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

What is Enthalpy? The total heat energy in one pound of air (Btu/lb) at its present condition: Enthalpy (h) = Sensible Heat + Latent Heat © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Tons Of Refrigeration STEP 1: Find enthalpies entering and leaving coil B C D A 32. 7 23. 5 © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Tons Of Refrigeration STEP 2: Solve the total refrigeration load equation 4. 5 × Supply Airflow × (h 1 – h 2) = Refrigeration Load (Btu/hr) where: h 1 = enthalpy of air entering coil (Btu/lb) h 2 = enthalpy of air leaving coil (Btu/lb) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Determining Tons Of Refrigeration STEP 2: Solve the total refrigeration load equation 4. 5 × 3, 430 cfm × (32. 7 – 23. 5) = 142, 000 Btu/hr = 11. 8 tons of refrigeration 12, 000 Btu/hr/ton © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

determining cooling coil… Sensible And Latent Loads Latent Load B Sensible Load A D C 32. 29. 7 23. 6 5 © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

determining cooling coil… Sensible And Latent Loads Sensible Coil Load: 4. 5 × 3, 430 cfm × (29. 6 – 23. 5) = 94, 150 Btu/hr 7. 8 tons of refrigeration (sensible) Latent Coil Load: 4. 5 × 3, 430 cfm × (32. 7 – 29. 6) = 47, 850 Btu/hr 4. 0 tons of refrigeration (latent) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometry period six Psychrometric Analyses © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

SHR Changes Throughout The Day Full-load conditions B C D 56. 5°F © American Standard Inc. 1999 A 78°F Air Conditioning Clinic TRG-TRC 001 -EN

SHR Changes With Room Load Full Load: 80, 000 Btu/hr SHR = = 0. 80 80, 000 Btu/hr + 20, 000 Btu/hr Part Load: 47, 000 Btu/hr SHR = = 0. 70 47, 000 Btu/hr + 20, 000 Btu/hr © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

New SHR Requires New SA Condition Part-load conditions B C D A © American Standard Inc. 1999 0. 70 SHR 0. 80 SHR Air Conditioning Clinic TRG-TRC 001 -EN

at part-load, with constant supply airflow … Raising SA Temp. Increases Room RH 1. 085 × (78°F – Supply DB) = 3, 430 cfm 60 50 % % 47, 000 Btu/hr Supply DB = 65. 4°F B D DI AI A C 0. 70 SHR 0. 80 SHR 65. 4°F © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Constant-Volume System D C OA B SA A Modulatin RA g Cooling Coil constant quantity of variable- temperature air © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Constant-Volume With Reheat D Reheat Coil E © American Standard Inc. 1999 C Coolin g Coil Room Thermostat B A adding reheat improves humidity control Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Adding Reheat… 47, 000 Btu/hr 1. 085 × (78°F – Supply DB) = 3, 430 cfm Supply DB = 65. 4°F B C D 56. 5°F © American Standard Inc. 1999 E A 0. 80 SHR 65. 4°F Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Adding Reheat… B C D 56. 5°F © American Standard Inc. 1999 E A 0. 70 SHR 0. 80 SHR 65. 4°F Air Conditioning Clinic TRG-TRC 001 -EN

Mixed Air Bypass D SA OA B C Face-and -Bypass Dampers A RA mixed air bypass improves humidity control © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Mixed Air Bypass… 82. 25°F × 0. 455 = 37. 4°F 51. 40°F × 0. 545 = 28. 0°F Mixture = 65. 4°F B C D 51. 4°F © American Standard Inc. 1999 E A 65. 4°F Air Conditioning Clinic TRG-TRC 001 -EN

Effect Of Mixed Air Bypass… B AI D 51. 4°F © American Standard Inc. 1999 E C 0. 70 SHR A 65. 4°F Air Conditioning Clinic TRG-TRC 001 -EN

Variable-Air-Volume (VAV) System D SA OA C VS D RA B A variable quantity of constanttemperature air © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Calculating Part-Load Airflow 47, 000 Btu/hr 1. 085 × (78°F – 56. 5°F) = 2, 015 cfm B AI C A D HR 0. 70 S 0. 80 SHR 55. 5°F © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

PC-based software tools… Simplify Psychrometric Analysis © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

Psychrometry period seven Review © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

review… Five Properties Of Air 220 200 Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) 180 160 140 120 100 Dew Point 80 Humidity Ratio 60 Wet Bulb 40 20 0 25 Dry Bulb Relative Humidity 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 Dry-Bulb Temperature (°F) © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

review… Determining Mixed Air Conditions 95°F × 0. 25 = 23. 75°F 80°F × 0. 75 = 60. 00°F Mixture = 83. 75°F B 70°F A C 95°F 83. 75°F 80°F © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

review… Determining Sensible Heat Ratio SHR = Sensible Heat Gain + Latent Heat Gain A tio Li a R t a e H Sensible © American Standard Inc. 1999 ne Air Conditioning Clinic TRG-TRC 001 -EN

review… Determining Coil Leaving Conditions Sensible Heat Gain 1. 085 × (Room DB – Supply DB) = Supply Airflow B Coil Curve D A C e SHR Lin Supply DB © American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN

review… Determining Tons Of Refrigeration 4. 5 × Supply Airflow × (h 1 – h 2) = Refrigeration Load B C D © American Standard Inc. 1999 A Air Conditioning Clinic TRG-TRC 001 -EN

review… Psychrometric Analysis B C A D SA e SHR Lin C D B OA RA © American Standard Inc. 1999 A Air Conditioning Clinic TRG-TRC 001 -EN

© American Standard Inc. 1999 Air Conditioning Clinic TRG-TRC 001 -EN