A Trane Air Conditioning Clinic Psychrometry Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Psychrometry period one The Psychrometric Chart Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Psychrometric Chart Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Properties Of Air s Dry-bulb temperature s Wet-bulb temperature s Dew-point temperature s Relative humidity s Humidity ratio

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Dry-Bulb Thermometer

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Wet-Bulb Thermometer

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Condensation Occurs At Dew Point Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Fog Occurs When Air Is Saturated Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Relative Humidity …describes the degree of saturation Relative Humidity 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-TRC001-EN © American Standard Inc %100% (saturated) Relative Humidity …compares moisture content to saturation

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Humidity Ratio …compares water vapor to dry air, by weight

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc 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

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc EXAMPLE Summer Design Conditions s 95°F DB (dry bulb) s 78°F WB (wet bulb)

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc “X Marks The Spot”… 95°F 78°F 50% 40% 72°F

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc °F 30°F 35°F 40°F 45°F 50°F 55°F °F 65°F 70°F 75°F 80°F 85°F 90°F DB Temp. Humidity Ratio DB Temp. Humidity Ratio Saturated Air …grains of moisture per pound of dry air

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) Plotting Saturation Points Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) Saturation Curve 100% Relative Humidity Curve Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) relationship between… Dry Bulb, Wet Bulb And Dew Point 60°F Dew Point 60°F Wet Bulb A B C D Dry Bulb60°F62°F75°F90°F Wet Bulb60°F60.8°F65.2°F70°F Dew Point60°F60°F60°F60°F Rel Humidity100%92%60%37% D D C C B B A A Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) moisture content doesn’t change by… Adding Sensible Heat 100% Saturation 60°F Dew Point 60°F Wet Bulb Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) Relative Humidity Curves Relative Humidity 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) intersection represents… Three Air Properties Humidity Ratio Dry Bulb Relative Humidity Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) Determining Wet-Bulb Lines A A BIBI BIBI CICI CICI DIDI DIDI B B C C D D AIAI AIAI Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) intersection of two known air properties… Determines The Remaining Three Humidity Ratio Dry Bulb Relative Humidity Wet Bulb Dew Point Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) A Final Property…Specific Volume Specific Volume Lines (cubic feet / pound of dry air) Specific Volume Lines (cubic feet / pound of dry air) Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Adding Sensible Heat Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Removing Sensible Heat Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Adding Moisture Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Removing Moisture Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

effect of changing… Sensible Heat And Moisture Content Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

effect of changing… Sensible Heat And Moisture Content Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Psychrometry period two Air Mixtures Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioner Supply Fan Mixture Outdoor Air (OA) Recirculated Air (RA) A A C C B B Cooling Coil Determining Entering Air Conditions Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

80°F 95°F Determining Entering Air Conditions B B A A Outdoor Air Recirculated Air Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

1,000 cfm 4,000 cfm = 0.25 OA RA Mixture ====== 25% 75% 100% A A C C B B 4,000 cfm Mixed Air 1,000 cfm OA 3,000 cfm RA Determining Entering Air Conditions Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc °F × 0.25 = 23.75°F 80°F × 0.75 = 60.00°F Mixture = 83.75°F Mixed Air Temperature Determining Entering Air Conditions

83.75°F 70°F Determining Entering Air Conditions B B 80°F 95°F C C A A Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Psychrometry period three Sensible Heat Ratio Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Removing Sensible Heat Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Removing Latent Heat Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

effect of… Removing Sensible And Latent Heat Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Supply Air Sensible Heat Sensible Heat Latent Heat Latent Heat Return Air supply air conditions determine… Heat And Moisture Transfer Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

sensible and latent heat… Effects Of Improper Removal Cooler & Damper Cooler & Damper Warmer & Drier Warmer & Drier Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

A Look At “Heat Gain”... Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc SHR Sensible Heat Gain Sensible Heat Gain + Latent Heat Gain = determining the… Sensible Heat Ratio (SHR)

78°F DB 65°F WB 78°F DB 65°F WB Index Point Sensible Heat Ratio Scale Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

0.80 SHR Line Drawing An SHR Line A A Index Point Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Sensible Heat Ratio Line Room SHR dictates… Supply Air Conditions A A Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

C C D D B B 80°F drawing an SHR line for… Other Room Conditions 0.60 SHR Line Index Point Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Psychrometry period four Air Quantity Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Coil Curves Coil Curves …show changes in air properties through a cooling coil Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc ,000 Btu/hr sensible heat gain 20,000 Btu/hr latent heat gain = 0.80 STEP 1: Calculate the sensible heat ratio (SHR) 80,000 Btu/hr 100,000 Btu/hr SHR = Determining Supply Airflow

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Room — 78°F DB, 50% RH OA — 95°F DB, 78°F WB Ventilation — 25% OA Determining Supply Airflow Design Conditions:

95°F × 0.25 = 23.75°F 78°F × 0.75 = 58.50°F Mixture = 82.25°F Determining Supply Airflow STEP 2: Plot room, outdoor, and entering conditions 0.80 SHR A A C C B B Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

56.5°F 78°F STEP 3: Identify supply air conditions 0.80 SHR A A C C B B D D Determining Supply Airflow Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Sensible Heat Gain × (Room DB – Supply DB) Supply Airflow = STEP 4: Solve the supply airflow equation Determining Supply Airflow

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc ,000 Btu/hr × (78°F – 56.5°F) 3,430 cfm = STEP 4: Solve the supply airflow equation Determining Supply Airflow

D A C B 3,430 cfm 56.5°F DB 55.2°F WB RA OA 82.2°F DB 68.6°F WB Mixture Determining Supply Airflow SA 56.5°F D D A A C C B B Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc effect of… Arbitrarily Using 55°F Supply Air 47,000 Btu/hr sensible heat gain 20,000 Btu/hr latent heat gain = ,000 Btu/hr 67,000 Btu/hr SHR =

A A C C B B D D 55°F DIDI DIDI AIAI AIAI effect of… Arbitrarily Using 55°F Supply Air 0.70 SHR 51°F Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Psychrometry period five Tons Of Refrigeration Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc What is Enthalpy? Enthalpy (h) = Sensible Heat + Latent Heat The total heat energy in one pound of air (Btu/lb) at its present condition:

Determining Tons Of Refrigeration STEP 1: Find enthalpies entering and leaving coil A A B B C C D D Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc 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)

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc = 11.8 tons of refrigeration 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 142,000 Btu/hr 12,000 Btu/hr/ton

determining cooling coil… Sensible And Latent Loads A A B B C C D D Sensible Load Latent Load Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Sensible Coil Load: 4.5 × 3,430 cfm × (29.6 – 23.5) = 94,150 Btu/hr 7.8 tons of refrigeration (sensible) determining cooling coil… Sensible And Latent Loads Latent Coil Load: 4.5 × 3,430 cfm × (32.7 – 29.6) = 47,850 Btu/hr 4.0 tons of refrigeration (latent)

Psychrometry period six Psychrometric Analyses Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

SHR Changes Throughout The Day Full-load conditions 56.5°F 78°F D D A A B B C C Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Full Load: 80,000 Btu/hr 80,000 Btu/hr + 20,000 Btu/hr SHR = Part Load: = ,000 Btu/hr 47,000 Btu/hr + 20,000 Btu/hr SHR == 0.70 SHR Changes With Room Load

D D A A B B C C New SHR Requires New SA Condition 0.80 SHR 0.70 SHR Part-load conditions Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

D D A A B B C C at part-load, with constant supply airflow … Raising SA Temp. Increases Room RH 0.80 SHR 0.70 SHR AIAI AIAI DIDI DIDI 50%50% 60%60% 47,000 Btu/hr × (78°F – Supply DB) = 3,430 cfm Supply DB = 65.4°F 65.4°F Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

constant quantity of variable-temperature air OA RA SA Constant-Volume System B D C A Modulating Cooling Coil Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Reheat Coil Cooling Coil Room Thermostat adding reheat improves humidity control B E D C A Constant-Volume With Reheat Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

D D A A C B B 47,000 Btu/hr × (78°F – Supply DB) = 3,430 cfm Supply DB = 65.4°F Effect Of Adding Reheat… E E 0.80 SHR 65.4°F 56.5°F Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Adding Reheat… D D A A C C B B E E 0.80 SHR 65.4°F 56.5°F 0.70 SHR Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

mixed air bypass improves humidity control Mixed Air Bypass OA RA SA B D C A Face-and- Bypass Dampers Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Mixed Air Bypass… D D A A C C B B E E 82.25°F × = 37.4°F 51.40°F × = 28.0°F Mixture = 65.4°F 65.4°F 51.4°F Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Effect Of Mixed Air Bypass… 0.70 SHR A A C C B B AIAI AIAI 65.4°F 51.4°F D D E E Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc Variable-Air-Volume (VAV) System OA RA SA B D A C variable quantity of constant-temperature air VSD

D D A A C C B B Calculating Part-Load Airflow 47,000 Btu/hr × (78°F – 56.5°F) = 2,015 cfm 0.80 SHR 0.70 SHR AIAI AIAI 55.5°F Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc PC-based software tools… Simplify Psychrometric Analysis

Psychrometry period seven Review Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

30 Dry-Bulb Temperature (°F) Grains Of Moisture Per Pound Of Dry Air When Saturated (grains/lb of dry air) review… Five Properties Of Air Humidity Ratio Dry Bulb Relative Humidity Wet Bulb Dew Point Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

80°F 95°F 83.75°F 70°F C C B B A A review… Determining Mixed Air Conditions 95°F × 0.25 = 23.75°F 80°F × 0.75 = 60.00°F Mixture = 83.75°F Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

A A Sensible Heat Ratio Line review… Determining Sensible Heat Ratio SHR = Sensible Heat Gain Sensible Heat Gain + Latent Heat Gain Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

A A C C B B D D Coil Curve Sensible Heat Gain × (Room DB – Supply DB) Supply Airflow review… Determining Coil Leaving Conditions SHR Line = Supply DB Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

A A C C B B D D review… Determining Tons Of Refrigeration 4.5 × Supply Airflow × (h 1 – h 2 ) = Refrigeration Load Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

C C OA RA B B A A D D SA review… Psychrometric Analysis SHR Line A B C D Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999

Air Conditioning Clinic TRG-TRC001-EN © American Standard Inc. 1999