29_ properties of air and water 61294_27

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Properties of Air and Water

27PA RT27

H VA C E Q U AT I O N S , D ATA , A N D R U L E S O F T H U M B



384 PART 27

27.01 Properties of Air/Water Vapor Mixtures

A. Psychrometric Definitions:

1. Dry Bulb Temperature. The temperature of air read on a standard thermometer. Units:° F.DB. Symbol: TDB or DB.

2. Wet Bulb Temperature. The wet bulb temperature is the temperature indicated by athermometer whose bulb is covered by a wet wick and exposed to air moving at a veloc-ity of 1,000 feet per minute. Units: ° F.WB. Symbol: TWB or WB.

3. Humidity Ratio. The weight of water vapor in each pound of dry air; also known as spe-cific humidity. Units: Lb.H 2O/Lb.DA or Gr.H 2O/Lb.DA. Symbol: W.

4. Enthalpy. A thermodynamic property which serves as a measure of the heat contentabove some datum temperature (Air 0 ° F.DB and Water 32 ° F.). Units: Btu/Lb.DA orBtu/Lb.H 2O. Symbol: h.

5. Specific Volume. The cubic feet of air/water mixture per pound of dry air. Units:Cu.Ft./Lb.DA. Symbol: SpV.

6. Dew Point Temperature. The temperature at which moisture will start to condensefrom the air. Units: ° F.DP. Symbol: T DP or DP.

7. Relative Humidity. The ratio of water vapor in the air/water mixture to the water vaporin saturated air/water mixture. Units: %RH. Symbol: RH.

8. Sensible Heat. Heat that causes a rise in temperature. Units: Btu/Hr. Symbol: H S.9. Latent Heat. Heat that causes a change in state (i.e., liquid water to gaseous water).

Units: Btu/Hr. Symbol: H L.

10. Total Heat. Sum of sensible heat and latent heat. Units: Btu/Hr. Symbol: H T.11. Sensible Heat Ratio. The ratio of the sensible heat to the total heat. Units: None. Sym-bol: SHR.

12. Vapor Pressure. Pressure exerted by water vapor in the air. Units: In.Hg. Symbol: P W.13. Standard Barometric Pressure. Pressure at Sea Level (29.921 InHg. = 14.7 Psi).

B. Thermodynamic Properties of Air/Water Mixtures are given in the followingtables:



Properties of Air and Water 385

Thermodynamic Properties of Moist Air @ 14.696 PSIA



386 PART 27




388 PART 27




390 PART 27




392 PART 27

27.02 Properties of Air

Barometric Pressures at Various Altitudes at 70 ° F.




Air Equation Constants for Altitude

Notes:

1. Equation Constants Units: BTU/Hr. CFM ° F.2. Equation Constants Units: BTU LbDA/Hr. Gr.H 2O CFM.3. Equation Constants Units: BTU LbDA/Hr. Lb.H 2O CFM.4. Equation Constants Units: Lb.DA/Hr. CFM.5. Use table values in lieu of constants in equations in Part 5, Equations.



394 PART 27

Air Equation Constants for Temperature

Notes:

1. Equation Constants Units: BTU/Hr. CFM ° F.2. Equation Constants Units: BTU LbDA/Hr. Gr.H 2O CFM.3. Equation Constants Units: BTU LbDA/Hr. Lb.H 2O CFM.4. Equation Constants Units: Lb.DA/Hr. CFM.5. Use table values in lieu of constants in equations in Part 5, Equations.




Air Equation Factors for Density

Notes:

1. Multiply constants in equations in Part 5, Equations, by values in the table.



396 PART 27


Notes:






Notes:




398 PART 27

Physical Properties of Gases




27.03 Properties of Water

Boiling Points of Water



400 PART 27

Thermodynamic Properties of Water



402 PART 27




404 PART 27




406 PART 27




408 PART 27




410 PART 27


Properties of Water




Water Equation Factors

Notes:

1. Water equation corrections for temperature, density, and specific heat.2. For glycol system equation factors, see Section 27.04, Glycol Systems, below.

27.04 Glycol Systems

Ethylene Glycol



Note:

1. Specific gravity with respect to water at 60 ° F.

412 PART 27

Propylene Glycol

29_ properties of air and water 61294_27

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