Sheet1Air PropertiesCommon properties for air can be taken from
the table below:TemperatureDensitySpecific heat capacityThermal
conductivityKinematic viscosityExpansion coefficientPrandtl's
number- t -- -- cp -- l - x 10-6b x
10-3Pr(oC)(kg/m3)(kJ/kg.K)(W/m.K)(m2/s)(1/K)-1502.7931.0260.01163.088.210.76-1001.9801.0090.01605.955.820.74-501.5341.0050.02049.554.510.72501.2931.0050.024313.303.670.715201.2051.0050.025715.113.430.713401.1271.0050.027116.973.200.711601.0671.0090.028518.903.000.709801.0001.0090.029920.942.830.7081000.9461.0090.031423.062.680.7031200.8981.0130.032825.232.550.701400.8541.0130.034327.552.430.6951600.8151.0170.035829.852.320.691800.7791.0220.037232.292.210.692000.7461.0260.038634.632.110.6852500.6751.0340.042141.171.910.683000.6161.0470.045447.851.750.683500.5661.0550.048555.051.610.684000.5241.0680.051562.531.490.68Absolute
and Kinematic ViscosityTemperatureDynamic ViscosityKinematic
Viscosity- t -- -- -(oC)(N.s/m2) x 10-5(m2/s) x
10-5-401.571.04-201.631.1701.711.3251.731.36101.761.41151.801.47201.821.51251.851.56301.861.60401.871.66501.951.76601.971.86702.031.97802.072.07902.142.201002.172.292002.533.393002.984.844003.326.345003.647.971,0005.0418.2Altitude
and Air
PressureAltitudeBarometer(m)(mmHg)0749757431507352507263007234507096006957506819006681,0006581,2006431,3506321,5006201,8005982,1005772,400555Altitude
and Air DensityAir density and specific volume as functions of
altitude above sea level are indicated in the diagrams below:STP -
Standard Temperature and PressureSTP - Standard Temperature and
Pressure is 0oC and 101.325 kN/m2.NTP - Normal Temperature and
PressureNTP - Normal Temperature and Pressure, commonly used for
testing and documentation of fan capacities, is 20oC and 101.6
kN/m2 (60oF , 30 in Hg)Altitude and Specific Volume CorrectionThe
specific volume of standard air at a certain altitude can be
calculated by multiplying with the volume correction factor
belowAltitudeVolume Correction
Factor(m)(ft)00148016001.0599033001.11150050001.17198066001.24246082001.31297099001.39Air
- Density and Specific WeightTemperatureDensitySpecific Weight- t
-- --
-(oC)(kg/m3)(N/m3)-401.51414.85-201.39513.6801.29312.6751.26912.45101.24712.23151.22512.01201.20411.81251.18411.61301.16511.43401.12711.05501.10910.88601.06010.40701.02910.09800.99969.803900.97219.5331000.94619.2782000.74617.3173000.61596.0404000.52435.1425000.45654.47710000.27722.719Temperature
and VolumeAir TemperatureVolume Correction
Factor(oC)(oF)-46-500.77-40-400.79-34-300.81-28-200.83-23-100.85-1800.87-9100.89-5200.91-1300.934400.9410500.9618600.9822701.0027801.0232901.04381001.06431101.08491201.10Air
volume used by single-acting pistonsThe diagram below indicates the
air volume used by single-acting pistons.1 cubic feet = 0.028 m31
in = 25.4 mmSpecific Heat Ratio of AirSpecific Heat Ratio of Air at
Standard Atmospheric Pressure in Imperial (BG)
Units:TemperatureSpecific Heat Ratio- t --
k(oF)-401.401-201.40101.401101.401201.401301.401401.401501.401601.401701.401801.400901.4001001.4001201.4001401.3991601.3991801.3992001.3983001.3944001.3895001.3837501.36710001.35115001.329Specific
Heat Ratio of Air at Standard Atmospheric Pressure in SI
Units:TemperatureSpecific Heat Ratio- t -- k
-(oC)-401.401-201.40101.40151.401101.401151.401201.401251.401301.400401.400501.400601.399701.399801.399901.3981001.3972001.3903001.3794001.3685001.35710001.321Speed
of Sound in AirSpeed of Sound in Air at Standard Atmospheric
Pressure in Imperial (BG) UnitsTemperatureSpeed of Sound- t -- c
-(oF)(ft/s)-401004-2010280105110106220107430108540109650110660111770112880113890114910011591201180140120016012201801239200125830013484001431500150975016851000183915002114Speed
of Sound in Air at Standard Atmospheric Pressure in SI
UnitsTemperatureSpeed of Sound- t -- c
-(oC)(m/s)-40306.20331.45334.410337.415340.420343.325346.330349.140354.750360.360365.770371.280376.690381.7100386.9200434.5300476.3400514.1500548.8Steam
and Vapor EnthalpyWhen a liquid evaporates its go through a process
wherethe liquid heats up to the evaporation temperaturethe liquid
evaporate at the evaporation temperature by changing state from
fluid to gasthe vapor heats above the evaporation temperature -
superheatingThe heat transferred to a substance when temperature
changes is often referred to as sensible heat. The heat required
for changing state as evaporation is referred to as latent heat of
evaporation.The most common vapor is evaporated water - steam or
moist.EnthalpyEnthalpy of a system is defined as the mass of the
system - m - multiplied by the specific enthalpy - h - of the
system and can be expressed as:H = m h (kJ)whereH = enthalpy (kJ)m
= mass (kg)h = specific enthalpy (kJ/kg)Specific EnthalpySpecific
enthalpy is a property of the fluid and can be expressed as:h = u +
p v (kJ/kg)whereu = internal energy (kJ/kg)p = absolute pressure
(N/m2)v = specific volume (m3/kg)Part of the water vapor - steam -
properties can be expressed in a table
as:ptsvfvgufughfhgsfsg(bar)(oC)(m3/kg)(m3/kg)(kJ/kg)(kJ/kg)(kJ/kg)(kJ/kg)(kJ/kg.K)(kJ/kg.K)0.006112
1)0.010.0010002206.102,3750.00062,50109.1550,01070.0010001129.2292,385292,5140.1068.974..........1.01325
2)1000.0010441.6734192,5074192,6761.3077.355..........220373.70.002690.003681,9492,0972,0082,1784.2894.552221.2
3)374.150.003170.003172,0142,0142,0842,0844.434.43s is the steam
entropysuffix - f - referrer to saturated liquidsuffix - g -
referrer to saturated vapor - steamInternal energy - u - can be
calculated from (2) and is often omitted in tables. vf - change
very little and is also often omitted.1) referrer to absolute
vacuum.2) referrer to water boiling at standard atmosphere.3)
referrer to water critical point. For pressures above the critical
point there is no definite transition from liquid to vapor.Specific
Enthalpy of Saturated WaterSpecific enthalpy of saturated water -
hf - can be obtained from tables as above. The value depends on the
pressure.For saturated water at standard atmosphere - 2) -the
specific enthalpy - hf - is 419 kJ/kg. At standard atmosphere - 1
bar (14.7 psi) - water starts boiling at 100 oC (212 oF).The
specific enthalpy of water (in SI units) can be calculated from:hf
= cw (tf - t0)wherehf = enthalpy of water (kJ/kg)cw = specific heat
of water = 4.19 (kJ/kg.oC)tf = saturation temperature (oC)t0 =
refer temperature = 0 (oC)Specific Enthalpy of Saturated
SteamSpecific enthalpy of saturated steam - hg - can be obtained
from tables as above. The value depends on the pressure.For
saturated steam at standard atmosphere - 2) - the specific enthalpy
- hg - is 2,676 kJ/kg.The specific enthalpy of evaporation can be
calculated from:he = hg - hf (4)wherehe = specific evaporation
enthalpy (kJ/kg)Specific evaporation enthalpy for water at standard
atmosphere is:he = 2,676 - 419 (kJ/kg) = 2,257 (kJ/kg)Specific
Enthalpy of Superheated SteamThe specific enthalpy of superheated
steam can be calculated from:hs = hg + cps (ts - tf)wherehs =
enthalpy of superheated steam (kJ/kg)cps = specific heat of steam
at constant pressure = 1.860 (kJ/kg.oC)tf = saturation temperature
(oC)ts = superheated steam temperature (oC)cps = 1.860 (kJ/kg.oC)
at standard atmosphere. Be aware that cps varies with
temperature.Common Units for Specific Enthalpy1 kJ/kg = 1,000 J/kg1
erg/g = 1E-4 J/kg1 Btu/lbm = 2,326 J/kg1 cal/g = 4,184
J/kgVacuumVacuum is defined as air pressure below atmospheric
pressureThe vacuum level is the difference in pressure between the
atmospheric pressure and the pressure in the evacuated system:0%
vacuum = 760 torr = 14.7 psia = 29.92 inc mercury abs = 101.4 kPa
abs50% vacuum = 380 torr = 7.3 psia = 15 inc mercury abs = 50.8 kPa
abs99.9% vacuum = 1 torr = 0.01934 psia = 0.03937 inc mercury abs =
1.3 kPa absFor perfect vacuum (100%) - the pressure is 0 torr, 0
psia or 0 Pa abs.Vacuum in %, torr, mm Mercury, psi and kPaThe
table below can be used to convert between common vacuum
units:%TorrMicronpsia,InchesIncheskPaVacuum(mm
Mercury)(lb/in2)MercuryMercuryabsabsAbsoluteGauge0760760,00014.729.920101.41.3750750,00015.529.50.4299.91.9735.6735,60014.228.91.0297.77.9700700,00013.527.62.3293.521600600,00011.623.66.3279.934500500,0009.719.710.2266.747400400,0007.715.714.2253.250380380,0007.31514.9250.861300300,0005.811.818.124074200200,0003.97.8522.0726.687100100,0001.933.9425.9813.3889090,0001.743.5426.381289.58080,0001.553.1526.7710.790.87070,0001.352.7627.169.392.16060,0001.162.3627.5689351.751,70012.0327.896.993.55050,0000.971.9727.956.794.84040,0000.771.5728.355.396.13030,0000.581.1828.74496.625.425,4000.14912128.923.497.42020,0000.390.78529.142.798.71010,0000.1930.39429.531.3997.67,6000.1470.29929.62199.911,0000.019340.0393729.880.1399.90.757500.01450.029529.890.199.990.11000.001930.0039429.9160.01399.9990.01100.0001930.00039429.91960.0013100000029.9201
psi (lb/in2) = 6,894.8 Pa (N/m2) = 6.895x10-3 N/mm2 = 6.895x10-2
barVelocities in Vacuum pipesThe air velocity in vacuum pipes can
be estimated with the diagrams below.Standard and Actual Air Volume
- cfmThe diagram is calculated for steel pipes schedule 40.Standard
and Actual Air Volume - l/s
TemperatureDensityKinematic viscosityTemperatureDynamic
ViscosityKinematic ViscosityTemperatureDensitySpecific
WeightTemperature- t -Temperature- t -s is the steam entropycps =
specific heat of steam at constant pressure = 1.860 (kJ/kg.oC)
Sheet2
Sheet3