2025 ASHRAE HANDBOOK
FUNDAMENTALS
SIEdition Supported by ASHRAE Research
CHAPTER1.PSYCHROMETRICS
Herrmann et al.(2009) Hyland and Wexler(1983a 1983b) and Nelson and Sauer (2002) developed formulas for thermodynamic properties of moist air and water modeled as real gases.However perfect gas relations canbesubstituted inmost air-conditioningproblems.Kuehnet al.(1998) showed that erors areless than 0.7% in calculating humidityratio enthalpyand specific volume of saturated air at standard atmospheric pressure foratemperature range of -50 to 50oC.Furthermore these errors decrease with decreasing pressure.
Herrmann et al. (2020) prepared formulas for transport properties of moist air.
1.COMPOSITIONOFDRYANDMOISTAIR
Atmosphericarcontainsmanygaseousponentsaswellaswatervaporandmiscellaneouscontaminantse.smokepollenandgaseouspollutantsnotnrmallypresentinfreeairfarfrompolltionsourcesaltitude.Harrison(1965) lists the approximate percentage position of dry air by volume as:nitrogen 78.084;oxygen 20.9476;argon 0.934;neon 0.001818;helium 0.000524;methane 0.00015; sulfur dioxide 0 to Dry air isatmospheric air with all watervapor and contaminants removed.Its positionisrelativelyconstant but smallvariations in theamounts of individual ponents occur with time geographic location and0.0001;hydrogen 0.00005;andminorponents suchaskrypton，xenonandozone 0.0002.Harrson1965）and HylandandWexler（1983a）usedavalue0.0314（circa195）forcarbondioxide.Carbondioxidereached0.0379 in2005 is currently increasingby0.00019percent peryearand isprojected toreach0.0438in2036（Gatley et al.2008;Keeling and Whorf 2005a 2005b).Increases incarbon dioxide areoffset by decreasesinoxygen; consequently the oxygen percentage in 2036 is projected to be 20.9352. Using the projected changes the mole mass for dry air for at least the first halfof the 21st century is 28.966 kgda/kmol based on the s ( e o s
(1)
Rda =8314.472/28.966 = 287.042 J/(kgdaK)Moist airis a binary (two-ponent)mixture of dry air and water vapor. The amount of watervapor varies fromzero(dry air) to a maximum that depends on temperature and pressure.Saturation is a state of neutralequilibrium between moist air and the condensed water phase (liquid or solid); unless otherwise stated it assumes a flat interface surface between moist air and the condensed phase. Saturation conditions change when theinterface radius is very small (e.g. with ultrafine water droplets).According to the Industrial Formulation IAPWS-IF97 (R7-97 2012) the mole mass of water is 18.015 257 kgw/mol. The gas constant for water is
(2)
2.U.S.STANDARDATMOSPHERE
propertiesat various altitudes.At sea level standard temperature is15°C;standard barometric pressure is101.325kPa.Temperatureis assumed to decrease linearly with increasing altitude throughout the troposphere（lower The temperature and barometricpressure of atmospheric air vary considerablywith altitude as wellas withlocalgeographic and weather conditions.The standard atmosphere givesastandard of referencefor estimatingatmosphere) and to be constant in the lower reaches of the stratosphere. The lower atmosphere is assumed to consist of dry air that behaves as a perfect gas. Gravity is also assumed constant at the standard value 9.806 65 m/s2. Table 1 summarizes property data for altitudes to 10 000 m.
Pressure values in Table_1 may be calculated from
(3)
The equation for temperature as a function of altitude is
(4)
Z = altitude mp = barometric pressure kPa t = temperature °℃
where
Table 1Standard AtmosphericDatafor Altitudes to10 000 m
-500 18.3 107.47815.0 101.325500 11.8 95.4611 000 8.5 89.8751 500 5.3 84.5562 000 2.0 79.4952 500 1.3 74.6823 000 4.5 70.1084 000 11.0 61.6405 000 17.5 54.0206 000 30.5 24.0 47.1817 000 8 000 37.0 35.600 41.0619 000 43.5 30.74210 000 50.0 26.436
3.THERMODYNAMICPROPERTIESOFMOISTAIR
temperatures from 60 to 90°C.
The following properties are shown in Table 2:
t= Celsius temperature C based ntheIS90 and expressed relative toabsolute temperatureinKelvin by thefollwing reltion:
Ws = humidity ratio at saturation kgw/kgdagaseous phase (moist air) exists in equiibrium with condensed phase (liquid or solid) at given temperature and pressure (standard atmospheric pressure).At given values oftemperature and pressure humidity ratio W can have any value from zero to W s
Vs = speci volume of mois arat saturation m/kgdahs = specific enthalpy of moist air at saturation k/kg da hda = specific enthalpy of dry air kl/kgda In Table 2 hda is assigned a value of 0 at 0°C and standard atmospheric pressure.(x.x) e Ap o Apede eau ypads = epdCp s = specic heat capaityof moist airatstration kb/(kgk)Sda = specific entropy of dry air k/(kgda * K). In Table 2 Sda is assigned a value of 0O at 0°C and standard atmospheric pressure.( . px)/ uogeges e e so yo doa yds = s
Vda = specicvolume o dry i m/kg da
Table 2 Thermodynamic Properties of Saturated Moist and Dry Air at Standard Atmospheric Pressure 101.325 kPa
Specific Volume m²/kgdaSpecific Enthalpy k/kgda SpecificHeat Capacity，kJ/(kgK) Specific Entropy k/(kgda*K)Temp.t °C Humidity Ratio Wykgw/kgda vda Vs hda hs t cp s Sda-60 0. 0.6027 0.6027 60.341 60.325 1.0062 1.0062 0.2494 0.249459 0. 0.6055 0.6055 59.335 59.317 1.0062 1.0062 0.2447 0.2446
85- 0. 0.6084 0.6084 58.329 58.308 1.0061 1.0061 0.2400 0.239957 0. 0.6112 0.6112 57.323 57.299 1.0061 1.0061 0.2354 0.235356 0. 0.6141 0.6141 56.317 56.289 1.0061 1.0061 0.2307 0.230655 0. 0.6169 0.6169 55.311 55.280 1.0060 1.0061 0.2261 0.2260t- 0. 0.6198 0.6198 54.305 54.269 1.0060 1.0060 0.2215 0.221353 0. 0.6226 0.6226 53.299 53.258 1.0060 1.0060 0.2169 0.216752 0. 0.6255 0.6255 52.293 52.247 1.0060 1.0060 0.2124 0.212151 0. 0.6283 0.6283 51.287 51.235 1.0059 1.0059 0.2078 0.2076-50 0. 0.6312 0.6312 50.281 50.222 1.0059 1.0059 0.2033 0.203049 0. 0.6340 0.6340 49.275 49.209 1.0059 1.0059 0.1988 0.19858 0. 0.6369 0.6369 48.269 48.194 1.0059 1.0059 0.1943 0.194047 -46 0. 0. 0.6397 0.6397 0.6426 47.263 46.257 47.179 46.162 1.0058 1.0058 1.0059 1.0058 0.1899 0.189545 0. 0.6425 0.6454 0.6454 45.252 45.144 1.0058 1.0058 0.1810 0.1854 0.1805 0.1850-44 0. 0.6482 0.6483 44.246 44.125 1.0058 1.0058 0.1766 0.176143 0. 0.6511 0.6511 43.240 43.104 1.0057 1.0058 0.1722 0.1716=42 0. 0.6539 0.6540 42.234 42.081 1.0057 1.0058 0.1679 0.167241 0. 0.6568 0.6568 41.229 41.057 1.0057 1.0058 0.1635 0. 0. 0.6596 0.6597 40.223 40.031 1.0057 1.0058 0.1592 0.15836- 0. 0.6625 0.6626 39.217 39.002 1.0057 1.0057 0.1549 0.15398- 0. 0.6653 0.6654 8.211 37.970 1.0057 1.0057 0.1506 0.149537 0. 0.6682 0.6683 37.206 36.936 1.0056 1.0057 0.1464 0.145136 0. 0.6710 0.6711 36.200 35.899 1.0056 1.0057 0.1421 0.140835 0. 0.6738 0.6740 35.195 34.859 1.0056 1.0057 0.1379 0.1364tE- 0. 0.6767 0.6769 34.189 33.815 1.0056 1.0057 0.1337 0.13200. 0.6795 0.6797 33.183 32.766 1.0056 1.0057 0.1295 0.127632 0. 0.6824 0.6826 32.178 31.714 1.0056 1.0057 0.1253 0.123231 0. 0.6881 0.6852 0.6855 31.172 30.656 1.0056 1.0058 1.0058 0.1211 0.1189o- 62- 0. 0. 0.6909 0.6883 30.167 29.593 1.0056 1.0058 0.1170 0.114587- 0. 0.6938 0.6912 0.6941 29.161 28.156 28.525 27.450 1.0056 1.0055 1.0058 0.1088 0.1129 0.1057 0.1101-27 0. 0.6966 0.6970 27.150 26.368 1.0055 1.0058 0.1047 0.101326 0. 0.6994 0.6998 26.144 25.278 1.0055 1.0058 -0.1006 0.096925 0. 0.7023 0.7027 25.139 24.181 1.0055 1.0059 0.0965 0.092424 0. 0.7051 0.7056 24.133 23.074 1.0055 1.0059 0.0925 0.088023 0. 0.7080 0.7085 23.128 21.958 1.0055 1.0059 0.0884 0.0835-22 0. 0.7108 0.7114 22.122 20.831 1.0055 1.0060 0.0844 0.079021 0. 0.7137 0.7143 21.117 19.693 1.0055 1.0060 0.0804 0.0745-20 0. 0.7165 0.7172 20.111 18.542 1.0055 1.0061 0.0765 0.0699-19 0. 0.7193 0.7201 19.106 17.377 1.0055 1.0061 0.0725 0.06538T- 0. 0.7222 0.7231 18.100 16.198 1.0055 1.0062 0.0685 0.0607
17 0. 0.7250 0.7260 17.095 15.003 1.0055 1.0063 0.0646 0.0560-16 0. 0.7279 0.7290 16.089 13.791 1.0055 1.0063 0.0607 0.051315 0. 0.7307 0.7319 15.084 12.560 1.0055 1.0064 0.0568 0.046514 0. 0.7336 0.7349 14.078 11.310 1.0055 1.0065 0.0529 0.0416-13 0. 0.7364 0.7378 13.073 10.037 1.0055 1.0066 0.0490 0.0367-12 0. 0.7392 0.7408 12.067 8.7408 1.0055 1.0067 0.0452 0.0317-11 0. 0.7421 0.7438 11.062 7.4193 1.0055 1.0068 0.0413 0.0267-10 0. 0.7449 0.7468 10.056 6.0705 1.0056 1.0069 0.0375 0.0215-9 0. 0.7478 0.7499 9.0505 4.6921 1.0056 1.0071 0.0337 0.01638- 0. 0.7506 0.7529 8.0449 1.8377 3.2820 1.0056 1.0072 0.0261 -0.0299 0.0110-7 0. 0.7534 0.7560 7.0393 1.0056 1.0074 0.0055s- 6 0. 0. 0.7563 0.7591 0.7591 0.7622 5.0282 6.0337 0.3565 1.1643 1.0056 1.0056 1.0076 1.0078 0.0223 0.0186 0.0000 0.0057-4 0. 0.7620 0.7653 4.0225 2.7276 1.0056 1.0080 0.0148 0.0115c- 0. 0.7648 0.7684 3.0169 4 3368 1.0056 1.0082 0.0111 0.0175-2 0. 0.7677 0.7716 2.0113 5.9952 1.0056 1.0084 0.0074 0.0236-1 0. 0.7705 0.7748 1.0057 7.7064 1.0057 1.0087 0.0037 0.0299o 0. 0.7733 0.7780 0.0000 9.4744 1.0057 1.0090 0.00000 0.03641 0. 0.7762 0.7813 1.0057 11.203 1.0057 1.0092 0.0037 0.04272 0. 0.7790 0.7845 2.0114 12.981 1.0057 1.0095 0.0073 0.04923 0. 0.7819 0.7878 3.0171 14.811 1.0057 1.0098 0.0110 0.05594 0. 0.7847 0.7911 16.696 1.0057 1.0101 0.0146 0.06275 0. 0.7875 0.7944 5.0285 18.639 1.0058 1.0105 0.0182 0.06976 0. 0.7904 0.7978 6.0343 20.644 1.0058 1.0108 0.0219 0.07697 0. 0.7932 0.8012 7.0401 22.714 1.0058 1.0112 0.0254 0.08438 0. 0.7961 0.8046 8.0459 24.853 1.0058 1.0116 0.0290 0.09199 0. 0.7989 0.8081 9.0517 27.065 1.0058 1.0121 0.0326 0.099710 11 0. 0.8046 0.8017 0.8116 10.058 29.354 1.0059 1.0130 1.0125 0.0362 0.1162 0.107812 0. 0. 0.8074 0.8152 0.8188 11.063 12.069 31.724 34.180 1.0059 1.0136 0.0397 0.124813 0. 0.8103 0.8224 13.075 36.727 1.0059 1.0059 1.0141 0.0432 0.0468 0.133714 0.010013 0.8131 0.8262 14.081 39.370 1.0060 1.0147 0.0503 0.143015 0.010694 0.8159 0.8299 15.087 42.114 1.0060 1.0153 0.0538 0.152516 0.011415 0.8188 0.8338 16.093 44.965 1.0060 1.0160 0.0573 0.162417 0.012181 0.8216 0.8377 17.099 47.929 1.0060 1.0167 0.0607 0.172618 0.012991 0.8245 0.8416 18.105 51.011 1.0061 1.0174 0.0642 0.183219 0.013851 0.8273 0.8457 19.111 54.218 1.0061 1.0182 0.0676 0.194220 0.014761 0.8301 0.8498 20.117 57.558 1.0061 1.0191 0.0711 0.205721 0.015724 0.8330 0.8540 21.124 61.037 1.0062 1.0199 0.0745 0.217522 0.016744 0.8358 0.8583 22.130 64.662 1.0062 1.0209 0.0779 0.22980.017823 0.8387 0.8626 23.136 68.443 1.0062 1.0218 0.0813 0.2426
