Chromalox Big Red Book

Technical

Reference Data Properties of Air

Specific Heat, Viscosity & Density (Weight) of Air at Various Pressures & Temperatures

Specific Heat (Btu/ Lbs/°F) 0.239 0.239 0.239 0.239 0.239 0.240 0.240 0.240 0.240 0.240 0.240 0.240 0.240 0.240 0.241 0.241 0.241 0.242 0.243 0.244 0.245 0.248 0.25 0.254 0.257 0.259 0.262

Absolute Viscosity (Lbs/ Ft/Hr)

Gauge Pressure in Lbs/In 2 (based on atmospheric pressure of 14.7 Lbs/In 2 absolute at sea level)

Air Temp (°F)

0

10

20

30

40

50

60

70

80 100 120 150 200 250 300

Density (Weight) in Lbs/Ft 3

-20 -10 0

0.039 0.039 0.040 0.040 0.041 0.041 0.042 0.042 0.043 0.044 0.045 0.045 0.046 0.047 0.049 0.051 0.052 0.055 0.058 0.060 0.063 0.067 0.072 0.076 0.080 0.085 0.089

0.0900 0.0882 0.0864 0.0846 0.0828 0.0811 0.0795 0.0780 0.0764 0.0750 0.0736 0.0723 0.0710 0.0686 0.0652 0.0626 0.0603 0.0560 0.0523 0.0491 0.0463 0.0414 0.0376 0.0341 0.0314 0.0295 0.0275

0.152 0.149 0.146 0.143 0.140 0.137 0.134 0.131 0.128 0.126 0.124 0.122 0.120 0.116 0.110 0.105 0.101 0.094 0.088 0.083 0.078 0.067 0.063 0.058 0.053 0.049 0.046

0.213 0.209 0.204 0.199 0.196 0.192 0.188 0.184 0.180 0.177 0.174 0.171 0.168 0.162 0.154 0.148 0.143 0.132 0.124 0.116 0.109 0.098 0.089 0.081 0.071 0.069 0.064

0.274 0.268 0.263 0.257 0.252 0.247 0.242 0.237 0.232 0.228 0.224 0.220 0.215 0.208 0.199 0.191 0.184 0.171 0.159 0.150 0.140 0.126 0.114 0.104 0.096 0.089 0.083

0.336 0.328 0.322 0.315 0.307 0.302 0.295 0.291 0.284 0.279 0.274 0.269 0.264 0.255 0.243 0.234 0.225 0.208 0.195 0.184 0.172 0.154 0.140 0.127 0.117 0.109 0.101

0.397 0.388 0.380 0.372 0.365 0.357 0.350 0.343 0.336 0.330 0.324 0.318 0.312 0.302 0.287 0.275 0.266 0.247 0.230 0.216 0.203 0.182 0.165 0.151 0.139 0.129 0.120

0.458 0.448 0.438 0.429 0.421 0.412 0.404 0.396 0.388 0.381 0.374 0.367 0.360 0.348 0.331 0.318 0.305 0.285 0.265 0.249 0.235 0.210 0.190 0.174 0.160 0.148 0.138

0.519 0.508 0.497 0.486 0.477 0.467 0.458 0.449 0.440 0.432 0.423 0.415 0.408 0.394 0.375 0.361 0.347 0.322 0.301 0.282 0.266 0.238 0.216 0.198 0.181 0.168 0.157

0.580 0.567 0.556 0.543 0.533 0.522 0.511 0.501 0.493 0.482 0.473 0.464 0.455 0.440 0.419 0.403 0.388 0.360 0.336 0.316 0.298 0.266 0.241 0.221 0.203 0.188 0.175

0.702 0.687 0.672 0.658 0.645 0.632 0.619 0.607 0.596 0.584 0.572 0.561 0.551 0.533 0.508 0.488 0.470 0.436 0.407 0.382 0.360 0.322 0.292 0.267 0.246 0.228 0.212

0.825 0.807 0.790 0.774 0.757 0.742 0.727 0.713 0.700 0.686 0.673 0.660 0.648 0.626 0.596 0.573 0.552 0.513 0.478 0.449 0.423 0.379 0.343 0.328 0.314 0.289 0.268

1.010 0.989 0.968 0.947 0.927 0.908 0.890 0.873 0.856 0.839 0.824 0.809 0.794 0.767 0.730 0.701 0.674 0.627 0.585 0.549 0.517 0.463 0.419 0.383 0.353 0.327 0.304

1.318 1.288 1.260 1.233 1.208 1.184 1.161 1.139 1.116 1.095 1.074 1.054 1.035 1.001 0.953 0.914 0.879 0.817 0.762 0.715 0.674 0.604 0.547 0.500 0.460 0.427 0.397

1.625 1.588 1.553 1.520 1.489 1.460 1.431 1.403 1.376 1.350 1.325 1.300 1.276 1.234 1.175 1.128 1.084 1.007 0.940 0.883 0.831 0.746 0.675 0.616 0.568 0.526 0.490

1.934 1.890 1.850 1.810 1.770 1.730 1.705 1.661 1.638 1.604 1.573 1.546 1.517 1.465 1.392 1.337 1.287 1.197 1.118 1.048 0.987 0.885 0.801 0.733 0.675 0.625 0.582

10 20 30 40 50

60 70 80 90 100 120 150 175 200 250 300 350 400 500

600 700 800 900 1000

Water Vapor Content of Air in Pounds of Water/100 Ft 3 at Various Temperatures & Relative Humidity Lbs/100 Ft 3 at Specified Relative Humidity 20% 25% 30% 35% 40% 45% 50% 55% 60% 65% 70% 75% 80% 85% 90% 95% 100%

Calculation of Density at Other Tem- peratures & Pressures Density at a specific pressure and tempera- ture can be converted to density at another pressure and temperature using the following equation: D 2 = D 1 T 1 x P 2 T 2 P 1 Where: T 1 = (°F + 460°) initial condition T 2 = (°F + 460°) new condition D 1 = density lbs/ft 3 initial condition D 2 = density lbs/ft 3 new condition P 1 = absolute pressure (psia) initial condition P 2 = absolute pressure (psia) new condition Calculation of Flow or Volume The same formula can be used to convert air flow or volume at gauge pressure (psig) to standard conditions (atmospheric pressure at 70°F) by substituting cubic feet (ft 3 ) or cubic feet per minute (CFM) for density (D): Std. CFM = Actual CFM (70 + 460) x (psig + 14.7) (T 2 +460) 14.7 psia

Air (°F) -20 -10 0 10

.001 .001 .001 .002 .004 .006 .008 .012 .017 .020 .022 .023 .024 .025 .025 .026 .027 .030 .032 .037 .043 .049 .057

.001 .001 .002 .003 .005 .007 .010 .015 .021 .025 .027 .029 .030 .031 .032 .033 .034 .037 .040 .046 .053 .062 .071

.001 .001 .002 .003 .005 .008 .012 .018 .025 .029 .032 .035 .036 .037 .038 .039 .041 .044 .047 .055 .064 .074 .036

.001 .001 .002 .004 .006 .010 .014 .021 .029 .034 .038 .040 .042 .043 .044 .046 .047 .052 .055 .064 .075 .086 .100

.001 .002 .003 .004 .007 .011 .016 .024 .033 .039 .043 .046 .048 .049 .051 .052 .054 .059 .063 .074 .085 .099 .114

.002 .002 .003 .005 .008 .013 .018 .027 .037 .044 .049 .052 .054 .055 .057 .059 .061 .067 .071 .083 .096 .111 .128

.002 .002 .004 .006 .009 .014 .021 .030 .042 .049 .054 .058 .060 .062 .064 .066 .068 .074 .079 .092 .107 .124 .143

.002 .002 .004 .006 .010 .015 .023 .032 .046 .054 .059 .063 .065 .068 .070 .072 .074 .081 .087 .101 .117 .136 .157

.002 .003 .004 .007 .011 .017 .025 .035 .050 .059 .065 .069 .071 .074 .076 .079 .081 .089 .095 .110 .128 .148 .171

.002 .003 .005 .007 .012 .018 .027 .038 .054 .064 .070 .075 .077 .080 .083 .085 .088 .096 .103 .120 .138 .161 .185

.002 .003 .005 .008 .013 .020 .029 .041 .058 .069 .076 .081 .083 .086 .089 .092 .094 .104 .111 .129 .149 .173 .200

.002 .003 .005 .008 .014 .021 .031 .044 .062 .074 .081 .086 .089 .092 .095 .098 .101 .111 .119 .138 .160 .185 .214

.003 .003 .006 .009 .014 .022 .033 .047 .066 .078 .086 .092 .095 .098 .102 .105 .108 .118 .126 .147 .170 .198 .228

.003 .003 .006 .009 .015 .024 .035 .050 .071 .083 .092 .098 .101 .105 .108 .111 .115 .126 .134 .156 .181 .210 .242

.003 .004 .006 .010 .016 .025 .037 .053 .075 .088 .097 .104 .107 .111 .114 .118 .122 .133 .142 .166 .192 .222 .257

.003 .004 .007 .010 .017 .027 .039 .056 .079 .093 .103 .109 .113 .117 .121 .124 .128 .141 .150 .175 .202 .225 .271

.003 .004 .007 .011 .018 .028 .041 .059 .083 .098 .108 .115 .119 .123 .127 .131 .135 .148 .158 .184 .213 .247 .285

20 30 40 50 60 65 68 70 71 72 73 74 75 78 80 85

90 95 100

Note — To convert “grains of moisture” to pounds, multiply grains by 0.0001428.

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