湿空气的概念
湿空气是指干空气和水蒸气的混合物。室内空气都是含有一定水分的湿空气。在一定的温度与压力条件下,一定容积的干空气所能容纳的水蒸气量是有一定限度的，达到这个限度称为饱和水蒸气，未达到这个限度的称为未饱和
水蒸气。
处于饱和状态的湿空气中，水蒸气呈现的压力称作饱和蒸汽压或最大水蒸气压力，用符号?来表示，未饱和空气的蒸汽压用e来表示，单位是毫米水银柱高(mmHg)。由于空气所含的水分越多，空气的水蒸气压力就愈大，因水蒸气分压力的大小能反映空气中含水分的多少。可以用它来表示空气的绝对湿度，而相对湿度则是空气的水蒸气分压力与同温度下空气的最大水蒸气分压力之比(以百分数来表示）。
^=ixl00%(3-28)
式中0——空气的相对湿度，％
e–同温度下空气中的水蒸气的最大水蒸气分压力,mmHg(可从实际
查得）
实际在各种温度下最大水蒸气分压力?值(大气压力p=760mmHg时）
t/x：02468tlX：02468
-400.09————-200.770.760.750.730.71
-390.10————-190.850.830.820.800.79
-380.12————-180.940.920.900.880.87
-370.13————-171.031.010.990.970.96
-360.15————-161.131.111.091.071.05
-350.17————-151.241.221.191.171.15
-340.18———.—-141.361.341.311.291.26
-330.20————-131.491.461.431.411.38
-320.230.230.220.220.21-121.631.601.571.551.52
-310.250.250.240.240.23-111.781.751.721.691.66
-300.280.280.270.260.25-101.951.911.881.841.81
-290.310.300.290.290.28-92.132.092.052.011.98
-280.340.340.330.330.32-82.322.282.242:202.17
-270.380.370.360.360.35-72.532.492.452.412.36
—260.420.410.400.390.39-62.762.722.672.632.58
-250.470.460.450.440.43-53.012.962.912.862.81
-240.520.510.500.490.48-43.283.223.173.113.06
-230.580.560.550.540.53-33.573.513.453.393.34
-220.640.620.610.600.59-23.883.923.753.693.63
-210.700.690.670.660.65-14.224.154.084.013.95
续表
tlx：02468tlX：02468
584.514.444.364.302523.7624.0424.3324.6224.91
654.724.794.862625.2125.5125.8126.1226.46
935.005.075.145.222726.7427.0627.3727.7028.02
295.375.455.535.612828.3528.6829.0229.3529.70
695.775.855.936.022930.0430.3930.7531.1031.46
106.196.276.366.453031.8232.1932.5932.9333.31
546.646.736.826.92.3133.7034.0834.4734.8635.26
017.117.217.317.413235.6636.0736.4836.8937.31
517.627.727.837.933337.7338.1638.5839.0239.46
8「8.058.168.278.388.493439.9040.3440.80^41.2541.77
618.738.858.979.093542.1842.6443.1243.6044.08
219.339.469.599.713644.5645.0545.5546.0546.56
849.9810.1110.2410.3B3747.0747.5848.1048.3649.10
5210.6610.8010.9411.093849.6950.2350.7751.3251.909
23U.3811.5311.6811.833952.4453.0153.5854.1654.74
9912.1412.3012.4612.624055.3255.9156.6157.1157.72
7912.9513.1213.2913.464158.8458.%59.5960.2260.86
6313.8113.9914.1714.354261.5062.1462.8063.4664.12
5314.7214.9015.0915.284364.8065.4866.1666.8667.56
4815.6715.8716.0716.274468.2668.9769.6970.4171.14
4816.6916.8917.1117.324571.8872.6273.3674.1274.88
5417.7517.9718.2018.424675.6576.4377.2178.0078.80
6518.8819.1119.3519.594779.6080.4181.2382.0582.87
8320.0720.3220.5720.824883.7184.5685.4286.2887.14
0721.3221.5821.8522.114988.0288.9089.7990.6991.59
3822.6522.9223.2023.485092.51
注：本表摘自西安冶金建筑学院物理实验室《建筑热工设计》。
从上式中可知，影响空气相对湿度的大小有两种情况：
一是e值不变，即空气中水蒸气含量不变。?：值变大则相对湿度变小，?变小则相对湿度变大。则附录n可见温度越低?值愈小，当温度降到?值与e
值相等时，空气的相对湿度为100%;
空气中水蒸气的含量大小而改变，当e值增加到与?值相等时，相对湿度为100%。在上述两种情况下空气中的水蒸气的含暈都达到饱和状态，这时空气的温度称为露点，用、广来表示，当空气温度达到露点温度时，将开始从空气中凝结出水分来。
[例3-1]已知空气f=20t，相对湿度4=70%。求露点温度。
解：查实际,当t=20t：时，?=17.54mmHg,
因必二70%,故此时空气的水蒸气分压力另可查实际,当空气温度为20t：和相对湿度为70%时的露点酿为14.Ot：。
实际各种气温、相对湿度下的露点温度单位：X：
露点空气的相对湿度/%
父’面义/乙6065707580859095100
528.029.330.531.732.934.035.136.0
626.127.428.629.831.032.133.134.0
724.225.426.727.829.030.031.132.0
922.323.624.825.927.028.129.130.1
020.421.722.924.025.126.127.128.1
218.519.821.022.123.124.125.126.0
216.617.819.020.121.122.123.124.0
414.715.917.018.119.120.121.122.0
512.814.015.116.217.218.219.120.0
610.912.113.214.215.216.217.118.0
010.211.312.313.314.315.216.0
08.29.311.311.812.313.214.0
16.37.49.39.410.311.212.0
34.45.47.47.48.39.210.0
42.53.55.45.46.37.28.0
6-1.5-0.40.71.73.53.64.45.26.0
4-3.2-2.1-1.1~0.21.71.82.53.34.0
2-4.9-3.9-3.0-2.1-d.20.30.51.32.0
续表
露点空气的相对湿度/%
i飞胆次/16065707580859095100
0-6.5-5.5-4.6-3.7-2.9-2.1~1.3-0.60
-2-8.4-7.4-6.4~5.6-4.8-4.0-3.3-2.6-2.0
-4-10.3-9.3-8.3-7.5-6.7-6.0-5.3-4.6-4.0
-6-12.1-11.2-10.3-9.5-8.7-8.0-7.3—6.6-6.0
-8-13.9-13.j0-12.2-11.4—10.7-10.0-9.3-8.6-8.0
-10-15.4-14.8-14.1-13.3-12.6-11.9-11.2-10.6-10.0
-12-17.7—16.7-15.9-15.1-14.413.8-13.2-12.6-12.0
-14-19.8-18.8-17.9-17.1-16.4-15.8-15.2-14.6—14.0
-16-21.9-20.9-20.0-19.2-18.4-17.8—17.1—16.5-16.0
-18-24.1-23.0-22.2-21.4-20.9-19.8-19.1-18.5—18,0
-20-26.2-25.2-24.2—23,4-22.6-21.8-21.1-20.5-20.0
[例3-2]已知空气?=18t：，相对湿度—90%。求露点温度。
解：查实际,当i=18X：时，制冷机组?=15.48mmHg，
因分=90%,故此时空气的水蒸气分压力e=15.48X0.9=13.932(mmHg)
-查实际,当温度为16.41C时水蒸气最大分压力为13.99mmHg。故该温度即当空气温度为18X：和相对湿度为90%时的露点温度。
另可查实际,当空气温度为18t和相对湿度为90%时的露点温度为16.2X：。
食品冷库围护结构的隔热设计
本文转载自绍兴艾思吉制冷设备有限公司
制冷机组www.china-iceage.com