Vapour pressure of water | Water Vapour Pressure temperature chart

Water Vapour Pressure Table at Different temperatures

Vapour pressure definition: It is the pressure exerted by the saturated vapour in contact with the surface of the liquid at that temperature. Vapour pressure is also called the vapour tension

Vapour pressure of water Concept:

All liquids have a tendency to evaporate when exposed to atmosphere. The rate at which this evaporation to atmospheric. The rate at which this evaporation occurs depends on the molecular energy of the liquid.

Vapour pressure of water | Water Vapour Pressure temperature chartConsider a liquid contained in a sealed breaker and assume a constant temperature is maintained. In Fig – 1 some of the liquid molecules have sufficient energy to break away from the liquid and enter the air in the vapour form. As some increased container temperature the air  will contain vapour molecules to the extent that some of them will be forced to re-enter the liquid by partial air pressure as shown in Fig – 2.

Finally in Fig- 3 an equilibrium condition will exists, when the rate at which molecules are leaving the liquid will be equal to the molecules re-entering the liquid. Under such conditions the air above the liquid is saturated with liquid molecules and the pressure on the liquid surface is called its vapour pressure at prevailing temperature.

Water vapour pressure at 100 0C is 1 atm or 1 kg/cm2 abs. at sea level.

Vapour Pressure of water versus temperature Table

Vapour Pressure table for water from 1 oC to 100 oC

Temperature of water in 0C Vapour pressure in bar Temperature of water in 0C Vapour pressure in bar
1 0.00657 51 0.12961
2 0.00706 52 0.13613
3 0.00758 53 0.14293
4 0.00813 54 0.15002
5 0.00872 55 0.15741
6 0.00935 56 0.16511
7 0.01001 57 0.17313
8 0.01072 58 0.18147
9 0.01147 59 0.19016
10 0.01227 60 0.1992
11 0.01312 61 0.2086
12 0.01401 62 0.2184
13 0.01497 63 0.2286
14 0.01597 64 0.2391
15 0.01704 65 0.2501
16 0.01817 66 0.2615
17 0.01936 67 0.2733
18 0.02062 68 0.2856
19 0.02196 69 0.2984
20 0.02337 70 0.3116
21 0.02485 71 0.3253
22 0.02642 72 0.3396
23 0.02808 73 0.3543
24 0.02982 74 0.3696
25 0.03166 75 0.3855
26 0.0336 76 0.4019
27 0.03564 77 0.4189
28 0.03738 78 0.4365
29 0.04004 79 0.4547
30 0.04241 80 0.4736
31 0.04491 81 0.4931
32 0.04753 82 0.5133
33 0.05029 83 0.5432
34 0.05318 84 0.5557
35 0.05622 85 0.578
36 0.0594 86 0.6011
37 0.06274 87 0.6249
38 0.06624 88 0.6495
39 0.06991 89 0.6749
40 0.07375 90 0.7011
41 0.07777 91 0.7281
42 0.08198 92 0.7561
43 0.08639 93 0.7849
44 0.091 94 0.8146
45 0.09582 95 0.8453
46 0.10086 96 0.8769
47 0.10612 97 0.9094
48 0.11162 98 0.943
49 0.11736 99 0.9776
50 0.12335 100 1.0133

Vapour Pressure table for water from 102 oC to 370 oC

Temperature of water in oC Vapour pressure in bar Temperature of water in oC Vapour pressure in bar
102 1.0878 200 15.55
104 1.1668 205 17.243
106 1.2504 210 19.077
108 1.339 215 21.06
110 1.4327 220 23.198
112 1.5316 225 25.501
114 1.6362 230 27.976
116 1.7465 235 30.632
118 1.8628 240 33.478
120 1.9854 245 36.523
122 2.1145 250 39.776
124 2.2504 255 43.246
126 2.3933 260 46.943
128 2.5435 265 50.877
130 2.7013 270 55.058
132 2.867 275 59.496
134 3.041 280 64.202
136 3.223 285 69.186
138 3.414 290 80.037
140 3.614 300 85.927
145 4.155 305 92.144
150 4.76 310 98.7
155 5.433 315 106.61
160 6.181 320 112.89
165 7.008 325 120.56
170 7.92 330 128.63
175 8.924 340 146.05
180 10.027 350 165.35
185 11.233 360 186.75
190 12.551 370 210.54
195 13.987 374.15 221.2

Vapour pressure of liquids at different temperatures for pump NPSH calculation

The term vapour pressure is frequently used in connection with calculation of  Net Positive Suction Head available (NPSHa) in pumps.

In NPSH available calculation vapour pressure head of the liquid is very essential. It is calculated by the following formula.

Vapour \ pressure \ head \ in \ metres = \frac{Vapour \ Pressure \ of \ Water \ at \ Liquid \ Temperature \ in \ mwc}{Specific \ \ Gravity \ of \ the \ liquid}

Example – 1 :   Calculate vapour pressure head of the gasohol at 50 0C and its specific gravity 0.8.

According to above water vapour pressure vs temperature table

Water vapour pressure at 50 0C = 0.12335 bar = 1.2335 mwc (mwc –  metres of water column)

Now according to above formula

Vapour tension / vapour pressure of the liquid = 1.2335 / 0.8 = 1.54 metres

Example – 2 : Calculate vapour pressure head of the sulphited sugar syrup at 65 0C and its specific gravity 1.25

According to above water vapour pressure vs temperature table

Vapour pressure of water at 65 0C =0.2501 bar = 2.501 metres.

Now according to above formula

Vapour pressure head of the sulphited syrup = 2.501 / 1.25 =  2.0 metres.

Vapour pressure definition | Vapour pressure of water at different temperatures from 0 oC to 370 oC | Vapour pressure head of liquids calculation for NPSH

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Post Author: siva alluri

The aim of this Blog "sugarprocesstech" is Providing basic to advance knowledge in sugar process industry and providing maximum calculation regarding capacity and equipment design online calculators .

2 thoughts on “Vapour pressure of water | Water Vapour Pressure temperature chart

    Rajendra Tatoba Shirdhone

    (June 24, 2018 - 5:09 pm)

    Good information about vapour pressure

      siva alluri

      (June 27, 2018 - 4:24 pm)

      Thank you Mr.Rajendra Tatoba Shirdhone

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