Basics of
Steam System Design
by W. M. (Bill) Huitt
Steam Tables
All of the information just discussed has fortunately been compiled into steam tables. One table referred to is "Properties of Saturated Steam and Saturated Water"; the other is "Properties of Superheated Steam". These tables show us the correlation of this data for various pressures and temperatures. By referring to the steam tables we find the constants that were discussed plus a column for "Total Heat of Steam" and "Specific Volume of Liquid". The "Heat of the Liquid" is also referred to as "Sensible Heat". It should also be noted that in the "Properties of Superheated Steam" there is no liquid heat content since liquid does not exist in superheat. There are also various temperatures at any given pressure because there is no correlation in superheated steam between pressure and temperature.
The information given in these steam tables is as follows:
Gauge Pressure:
Indicated in Inches of Hg for vacuum below atmospheric pressure, and P.S.I.G. for pressures above atmospheric.
Absolute Pressure:
Indicated in P.S.I.A. with zero being absolute zero or 14.7 P.S.I. below atmospheric pressure.
Temperature:
In degrees F for the pressure indicated.
Heat of the Liquid (sensible heat):
The figures in this column represent the heat content, in BTU/lb, for water at the indicated pressure/ temperature.
Latent Heat of Evaporation:
Indicated in BTU/lb, this is the amount of heat content in every pound of steam at the indicated pressure/temperature.
Total Heat of Steam:
Indicated in BTU/lb, this is the sum of both the Heat of the Liquid and the Latent Heat of Evaporation or the total heat content of the steam at the indicated pressure/temperature.
Specific Volume:
Indicated in cubic ft./lb, this is the space occupied by 1 pound of water or 1 lb of steam at the indicated pressure/temperature.
Pressure |
Temperature |
Heat of |
Latent Heat |
Total Heat |
Specific Volume |
||
Lbs. Per sq. in. |
the |
of |
of Steam |
||||
Absolute |
Gage |
t |
Liquid |
Evaporation |
hg |
Water |
Steam |
P1 |
P |
Deg. F |
Btu/lb |
Btu/lb |
Btu/lb |
Ft.3/lb. |
Ft.3/lb. |
14.696 |
0.0 |
212.00 |
180.17 |
970.3 |
1150.5 |
0.016719 |
26.799 |
15.00 |
0.3 |
213.03 |
181.21 |
969.7 |
1150.9 |
0.016726 |
26.290 |
16.00 |
1.3 |
216.32 |
184.52 |
967.6 |
1152.1 |
0.016749 |
24.750 |
17.00 |
2.3 |
219.44 |
187.66 |
965.6 |
1153.2 |
0.016771 |
23.385 |
18.00 |
3.3 |
222.41 |
190.66 |
963.7 |
1154.3 |
0.016793 |
22.168 |
19.00 |
4.3 |
225.24 |
193.52 |
961.8 |
1155.3 |
0.016814 |
21.074 |
20.00 |
5.3 |
227.96 |
196.27 |
960.1 |
1156.3 |
0.016834 |
20.087 |
21.00 |
6.3 |
230.57 |
198.90 |
958.4 |
1157.3 |
0.016854 |
19.190 |
22.00 |
7.3 |
233.07 |
201.44 |
956.7 |
1158.1 |
0.016873 |
18.373 |
23.00 |
8.3 |
235.49 |
203.88 |
955.1 |
1159.0 |
0.016891 |
17.624 |
24.00 |
9.3 |
237.82 |
206.24 |
953.6 |
1159.8 |
0.016909 |
16.936 |
25.00 |
10.3 |
240.07 |
208.52 |
952.1 |
1160.6 |
0.016927 |
16.301 |
26.00 |
11.3 |
242.25 |
210.7 |
950.6 |
1161.4 |
0.016944 |
15.7138 |
27.00 |
12.3 |
244.36 |
212.9 |
949.2 |
1162.1 |
0.016961 |
15.1684 |
28.00 |
13.3 |
246.41 |
214.9 |
947.9 |
1162.8 |
0.016977 |
14.6607 |
29.00 |
14.3 |
248.40 |
217.0 |
946.5 |
1163.5 |
0.016993 |
14.1869 |
30.00 |
15.3 |
250.34 |
218.9 |
945.2 |
1164.1 |
0.017009 |
13.7436 |
31.00 |
16.3 |
252.22 |
220.8 |
943.9 |
1164.8 |
0.017024 |
13.3280 |
32.00 |
17.3 |
254.05 |
222.7 |
942.7 |
1165.4 |
0.017039 |
12.9376 |
33.00 |
18.3 |
255.84 |
224.5 |
941.5 |
1166.0 |
0.017054 |
12.5700 |
34.00 |
19.3 |
257.58 |
226.3 |
940.3 |
1166.6 |
0.017069 |
12.2234 |
35.00 |
20.3 |
259.29 |
228.0 |
939.1 |
1167.1 |
0.017083 |
11.8959 |
Table 1
Typical Steam Table