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is subtracted from 9.403 cu. ft., since the volume is less for a pressure of 44.7 lb. than for a pressure of 44 lb.

9.268 X 14 = 129.752 cu. ft.

EXAMPLE 5.-Find the weight of 40 cu. ft. of steam at a temperature of 254° F.

SOLUTION. The weight of 1 cu. ft. of steam at 254.0020, from the table, is .078839 lb. Neglecting the .0020, the weight of 40 cu. ft. is, therefore,

.078839 X 40 = 3.15356 lb.

EXAMPLE 6.-How many pounds of steam at 64 lb. pressure, absolute, are required to raise the temperature of 300 lb. of water from 40° to 130° F., the water and steam being mixed?

SOLUTION. The number of heat units required to raise 1 lb. from 40° to 130° is 130-40 90 B. T. U. (Actually a little more than 90 would be required, but the above is near enough for all practical purposes.) Then, to raise 300 lb. from 40° to 130° requires 90 X 300 == 27,000 B. T. U. This quantity of heat must necessarily come from the steam. Now, 1 lb. of steam at 64 lb. pressure gives up, in condensing, its latent heat of vaporization, or 905.9 B. T. U. But, in addition to its latent heat, each pound of steam on condensing must give up an additional amount of heat in falling to 130°. Since the original temperature of the steam was 296.805° F. (see table), each pound gives up by its fall of temperature 296.805-130 = 166.805 B. T. U. Therefore, each pound of the steam gives up a total of

905.9166.805

=

=

1,072.705 B. T. U.

27,000

1,072.705

It will, therefore, take

accomplish the desired result.

With the steam tables a reliable thermometer may be used for ascertaining the pressure of saturated steam or for testing the accuracy of a steam gauge. The temperature of the steam being measured by the thermometer, the corresponding absolute pressure is found from the steam tables; the gauge pressure is then found by subtracting 14.7 from the absolute pressure. Thus, the temperature of the steam in a condenser being 1420, we find from the steam tables that the correspond. ing absolute pressure is 3 lb. per sq. in., nearly.

=

25.17 lb. of steam to

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THE PROPERTIES OF SATURATED STEAM.

2

Degrees.

Required to Raise Temperature of the Water From 32° to to.

t

Quantity of Heat in
British Thermal Units.

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Total Latent Heat at
Pressure p.

L

11 197.814 166.225 12 202.012 170.457 13 205.929 174.402 14 209.604 178.112

14.69 212.000 180.531

15 213.067 181.608) 16 216.347 184.919 17 219.452 188.056 18 222.424 191.058 19 225.255 193.918

Total Heat Above 32°.

10

1

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170.173 138.401 995.441 1,133.842 .016357 61.14 176.945 145.213 990.695 1,135.908.018908 52.89 182.952 151.255 986.485 1,137.740 .021436 46.65 188.357 156.699 982.690 1,139.389 | .023944 41.77 10 193.284 161.660 979.232 1,140.892 .026437 37.83

Ratio of Vol. of Steam to Vol, of
Equal Weight of Dist. Water at
Temp. of Maximum Density.

102.018 70.010, 1,043.015 1,113.055 .003027 330.4 20,623
126.302 94.368 1,026.094 1,120.462 .005818 171.9 10,730
141.654 109.764 1,015.380 1,125.144 .008522 117.3+ 7,325
153.122 121.271 1,007.370 1,128.6441 | .011172 | 89.51
162.370 130.563 1,000.899 1,131.462 .013781 72.56

5,588 4,530

8

R

3.816

3,302

2,912

2,607

2,361

[blocks in formation]
[blocks in formation]

30 250.293 219.261 939.019 32 254.002 223.021 936.389 34 257.523 226.594 933.891 36 260.883 230.001 931.508 38 264.093 233.261 929.227

H

6

W

20 227.964 196.655 954.814 1,151.469 .050696 19.730
22 233.069 201.817 951.209 1,153.026 .055446 18.040
24 237.803 206.610 947.861 1,154.471 .060171
26 242.225 211.089 944.730 1,155.819 .064870 15.420
28 246.376 215.293 941.791 1,157.084.069545 14.380

16.620

7

1,158.280 .074201 13.480
1,159.410.078839 12.680
1,160.485 .083461 11.980

1,161.509.088067

1,162.488 .092657

40 267.168 236.386 927.040 1,163.426
42 270.122 239.389 924.940 1,164.329
44 272.965 242.275 922.919 1,165.194
46 275.704 245.061 920.968 1,166.029
48 278.348 247.752 919.084 1,166.836.115411

1,167.615.119927

.124433

50 280.904 250.355 917.260
52 283.381 252.875 915.494 1,168.369
54 285.781 255.321 913.781
56 288.111 257.695 912.118 1,169.813 .133414
58 290.374 260.002 910.501 1,170.503.137892

1,169.102.128928

60 292.575 262.248 908.928 1,171.176 .142362 62 294.717 264.433907.396 1,171.829 .146824 64 296.805 266.566 905.900 1,172.466.151277 66 298.842 268.644 904.443 1,173.087 .155721 68 300.831 270.674 903.020 1,173.694 .160157

V

1,174.286 .164584

70 302.774 272.657 901.629
72 304.669 274.597 900.269 1,174.866

.169003 74 306.526 276.493 898.938 1,175.431 .173417 76 308.344 278.350 897.635 1,175.985 .177825 78 310.123 280.170 896.359 1,176.529

.182229

.097231 10.280
.101794

9.826

.106345

.110884

80 311.866 281.952 895.108 1,177.060 .186627 82 313.576 283.701 893.879 1,177.580 .191017 84 315.250 285.414 892.677 1,178.091 .195401 86 316.893 287.096 891.496 1,178.592 .199781 88 318.510 288.750 890.335 1,179.085.204155

11.360

10.790

9.403

9.018

8.665

8.338

8.037

7.756

7.496

7.252

7.024

6.811

6.610

6.422

6.244

6.076

5.917

5.767

5.624

5.488

5.358

5.235

5.118

5.006

4.898

8

R

1,231.0

1,126.0 1,038.0

962.3

897.6

841.3

791.8

948.0

708.8

673.7

642.0

613.3

587.0

563.0

540.9

520.5

501.7

484.2

467.9

452.7

438.5

425.2

412.6

400.8

389.8

379.3

369.4

360.0

351.1

342.6

334.5

326.8

319.5

312.5

305.8

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.547831 1.825

114.0

250 400.883 373.750 830.459 1,204.209 260 404.370 377.377 827.896 1,205.273 .568626 1.759 109.8 270 407.755 | 380.905 825.401 280 411.048 384.337822.973 290 414.250 387.677 820.609 300 417.371 390.933 818.305

105.9

102.3

1,206.306 .589390 1.697
1,207.310 .610124 1.639
1,208.286 .630829 1.585
1,209.238 .651506 1.535

99.0

95.8

VENTILATION.

GENERAL INFORMATION.

Ventilation is a process of moving foul air from any space and replacing it with fresh air. A positive displacement, however, does not take place; the incoming fresh air chiefly dilutes the foul air to a point suitable for healthful respiration.

Pure air, such as exists in the open country, contains about 4 parts of carbon dioxide, CO2, per 10,000 parts of air, while badly ventilated rooms often contain as much as 80 parts of CO2 per 10,000 of air. Hygienists, after careful study, have decided that an increase of 2 parts of CO2 per 10,000 of air should be accepted as the standard of respirable purity, and any excess of CO2 above this may be considered as vitiation.

PRODUCTION OF CO2 PER HOUR.

Source.

Adult man

1 cu. ft. of gas, burning.

Ordinary lamp
Candle

Cu. Ft.

.6
.8

1.0

.3

Taking the figures above given-4 parts of CO2 per 10,000 parts of fresh air, and 6 parts (=4+2) per 10,000 of vitiated air-as the standard for proper health conditions, it is found that 3,000 cu. ft. of fresh air per hour is necessary for each adult person. If a different standard than 6 is used, the number of cubic feet per person will be found by dividing 6,000 by the difference between this standard and 4.

If any lights deliver their products of combustion into the room, the amount of CO2 given off by them should be converted into its equivalent in men, thus: One ordinary gas light equals, in vitiating effect, about 5 men, an ordinary lamp 13 men, and an ordinary candle about

man.

It is considered good practice to allow 2,000 cu. ft. of fresh air per hour for each inmate of a room or auditorium.

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