3-7.Three types of drying 2.Drying of the surface attached water

Even if it tells “dryness” to a mouthful, there are three kinds of dry work.

They are dryness of surface water of adhesion, dryness of the coating film, and internal dryness of material.
Since the preceding sections has explained the internal dryness, this section explains the surface dryness.

The drying time of surface adhesion water is determined by supply of evaporative latent heat.

Three types of drying 2.Drying of the surface attached water

The saturated vapor pressure of water and latent heat of evaporation

Temp. Pressure latent heat
mmHg kcal/kg kJ/g
0 4.6 597.1 2.502
1 4.9 596.6 2.500
2 5.3 596.0 2.498
3 5.7 595.4 2.495
4 6.1 594.9 2.493
5 6.5 594.3 2.491
6 7.0 593.8 2.488
7 7.5 593.2 2.486
8 8.0 592.6 2.483
9 8.6 592.1 2.481
10 9.2 591.5 2.478
11 9.8 590.9 2.475
12 10.5 590.4 2.473
13 11.2 589.8 2.471
14 12.0 589.3 2.469
15 12.8 588.7 2.466
16 13.6 588.1 2.464
17 14.5 587.5 2.461
18 15.5 587.0 2.459
19 16.5 586.4 2.456
20 17.5 585.9 2.454
21 18.6 585.3 2.452
22 19.8 584.8 2.450
23 21.1 584.2 2.447
24 22.4 583.6 2.445
25 23.8 583.1 2.443
26 25.2 582.5 2.440
27 26.7 581.9 2.438
28 28.3 581.4 2.436
29 30.0 580.8 2.433
30 31.8 580.2 2.431
31 33.7 579.7 2.428
32 35.7 579.1 2.426
33 37.7 578.5 2.423
34 39.9 578.0 2.421
35 42.2 577.4 2.419
36 44.6 576.8 2.416
37 47.1 576.2 2.414
38 49.7 575.7 2.412
39 52.4 575.1 2.409
40 55.3 574.5 2.407
41 58.3 574.0 2.405
42 61.5 573.4 2.402
43 64.8 572.8 2.400
44 68.3 572.2 2.397
45 71.9 571.7 2.395
46 75.7 571.1 2.392
47 79.6 570.5 2.390
48 83.7 570.0 2.388
49 88.0 569.4 2.385
50 92.5 568.8 2.383
51 97.2 568.2 2.380
52 102.1 567.6 2.378
53 107.2 567.1 2.376
54 112.5 566.5 2.373
55 118.1 565.9 2.371
56 123.9 565.3 2.368
57 129.9 564.7 2.366
58 136.1 564.1 2.363
59 142.7 563.6 2.361
60 149.4 563.0 2.359
61 156.5 562.4 2.356
62 163.8 561.8 2.354
63 171.5 561.2 2.351
64 179.4 560.6 2.349
65 187.6 560.0 2.346
66 196.2 559.5 2.344
67 205.0 558.9 2.341
68 214.3 558.3 2.339
69 223.8 557.7 2.336
70 233.8 557.1 2.334
71 244.1 556.5 2.331
72 254.7 555.9 2.329
73 265.8 555.3 2.326
74 277.3 554.7 2.324
75 289.2 554.1 2.321
76 301.5 553.5 2.319
77 314.2 552.9 2.316
78 327.4 552.3 2.314
79 341.1 551.7 2.311
80 355.3 551.1 2.309
81 369.9 550.5 2.306
82 385.0 549.9 2.304
83 400.7 549.3 2.301
84 416.9 548.7 2.299
85 433.6 548.1 2.296
86 450.9 547.5 2.294
87 468.7 546.9 2.291
88 487.2 546.2 2.288
89 506.2 545.6 2.286
90 525.9 545.0 2.283
91 546.2 544.4 2.281
92 567.1 543.8 2.278
93 588.7 543.2 2.276
94 611.0 542.6 2.273
95 634.0 541.9 2.270
96 657.7 541.4 2.268
97 682.1 540.7 2.265
98 707.3 540.1 2.263
99 733.3 539.4 2.260
100 760.0 538.8 2.257
101 787.0 538.1 2.254
102 815.2 537.4 2.251
103 844.2 536.8 2.249
104 874.5 536.2 2.246
105 906.1 535.6 2.244
106 938.4 535.0 2.241
107 971.6 534.3 2.239
108 1003.7 533.7 2.236
109 1040.0 533.0 2.233
110 1074.6 532.4 2.231

The quantity of heat which heated material becomes a constant drying period, while waterdrop is on the surface, since it is consumed as vapor-ized latent heat.

Although it can heated to the temperature which can untill withstand the material, as shown in the following table, there is only a difference of 10% to 100 ℃ from 0 ℃.

It seems that there is little necessity of raising material temperature by force.

<<Evaporation heat of the water 1g >>

Temp.℃ 0℃ 20℃ 40℃ 60℃ 80℃ 100℃
latent heat 2502J 2454J 2407J 2359J 2309J 2257J

The adhering water has been adhered by the interfacial tension on the material surface.

The vapor pressure of water adhering is equal to the saturated vapor pressure, and since the evaporation temperature of water is proportional to pressure, if low pressure and a vacuum are used, low-temperature drying will be made.

Guide to the optimal wind drying heater

contact us