Tímarit Verkfræðingafélags Íslands - 01.12.1967, Side 100

Tímarit Verkfræðingafélags Íslands - 01.12.1967, Side 100
98 TÍMARIT VFl 1967 heating plates is a medicated oil, as excessive pressure in the plates as in the case of water can thereby be avoided. The oil is recirculated but a sufficient amount of hot oil is added to keep the temperature, which at any moment is demanded by the AFD-amatic system, following the optimal temperature curve by cam control. The hot oil tank is kept at the desired constant temperature by means of an automatic oil fired heater. Great emphasis has been laid on the design of the condenser for the vapours from the products - the so-called vapour trap. This vapour trap has been built into the lower sector of the cabinet and divided into two separate halves. There is ample passage for the vapours from the cabinet to the vapour taps but a hydraulically operated door which can travel from one side of the cabinet to the other can alternatively seal either half of the vapour trap from the cabinet. The movement of the door is automatically controlled by a pre-set timer. When one half of the vapour trap has been in operation so that and adequate layer of ice has formed on the ammonia-cooled tubes, the door seals off this section, leaving the other half free for operation. The closed vapour trap is thereafter auto- matically connected to the vapour part of a water holding tank, whereby the water will evaporate and melt the ice on the tubes of the vapour trap. This melting takes place at low pressure and temperature and very little additional load is applied on the vacuum system when the vapour trap is reconnected, as no air is admitted during the melting. The necessary heat for evaporation from the water tank is supplied by hot ammonia gas, whereby a saving in the operation of the refrigeration plant is achieved. As the defrosting of the vapour trap can take place at any time during the operation, you will see that we have here a continuously working, self-cleaning, automatic vapour trap built into the cabinet, whereby space requirements are lowered and erection greatly facilitated as compared to the former outside vapour traps. Vacuum systems Improvements in the vacuum systems have also taken place. Whereas steam ejectors were only a few years ago the reliable „working horse“ of the industry with oilsealed pumps as the alternative, these are both being replaced today by a system consisting of a Rootes pump and water sealed pump, the latter being combined with an air injector. The Rootes pump will com- press from 0,5 Torr to abt. 6 Torr, whereafter the other pump will compress to the atmosphere. The use of this system has been facilitated by the fact that modern cabinets are built so tight that minimum air-leakage can easily be dealt with by the air injector system. Only for products like coffee, demanding a pressure below 0,2 Torr, a system of two Rootes pumps in combination with the air-injector watering pump is required. You will notice that in using this vacuum system in connection with the oilheating of the heating plates, we have completely done away with the necessity of installing a steam boiler in the plant. This piece of equipment is replaced by an inexpensive, automatic oilheater, needing practically no attention. A central control panel contains all instruments and switches for starting and operating the plant at a human fingertip. When the operation is finished the vacuum is broken by flushing with nitrogen, whereafter the trolleys are conveyed to the packing station for filling the products into bulk containers, cans or pouches. Yes. Freeze-drying is a new industry, but it has developed at a breath-taking pace since its break-through only six years ago. It is certainly an industry which has come here to stay. Útdráttur Hagnýting frostþurrkunar í iðnaði er ekki eldri en 6—7 ára, en hefur aukizt hratt og er 1965 áætluð 20.000 tonn af ýmis konar varningi. Stutt skýring á vísindalegum grundvelli frost- þurrkunar er eftirfarandi. Suðumark vatns lækk- ar við lækkaðan þrýsting. Við 4,6 mm Hg-þrýst- ing (4,6 Torr) sýður vatn við 0°C. Ef þrýsting- urinn er lækkaður frekar, þá frýs vatnið. Ef hita er veitt að ísnum við slíkar aðstæður, (þrýsting- ur lægri en 4,6 mm Hg) þá bráðnar ísinn ekki, heldur gufar upp. Þegar matvæli eru frostþurrkuð, þá eru þau fyrst fryst, og síðan sett í hólf, þar sem mögu- legt er að halda þrýstingi lægri en 1 Torr (1 mm Hg). Þegar hita er síðan veitt til matvæl- anna, gufar ísinn upp, og þar sem gufur bera ekki með sér vatnsleysanleg efni, þá breytast mat- væli ekki að öðru leyti en því, að vatnið hverfur. Kostir frostþurrkunar eru þeir, að gæði matvæl- anna eru meiri en við nokkra aðra þurrkunar- aðferð, hvað útlit, bragð o.fl. snertir. Geymslu- þolið er mörg ár og án kæligeymslu.
Side 1
Side 2
Side 3
Side 4
Side 5
Side 6
Side 7
Side 8
Side 9
Side 10
Side 11
Side 12
Side 13
Side 14
Side 15
Side 16
Side 17
Side 18
Side 19
Side 20
Side 21
Side 22
Side 23
Side 24
Side 25
Side 26
Side 27
Side 28
Side 29
Side 30
Side 31
Side 32
Side 33
Side 34
Side 35
Side 36
Side 37
Side 38
Side 39
Side 40
Side 41
Side 42
Side 43
Side 44
Side 45
Side 46
Side 47
Side 48
Side 49
Side 50
Side 51
Side 52
Side 53
Side 54
Side 55
Side 56
Side 57
Side 58
Side 59
Side 60
Side 61
Side 62
Side 63
Side 64
Side 65
Side 66
Side 67
Side 68
Side 69
Side 70
Side 71
Side 72
Side 73
Side 74
Side 75
Side 76
Side 77
Side 78
Side 79
Side 80
Side 81
Side 82
Side 83
Side 84
Side 85
Side 86
Side 87
Side 88
Side 89
Side 90
Side 91
Side 92
Side 93
Side 94
Side 95
Side 96
Side 97
Side 98
Side 99
Side 100
Side 101
Side 102
Side 103
Side 104
Side 105
Side 106
Side 107
Side 108
Side 109
Side 110
Side 111
Side 112
Side 113
Side 114
Side 115
Side 116
Side 117
Side 118
Side 119
Side 120
Side 121
Side 122
Side 123
Side 124
Side 125
Side 126
Side 127
Side 128
Side 129
Side 130
Side 131
Side 132
Side 133
Side 134
Side 135
Side 136
Side 137
Side 138
Side 139
Side 140
Side 141
Side 142
Side 143
Side 144
Side 145
Side 146
Side 147
Side 148
Side 149
Side 150
Side 151
Side 152
Side 153
Side 154
Side 155
Side 156
Side 157
Side 158
Side 159
Side 160
Side 161
Side 162
Side 163
Side 164
Side 165
Side 166
Side 167
Side 168
Side 169
Side 170
Side 171
Side 172
Side 173
Side 174
Side 175
Side 176
Side 177
Side 178
Side 179
Side 180
Side 181
Side 182
Side 183
Side 184
Side 185
Side 186
Side 187
Side 188
Side 189
Side 190
Side 191
Side 192
Side 193
Side 194
Side 195
Side 196
Side 197
Side 198
Side 199
Side 200
Side 201
Side 202
Side 203
Side 204
Side 205
Side 206
Side 207
Side 208
Side 209
Side 210
Side 211
Side 212
Side 213
Side 214
Side 215
Side 216
Side 217
Side 218
Side 219
Side 220
Side 221
Side 222
Side 223
Side 224
Side 225
Side 226
Side 227
Side 228
Side 229
Side 230
Side 231
Side 232
Side 233
Side 234
Side 235
Side 236
Side 237
Side 238
Side 239
Side 240
Side 241
Side 242
Side 243
Side 244
Side 245
Side 246
Side 247
Side 248
Side 249
Side 250
Side 251
Side 252
Side 253
Side 254
Side 255
Side 256
Side 257
Side 258
Side 259
Side 260
Side 261
Side 262
Side 263
Side 264
Side 265
Side 266
Side 267
Side 268
Side 269
Side 270
Side 271
Side 272
Side 273
Side 274
Side 275
Side 276
Side 277
Side 278
Side 279
Side 280
Side 281
Side 282
Side 283
Side 284
Side 285
Side 286
Side 287
Side 288
Side 289
Side 290
Side 291
Side 292
Side 293
Side 294
Side 295
Side 296
Side 297
Side 298
Side 299
Side 300
Side 301
Side 302
Side 303
Side 304
Side 305
Side 306
Side 307
Side 308
Side 309
Side 310
Side 311
Side 312
Side 313
Side 314
Side 315
Side 316
Side 317
Side 318
Side 319
Side 320
Side 321
Side 322
Side 323
Side 324
Side 325
Side 326
Side 327
Side 328
Side 329
Side 330
Side 331
Side 332
Side 333
Side 334
Side 335
Side 336
Side 337
Side 338
Side 339
Side 340

x

Tímarit Verkfræðingafélags Íslands

Direkte link

Hvis du vil linke til denne avis/magasin, skal du bruge disse links:

Link til denne avis/magasin: Tímarit Verkfræðingafélags Íslands
https://timarit.is/publication/860

Link til dette eksemplar:

Link til denne side:

Link til denne artikel:

Venligst ikke link direkte til billeder eller PDfs på Timarit.is, da sådanne webadresser kan ændres uden advarsel. Brug venligst de angivne webadresser for at linke til sitet.