Section 4.1 Evaporation

Internal calandria, horizontal short tube including all auxiliaries vapor piping, barometric condenser, vacuum equipment, integral piping, condensate receivers. 

Internal calandria, vertical short tube including vapor piping, barometric condenser, vacuum equipment, integral piping, condensate receivers. FOB cost 220000 at 45 m heat transfer area, n = 0.55 for the range 10-600. L+M = 1.6-1.9. L/M = 

Alloy cost factors c/s X 1.00 cast iron with copper tubes X 1.0 lead lined X 2.0 copper X 1.3 s/s X 2.3 nickel alloy X 2.8 titanium X 6.6. 

Agitated falling film including thermal section, separator, drive but exduding auxiliaries and vacuum equipment. FOB cost 80000 at 0.5 m heat transfer area, n = 0.36 (range 0.1-1 m ) 350000 at 10 m with n = 0.62 for the range 1-25. L+M = 1.4-2.5. L/M = 0.35. Alloy cost factors 304 s/s X 1.00 316 s/s X 1.1. Including vacuum equipment X 1.5. 

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Steam generating installations consist of two types of elements (a) basic-the boiler itself, and (b) the accessory-pumps and treatment apparatuses for water and fuel, water and steam piping, air fans and smoke stacks. An oil- or gas-fired steam generator is shown in Fig. 96. The heating surfaces are divided into economizer section, evaporation elements, and steam superheaters (if present). The steam generator design may differ from the one shown in Fig. 96. 

The caustic systems for the three difierent methods of production are entirely different from each other and are discussed separately in this section. Evaporation is the subject of Section 11.6. 

Quantity YOM Cross Sections Parker Cross Sections Evaporation Theory with Temperature Reduced 30% ... 

Dry the combined organic layers over granular anhydrous sodium sulfate, following the instructions given in Technique 12, Section 12.9, "Drying Procedure with Anhydrous Sodium Sulfate". Read these instructions carefully and complete Steps 1-3 in the "Microscale Drying Procedure." Step 4 is described in the next section, "Evaporation of Solvent."... 

Generally, evaporation of liquid water is an important mechanism of fuel cell cooling and the evaporation term should be added to the right-hand side of Equation 4.282. For simplicity, in this section, evaporation will be ignored, which is equivalent to the assumption that the water vapor pressure in the CCL is equal to the saturated pressure. Thus, solution to Equation 4.282 gives a maximal heat flux from the CCL, which is of large interest for cell and stack modeling. 

The topic of spreading rates is of importance in the technology of the use of mono-layers for evaporation control (see Section IV-6) it is also important, in the opposite sense, in the lubrication of fine bearings, as in watches, where it is necessary that the small drop of oil remain in place and not be dissipated by spreading. Zisman and coworkers have found that spreading rates can be enhanced or reduced by the presence of small amounts of impurities in particular, strongly adsorbed surfactants can form a film over which the oil will not spread [48]. 

It is instructive to consider just how mobile the surface atoms of a solid might be expected to be. Following the approach in Section III-2, one may first consider the evaporation-condensation equilibrium. The number of molecules hitting a 1-cm surface per second is from kinetic theory... 

Bikerman [179] has argued that the Kelvin equation should not apply to crystals, that is, in terms of increased vapor pressure or solubility of small crystals. The reasoning is that perfect crystals of whatever size will consist of plane facets whose radius of curvature is therefore infinite. On a molecular scale, it is argued that local condensation-evaporation equilibrium on a crystal plane should not be affected by the extent of the plane, that is, the crystal size, since molecular forces are short range. This conclusion is contrary to that in Section VII-2C. Discuss the situation. The derivation of the Kelvin equation in Ref. 180 is helpful. 

Deposited monolayers of such RX-type compounds as fatty acids and amines can be extremely tenaciously held, as evident for example, in frictional wear experiments (see Section XII-7) and in their stability against evaporation under... 

Method 1. Mix 1 0 g. of 3 5-dinitrobenzoic acid (Section IV,168) with 4 ml. of thionyl chloride in a dry 50 ml. conical flask fit a reflux condenser, carrying a plug of cotton wool at the upper end, into the flask and heat on a water bath for 15-30 minutes. Remove the condenser and heat the flask in a boiling water bath FUME CUPBOARD 1) until the excess of thionyl chloride has evaporated. Use the resulting 3 5-dinitrobenzoyl chloride (about 10 g.) immediately. 

Add 1 ml. of the alcohol-free ether to 0-1-0-15 g. of finely-powdered anhydrous zinc chloride and 0 5 g. of pure 3 5-dinitrobenzoyl chloride (Section 111,27,1) contained in a test-tube attach a small water condenser and reflux gently for 1 hour. Treat the reaction product with 10 ml. of 1-5N sodium carbonate solution, heat and stir the mixture for 1 minute upon a boiling water bath, allow to cool, and filter at the pump. Wash the precipitate with 5 ml. of 1 5N sodium carbonate solution and twice with 6 ml. of ether. Dry on a porous tile or upon a pad of filter paper. Transfer the crude ester to a test-tube and boil it with 10 ml. of chloroform or carbon tetrachloride filter the hot solution, if necessary. If the ester does not separate on cooling, evaporate to dryness on a water bath, and recrystallise the residue from 2-3 ml. of either of the above solvents. Determine the melting point of the resulting 3 5 dinitro benzoate (Section 111,27). 

Upon heating the polymers, anhydrous gaseous formaldehyde is produced (compare Section 111,17). By allowing a mixture of concentrated ammonia solution and formalin to evaporate, hexamethylenetetramine (also called hexamine, vrotropine) CjHjjNj is formed ... 

The above simple experiments illustrate the more important properties of aliphatic acid chlorides. For characterisation, the general procedure is to hydrolyse the acid chloride by warming with dilute alkali solution, neutralise the resulting solution with dilute hydrochloric acid (phenol-phthalein), and evaporate to dryness on a water bath. The mixture of the sodium salt of the acid and sodium chloride thus obtained may be employed for the preparation of solid esters as detailed under Aliphatic Acids, Section 111,85. The anilide or p-toluidide may be prepared directly from the acid chloride (see (iii) above and Section III,85,i). 

Acidify the residue in the flask with dUute sulphuric acid and distil off 10-15 ml. of the solution. Test a smaU portion of the distillate for acidity, and also observe the odour. Neutralise the main portion with sodium hydroxide solution (add a drop of phenolphthalein to act as indicator), evaporate to smaU bulk, and convert the sodium salt into the p-bromophenacyl ester or into some other suitable derivative (Section 111,85) determine the m.p. of the derivative. 

The excess of alkah is then neutralised with dilute hydrochloric acid (phenolphthalein) and the solution is evaporated to dryness on the water bath. The acid may then be characterised as the S-benzyl-tao-thiuronium salt or as the p-bromophenacyl ester (Section 111,85). In many instances the derivative may be prepared directly from the neutralised solution. 

Place 425 ml. of concentrated ammonia solution (sp. gr. 0-88) in a 500 ml. round-bottomed flask and add slowly 75 g. of a-bromocaproic acid (Section 111,126). Stopper the flask tightly and allow it to stand in a warm place (50-55°) for 30 hours. Filter the amino acid at the pump and keep the filtrate A) separately. Wash the amino acid (ca. 26 g.) well with methyl alcohol to remove the ammonium bromide present. Evaporate the aqueous filtrate (A) almost to dryness on a steam bath. 

Saccharic acid. Use the filtrate A) from the above oxidation of lactose or, alternatively, employ the product obtained by evaporating 10 g. of glucose with 100 ml. of nitric acid, sp. gr. 1 15, until a syrupy residue remains and then dissolving in 30 ml. of water. Exactly neutralise at the boiling point with a concentrated solution of potassium carbonate, acidify with acetic acid, and concentrate again to a thick syrup. Upon the addition of 50 per cent, acetic acid, acid potassium saccharate sepa rates out. Filter at the pump and recrystaUise from a small quantity of hot water to remove the attendant oxahc acid. It is necessary to isolate the saccharic acid as the acid potassium salt since the acid is very soluble in water. The purity may be confirmed by conversion into the silver salt (Section 111,103) and determination of the silver content by ignition. 

Mix together in a 250 ml. flask carrying a reflux condenser and a calcium chloride drying tube 25 g. (32 ml.) of freshly-distilled acetaldehyde with a solution of 59-5 g. of dry, powdered malonic acid (Section 111,157) in 67 g. (68-5 ml.) of dry pyridine to which 0-5 ml. of piperidine has been added. Leave in an ice chest or refrigerator for 24 hours. Warm the mixture on a steam bath until the evolution of carbon dioxide ceases. Cool in ice, add 60 ml. of 1 1 sulphuric acid (by volume) and leave in the ice bath for 3-4 hours. Collect the crude crotonic acid (ca. 27 g.) which has separated by suction filtration. Extract the mother liquor with three 25 ml. portions of ether, dry the ethereal extract, and evaporate the ether the residual crude acid weighs 6 g. Recrystallise from light petroleum, b.p. 60-80° the yield of erude crotonic acid, m.p. 72°, is 20 g. 

Place a mixture of 25 g. of a-naphthylamine (Section IV,37) and 125 g. (69 -5 ml.) of concentrated sulphuric acid in a 250 ml. conical or round-bottomed flask, and heat in an oil bath for 4-5 hours or until a test sample, when made alkaline with sodium hydroxide solution and extracted with ether, yields no naphthylamine upon evaporation of the ether. Pour the warm reaction mixture cautiously and with stirring into 300 ml. of cold... 

Add dilute sulphuric acid, with stirring, to the cold alkahne solution until the solution is acid to htmus or Congo red paper and the acid, if a solid, commences to separate as a faint permanent precipitate. Now add dilute sodium carbonate solution until the solution is alkahne (litmus paper) and any precipitate has completely redissolved. Extract the clear solution twice with ether evaporate or distil the ether from the ethereal solution on a water bath CAUTION no flames may be near) and identify the residual phenol as under 1. Remove the dissolved ether from the aqueous solution by boiling, acidify with dilute sulphuric acid and identify the organic acid present (see Sections 111,85 and IV, 175). 

Mix 42 5 g. of acetone cyanohydrin (Section 111,75) and 75 g. of freshly powdered ammonium carbonate in a small beaker, warm the mixture on a water bath FUME CUPBOARD) and stir with a thermometer. Gentle action commences at 50° and continues during about 3 hours at 70-80°. To complete the reaction, raise the temperature to 90° and maintain it at this point until the mixture is quiescent (ca. 30 minutes). The colourless (or pale yellow) residue solidifies on coohng. Dissolve it in 60 ml. of hot water, digest with a little decolourising carbon, and filter rapidly through a pre-heated Buchner funnel. Evaporate the filtrate on a hot plate until crystals appear on the surface of the liquid, and then cool in ice. Filter off the white crystals with suction, drain well, and then wash twice with 4 ml. portions of ether this crop of crystals of dimethylhydantoin is almost pure and melts at 176°. Concentrate the mother liquor to the crj staUisation point, cool in ice, and collect the... 

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