Condensers for evaporation

Figure 8-4 A standard jacketed stirred tank with baffles and an overhead condenser for evaporative crystallization. During distillation, a second stream of solvent can be charged to maintain a constant batch volume in the vessel.

At first we tried to explain the phenomenon on the base of the existence of the difference between the saturated vapor pressures above two menisci in dead-end capillary [12]. It results in the evaporation of a liquid from the meniscus of smaller curvature ( classical capillary imbibition) and the condensation of its vapor upon the meniscus of larger curvature originally existed due to capillary condensation. We worked out the mathematical description of both gas-vapor diffusion and evaporation-condensation processes in cone s channel. Solving the system of differential equations for evaporation-condensation processes, we ve derived the formula for the dependence of top s (or inner) liquid column growth on time. But the calculated curves for the kinetics of inner column s length are 1-2 orders of magnitude smaller than the experimental ones [12]. 

Remove the condenser, then with the aid of a funnel add the water slowly, keep stirring. If the solution is too hot the water will evaporate and make a big mess. As the water is added you will notice that loads of stodgy crapp will form, this is normal, connect the condenser for the distillation with a receiving flask at least 500ml in capacity. 

Thus, as pointed out by Cohan who first suggested this model, condensation and evaporation occur at difi erent relative pressures and there is hysteresis. The value of r calculated by the standard Kelvin equation (3.20) for a given uptake, will be equal to the core radius r,. if the desorption branch of the hysteresis loop is used, but equal to twice the core radius if the adsorption branch is used. The two values of should, of course, be the same in practice this is rarely found to be so. 

The variant of the cylindrical model which has played a prominent part in the development of the subject is the ink-bottle , composed of a cylindrical pore closed one end and with a narrow neck at the other (Fig. 3.12(a)). The course of events is different according as the core radius r of the body is greater or less than twice the core radius r of the neck. Nucleation to give a hemispherical meniscus, can occur at the base B at the relative pressure p/p°)i = exp( —2K/r ) but a meniscus originating in the neck is necessarily cylindrical so that its formation would need the pressure (P/P°)n = exp(-K/r ). If now r /r, < 2, (p/p ), is lower than p/p°)n, so that condensation will commence at the base B and will All the whole pore, neck as well as body, at the relative pressure exp( —2K/r ). Evaporation from the full pore will commence from the hemispherical meniscus in the neck at the relative pressure p/p°) = cxp(-2K/r ) and will continue till the core of the body is also empty, since the pressure is already lower than the equilibrium value (p/p°)i) for evaporation from the body. Thus the adsorption branch of the loop leads to values of the core radius of the body, and the desorption branch to values of the core radius of the neck. 

Fig. 38. Caustic purification system a, 50% caustic feed tank b, 50% caustic feed pumps c, caustic feed preheater d, amonia feed pumps e, ammonia feed preheater f, extractor g, trim heater h, ammonia subcooler i, stripper condenser j, anhydrous ammonia storage tank k, primary flash tank 1, evaporator reboiler m, evaporator n, caustic product transfer pumps o, purified caustic product cooler p, purified caustic storage tank q, ammonia stripper r, purified caustic transfer pumps t, overheads condenser u, evaporator v, evaporator vacuum pump w, aqueous storage ammonia tank x, ammonia scmbber y, scmbber condenser 2, ammonia recirculating pump aa, ammonia recycle pump. CW stands for chilled water.

Other dairy substitutes have penetrated the U.S. market to the extent of 1% for fluid whole milk, 58% for creams, <1% for low-fat milk, 6—7% for cheeses, 10% for evaporated and condensed milks, and 2% for ice cream (30). About 60% of the substitute and imitation cheese sold in the United States is being used as the cheese material for pi22a (2). 

C 0.35 Recovery of low level waste heat f space heating, district heating syste Absorption cooling. Recovery of steam condensate and flash steam. Heat pump for evaporation, drying, etc. 3r m. 

Fig. 6 shows both the actual cycle (shown in dashed lines) and the idealised cycle, which consists of two isosteres and two isobars. Heat flows in J/kg adsorbent q) are shown as shaded arrows. For most purposes, analysis of the ideal cycle gives an adequate estimate of the COP and cooling or heating per kg of adsorbent. An accurate calculation of the path of the actual cycle needs information on the dead volume of the whole system and of the heat transfer characteristics of the condenser and evaporator. General trends are more apparent from an analysis of the idealised cycle. 

SLAB calculates chemical concentrations at positions downwind and heights above the ground. Tlic plume may be denser-than-air, neutrally-buoyant, or less dense than air. Thermodynamics effeci.s are accounted for, including latent heat exchanges due to the condensation or evaporation ot liquids, Time averaged results may be calculated. SLAB is the easiest of the publicly-available dense gas models to set up and mn. It has been extensively validated against large-scale field data. 

The balance equations for water vapor flows are similar to balance equations for contaminant flows, but in addition possible condensation and evaporation must be calculated. Also they must be considered in heat flow equations. 

Here rj is the viscosity of the dewetting liquid. Note that a relaxational term proportional to a has been added, with fi(j)) being the chemical potential of the vapor. This term alone guarantees that a homogeneous liquid film will relax to its equilibrium value hooip) by evaporation or condensation. For h = hooip) this term vanishes. 

It h-ds been prepared artificially by Wallach as a bye-product in the reduction of nitrosopinene, C Hj NOH. It is best prepared as follows Five grams of nitrosopinene are dissolved in 40 c.c. of warm glacial acetic acid, and sufiScient water added to produce a slight cloudiness. A large amount of zinc-dust is then added. After the reaction has become gradual, the mixture is heated on a water-bath under a reflux condenser for four hours, i he liquid is then filtered, and the filtrate steam distilled. Ihe distillate is exhausted with ether, the ether evaporated... 

To a solution of 14.5 g of 2-bromo-2 -(2-chlorobenzoyl)acetanilide in 100 ml of tetrahy-drofuran, an excess of liquid ammonia (ca 150 ml) was added. The ammonia was kept refluxing with a dry-ice condenser for 3 hours after which time the ammonia was allowed to evaporate and the solution was poured into water. Crystals of 2-amino-2 -(2-chloro-benzoyOacetanilide were collected, which after recrystallization from ethanol melted at 162° to 164 C. 

Acetylene was passed into a stirred solution of 3.05 grams (0.44 mol) of lithium in 300 ml of liquid ammonia until the blue color exhibited by the mixture had disappeared. Ethyl /3-chlorovinyl ketone (47.4 grams 0.40 mol) dissolved in 50 ml dry ether was then added to the resulting solution of lithium acetylide over a period of 20 minutes, during which the color deepened through yellow to reddish-brown. The mixture was stirred under reflux maintained with a Dry Ice condenser for 2 hours. Thereafter, dry ether (200 ml) was added and the ammonia was permitted to evaporate with stirring overnight. 

Ambient dry bulb temperature for air-cooled condensers Available water temperature for water-cooled condensers Ambient wet bulb temperature for evaporative types... 

Example 6.7 In Example 6.1, the required plant capacity is 218 kW and the running time is 2000 h/year at an electricity cost of 5 p/ (kW h) and a motor efficiency of 75%. In order to achieve the condensing temperature of 85°F (29.4°C) the condenser would cost 7250, while a smaller condenser for a temperature of 100°F (37.8°C) would cost 4600. (Prices of evaporative condensers at April 1987.) Estimate the break-even time if the larger condenser is fitted. 

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