Liquids evaporation and

In most diying operations, water is the liquid evaporated and air is the normally employed purge gas. For diying purposes, a psychro-metric chart found very useful is that reproduced in Fig. 12-36. 

In addition to volume changes the effect of temperature is also important. Thus the specific latent heat of vaporization of a chemical is the quantity of heat, expressed as kJ/kg, required to change unit mass of liquid to vapour with no associated change in temperature. This heat is absorbed on vaporization so tliat residual liquid or tlie sunoundings cool. Alternatively an equivalent amount of heat must be removed to bring about condensation. Thus the temperature above a liquefied gas is reduced as tlie liquid evaporates and tlie bulk liquid cools. There may be consequences for heat transfer media and the strength of construction materials at low temperatures. 

If the pressure on a liquefied gas is reduced, some of the liquid evaporates, and the rest gets colder. All refrigeration plants, domestic and... 

The idealized picture of the flow in a heated micro-channel is shown in Fig. 8.1a. Such flow possesses a number of specific properties due to its unique structure, which forms because of liquid evaporation and the interaction of pure vapor and liquid flows separated by the interface surface. The latter has an infinitely thin surface with a jump in pressure and velocity, while the temperature is equal. One can... 

The wall heat flux is the cause for the liquid evaporation, and perturbation of equilibrium between the gravity and capillary forces. It leads to the offset of both phases (heated liquid and its vapor) and interface displacement towards the inlet. In this case the stationary state of the system corresponds to an equilibrium between gravity, viscous (liquid and vapor) and capillary forces. Under these conditions the stationary height of the liquid level is less than that in an adiabatic case... 

Unlike at adiabatic conditions, the height of the liquid level in a heated capillary tube depends not only on cr, r, pl and 6, but also on the viscosities and thermal conductivities of the two phases, the wall heat flux and the heat loss at the inlet. The latter affects the rate of liquid evaporation and hydraulic resistance of the capillary tube. The process becomes much more complicated when the flow undergoes small perturbations triggering unsteady flow of both phases. The rising velocity, pressure and temperature fluctuations are the cause for oscillations of the position of the meniscus, its shape and, accordingly, the fluctuations of the capillary pressure. Under constant wall temperature, the velocity and temperature fluctuations promote oscillations of the wall heat flux. 

Addition of chloride ions (as solid calcium chloride, potassium chloride or sodium chloride) to aqueous solutions containing 40% of peroxyacetic acid and 1 % of acetic acid leads to a violently exothermic decomposition reaction. Chlorine is evolved, most of the liquid evaporates and the residue (often red coloured) deflagrates. 

If wet steam is throttled to a considerably low pressure, the liquid evaporates and the steam becomes superheated. 

Next heat the sealed container until all of the liquid evaporates, and repeat Experiment 1. 

Seal the plate with parafilm or an adhesive film to avoid liquid evaporation and incubate overnight at RT until the formazan crystals completely dissolve. 

Mix the solutions and a sulphate of lead will be precipitated. Decant the clear supernatant liquid, evaporate and crystallize. 

WET-BULB TEMPERATURE. The wet-bulb temperature is the steady-state, non-equilibrium temperature reached by a small mass of liquid immersed under adiabatic conditions in a continuous stream of gas. The mass of the liquid is so small in comparison with the gas phase that there is only a negligible change in the properties of the gas, and the effect of the process is confined to the liquid. The method of measuring the wet-bulb temperature is shown in Fig. 23.4. A thermometer, or an equivalent temperature-measuring device such as a thermocouple, is covered by a wick, which is saturated with pure liquid and immersed in a stream of gas having a definite temperature T and humidity ff. Assume that initially the temperature of the liquid is about that of the gas. Since the gas is not saturated, liquid evaporates, and because the process is adiabatic, the latent heat is supplied at first by cooling the liquid. As the temperature of the liquid decreases below that of the gas, sensible heat is transferred to the liquid. Ultimately a steady... 

Depending on temperature and pressure, all materials in the solid and liquid state have a vapour pressure, that is, some of their surface atoms or molecules exist as a vapour or gas above the material. Thus under certain conditions a liquid evaporates and some solids sublimate. This is most familiar to us as we smell coffee or perfumes the fragrant molecules leave the liquid and enter the surrounding atmosphere. Mothballs are an example of the tendency of solids, like naphthalene, to enter the gaseous state. Volatility is the meas-... 

In case of a primary liner failure, liquid can penetrate the inner insulation layer, exposing the intermediate liner to the tank static pressure distribution. In the particular system considered, liquid evaporation and condensation occur in the inner insulation layer. The intermediate liner is, therefore, exposed to vapor at the local tank pressure level, which causes circulation through the intermediate liner and the outer insulation layer. This vapor circulation may cause local degradation in the insulation thermal performance. 

Fine PVC suspension in a volatile, organic liquid. At room temperature, the resin is swollen, but not appreciably dissolved. At elevated temperatures, the liquid evaporates, and the residue upon cooling forms homogenous plastics. Plasticizers may be dissolved in the volatile liquid. See also Plastisols. ... 

Figure 1.11 Schematic diagram illustrating the enormous shrinkages accompanying the drying by liquid evaporation and the firing of a polymeric gel (AL/Lo = linear shrinkage and AV/To = volumetric shrinkage). The solids content of the gelled material, the dried gel, and the final product are assumed to be 5, 50, and 100%, respectively.

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