Naphthalene sublimation rate

Direct evaluation of the convective heat transfer coefficient (h ) of subjects clothed in undergarments and socks (normal ventilated environment) was achieved by observing the sublimation rate of naphthalene balls uniformly positioned three centimeters from the body surface. Equations were developed for prediction of h as a function of metabolic activity and posture, calculation o average skin temperature, and estimation of maximum evaporative heat losses from the body (U2 ). In another approach, the coefficients of dry heat transfer at varying wind speeds for nude and clothed sectional mannequins were determined (U3). At air flow rates above 2 m/sec, percentage contributions of individual body sections to total heat transfer remain constant for the nude and clothed mannequin, yet increased for normally uncovered units such as the face and hands. Generally, the ratio of total heat flow for the nude to clothed mannequin increased with air flow. 

Haider et al. [33] conducted experiments in a turbulent fluidized bed using naphthalene sublimation technique. Their results are plotted in Figure 7. Researchers [2] also calculated mass transfer coefficients from burning rate experiments in a hot turbulent bed. Mass transfer coefficients are obtained by using measured values of burning rates and chemical rate coefficient. 

Determine percent saturation of air and rate of naphthalene sublimation at 15.24 m/sec ... 

Figure 3. Sublimation rate of naphthalene in various cell-reactor prototypes as influenced...

Figure 5.B-9 shows effective interfhcial areas that were deduced by Shulman et al.N from experiments on tha sublime ion of naphthalene Rase hi g rings. Many other studies have been inede in na attempt to relate effective area to specific packing surface, as a function or liquid and vapor flow rates. Generally, it is thought that the effective area reachas the specific area near the onset of flooding, but Pig. 3.8-9 shows that this mey not be the case. It also should be noted that the total area available for main transfer includes film surface ripples, entrained liquid within the bed, and vapor bubbling through pockets of liquid held up in the bed. Another important point relative specific surface of differeat packings might indicate relative mass transfer efficiencies, but this Is often sot the case.

In typical applications, pure solid naphthalene is melted and poured into a mold so it will have the desired shape such as a flat plate [127], a circular cylinder [128], or a turbine blade [129]. For average mass transfer measurements on a test surface, the section coated with naphthalene can be weighed before and after exposure to air flow to determine the mass transfer rate. Local mass transfer coefficients can be determined from the sublimation depth, which is the difference in surface profiles, measured using a profilometer, before and after each test run. Once the vapor density of naphthalene is known, the local mass transfer coefficient hD can be evaluated from the following expression ... 

As crystalline drugs generally have very low vapor pressure at room temperature, almost no drugs noticeably sublime except for volatile drugs such as naphthalene. However, when the drugs are mixed with porous powder, the capillaries can provide a sink condition for the diffusion of the drug molecules in the mixture. The rate of diffusion of benzoic acid was calculated for a mixture of 50 mg benzoic acid and 950 mg CPG at 300 K. The diffusion equation... 

Compounds such as naphthalene and 1,4-dichlorobenzene find use as mothballs since they sublime at a slow rate at atmospheric pressure. Explain this behavior in terms of the structure of fhe molecules. 

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