Examples drying calculations

Drew. T. B. 477, 497, 499, 564, 565 Drift factor 578, 580 Drops, mass transfer 651 Dropwise condensation 476 DRTlNA, P. 307.312 Drying calculations, example 749 Duckworth, R. A. 209. 228 Duct, non-circular 86... 

The weight of the precipitate after filtering and drying can then be measured free of any influence from the NaCl and converted back to the weight of the analyte with the use of a gravimetric factor (see the next section) and its percent in the sample calculated. Examples are given in Section 3.6.4. 

Calculating the amount of gas collected over water Given the volume, total pressure, and temperature of gas collected over water, calculate the mass of the dry gas. (EXAMPLE 5.11)... 

Some dry chemicals contain varying amounts of the active ingredient for chemical application. The chemical feed calculations then require an adjustment for the amount of the active ingredient available in the dry chemical. Examples of this type of chemical... 

A method for calculating temperature, fiiction and working life of dry rubbing bearings that is based on theoretically and experimentally established data is offered afterwards. In addition the positive effect of a wear particle trap is demonstrated. Finally, calculation examples show the mode of operation of the calculation method. 

General hydrodynamic theory for liquid penetrant testing (PT) has been worked out in [1], Basic principles of the theory were described in details in [2,3], This theory enables, for example, to calculate the minimum crack s width that can be detected by prescribed product family (penetrant, excess penetrant remover and developer), when dry powder is used as the developer. One needs for that such characteristics as surface tension of penetrant a and some characteristics of developer s layer, thickness h, effective radius of pores and porosity TI. One more characteristic is the residual depth of defect s filling with penetrant before the application of a developer. The methods for experimental determination of these characteristics were worked out in [4]. 

Let us consider the calculation of sensitivity threshold in the case when the cracks are revealing by PT method. Constant distance H between crack s walls along the whole defect s depth is assumed for the simplicity. The calculation procedure depends on the dispersity of dry developer s powder [1]. Simple formula has to be used in the case when developer s effective radius of pores IC, which depends mainly on average particle s size, is smaller than crack s width H. One can use formula (1) when Re is small enough being less than the value corresponding maximum sensitivity (0,25 - 1 pm). For example. Re = 0,25 pm in the case when fine-dispersed magnesia oxide powder is used as the developer. In this case minimum crack s width H that can be detected at prescribed depth lo is calculated as... 

The case considered above corresponds to R < H. The calculation using formula (1) gives the next results. For example, consider the thickness of dry developer layer h = 20 pm. In the absence of sedimentation process our product family (penetrant and developer indicated above) could not detect the cracks with the depth lo < 1,33 mm of any widths. Nevertheless due to the sedimentation one can get the decrease of developer s thickness from h = 20 pm till h s 5 pm. As a result, our product family can ensure the detection of the cracks with H > 2,3 pm even with very small length lo = 0,4 mm. At the same time if lo = 1 mm, then the cracks with extremely small width H > 0,25 will be revealed. 

The water-vapor transmission rate (WVTR) is another descriptor of barrier polymers. Strictly, it is not a permeabihty coefficient. The dimensions are quantity times thickness in the numerator and area times a time interval in the denominator. These dimensions do not have a pressure dimension in the denominator as does the permeabihty. Common commercial units for WVTR are (gmil)/(100 in. d). Table 2 contains conversion factors for several common units for WVTR. This text uses the preferred nmol/(m-s). The WVTR describes the rate that water molecules move through a film when one side has a humid environment and the other side is dry. The WVTR is a strong function of temperature because both the water content of the air and the permeabihty are direcdy related to temperature. Eor the WVTR to be useful, the water-vapor pressure difference for the value must be reported. Both these facts are recognized by specifying the relative humidity and temperature for the WVTR value. This enables the user to calculate the water-vapor pressure difference. Eor example, the common conditions are 90% relative humidity (rh) at 37.8°C, which means the pressure difference is 5.89 kPa (44 mm Hg). 

Example Calculate the dry flare header size, which is connected to the above knock-out drum. Previously noted conditions remain the same. Additional data are ... 

Comparing Examples 2a and 2b we notice that the total air pressure has effects on the humidity x, partial density of dry air p total pressure or pressure of humid air, and enthalpy h. Knowing the total pressure is therefore essential in calculations of the thermodynamic properties of humid air. 

Pressure and humidity have also an effect on the mass flows. We continue Examples 2a and 2b by calculating the dry air mass flow in a fan when the humid air volume flow in the fan is 0.8 m /s. According to Eq. (4.91) and the calculations above, we obtain... 

A useful rule of thumb is that the turbine work in a STIC plant is increased by a factor of about (1 + 25), since the specific heat of the steam is about double that of the specific heat of the dry gas. This is in agreement with the example given above and with the earlier detailed calculations by Fraize and Kinney [3]. (Their work was based on the assumption that the mixture of air and steam in the turbine behaved as a semi-perfect gas, with specific heats being determined simply by mass averaging of the values for the two components.)... 

Example ps at the sublimation front is 0.937 mbar (-21 °C) (see example in Table 1.9), in the chamber a pU20 = 0.31 mbar has been measured, resulting in a pressure difference of approx. 0.6 mbar. With these data, the water vapor permeability blp = 1.1 10 2 kg/h m mbar is calculated. With this data known, it is possible to calculate dp for different conditions, if the mass of frozen water miCL, the time /MD, the thickness (d) and the surface (F) are known. This dp depends from the amount vapor transported and thereby from the heat transfer (Table 1.9). In the examples given it changes between 0.17 mbar in a slow drying process (6 h) to 0.6 mbar for a shorter drying time, 2.5 h. 

An example is given in Fig. 2.38 plot 1 is extrapolated to DR < 0.1 %/h. At this time, one more hour drying time would contribute to the desired moisture content of e. g. I % by only 0.1 %. If the computer starts the integration from this calculated time the result is the residual moisture content as a function of time. 

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