Moisture ratio

As the test showed, the formation of the hydroxide carbonate and the speed at which this takes place are dependent on the composition of the test atmosphere, especially on the water pressure. The zinc oxide did not show any weight gain in a C02 atmosphere with a moisture ratio (p/p0) less than 0.1 i.e., no formation of hydroxide carbonate takes place. Only above a moisture ratio of 0.35 did the zinc oxide take up more water in a relatively short period of time than was necessary for the formation of basic zinc carbonate. In the moisture ratio range of 0.1—0.3, the formation was slower and did not lead to complete formation of hydroxide carbonate. 

The selection of factors from the work [16] was done hy the significance of their effects on caoutchouc drying and after processing the opinions of eighteen researchers. The analysis included these eleven factors Xi inlet and outlet moisture ratio X2 pH value in the sixth apparatus X3 pH value in the seventh apparatus X+ NaCl consumption X5 serum consumption in the sixth apparatus X6 serum consumption in the seventh apparatus X serum temperature X8 latex type X9 fat content in caoutchouc X10 latex fat consumption on machine and Xu quantity of latex on the surface. Outcomes of the ranking of the factors are shown in Table 2.16. Determine the concordance coefficient and check its significance. 

Figure 1. General diagram of the shrinkage curve and its derivatives. On the horizontal axis is the moisture ratio (volume of water per unit volume of solids, dimensionless). On the vertical axis is, for the solid line (the shrinkage curve), the void ratio (volume of voids per unit volume of solids, dimensionless), and, for the broken line, the value of the slope of the shrinkage curve (dimensionless), and, for the dotted line, the absolute value of the curvature of the shrinkage curve (dimensionless). The following values were used for the parameters k. = 2, k. = 1.6, n = 1.6, and e = 1.9.

Higher conversions of xylan and glucan were seen with increases in both moisture content and inoculum size (Table 4), but no correlation was observed between the conversions and the relative amounts of inoculum and moisture (ratio of inoculum to moisture content not shown). Thus, it is unlikely that these two parameters comprise an interaction effect that is important to the operation of the system. Lower moisture contents gave lower overall amounts of degradation, but seemingly better selectivities for xylan degradation although coefficients of variation for conversions were... 

FIGURE 5.2 Variation of moisture ratio during drying of pineapple. (From Kingsly, A.R.P. et al., J. Food Process Eng., 32, 369, 2009a. With permission.)... 

The pine samples had moisture ratios of 112-170% before and 18-72% after preservation treatment and PEG ratios after treatment of 39-92%. Thus, the amount of PEG in the pine pieces could be rather high. One of the objects even cracked under the strain of too much PEG. 

The oak samples had about the same moisture ratios before preservation treatment as the pine samples. One oak sample, though, had a moisture ratio of 290%. This moisture ratio indicated a higher degree of degradation of the particular oak piece than of the other oak pieces in the test batch. After preservation it had a moisture ratio of only 12%, which fits in well with the rest of the oak pieces (3.5-40%). The PEG ratios after the preservation treatment were 0-47%, except for the piece with 290% beforepreservation moisture ratio. That piece acquired a PEG ratio of 118%, half of that amount during the latter part of the 2.5-month preservation period, when the PEG concentration in the conservation solution was raised from 70 to 100%. The effect on the PEG ratios during that part of the preservation schedule was less obvious in the rest of the oak samples. 

Moisture ratios of the pine core after preservation are much higher than those of the oak core. This contrast may point to differences in wood qualities of the oak and pine pieces. The maximum water contents of the two pieces of wood are deduced from the core samples taken at the beginning of the preservation. This investigation revealed that the maximum water contents of the surface layers of the oak and pine pieces are 200 and 240%, respectively. The layers beneath the surface layers have 150% maximum water ratios in both cases. The next question to be considered is whether the differences in preservation results depend upon the method of treatment used. To get some spray-treated material for comparison, the orlop deck of the Wasa was chosen because the sternmost third of that deck is made of oak and the other two thirds are made of pine planks. The PEG and HgO ratios of the cores from the two different parts of that deck after the automatic spray treatment was stopped (samples 33 and 34) were compared. 

For a more rigorous treatment of the dry mass of cake per unit filter area it is usual to start with the cake moisture ratio, defined as ... 

Using the definition of Equation (2.15) reduces to Equation (2.14) en die cake moisture ratio is unity. Both equations are of a amilar form ... 

The average pressure allows for some fluctuation in the total pressure over the cake and medium. Moisture ratio mass of sample of wet cake over mass of same sample when dry... 

Moisture ratio converted into a cake concentration by volume fraction from a knowledge of the solid and liquid m- l)ps P... 

From sorption isotherms such as those in Figure 4 it is possible to transform the relative humidity x-axis of Figure 3 to a moisture ratio axis (utilizing functions of moisture content as a function of temperature at various relative humidities). The results of such calculations are shown in Figure 5 where the softening point measured as the logarithm of the load frequency is plotted versus the moisture ratio for different temperatures. As seen in the figure, there is a somewhat lower scatter in the data when moisture content is used. The 95% confidence interval of the moisture ratio determinations was 0.35%. 

The data in Figure 5 may then be converted to Arrhenius plots (8) that show the logarithm of the load frequency versus the inverse of the temperature of the softening constructed at a given moisture ratio, as indicated by the procedure in Figure 6. 

Figure 7 shows Arrhenius plots for the softening at different moisture ratios for the birch xylan obtained by this procedure. At higher moisture ratios the slope of the Arrhenius curve is lower. From such a slope an apparent activation energy, AHa, for the softening process can be calculated as ... 

In this case for xylan, the activation energy was found to be around 500 kJ/mol at a moisture ratio of 16%, decreasing to 400 kJ/mol at a moisture ratio of 26%, as shown in Figure 8. The standard deviation in the determinations of the activation energy was about 40 kJ/mol. 

Figure 5. Softening points for the birch xylan at various temperatures shown in a diagram of the logarithm of the loading frequency versus moisture ratio, convertedfrom Figure 3 using the isotherms in Figure 4. The 95% confidence interval for the moisture ratio determinations of the softening points was 0.35%. The lines are based on a linear regression of the data for each...

Figure 6. Illustration of the procedure for converting softening points as a function of moisture ratio to an Arrhenius plot, showing the logarithm of the load frequency versus the reciprocal of the softening temperature at a moisture ratio of 16% in the birch xylan. The left part of the figure is a partial view of...

Figure 7. Arrhenius plots for the glass transition of birch xylan at different moisture ratios. The values are derived from the results in Figure 5.

Figure 8. The apparent activation energy, AHa,for the glass transition of xylan as a function of the moisture ratio of the xylan. The standard deviation of the activation energy was about 40 kJ/mol as indicated by the error bars.

Figure 10 shows the derived values of the glass transition temperature for the birch xylan and the glucomannan as a function of moisture ratio compared with data for the transition temperature for softwood hemicelluloses taken from literature (4). In the xylan, the glass transition temperature at 50°C and 1 Hz occurred at 76 %RH, which corresponded to a moisture ratio of 22%, whereas for the glucomannan at 50°C and 1 Hz it occurred at 65 %RH, corresponding to a moisture ratio of 16%. 

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