Lynne Wong's PhD thesis
Lynne Wong's PhD thesis Lynne Wong's PhD thesis
mW K2aw + K1 = 1800 + m 2 2 2 K2 ( aw ) + K1K2aw − K1K2 ( aw ) ( 1 − K a ) ( 1 K K a ) 2 a w ⎡ 1 + ( K K − K ) a − K K ( a ) = = ⎢ ⎣ 2 2 w 1 2 1 2 w ⎤ ⎥ ⎦ 1800 2 1 2 2 w 1 2 w W K ( + K K ) + K K ( K1K2 + K2 ) aw ( K + K K ) 2 1 2 1800 2 1 2 1800 2 2 2 1K2 ( aw ) ( K + K ) W W W K + − 1800 K K The parameters K 1 , K 2 and W can then be calculated from their algebraic relationship to b, c and d. 2 1 2 hence b c W ( K1 K2 − K2 ) 1800( K2 + K1K2 ) = × = K1K2 − K2 1800( K2 + K1K2 ) W (6) and d b = − W K 1800( K + 2 2 1 K2 1800( K2 + K1K2 ) × K K ) 1 2 W = K K 1 2 2 (7) from equation (6), K 2 = c / b ( K , 1) 1 − substituting K 2 into equation (7), K1 ( c / b) ( K − 1) 1 1 K 1 ( K − 1) 2 2 = d / b d / b = = z 2 ( c / b) 2 zK1 − ( 2z + 1) K1 + z = 0 2 The quadratic equation K 1 Ax + Bx + C = 0 was found to be A = z, B = − 2z − 1 and C = z and the root of the equation is − B ± 2 − B 2A 4AC K 1 = ± 2z + 1 ± ( − 2z − 1) 2z 2 − 4z 2 The positive value is taken for K 1 , and this value was used to calculate K 2 from the equation given above. W is calculated from the equation b = W 1800 K K ( + K ) 2 1 2 W = b × 1800 ( K + K K ) 2 1 2 265
The values of K 1 , K 2 and W were used to calculate m h , m s and m for each experimental a w value at each of the four temperatures for all the cane components. The results are compared with the experimental values of the equilibrium moisture content, and are shown in Tables 6.7 for all nine components aged 52 and 36 weeks. Similarly the results for reconstituted cane stalk, dry leaf and green leaf are compared in Table 6.8. These results are plotted against water activity a w in Figures 6.13.1 – 6.13.8 for nine cane components aged 52 and 36 weeks at 30, 45, 55 and 60 °C and are shown on the CD (File: Fig.6.13.1-6.13.8 Hydrated and dissolved water.xls). Typical plot for nine cane components aged 52 weeks at 30 °C is shown in Figure 6.13, and similar plots for reconstituted cane stalk, dry leaf and green leaf aged 52 and 36 weeks at four temperatures are presented in Figures 6.14 and 6.15 respectively. From Tables 6.7 – 6.8, we observe that m h decreases with decrease in water activity and with increase in temperature. The latter is in keeping with the fact that, in general, for a fixed a w the EMC decreases with increase in temperature at the smaller values of water activity. At 52 weeks and at 30 °C, dry leaf fines has the highest m h value of 6.47 and rind fines, the lowest value of 4.20. At 36 weeks and 30 °C, top fibre has the highest m h value of 5.01 and stalk fibre, the lowest value of 3.99. From Fig 6.13 it can be seen that the m h curves exhibit a Langmuir-type monolayer isotherm, and become saturated in the high water activity region, in fact the m h values obtained from the Hailwood-Horrobin model agree fairly well with the monolayer moisture content, m o values derived from the GAB model. It therefore appears that this hydrated water corresponds to the initially bound water that binds directly to the polar groups on the surface of the fibre. This stronger binding is reflected in the larger heats of sorption observed when the EMC is between 0 and 5%. The dissolved water, m s , values decrease with decrease in water activity and increase with increase in temperature. This is in keeping with the fact that at large a w values the EMC at given value of a w increases with temperature. At 52 weeks and at 30 °C, stalk pith has the highest m s value of 27.87 and rind fibre, the lowest value of 16.94. At 36 weeks and at 30 °C, stalk pith has the highest m s value of 24.28 and rind fibre, the lowest value of 16.54. The m s curves depicted in Fig 6.13 increase sharply within the whole water activity region. This dissolved water therefore corresponds to multilayer adsorption where water molecules hydrogen bond to water molecules already attached to the surface of the fibre. The binding 266
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- Page 275 and 276: Modified GAB Kuhn Iglesias - Chirif
- Page 277 and 278: Table 5.28. Classification of resid
- Page 279 and 280: Stalk fibre Stalk pith Rind fibre 4
- Page 281 and 282: 5.6.4.5 Calculated EMC values of re
- Page 283 and 284: Table 5.30. Calculated equilibrium
- Page 285 and 286: m/m of 96% Table 5.32. Calculated e
- Page 287 and 288: Table 5.33. Parameters of the Hailw
- Page 289 and 290: CHAPTER 6. PROPERTIES OF THE SORBED
- Page 291 and 292: where m is the equilibrium moisture
- Page 293 and 294: Stalk fibre Stalk pith Rind fibre 8
- Page 295 and 296: Stalk fibre Stalk pith Rind fibre 4
- Page 297 and 298: 6.2 THE NUMBER OF ADSORBED MONOLAYE
- Page 299 and 300: 6.3 TOTAL SOLID SURFACE AREA AVAILA
- Page 301 and 302: Thus, for each cane component of ea
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- Page 305 and 306: Stalk fibre Stalk pith Rind fibre 1
- Page 307 and 308: A similar procedure was followed to
- Page 309 and 310: 10 0 Stalk fibre Stalk pith Rind fi
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- Page 313 and 314: Table 6.5. Characteristic parameter
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- Page 327 and 328: 3 0 Reconstituted cane at 30 o C 3
- Page 329 and 330: when water is added to dry wood, wh
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- Page 333 and 334: The number of adsorbed monolayers,
- Page 335 and 336: Data in Tables 2.9 and 2.11 show th
- Page 337 and 338: particular fibre is systematically
- Page 339 and 340: Anon. (1985b). Laboratory manual fo
- Page 341 and 342: Blanchi R.H. and A.G. Keller (1952)
- Page 343 and 344: Day D.L. and G.L. Nelson (1965). De
- Page 345 and 346: Heyrovsky J. (1970). Determination
- Page 347 and 348: Kuhn I.J. (1964). A new theoretical
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- Page 351 and 352: Prinsen Geerligs, H.C. (1897). Stud
- Page 353 and 354: Sing K.S.W., D.H. Everett, R.A.W. H
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The values of K 1 , K 2 and W were used to calculate m h , m s and m for each experimental a w<br />
value at each of the four temperatures for all the cane components. The results are<br />
compared with the experimental values of the equilibrium moisture content, and are shown<br />
in Tables 6.7 for all nine components aged 52 and 36 weeks.<br />
Similarly the results for reconstituted cane stalk, dry leaf and green leaf are compared in<br />
Table 6.8. These results are plotted against water activity a w in Figures 6.13.1 – 6.13.8 for<br />
nine cane components aged 52 and 36 weeks at 30, 45, 55 and 60 °C and are shown on the<br />
CD (File: Fig.6.13.1-6.13.8 Hydrated and dissolved water.xls). Typical plot for nine cane<br />
components aged 52 weeks at 30 °C is shown in Figure 6.13, and similar plots for<br />
reconstituted cane stalk, dry leaf and green leaf aged 52 and 36 weeks at four temperatures<br />
are presented in Figures 6.14 and 6.15 respectively.<br />
From Tables 6.7 – 6.8, we observe that m h decreases with decrease in water activity and<br />
with increase in temperature. The latter is in keeping with the fact that, in general, for a<br />
fixed a w the EMC decreases with increase in temperature at the smaller values of water<br />
activity. At 52 weeks and at 30 °C, dry leaf fines has the highest m h value of 6.47 and rind<br />
fines, the lowest value of 4.20. At 36 weeks and 30 °C, top fibre has the highest m h value<br />
of 5.01 and stalk fibre, the lowest value of 3.99.<br />
From Fig 6.13 it can be seen that the m h curves exhibit a Langmuir-type monolayer<br />
isotherm, and become saturated in the high water activity region, in fact the m h values<br />
obtained from the Hailwood-Horrobin model agree fairly well with the monolayer<br />
moisture content, m o values derived from the GAB model. It therefore appears that this<br />
hydrated water corresponds to the initially bound water that binds directly to the polar<br />
groups on the surface of the fibre. This stronger binding is reflected in the larger heats of<br />
sorption observed when the EMC is between 0 and 5%.<br />
The dissolved water, m s , values decrease with decrease in water activity and increase with<br />
increase in temperature. This is in keeping with the fact that at large a w values the EMC at<br />
given value of a w increases with temperature. At 52 weeks and at 30 °C, stalk pith has the<br />
highest m s value of 27.87 and rind fibre, the lowest value of 16.94. At 36 weeks and at<br />
30 °C, stalk pith has the highest m s value of 24.28 and rind fibre, the lowest value of 16.54.<br />
The m s curves depicted in Fig 6.13 increase sharply within the whole water activity region.<br />
This dissolved water therefore corresponds to multilayer adsorption where water molecules<br />
hydrogen bond to water molecules already attached to the surface of the fibre. The binding<br />
266
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