Drying schedule

Equation (23) contains G, S, and as parameters. G kg Pit,/hTR) is a function of Tr and the psychrometric ratio. The psychrometric ratio can be calculated and is fairly constant. Therefore G is a function of Tr only (Pr, being the vapor pressure at Tr). < is a function of Tr and S is a function of Tr and Tw. In Figs. 3 and 4, moisture concentration and time, in dimensionless coordinates, have been plotted with Tr and Tr — Tyr as parameters. Given Tr, Tyy, and BhTRAo/ KWy, one can determine the drying schedule by using these plots. A /W is the area of heat transfer per pound of water at the critical water content. 

Experimental data from various sources (C5, K2, G4, S16) were taken for comparison. Kauh (K2) determined the drying schedules for balsa wood slabs of various thicknesses (, j, f in.) at different wind velocities (100-124 ft/min). It was not possible to apply boundary-layer theory to calculate heat- and mass-transfer coefficients because the length of the slabs was not recorded. 

G4. Garud, B. S., Drying schedules of welding electrodes. M.S. Thesis, Illinois Institute of Technology, Chicago, 1949. 

K2. Kauh, J. Y., Evaluation of drying schedules. Ph.D. Thesis, Dlinois Institute of Technology, Chicago, 1966. 

Designing of a safe drying schedule for ceramic ware requires knowledge of the distribution of water in the porous system and familiarity with the rules of water and vapour transport through porous media. 

The optimum drying schedule is determined experimentally calculation of the drying schedule is usually impossible owing to the large number of parameters, many of which are difficult to measure. 

The overall consequence is that despite over-drying a load of lumber some boards will still not achieve the desired end-moisture content. Merely extending the drying schedule does not solve the problem of airflow maldistribution and uneven drying this is especially true when drying permeable species using low air velocities of <3.5 m s ... 

Journal of the American Chemical Society, 40 1361-403 Langrish TAG, Keey RB, Kho PCS and Walker JCF (1993) Time-dependent flow in arrays of timber boards flow visuahsation, mass-transfer coefficients and numerical simulation. Chemical Engineering Science, 48 12) 2211-23 Langrish TAG, Brooke AS, Davis CL, Musch HL and Barton GW (1997) An improved drying schedule for Australian ironbark timber optimisation and experimental validation. Drying Technology, 25(1) 47-70... 

Z.-X. Gong, and A.S. Mujumdar, Development of drying schedules for one-side-heating drying of refractory concrete slabs based on a finite element model, J. Am. Ceram. Soc., 79(6) 1649-1658 (1996). 

It was disclosed that some organic compounds, including dimethylfor-mamide [56], formamide, glycerol, and oxalic acid [14], allow shorter drying schedules. This technique was used successfully to prepare binary and ternary systems [57]. Drying, however, which depends on gel volume, requires several days. Moreover, organic compounds, especially glycerol [58], are sometimes very difficult to remove. 

The code can also be nsed to test different drying schedules (Figure 40.37). The first one (Schedule A) is recommended for softwoods while the second one (Schedule B) is recommended for hardwoods. Schedule B proposes lower temperature levels and higher relative humidity values. In... 

FIGURE 40.37 Simulation of two different drying schedules moisture content, temperatnre, and stress level at different positions vs. time. 

Doe, P.E., Oliver, A.R., and Booker, J.D., 1996a. A non-lineal strain and moisture content model of variable hardwood drying schedules, in Proceedings of the Fourth lUFRO Wood Drying Conference, Rotorua, New Zealand, pp. 203-210. 

Langrish, T.A.G., Booker, A.S., Davis, C.L., Muson, H.E., and Barton, G.W., 1997. An improved drying schedule for Australian ironbark timber Optimisation and experimental verification. Drying Technol., 15 47-70. 

Pandey, C.N., 2001. Systemization of kiln drying schedules for commercial Indian woods, in Proceedings of the Seventh International lUFRO Wood Drying Conference, Tsukuba,... 

Tetzlaff, A.R., 1967. An investigation of drying schedules when kiln-drying radiata pine, BE Report, University of Canterbury, Christchirrch, New Zealand. 

However, with the modified configuration that the drying air enters the second half of the dryer, upward flow, and is then forced to flow downward in the first half of the dryer, the final me of 15%-18% can be achieved as shown in Figure 41.6. The corresponding air humidity and air temperature in this case are shown in Figures 41.7 and 41.8, which can be used for designing drying schedules. 

The LCA use in drying timber is a relatively new area and no study is available in the literature. In this section, the use of LCA has been demonstrated using an example of radiata pine drying. The drying schedules, drying time, and energy footprint data have been used from a published study (Ananias et al., 2012). These data have further been judged, analyzed, and validated independently for use in this LCA study. 

Drying Schedules Used for Estimating GHG Emission (Ananias et al., 2012) and Used by the Kiln Model for Prediction of Drying Time for This Study... 

The drying schedule that Is being used now for our plate specimens is 3 days at room temperature and 92% relative humidity, followed by accelerated drying to finish. 

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