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SOME ASPECTS REGARDING MICROWAVE DRYING OF MATERIALS
Table1. Water temperature in beaker during microwave heating (continuation)
Time
[minutes]
L Level
[ 0 C]
ML Level
[ 0 C]
M Level
[ 0 C]
MH Level
[ 0 C]
H Level
[ 0 C]
0 20 20 20 20 20
5 50 - - - -
0 20 20 20 20 20
6 60 - - - -
L = low level; ML = medium - low level; M = medium level; MH = medium - high level; H = high level.
Table 2. Water temperature in tray during microwave heating
Time
[minutes]
L Level
[ 0 C]
ML Level
[ 0 C]
M Level
[ 0 C]
MH Level
[ 0 C]
0 20 20 20 20
1 35 42 55 70
0 20 20 20 20
2 37 55 69 77
0 21 21 21 21
3 43 63 77 -
0 21 21 21 21
4 47 64 75 -
0 21 21 21 21
5 50 68 - -
0 21 21 21 21
6 56 - - -
Each temperature is the average of at least three measurements
carried out in the same conditions.
Considering the difference of temperature between initial moment
and final moment of each heating experiment, the effective power absorbed
by water can be determined by the relation [4]:
Pef = (m water cp water·ΔT water /τ),
where: m water is the mass of heated water, 100 [g] = 0.1 [kg]; cp water - specific
heat of water 4,185 [J/kg 0 K]; ΔT water - difference of temperature between
the initial moment and the final moment of the heating process [ 0 K]; and τ -
irradiation time [ s].
The resulted values are presented in Table 3 and Table 4.
Table 3. The effective power absorbed by water during microwave heating in beaker
Heating time L Level ML Level M Level MH Level H Level
[min] [W] [W]
[W]
[W]
[W]
1 55.8 128.825 230.175 397.575 523.125
2 48.825 129.5 237.16 372.025 -
3 48.825 123.212 - - -
4 43.594 120.319
5 43.245 - - - -
6 46.5 - - - -
Pef av 47.798 125.464 233.667 384.480 523.125
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